texts: Mathematical Model for SiC MOSFET C2M0080120D, transconductance and capacities

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I am currently trying to use the model described in the paper "An Improved Analytical Model for Predicting the Switching Performance of SiC MOSFETs" in MathLab to simulate/imitate it. The paper can be downloaded for free. I use the parameters presented in the paper. A more recent paper that describe such a model in such detail is unfortunately not known to me. Unfortunately, I don't get any good results yet. In my opinion I don’t understand some things correctly. My questions:

In many data sheets of SiC-MOSFETs, parameters such as the transconductance gfs are given under certain conditions. I use the data sheet C2M0080120D Rev. C, 10-2015, since this SiC-MOSFET was used in the paper to evaluate the model. In this datasheet, gfs is given at Ids = 20 A. Other parameters such as the gate threshold voltage are given at a specific current Id. My question is: What is the difference between Id and Ids. Aren’t they both the drain-source-current or does Id correspond to the channel current Ich?
I don't understand how I can get gfs from the datasheet. According to the paper and to my knowledge gfs is defined by: Ich = gfs(vgs - Vth). If Id = Ich, I should be able to determine gfs from fig. 7 of the datasheet.  Let's take gfs = 8.1 S, which is given in the datasheet for Vds = 20 V and Ids = 20 A. I suppose the junction temperature is Tj = 25 °C. If I try to determine gfs = 8.1 S, I would get gfs = Ich/(vgs - Vth) = 20 A/(11 V - 2.5 V) = 2.35 S and not 8.1 S:

What am I doing wrong?

In the paper the author presents the characteristic curve (fig. 5) from where you can determine gfs with Ich(vgs). Let's compare his characteristic curve with the one from the data sheet, it does not match. Does anyone have any idea how the author came up with this data/curve?

I am also confused by the specifications on the parasitic capacities in the data sheet. Ciss, Coss and Crss are given with 950pF, 80pF and 7.6pF at Vds = 1000 V respectively. I can confirm Coss and Crss but in my opinion Ciss has a much higher value in the diagram. Let's have a look at the characteristic curves in the data sheet (fig.17 and 18):

Am I getting something wrong?

My last question is about the matrices given in the appendix of the paper. These were created by equations derived by the author from his circuit. Let's take matrix A (37) as an example, which (as I understood it) was derived from equations 4-7, 12 and 14. I don't understand how he gets to lines 2 and 4 because he seems to use some relationship between Coss, Ciss and Crss that I don't know yet. Does anyone have any idea how to get these rows of this matrix?

Many Thanks in advance!


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Note: pseudo transient analysis issue means that the LTSpice simulator is stucked with running pseudo transient analysis forever without any output waveform results.
The pseudo transient analysis issue happens only when I replace the OR gates (A5, A6, A9, A11) in favour of NOR gates inside the ZD one-shot circuit blocks.
Could anyone advise about the pseudo transient analysis issue in my GFSK demodulator circuit ?


texts: OPA211 weird frequency response --- why?

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I'm using an OPA211 in differential mode with unity gain; no external compensation. I'm getting a puzzling ~10MHz bandwidth (specs indicate a bandwidth of 45MHz at G=1) with a peak at 8MHz (consistent with the horrible overshoot/ringing that I see when I feed a square wave input).

Here are the details of my design and my setup to measure the frequency response:

Schematic:

PCB:

And this is the frequency response that I get:

The ground plane is at the bottom layer, and the top layer has a copper fill that is connected to GND at the pins of the BNC edge connector (J1).  This BNC connector (J1) is 50Ω; I connect it to a 50Ω BNC cable that goes to a 50Ω-terminated input capture device (a 180MSPS 16-bit Digitizer card on a PC --- the card itself specifies a 65MHz input bandwidth).

On the input side, however, there is no impedance matching --- to measure the frequency response, I use a signal generator with 50Ω BNC output, but I connected a cable that goes from BNC/coaxial to clips, and as you can see, the input goes to my board through a header type connector (more like a Molex-type, with locking housing).

BTW, when measuring the frequency response, I used a sine waveform with 100mV pk-to-pk to avoid issues with the slew rate (27 V/us as per the datasheet).

The ringing should not be surprising: it could be attributed to the op-amp getting closer and closer to instability when pushed to a low gain. But the low bandwidth is quite surprising --- precisely, at the lower gains I should expect higher bandwidth, right?

I also expect that parasitic capacitance or inductance (board, traces, ground plane, etc.) should not be an issue at such low frequencies  (I would expect those to kick in at the hundreds of MHz range).  For that matter, impedance matching (or lack of impedance control when ordering the PCB) should not play any role on the ringing at such low frequency, right?

Any ideas why such low bandwidth and why the peak at 8MHz?


texts: Nest thermostats wiring problem 3 storey house (3rd gen, E, analogue one)

texts: My house has 3 storeys and 3 thermostats. 2nd and 3rd floor have nest e and nest thermostats respectively. The 1st floor has an old analogue one that used to work ok. After the nest upgrade I noticed that the boiler was working, even though I did not give the order to the thermostats but I believed that there was something wrong with the settings of the nest app (pre heat, schedule etc). But this was happening even in "off" state.After a pump fix I noticed that the 1st floor radiators were hot even though the thermostat was also off. The 2nd and 3rd nest thermostats work as expected. Could it be a compatibility problem or a wrong wiring by myself?


texts: How to control op amp gain with atmega 32 MCU?

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I am attempting to control the gain of an amplifier circuit I am building programmatically. I am using the atmega 32 MCU to control an LCD screen and take input from some buttons. Basically, I would like to include a volume up and down button that tell the MCU to change the amplifier gain.
The amplifier circuit is shown below and the 10k pot is circled in red:

I have thought of using a transistor to do PWM control in place of the 10k pot, but I was advised that this would not work and that I should use a resistor bank instead or perhaps a switch capacitor circuit.
Can anyone point me in the right direction, and is there any reason why I wouldnt be able to replace the potentiometer with a digital pot like this one: https://www.sparkfun.com/products/10613 ??


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I would like to build a control panel to direct K power sources to N loads. A power source can control any number of loads, but a load can only be connected to a single power source. Each power source is variable (0 to 16V at up to 2A).

In a purely mechanical version, I imagine using a K+1 rotary switch for each load, where "+1" represents a no-power-source state.

I would like to implement this with a minimal set of small pushbuttons. I imagine a multiplex-like setup of pushbuttons as follows: each power source is represented by a pushbutton; each load is represented by a pushbutton. When a pair of pushbuttons(source,load) is pressed, the load is powered by source.

I've put together a circuit with AND gates to represent each pushbutton(source,load) combination; latches to hold state; and a grid of transistors to connect variable power sources (P1, P2, ..) to loads (targets 1, 2, ..). A separate constant power source Pc is used for the circuitry.

Missing from the diagram is reset logic which would ensure that at most one power source is connected to a load. Also missing is logic for the no-power-to-load option, which I imagine could be a P(zero) pushbutton.

I am seeking input to this design. Am I missing something substantial? Have I oversimplified the problem? Working with multiple power sources, does this circuit create undesired effects?

Thank you.


texts: Confirm transformer fault vs markings / spec

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I'm trying to troubleshoot a German ceramics kiln controller from about 1989.
There is a 100ma glass fuse in front of this PCB transformer that blows after a second or two when power is applied.

Schaffer B 222-1-01276

I de-soldered some components "downstream" to isolate its output, and the fuse now survives. That could point to anything downstream of course, but then I measured the transformer output.

I have not been able to find a spec sheet or on this transformer, but from the markings, I naively expected to measure about 9v ac across both outputs. What I see instead is about 13v on both, and also between them.

This does not make any sense to me. Can output voltage rise that much when there is no load? I'm starting to doubt what I thought I knew about transformers, but then my experience is limited.

To be more specific, there are four inputs, 1,2,3,4 where 2 and 3 are bridged, and 255v is applied between 1 and 4. (yes, the mains supply transformer is just outside in the street)

Between the four outputs 1,2,3,4 I expected 9v from 1-2 and 3-4, but measure 13v. I also see 13v on 1-4, and some lesser voltages on 2-3, 1-3, 2-4.
With the power off I have verified there is no contact between 2 and 3.

I'm grateful for any pointers to put me on the right track here.

PS.
This controller board is not supplied directly from the mains but a massive 400VA isolation transformer. Not sure how exactly that could affect things


texts: 10A 5v Relay control Submersible (Water motor)

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Is it possible to control Submersible (Water motor) with 5v 10A relay. Here is the details of the Submersible water motor.

My mains voltage is 225V to 250V

If this won't work then what relay should I plan to use here. Any good relay you can suggest.


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I try to build simple unitary push-pull amplifier which amplifies also DC. Here is a result of my work:

Unfortunately high frequency oscillation effect occured due to strong negative feedback:

My idea to resolve the problem is to limit bandwidth of my circuit by using low pass filter. I found "simplified non-inverting amplifier filter circuit" on this site: http://www.electronics-tutorials.ws/filter/filter_5.html

Here is the schematic:

Is this good approach to resolve my problem? Let me know:
1. Where in literature I can find information about especially this filter circuit?
2. Will this filter circuit work if I embrace in negative feedback loop also push-pull stage?
3. How to calculate the filter (the cutoff frequency and ensure unitary gain in passband).

Why I could't find much information about non-inverting amplifier filter in the Internet?


texts: Why is there a need of external clock even though MCUs can provide timing?

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Why is there a need sometimes for an external crystal, even though the MCU  have an internal oscillator?

To give you an example, the Atmega328P used in Arduino Uno has an internal 8Mhz internal oscillator, but also has settings for higher clocks. And additionally can be configured to use external oscillators as well. Why?

Similarly, there was a personal project where a PIC32, having 50Mhz CPU, was used with an external 8Mhz crystal for an audio codec.

Many of my assumptions maybe wrong, that is because of an unclear understanding of the need for something external, if there is a default choice.

Some assumptions

Stability
Accuracy
Cost

Please elaborate the exact purpose.


texts: How to calculate the DC rail voltage for Variable frequency drive (VFD) for single phase induction motor?

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I am working on VDF for Sigle phase induction motor. I just want to compute the total voltage of single-phase induction motor that will need to create from DC link. I am not sure about the calculation. As we need SPWM based inverter for VFD of the Single induction motor. The input of the inverter is DC link voltage. how can I calculate the required voltage for DC link for Single phase induction motor?
The voltage rating for induction motor is 220V,


texts: Arduino to Attiny841 with ATTinyCore -- pins not working

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I have code that works using Arduino.

Because I wanted to size down the project, I replaced it with an Attiny841.

Process:

I soldered the 841 on an adapter and checked all pins using a multimeter for cold joints.

Then I connected the pins using this schematic from http://elecrab.com, but with a cap for RESET in addition:

I used the online Arduino environment to burn the ArduinoISP sketch to my Arduino.

Then I used the offline Arduino program, using ATTinyCore as such:

I burned the bootloader and it did so succesfully.

I then copy-pasted my own sketch in the offline environment and uploaded it, which also worked without a single error.

(For some weird reason I cannot burn the ArduinoISP using the offline program, hence the two-step method.)

Sketch:

I left my sketch unaltered, except for the selected pins which became:

#define BEAM_One 2
#define BEAM_Two 3

#define LED_Install 4
#define BUTTON_Install 5

#define AT_Mode 6
#define POWER_On 7

#define LED_Occupied 10

Basically, I thought, 841 physical pins 11 and 12 are TX/RX and 2 to 4 are special cases, so I can simply select pins 5 to 10 and 13 for I/O.

I then choose the above pins, using the pin mapping in the ATTinyCore documentation:

ATTinyCore already preconfigures PWM, so it can be used without any extra steps or coding, I read somewhere.

Physical pins 5 and 6 allow for attachInterrupt(), see PCINT10 and PCINT7 on PB2 and PA7.

Result:

I connected some LEDs at the 841's output pins.

Some don't react, which might be due to a cold joint.

However, others do react but not in the expected way.

The LED connected to 841 pin 10, or pin 7 in the Arduino code, should go HIGH, then LOW, then HIGH with noticeable delays. In reality, it is HIGH and stays that way.

The attachInterrupt() functions are something else still. I think I just figured out that I am trying to use INT on PB2 and PA7, but it only exists on PB1 contrary to Arduino. I can use PB2 and PA7, but those are PCINT, that change ports and only use CHANGE (not RISING or FALLING). I hope to fix this specific issue by using this library: https://github.com/NicoHood/PinChangeInterrupt.

Does anyone have a clue what the issue might be with the pins not reacting as expected?

Thank you for reading my small novel.


texts: Designing a 1A current source with high-side current sense

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I want to design a 1A current source on a PCB. I have bunch of MAX9611 chips laying around. In their datasheet it says it can be configured as inrush current limiter and current source (in a closed-loop system). The problem is, there is no application example of current source in the datasheet. The only thing there is:

The relation for I_limit is given (correction as Neil_UK pointed out):
$$I_{LIMIT} = \frac{V_{CC} \times R_{3}}{(R_{3}+R_{4})(2.5\times R_{SENSE})}$$

I know a simple current source can be built by a p-channel MOSFET:

I am failing at relating these two concepts together. Is what I want to achieve even possible? If so, can I get some clues? If not, please let me know an alternative.


texts: Solar charging with a super capacitor buffer

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I have a 20W 5V solar panel (real output more like 10W in bright sun). Would like to harvest as much solar power as possible to a power bank to power a bluetooth speaker (< 5W consumption). Bright clear skies are a luxury where I am. The panel voltage fluctuates depending on the clouds etc, - damaged the circuit of a powerbank. Need something to act as a buffer.

I am considering a circuit using super capacitors (2 in series 2.7V 500F) as energy collectors / buffer -- let the voltage build up to ~ 4.5V. Switch on the circuit at 4.5V and a boost/buck circuit mops up the power to charge a power bank. The switch is on till the voltage drops to ~2V. When the voltage drops to ~2V the switch turns off and stays off till  the voltage rises up to ~4.5V again.

Are such configurable switching circuits available where one can set the upper and lower voltages? Or Is it easy to make one?

Or should I try a different approach altogether?

Looking forward to your suggestions.

simulate this circuit – Schematic created using CircuitLab

PS - Apologies, I am a newbie in the world of circuits.


texts: How does current flow inside a grounded coax shield?

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I have been trying to reconcile the fact that current flows on the inside of a coax shield with the common practice of grounding the shield. These ideas seem contradictory at the moment.
For a 2-wire transmission line it seems intuitive that both wires have a varying voltage wave along them, creating an electric field between the wires and also a potential difference along the wires, due to the peaks and troughs of the wave. Hence, current flows backwards and forwards in each wire.

For coax the argument is the same, until we connect the shield to ground. Now it seems that I have locked the shield potential, so now it seems that all the voltage variation is on the centre conductor, while the shield remains at a fixed potential. If the potential is fixed, how can there be current flow on the inside of the shield?

I know there is a high impedance between the inside and outside of the shield, but I can't see how that solves anything. Clearly I am misunderstanding the electromagnetic effects in some way. Appreciate any advice.

This diagram tries to illustrate the issue:

At a given moment, the shield has a sinusoidal current distribution, which to me suggests a potential difference along the shield. Yet we have the shield grounded?

Thanks, Ian


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This is my Bode plot
The solution manual says the function plotted is $$\frac{s^2+0.02s+1001}{s^2+2s+101)(s^2+20s+10100)}$$ What I know is the Bode plot for $$\frac{s^2+2ζω_ns+ω_n^2}{ω_n^2}$$ and the inverse of that.

I can see three peaks at ω=1 , ω=10 , ω=100.

Since the plot is going up after the peak we have a second order equation on the numerator. Then we have a second peak and then the plot is almost a straight line so I guess there is a second order equation in the denominator followed by another one afterwards because of the next peak. The phase diagram makes sense as well for the above.

The initial value is -120 so we must have a constant given by :$$ 20logK=-120=>K=10^{-6}$$ So my transfer function must be of the following form : $$10^{-6}\frac{s^2+2ζ_1 1s+1^2}{\frac{s^2+2ζ_2 10s+10^2}{10^2}\frac{s^2+2ζ_3 100s+100^2}{100^2}} $$

Can I find the ζs? This is a question from an exam so I should be able to , by hand . But I also get a quite different result.

This is what I'm using :


texts: Would this design carry too much current and damage battery charger ICs?

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I'm planning on designing a system to charge multiple 3.7V 500mAh lithium-ion batteries simultaneously. The batteries are each going to be charged through a battery charger IC, here is the link to the datasheet.

I'm planning to employ the fast charge constant-current mode with a charge current of 500mA. I've tested it for a single battery and it works perfectly.

Now I want to scale it up to charge 10 or more batteries at once, so the system consists of a 5V 60A DC switching power supply and the batteries and its ICs connected in parallel between the outputs of the power supply.

Since I'm charging many batteries at once with each pulling 500mA, the main supply line coming from the power supply will carry a high current. I'm not sure if this will damage the ICs, or if this design is feasible. For example, if I intend to charge 10 batteries simultaneously with each at 500mA, the main supply line would carry 5A. Will this current be too high for the battery charger ICs and will each battery charger IC only pull the required 500mA of current from the main supply line? Will this design work, and can it scale to even larger numbers?

Thanks.

Edit: Many of the previous posts I have seen mention soldering the leads of batteries together and charging them in aprallel using a single battery charger IC. Mine is slightly different. It uses a separate battery charger IC for each cell but those ICs are arranged in parallel like the picture shown below. The IC is capable of monitoring the voltage of the battery, so I guess this design would not have issues of some batteries discharging to charge other batteries. I'm still not sure if this design will work, and if the main branch carrying the high current is a cause of concern, if each battery charging IC is pulling 500mA, 10 of them in parallel would result in 5A in the main line. Would a person touching the main line risk getting electrical shock?


texts: How to connect power phototriac's gate pin?

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I have inherited a design that uses a power phototriac (basically an optotriac with a built-in TRIAC) -- the VO2223B -- that includes a pin to access the power TRIAC's gate (pin 5 below).

The datasheet gives no hints on what to do with this pin, and neither do any app notes from Vishay that I have found.  Should I keep this pin floating as in its current design, or should it be tied to one of the anodes through some passives?


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I'm trying to make a Tesla coil with approximately 200 turns in the secondary coil using 28 gauge enameled copper wire. My primary coil has 3-6 turns with a thicker wire. I've made all the connections according to the schematic and yet, my Tesla coil doesn't work. What am I doing wrong?
The current flows through the primary coil but there's no response in secondary coil and thus the CFL doesn't glow


texts: what is the real DC power dissipated by an inductor that is pulsed on off

texts: A meter indicates a higher DC power being delivered to a circuit consisting of an inductor switched on and off by a MOSFET on both the high and low side, than the heat measured by a thermistor. The thermistor test indicates only a small fraction of the input power is actually dissipated by the inductor. This makes it appear that the power is going somewhere else. For this test, the coil is the only load. Current and voltage measurements were taken with both digital and analog meters to reduce possibilities of error. What am I missing?


texts: How does the energy of non-resolved spectral lines get distributed in an FFT?

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For example, if my FFT has a poor resolution of 170Hz (data sequence length is small due to latency constraints) and I am trying to detect a sinusoid in the 150-250 Hz range, will this FFT be good enough?

I feel if the sinusoid is in the neighborhood of 170 Hz (150-200Hz), my frequency bin at 170Hz will show an increase in magnitude which I can use to detect. But what if a sinusoid is present at 250 Hz? Will its energy be distributed between the 170 Hz bin and the 340 Hz bin? And if so, in what proportion? (perhaps I can use a weighted sum to detect in that case)


texts: Is it possible to change direction of DC motor using a 3-state rocker switch?

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I have a 3-state switch, It has 3 pins. It can have 3 state as you can see in the picture below. when it's off (i.e on O) the middle pin is not connected to anything. When it's on I, the middle pin is connected to I and when it's on II the middle pin is connected to II.

Now, I have one DC motor and a 9 volt battery. I wanted to build a connection between these three elements that when the switch is on O, the motor is off. When it's on I, it turns in one direccion and when it's on II it turns to the other direction. I wanted to avoid using any other logical elements like gates or diodes, etc...

All I want to have is just one switch, one DC motor and one DC battery. I've got no idea how to make this happen.

If there is no way of doing it, is there a way to build it with minimum extra required elements?


texts: synchronous reset D flip-flop with three inputs

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I can't find the schematic of D flip-flop with synchronous reset , that is , D flip-flop with three inputs, D,CLK and reset ; and two outputs ,Q1 and Q2

I only found the schematic with "two"  inputs,D and CLK;or  "four"  inputs, D,CLK,reset and set,from the Internet.

Can anyone help me??please.......


texts: Theory behind the "Joule Ringer" circuit

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The less-than-critical thinking free energy types are pointing to the "Super Joule Ringer" demonstrations online, where a quick touch with a 9 V battery illuminates an LED for hours.

http://laserhacker.com/?p=406

I see an oscillating tank circuit, with the inductor and cap trading energy back and forth.  If I'm not mistaken, we can combine the energies stored in the two components, since they're both charged up with the battery (unlike the traditional tank circuit in textbooks which has a cap or inductor getting switched in).

$$
E=\frac{1}{2}(CV^2 + LI^2)
$$

So, assuming a 3000 uF cap and a 500 mH inductor (guessing), and 10 A from the battery, we'd have 25 J of energy stored.

Since the time to discharge that much energy for a given power draw is given by:

$$
t=\frac{E}{P}
$$

Ignoring losses, an LED drawing 10 mA at 1.6 V would be dissipating 12 mW, so the circuit could power the LED for 34.7 minutes.

Is this circuit capable of achieving that?  What explains the weird sawtooth-with-ringing waveform he shows on the oscilloscope?


texts: How to design an STM32 board with UART over a USB connection?

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Sorry if this seems a stupid question but I'm designing a custom PCB based on the STM32F303RE microcontroller and am slightly confused as to how the UART should be connected in the hardware in order to communicate via serial over USB.

I have a microUSB connector on board, should the UART pins be connected directly to this connector? Or do I need to use the USB pins on the STM32 and set up the micro controller as a USB device and connect the UART to these pins somehow (or not use them at all)?

I started with a Nucleo board for development and can communicate via UART on there (using HAL UART functions) but looking at the schematic is confusing due to the on-board ST-LINK. As far as I can see, the UART signal of the STM32 is passed to the UART pins of the ST-LINK MCU and the USB pins of the ST-LINK MCU are connected to the MicroUSB port but I'm not sure how the data is passed through? Is it in fact using the USB HAL functions to convert the received UART data?


texts: My 9v battery reads 20v ac in multimeter

texts: I have a 9v battery for my project. It shows 9vdc dc mode in multineter, and surprisingly I get 20vac in ac mode. What is this happening? Can this happen? An ac voltage from a dc storage!?


texts:
The digital chapters of LAoE require a custom display with added functionality that is not sold in the UK (details on the LAoE website at the link below). Do you have any ideas for an alternative approach please, for example:

Using a simulator for the circuits in the digital chapters. It would be a good opportunity to learn how to use a simulator but I have no idea how feasible that is. For example, would the simulator suffer from not having details of the custom display or would input and output functionality be provided anyway in most simulators?
Building a display and other functionality from generic components. I am quite happy to have a go at building something from scratch but have so far not found a good reference on the web.
Some other approach that I haven't thought of.

The digital pages of LAoE involve building a microcomputer from parts, but not the display, so I'm guessing it must be pretty complicated. However, LAoE is a brilliant course and I'm thoroughly enjoying the analogue chapters and do not want to miss the digital.

Any ideas about alternative approaches would be much appreciated.

/https://learningtheartofelectronics.com/parts-lists/lcd-display-and-programming-board/


texts: Help understanding RV/Marine battery chargers

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I am trying to understand how modern 3-stage marine/RV lead-acid battery charge systems work. It's very common to wire a charger in parallel with both the battery bank and the "house" power.  This means that when plugged in, the charger is both charging up the batteries and powering any DC electronics.

My understanding of IUoU Charging is that during the "Uo" phase the charger puts out constant voltage until the current draw drops below a given threshold. If the house electronics are drawing from the charger, then how could the charger possibly know what that threshold is? Shouldn't it be quite common for the charger to never hit that threshold and constantly overcharge the batteries (e.g. if the house refrigerator is in the circuit)?


texts: I have somehow hit a shortcut in Altium that causes all of the layers that I am not currently working on to become grey. I can change layers and they are still there. How do I turn this off? It is not "mask level" of layers feature too. I am in footprint editor if that helps.


texts:
I'm putting together a board and it's requiring a footprint for a 16 lead Plastic MSOP.

Usually I try to dig around and find a manufactures recommended footprint and try to stick with that. I figure they're building their parts and should generally know what will work best for a footprint (or Layout).

Anyway I came across a 16 MSOP package from Linear:  data sheet (The package and associated footprint I wasn to use is on page 22)

Anyway as I'm sitting there crunching the numbers double checking the width on the part it gives 5.23mm. Now I always try to  double check so I subtracted .889mm (twice for both the pads) so I should be left with something close to the 3.2-3.45mm dimension for the distacts between the inside edges of the pads.

Well usually when I do this things check out and I feel confident the footprint is correct. However in this circumstance I didn't end up with that dimension.

Now here's where all my confusion (OCD) kicks in.

I don't believe I can make the footprint work with it's given dimensions.

"5.23 mm MIN" is saying I have to make the outside of the pads be at least 5.23mm long.

"3.23-3.45 mm" is saying the inside spacing between the two rows of pads can very

".889 +/- .127mm" is saying the pads themselves can very that much but probably no more right?

However if I take the smallest inside spacing and add it to the smallest pads spacing I can't get 5.23 mm.

((smallest pad distance) *2 + (smallest inside diameter) = total width for part.

((.889 - .127)*2 + (3.2) ) = 4.724

Not 5.23mm!

(As a side note I also noticed that right above the recommended pad layout they point you to the packaging page for the latest version of their footprints and the footprint there is close. Except they've changed the 5.23mm to 5.1mm. Closer to that 4.724 mm I get when I calculate it but still not exactly there)

So which one of these rules should I break for this given footprint?


texts:
Recently I came across an exercise which I can’t confirm myself If I’m doing it right.
The question itself asked to Design a Band Pass Filter

Properties:

Lower -3db
cutoff-frequency 500Hz
Higher -3db
cutoff-freuqency 1000Hz
Gain in Pass-Band   20db
List item
Attenuation:   20bd/Dekade

Below is a picture of what I came up with, this no homework. It just interested me and tried to solve it considering that I don’t know much about band pass filters I came here .


texts: Signal Detector (UHF Field Strength Meter)

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after some reading I ended up finding a relatively basic FSM, using a antenna, an LC circuit to tune to a specific frequency, and a RF diode and final a ammeter to measure signal strength.

My target frequency is around 500Mhz and I used the resonant frequency equation for LC circuits to calculate a hypothetical L and C.

My big question basically is, is this even going in the right direction? and if there are anything I should change about the values of my components and/or antenna. Also would I be able to replace the ammeter with a typical LED to judge the strength of the signal instead?

If this is completely wrong, please dont hesitate to say so.

I have attached the basic circuit schematic below with my calculations.


texts:
I need to generate a fixed frequency and variable duty cycle PWM signal. Normally I would've used a microcontroller , but due to unavoidable circumstances , I have to use the TL494. I did an extensive study of the datasheet , but there are some doubts which need to be cleared. The picture shows the block diagram of the TL494.

What I've decided to do is to connect the Vref pin to the FEEDBACK pin. According to the datasheet , the Vref pin is a reference voltage source of 5V. I'll put a pot in between the Vref pin and the FEEDBACK pin. That way I can control the voltage input into the FEEDBACK pin from 0 - 5V. If my understanding of PWM generation is correct , the PWM comparator should do its work by comparing the DC signal from feedback and the sawtooth from the oscillator. I have 4 questions.

Am I doing this right ? I know the TL494n is supposed to be used as a closed loop system with the feedback coming from the output section of the power supply. I want to re-purpose it as a PWM generator with duty cycle controlled by a pot.
What confuses me is what am I supposed to do with the other pins , like the error amplifiers and the DTC . Should I leave them unconnected ? Should I pull them to ground ?
I'm using the Vref pin as a voltage source. Is this good practice ? Or should I use a separate 5V source ?
I want to get single-ended output from the chip  , not push pull. This is kind of a newbie question , but how do I wire up the pins for this mode ?

Datasheet : http://www.ti.com/lit/ds/symlink/tl494.pdf


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Hi I have a basic electrical circuit and I am trying to make loops.

Those things on IMG-2.

I just don't understand how are they made.

Why are the "one square loops" only in upper squares and not down too. If you have any source with this how it is made please share or if you have time to explain it.


texts: Reason for parametric variation in a power system

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Let us take an example of a single area power system consisting of a governor, noon-reheated turbine, load and machine, droop characteristics.

It is written in the literature that T_g, T_t, T_p, R, i.e, the time constant of the governor, turbine and plant may vary, thus there is a large parametric uncertainty in this system. Thus, we often design fractional order PID as compared to a classical PID for such a system.

My doubt is, that under what conditions and why (or how) do these parameters vary ?


texts:
I want a relay to turn on a 120V device when another 120V device is turned on.
Unfortunately most relays I've encountered are 12 or 24 volt DC.  I could simply slap a power brick in there and get the job done, but is there such a thing as a relay that does this without fiddling around with converting?


texts: Explanation for parallel darlington behavior

texts:
I've built and simulated the circuit below in real life, LTSpice and Stack-Echange-Spice. It behaves in a similar fashion in all of these Environments. When the "LAMP2" load is disconnected, the Base currents become unbalanced, with most going through Q2 - This, in turn, turns Q1 all but off, since only a very small current is going through its base:

simulate this circuit – Schematic created using CircuitLab

Now i drew myself what i believe is the equivalent circuit of those darlingtons:

I suspect that when the top load on the right side is disconnected, the base current of Q2 turns on the "main" NPN of Q2 and allows current to flow through the first BC diode, increasing consumption. But why does this not happen with the load connected as well? What is happening here?


texts: Bang-for-buck in purchasing an instrumentation amplifier for three-electrode EEG recording?

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While my forte has been in digital signal processing for most of my life, not-so-recently I've made the mistake of venturing into analog signal processing for a well-endowed client. I've primarily been focused on inexpensive, three-electrode EEG applications involving instrumentation amplifiers such as the INA122 ($6.22 / piece on Digikey). Now that we're moving forward to production, I'm questioning whether the INA122 is really the most cost-effective part for the job.

What are some qualities to look for in cheaper instrumentation amplifiers that might make them suitable for EEG recording? For the purposes of explanation, assume that I have three electrodes: Vin+, Vin-, and GND, The final output voltage relative to the GND electrode being some gain times Vin+ minus Vin-.

1) Gain: The thing that sticks out in cheaper instrumentation amplifiers is that the gain might be as little as 100. Previously, my INA was using only a gain of about 1,000. I'm wondering if I can continue to amplify my signal after this stage in subsequent low-pass-filter opamps safely -- what should I look for in these op-amps that would allow them to do this? Open to many suggestions /feedback here -- the EEG is actually a minor part of the circuit that has not been as well-tested as some other components.

2) Single supply vs dual supply: In the single-supply case, if Vin- is a higher voltage relative to GND than Vin+, my output will rail to 0. Then, doesn't a dual supply voltage effectively double the signal bandwidth?

3) Offset voltage: If I'm recording a microvolt signal, what's the maximum offset voltage I should look for?

I would really like an instrumentation amplifier that is about $1 but is effective in recording brainwaves. I do not need a multi-channel EEG>


texts: What's the advantage of using cotton braid wires over normal wires?

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I recently notice sudden trending use of cotton braid wires over
normal wires in eletronic units. Is there any special advantage to it?

Google shows me about images but not helping with advantages.


texts:
How can I fill the complete pad with polygon pour ? (I dont know the correct question in english)

I am using Altium Designer 17


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I need a 50 mA current source despite the load value (resistor LOAD), and I need the current flowing just when the microcontroller says so.

It works fine with LOAD = 0 ohm and IL = 50 mA, but when I enlarge LOAD the current decreases (LOAD = 330 ohm and IL = 11 mA / LOAD = 1,330 ohm and IL = 3 mA).

What am I missing in the design?

simulate this circuit – Schematic created using CircuitLab


texts: Transistor Schmitt trigger vs opAmp Schmitt trigger

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Schmitt trigger was originally implemented by using two transistors long time ago.

Are there any advantages using Transistor Schmitt trigger instead of using opAmps?


texts: I've recently been trying to figure out how to use transformers, coils, and inductors in general. My question here is whether transformers produce a load or not. For example, if I apply current to the primary coil, is it a short circuit, and how to they do it with mains power? My guess is that a load on the secondary coil produces a load on the primary coil. Is this true? Please correct me if I'm wrong.


texts: Removing output of low pass filter when turning off power

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I'm constructing a presence detect circuit using a pulse modulated signal of 5 kHz and an infrared transmitter and receiver.
The 5 kHz signal drives an infrared transmitter through a 3904 NPN transistor.
This signal is received by an infrared receiver in reverse bias mode using a 5V and 3904 NPN transistor. The receiver is located at 10 cm from transmitter. This signal after the transistor amplification is fed to a simple RC filter and it is successfully filtered (green signal in attached.)
If there is physical interruption to the path of the signal, the pulse will be high as I'm inverting the the transistor and RC filter signal using hex inverter Schmitt trigger IC.

My problem is, when the circuit loses power / it is turned off, it has a spike (red signal in the attached image) which may create a false positive for other connecting circuits.
What I understood of this, this behavior natural of such circuit as we can imagine when transmitter is turning off, the signal is turning off and filtering circuit thinks that pulses signal is not received so it is physical interruption for a short amount of time at the shutdown because of power stored in the capacitors in power supply as well as RC network.
I want to modify my circuit so I don't get such spike at shutdown and if there is any spike, its voltage level is low enough not to trigger false pulse out (presence detected.)
I searched the internet and forums but I have not been able to find any lead on this. I also tried using an active filter but got same problem.
I thought of even logic gates to tackle this problem using transmitter signal and receiver signal but because a quick thought stopped me doing this as power supply capacitors will keep circuit alive for few microseconds or milliseconds and I'll end with shutdown spike with that modification, too.


texts:
Is is possible, and if so, is it viable, to use UHF RFID RSSI to measure distance in the 1-25 millimeter range from the RFID Reader antenna with a resolution down to below half a millimeter?

If it is, could anyone offer some hardware tips to make this work reliably?

Any insight would be appreciated, as we are concerned that the tolerances in the hardware will render this impossible.


texts: How do I convert 50Hz AC to 60Hz AC using a cyclo-converter?

texts:
I want to design a 3 phase cyclo-converter to run a 7.5kW induction motor. The input to the cyclo-converter is 50Hz AC and the output of the cyclo-converter should be 60Hz AC.

What are the specific ratings of thyristors for designing the above?


texts: Wiring Li Ion cells in parallel to make a 3S8P pack

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I'm making a 3S, 8P Li Ion battery pack with balance leads. While wiring, I was wondering if there's a difference between bridging the parallel cells versus not bridging them down the center:

simulate this circuit – Schematic created using CircuitLab

What would the impact on my circuit be both ways, if any?


texts:
i am using a meanwell LDD-H driver to drive some led for a reef light.
(datasheet http://www.kosmodrom.com.ua/pdf/LDD-H.pdf)

standing to datasheet i can use a pwm of 100 ~ 1KHz

what's the difference?

i mean, what should change if i set the pwm to 100 or 1000 on my controller? light will flicker? ldd will consume less? make less 'acoustic' noise? i have to try by myself? there is a scientific explanation about what should happen if i change it? (i can hear a very light biiiiiiiii while they operate)

i am using
https://www.adafruit.com/product/815

as pwm generator, that support 12bit, and well into range of LDD datasheet of pwm frequency.

on my test, i setup 1000hz, use the full 12bit resolution and leds work perfectly (i can setup of course 2^12 different 'intensity' of light)


texts:
When two devices are connected via wireless, one device sends a character using its TX line, and the character is received by the other device on its RX line, and vice versa.

My question is, RF signals reflect, get absorbed etc. Does the signal reflects and go back to transmitter sometimes ? If it does, how the transmitter recognizes it and discard the character ?


texts:
I have a buck converter. TPS54260

Vin = 7V-20V
Vout = 5V
Iload=600mA.

I realise that there is a similar question in this forum but I was not able to get clarity.

I want to understand what do you mean by loop compensation and how to select my output capacitors based on this loop compensation . I gone to youtube videos and seminars for TI. But I am not able to understand it clearly.

Can someone help me understand the the concept of Loop compensation and how to choose my output capacitor value?

Thank you


texts: Output capacitor size for Boost converter under pulsed load

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I have a load driven at 24VDC that draws very high current for a short period of time. The following picture is the output of a current amplifier, it reads 2A/V, meaning I have to deal with roughly a 18A pulse that lasts for 50ms.

So far I have calculated the energy of this pulse like this:

Charge spent: 18A @ 50ms, using Q=I.T -> Q = 18*0.05 = 0.9 Coulombs.

Energy drawn: E = 0.5*V*Q = 0.5*24*0.9 = 10.8 Joules.

The 24V is generated by a boost converter, let's suppose I want the output capacitors of this converter to be able to provide all the energy:

E=0.5*C*V² -> C = 2*E / V² -> C = 2*10.8/576 = 37.5mF, or 37,500uF.

That is a humongous ammount of capacitance to install @ 24V.
This leads to the question: What percentage of the pulse energy do I need to store on my output capacitors in order not to stress my BOOST converter too much?

I know it might have to do with the impedance between the output capacitor and the load itself, and also that I don't need output caps to be able to provide ALL the energy for the pulse, as the converter should be able to deal with some ammount of load transients.

EDIT#1 @ Brian & Peufeu: I'm considering 0.9F as the correct answer for my previous calculations, using C=dV/dt, from this point on. The boost circuit that generates the 24V is as follows:

Upstream this converter is a 4S3P - 12 x 18650 cell Li-Ion battery, more than capable of providing the current needed. Cabling is also cut to minimum lenght and twisted to minimize media impedance.
At the time of design I wasn't sure of what the peak currents on the system would be, so I think I might have chosen my inductor poorly already... here are the specs:

AFAIC, my switch and diode are far beyond capable of withstanding the aforementioned scenario.


texts: How to best choose a method of driving a MOSFET

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I want to be able to control 12V as well as 24V LED strips that will be used in a video recording environment (so high switching frequency). In a few bullet points I will explain the planned circuit:

Power supply will be either 12V or 24V
LED strip will be controlled with a MOSFET ('logic-level' IRLR7843 for example)
MCU controls the MOSFET with a 3.3V PWM signal
To ensure that 3.3v is available to the MCU regardless of the input voltage LM2596 is used

So the question is how to drive the MOSFET? My first thought was to drive the MOSFET directly form the MCU but the problem with that is that the switching frequency would be limited due to the gate capacitance. So I have to use a MOSFET driver. Since I have only 24V/12V and 3.3V available on the board I would have to do one of the following:

Use a driver that has a minimum supply voltage of at least 3.3V to drive the MOSFET (not easy to find, on ebay or aliexpress at least)
Use a secondary Step-Down Voltage Regulator that steps down 24V/12V to a more usable voltage (like 10V or something) that a more readily available drivers support.
Use a different MOSFET that allows for a larger Gate-to-Source Voltage that I can drive with 24V/12V. And find a driver that supports 24V supply voltage.

Any other option?


texts: Which semiconductor manufacturer names parts RTCxxx

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I am in the process of reverse engineering/tearing down a small Bluetooth speaker.  In the audio path, there are two amplifiers.  Their top markings are RTC002 and RTC005.  Note that these are NOT Real Time Clocks.  I'm positive they are amplifiers.  Google hasn't turned anything up in regard to that part number.  Any leads on the possible vendor?  I'd like to try and find a datasheet.  Thank you.

EDIT: Picture of first IC attached.  SOP-8.  Appears to be a dual op amp (left/right channels) connected as high-pass filter.  Was shocked how clear the image came out with jeweler's loop and phone camera!

Jon, I don't know the make/model of the speakers as I came by the board second-hand.  I'll try to ask the original owner.

EDIT 2: Picture of the second IC.  MSOP-8.  Seems to be hooked up as a diff in/diff out amplifier.  There are 2 of this one, one for each channel.

Jon, definitely not made in U.S.  Chinese ICs, perhaps?


texts:
I notice that in solution manuals to problems like these, when the gate is shorted to the drain on an NMOS, Vds = Vgs. So Vds >= Vds - Vtn, making the MOSFET always in saturation.
I do not understand why this is, and have not been able to find a diagram that I could make sense of. How can we explain this more visually?

Here is the problem this schematic came from. Microelectronic circuit design, 5th edition.


texts:
I'm trying to design a mini workbench power supply to use for small electronics that is powered from the 12V rail of an old ATX power supply. I want it to be able to provide an adjustable voltage of 2V-30V and an adjustable current limit from 0-3A. Therefore, I'm going to need a buck and boost converters to do so. I have two ideas so far which is :-

-LM2577(Boost), LM2596(Buck) & LM350(Current Limiting)

My first idea is to connect a LM2577 boost circuit, LM2596 buck circuit and a LM350 current limiting circuit in series. Problem with this is I need to have two separate potentio to control the buck and boost. And another problem is I'm not very sure on the LM350 as a current limiter. Is it good and stable? Is there any other better current limiting circuit that can handle 3A

-LM2577(Boost) & L296(Buck and Current Limiting)

My second idea is to connect a LM2577 circuit and L296 circuit in series. I have the same problem with this that I need two separate potentios and it can only adjust voltages from 5V-40V. However, it does have a built in current limiter. Is this current limiter stable?

Which circuit is a better idea or are there any better circuits that can be used? Are there any better boost converters or a chip that has all in one? And lastly how do I measure the current limit? Sorry for lots of question. A reply will me much appreciated.
Thank you!


texts: How do I get 5V for a Raspberry Pi from 4 D batteries?

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I'm hoping to run a Raspberry Pi and a hobby servo off 4x1.5V D size Alkaline batteries. The batteries are brand new and at the moment I am measuring 6.5V from the 4 in series. I'm guessing each cell is about 8000mAh although they don't say on them. The servo in question is this one.

I have an LM7805 voltage regulator but I'm guessing even if I found it a heatsink it won't be able to handle the current, also I believe they stop being able to regulate properly if the input voltage is below 9V.

What are my options to use instead?


texts: Atmel SAM3X / SAM3A, handle interrupts from Parallel Input/Output Controller (Peripherals)

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I want to enable the PA8 pin in a processor (Atmel SAM3X / SAM3A).

I have set:

PIOA_MDER[7]=0
PIOA_MDDR[7]=0
PIO_OER[7]=0
PIO_ODR[7]=1

so that the tri-state buffer will no longer send data out of the pin, and the pin is enabled to receive data from the environment and to send interrupts if needed.

I also want to set my interrupt to rising edge, so I also set:

PIOA_RHLSR[7]=1
PIOA_FELLSR[7]=0
PIO_ESR[7]=1
PIOA_LSR[7]=0

My problem now is how to modify NVIC registers so that this interrupt is enabled. I mean, on a rising edge on this pin, the state of this pin is pending, and then the changes I will apply to NVIC causes this pending state to active state.

My interrupt group priority and subgroup priority are both 3. I know how to modify Interrupt set-enable register, interrupt clear-enable register, application interrupt and reset control register, and interrupt priority register.

Still, my problem is that now I don't have any number for interrupts from this specific pin (PIOA8), so it is different from the time I had my interrupt number (from 1 to 240)

Does someone know which register in the NVIC I should modify? Thanks for your help.

update

I think I'd better say that I need to work with peripherals, now, how to inform NVIC about interrupts?


texts:
I recently purchased an Arduino Uno and I've had lots of fun tinkering with it. I'm now interested in measuring the amount of water that flows into my house through the water line.

I'm having trouble finding an appropriate device that will let me measure the flow of water from my well and capture it with my Arduino. Can you guys please recommend a specific component or some general search terms so I can start looking?

Thanks in advance!


texts:
I'm trying to create a circuit that will divide the input voltage in half, but still be able to supply a high current to the load.

My input voltage varies from 10-15v and I want the output voltage to variate in proportion to this. So between 5-7.5V. The load should be able to draw about 1A, so the components needs to be able to handle this.

I'm thinking it's going to be a voltage diveder and a voltage follower, but I'm not completely sure. Whats the best solution to this?

Tnx.


texts: How to connect a mains 24Vdc and an Emergency 24Vdc supply to lights that should switch the mains supply off when the emergency feed is switched on

texts:
I am looking for a solution for some lighting that was installed recently. The lights are single LED downlights that are connected from a direct connection to 24Vdc through a constant current driver to the LED.
The problem is, there was supposed to be an emergency lighting supply connected to some of these lights as well, and there is a test button that will turn this supply on. This obviously would be problematic without some additional electronics that would allow the presence of the emergency supply to cut off the mains supply from an individual light (lights on a given circuit are not all fed with an emergency supply) and allow the emergency feed to take over, and of course, when the emergency feed is switched off, the mains would take over again.
I have been looking for a commercial product for such applications, but I have not yet come across any.
Does anyone know where I could look, or know how to do a DIY resolution with electronics?
Thanks.


texts:
Source: https://ozhealth.com.sg/product/genial-digital-thermometer-t15-orange/
I tore down a digital thermometer today (a Genial T15), and the interface to the LCD caught my eye: although there were conventional solder pads on the PCB, there was curiously no direct connection between the PCB and the LCD, which was offset some millimeters above by a rubber spacer of sorts. The entire assembly was fixed in a rigid enclosure (not shown) to prevent relative motion of the PCB and LCD:

My guess upon seeing this arrangement is that the LCD is capacitively coupled to the PCB, and the rubber spacer acts as a dielectric.
My questions are:

Is this guess correct? Is there indeed capacitive coupling going on?
What are the pros and cons of this design?
Is this approach to interfacing with an LCD common in industry?

NOTE: I'm asking about a capacitively coupled LCD, not a capacitive touchscreen.


texts: How can I maximize the source impedance of the Arduino Due's ADC?

texts:
I know that the ADC on the Arduino Due has a clock speed from 1 MHz to 20 MHz. This is given by the data sheet:

I want to lower f_ADC to maximize source impedance:

I want to slow down the ADC as much as possible is to obtain the maximum source impedance. However, according to this post, Arduino sets the ADC clock to 125 KHz.

How is this possible, if the data sheet says that the minimum is 1 MHz? Finally, if I utilize the Arduino backend C++ code to slow down the ADC, then can I extrapolate that the source impedance will reach MΩ values?)


texts: Limiting current of a transformer used for resistance soldering

texts:
I'm working on a device capable of soldering wires to tiny components (3mm brass rings).
I've used a PSU of a computer to make a resistance soldering device. Using the 5V line and a graphite stick of 5 mm I'm able to generate enough heat for the process. The only disadvantage is that the PSU has a short-circuit protection and therefore shuts down when the soldering process is repeated.

Now I've bought a transformer 230V --> 6V rated at 50VAC to use as power supply. On the primary winding the current was limited by a power controller (KEMO M160) rated at 300W. The power controller was initially able to control the current.
After a few test it didn't have any effect. I suspect it's broken now.

I suspect the power controller might not be the best way to control the current for this application.

My question is, what is a good way to limit the current drawn by the transformer, for the application of resistance soldering?


texts:
I've a full bridge dc-dc converter and I'm trying to understand it. It has 48V input and 400V output with 1600W rating, 30kHz switching frequency.

At the input of this SMPS there's a filter additional to SMPS input filter. I gues it's a EMI/EMC filter but I've no idea on them, I don't know much about filters.

simulate this circuit – Schematic created using CircuitLab

How can I design one of these?

I couldn't find a suitable source since I don't know its name and purpose exactly.


texts: How do you use a screwless terminal block?

texts:
I know next to nothing about electronics, so treat me accordingly :D

I have these terminal blocks:

To the best of my understanding, wires go in, and the levers clamp down to hold the wires in the place.

1) The levers are really stiff. Am I supposed to be able to flick them with my bare hands?

2) The wires go in the holes on the bottom as seen in the left-hand block, right?

3) Why are there two rows of pins?

4) If I want to connect these blocks together, do I have to pry off that excess plastic piece on the side?

Thanks very much :D

EDIT: Turns out you push down the levers to open the hole, and then they spring back to keep the wire in. The levers are really stiff, but I think they get a little easier to use after pressing them a few times.


texts:
I designed the following circuit in Cadence Virtuoso:

It is a two stages op-amp with a compensation network (resistor and capacitor). VDD=1.8 V, VCM=900 mV, VB2=1.28 V.
The DC gain is 73 dB.

1st question: I have to calculate the PSRR (power supply rejection ratio). The book on which I study defines the PSRR as the ratio between the differential gain and the gain from one supply (either VDD or GND) to the output. In order to find the gain from VDD to the output I placed a small signal voltage generator in series with VDD, as in the following picture:

With the two inputs set to the analog ground VCM=900 mV (I removed the input differential signal). I then made an AC analysis. Is this procedure correct to find the gain from VDD to the output?

2nd question: The AC analysis gives this result:

It seems to me that the small signal gain from VDD to the output is too much large: 30 dB. This means that if I have 10 mV ripple on the VDD line, then I will have more or less 300 mV at the output! Moreover, the PSRR = (73-30)dB = 43 dB.
How can I decrease the gain from VDD to the output (thus improving the PSRR)?


texts: Standalone current limiting circuit for Ultracap banks

texts:
I've been experimenting with ultracaps for a while now and I have a very specific problem:
I use the ultracapacitors to compensate for line inductances and general power filtering. When I install a capacitor (16F to 33F) in a vehicle (14Vdc) I obviously have to precharge them to avoid the huge inrush current. However this is not a permanent solution because when the battery is disconnected for service the capacitor would discharge and would have to be recharged again.
My plan is to use a high power resistor to limit the current until the voltage has reached a certain level. Then a Mosfet/SSR/Relay will short the resistor, connecting the bank to the system.
Now my question is, what is the simplest most robust (not cheapest) solution that can be left unattended. Obviously once the system is charged I want the lowest possible current draw and resistance.
Maybe an opamp as an comparator switching a mosfet? How do I avoid the ohmic region?
Heres the datasheet for one of my typical caps:
https://cz.mouser.com/datasheet/2/257/2_7_100F_ds_3001959_datasheet-1517387.pdf


texts: Can cell phones be reprogrammed for peer-to-peer connectivity avoiding carrier base stations to create a free meshed network?

texts:
In light of recent events concerning the freedom of internet, thoughts are going in the direction of breaking free from the control of wired internet service providers. One widely discussed option is WiFi router based network, but its range is quite limited. Cell phones have a much greater range though, and everybody has one.

Legalities aside (laws can be changed, after all) is it possible to reprogram existing cell phones mobile network modules to ultimately create a wireless internet on the mobile frequencies? Or is there a fundamental component missing for two-way communication between two cell phones?


texts: How do I get a closed-loop PID controller from a transfer function?

texts:
I have the transfer function below:

  $$T_c(s) = \frac{s+k_i}{m_0s^3+s+k_i}$$

It is assumed that \$k_p=1\$ and \$k_d=0\$. I am given that \$x_l(t)=[x_l(t),y_l(t)]^T\$ is the trajectory and the tracking error is \$e(t)=x(t)-(x_l(t)-10)\$. I found the roots in terms of \$k_i\$, but I can't figure out what to do next or what other information I need.


texts: Severe ringing when using high-level gate driver (HIP4081)

texts:
I am working on a project using the HIP4081 full bridge driver. I prototyped the working circuit on a breadboard experiencing heavy ringing on the gates of the high side MOSFETs (the ringing also shows up on the 12V VCC of the HIP4081 supply). The driver IC also stops working when trying to switch voltages above approximately 60V. My thought at the time was that it could be due to parasitic inductances on the breadboard so I went ahead and designed a small PCB but the issue remains essentially the same.
The oscilloscope screenshot below shows:

Magenta : VCC voltage of HIP4081 bypass capacitors (400nF)
Cyan: Voltage at load (e.g. source of MOSFET)
Orange: Turn-On Logic signal

Another measurement shows:

Magenta : HIP4081 output to gate of high side MOSFET
Cyan: Voltage at load (e.g. source of MOSFET)
Orange: Turn-On Logic signal

I tried to minimize the loop-area of the gate drives, the figure below shows part of the layout. I run some of the power lines relatively close to the HIP4081 chip (I made sure the clearances are respected), but I'm not sure if that could cause issues?

The components used are the following:

MOSFETs are CSD19535KCS with around 120nC of gate charge at 12V
I use 10Ohm gate resistance
I use around 400nF (ceramic) bypass capacitance on the HIP4081
I use 100nF (cermaic) bootstrap capacitors
I use a BAT46 150mA Schottky Diode as bootstrap diode

So far I'm mostly planning on using different MOSFET's for the next iteration (since I only need around 10A of output current). Other than that I don't quite know yet what I should change to get rid of the oscillations. I tried replacing the 10Ohm gate resistors with 30Ohm gate resistors which reduced the ringing a little bit but I think the real issue lays somewhere else?

Edit: It looks like the issue of the oscillating gate voltage occurs at all four MOSFETs. (Magenta is the gate voltage measured at the HIP4081 pin, cyan is the load voltage, orange the logic signal).


texts: finding the sinusoidal values of a complex current or voltage

texts:
I am having some trouble understanding this type of transformation. The materials provided by my professor doesn't even mention the method that is being used to switch from complex to sinusoidal and vise versa.
For instance

I= -10(1 +j sqrt(3)/3)) .

Becomes,

i= 20/3 sqrt(6) sin(wt +210).

I only understand that 180 degrees are added because of the minus in the first part of the equation but what about the rest ?

here is another example  in the opposite matter
i(t) = 6 sin (wt + 3pi/4).

becomes..

I= -3+3j


texts:
I am in the process of building a power bank with 18650 batteries for a trolling motor. The nominal voltage for this battery is 14.8 V. The motor specs are 12 VDC - 45 A max current draw.

Now the thing is that my battery pack will be 16.8V when fully charged.

Does that mean I will need a converter to lower the voltage output but my question is what happens with the load's current draw?
Does it affect the design of the converter?

So far I only found 10 - 15 A max for affordable buck converters.

Is it possible to build such thing?
Is it even worth it?
any other suggestions?


texts: Ethernet controller not recognized on PCIe bus

texts:
I designed a carrier board for this SOM: https://wiki.solid-run.com/doku.php?id=products:ibx:documents

As I need a second Ethernet port I added an Intel I217 Ethernet controller. Unfortunately it does not show up in the list of PCIe devices on Linux.

This is the first time I designed a device with a PCIe bus. So to be honest I have no idea what could be wrong.

This is the schematic. I tried to follow the Intel application note as good as possible:

This the layout around the Ethernet controller and the SOM connector:

I measured the 3.3V and 0.9V supplies, they both look ok. These are the clock signals:

XTAL_OUT:

XTAL_IN:

Is this ok? Does anyone have an idea what could be wrong in my design? I am grateful for any help...


texts: I'm a bit newbie in DSP. I'm trying to modulate two signals and create DSB-SC am signal. I choose ring modulator for it. So can anyone show me any working ring modulator circuit?


texts: What type of components necessarily pickup EM waves in antennas?

texts: I understand the transmitter part of telecommunications, but what type of electrical components are used in antennas?   I understand that the transmits a signal which the antenna recieves via an EM wave, and then recreates the signal, but exactly what electrical component(s) is responsible for processing the signal?


texts: Why the one-hot state encoding has an advantage in decoding compared to binary state encoding?

texts:
Before I asked the question, I've googled advantages of the one-hot state encoding compared to others such as binary and gray state encoding.

I could understand one-hot's advantages and disadvantages over others encoding scheme, such as constant hamming distance (two), fast but requiring an N flops, etc.

Many articles mentioned that the one-hot is fast and it suits high-speed design and they also mentioned the reason is that it has very small decoding time compared to gray coding and binary coding.

However, I couldn't understand why one-hot decoding is faster compared to others.
For example, when we decode the one-hot encoded state machine, it could be implemented by the case statement like below

parameter STATE_ONE    = 3'b001,
          STATE_TWO    = 3'b010;
          STATE_THREE  = 3'b100;
parameter STATE_ONE_ID = 'd0,
          STATE_TWO_ID = 'd1;
          STATE_THR_ID = 'd2;
reg [2:0] states;

switch(1'b1)
  states[STATE_ONE_ID]: begin end
  states[STATE_TWO_ID]: begin end
...

Also for the binary encoded states we could use below code for decoding

parameter STATE_ONE   = 2'b00,
          STATE_TWO   = 2'b01,
          STATE_THREE = 2'b10;
case (current_state)
  STATE_ONE   : begin end
  STATE_TWO   : begin end
  STATE_THREE : begin end
  ....

When we look at the RTL implementing the decoder for one-hot and binary, it looks not really different.

I would like to know why one-hot decoding is much faster than the binary case?

Is the difference induced when they are synthesized?


texts: What is a suitable device for fast temperature process control?

texts:
Here is a ceramic heater catalog:
product sheet

These heaters can ramp up as fast as 150 degrees C per second. I am not entirely sure what I am searching for but let's look at my use case:

Say I want a set point of 160 degrees C with acceptable variance of +/-5 degrees C as measured by the internal (to the heater) thermocouple. The thermal load in this case is one gram of aluminum in very good thermal contact and a large heatsink of PTFE with poor to no thermal contact.

Do solutions exist for this type of fast temperature control? If so I would prefer to go with that solution but if not, I am open to suggestions for damping the system for use with a normal on-off process controller.


texts: How do I convert between dBA, dBV and RMS values? For example, I have used a current probe (clamp) with a gain of 100mV = 1A to measure a series of currents in dB and I would like to know the equivalent RMS current values.


texts: Can I turn a Piezo Buzzer into an ultrasonic Mist Maker?

texts:
You may have been reading my questions for a project I am doing.  This one is a bit off the wall - I purchased a small 'bottle-top-humidifier' off of amazon and opened it up just to take out the ultrasonic mist maker.

I've been scouring the web for a couple of hours to try to find JUST the piezo ceramic disc that generates the mist.  I've come across a few articles explaining piezoelectronics and it seems that a piezo buzzer and a piezo mist maker are made up of the same materials.

Is this correct?  Can I go purchase some piezo buzzers and use them to create fog? Does anyone have any literature on this?


texts: How does a brushed motor's current change over its lifetime?

texts:
As the title says, what should I expect a DC brushed motor's current to look like over time?

I'm using a standard 12V DC brushed motor in a long-life application, and I've got a current sensor constantly monitoring it. I was wondering if I would be able to predict the wear on the motor from the current.

Does anyone know of any papers that have this information? I searched extensively online, but I couldn't find any data on this.


texts: How long will this appliance run from a battery?

texts:
How long can I run a water pump which requires 12V and 50W from a 12V, 40Ah, 400A car battery?

Can you explain how this was calculated?


texts: Why is the need and the value of the bias resistor is dependent to the source output resistance?

texts:
Regarding this information,

regarding the bias resistor the page says:

  The resistor value is equivalent to about 100 times the source
  impedance. If the source impedance is less than 100 Ω, you can connect
  the negative polarity of the signal directly to AI_GND, as well as the
  negative input of the Instrumentation Amplifier.

1-) Why a bias resistor needed if the source impedance is less than 100 Ω and otherwise not?

2-) What is so special for the source impedance being about 100 Ω in this context? It is not product specific since the same 100 Ω recommendation can be found in another source like this one at page 26 under Floating source and differential input.


texts: Where do I find documentation on Eagle XML file structure?

texts: I would like a glossary or documentation that will explain every single XML element and attribute in an Eagle document. Does anyone know where I can find one? I tried to find on Google without success.


texts: Why can't you just reduce the current instead of the voltage?

texts:
Why does voltage even matter, if it's the current that goes through a circuit? I understand the relationship V = IR (I think) and that increasing the voltage (pressure)  will increase the current.

However, there are some device there that requires a certain amount of voltage, say 5v. My question is why can't you connect it to a 10v power supply and add a 2-ohm- resistor so the current will be the same as the current a 5v will produce? Via I = V/R

I know this probably sounds very stupid, I know it's not going to work that way, and you can still potentially destroy circuits, if you only care about current and not voltage, but I'm just wondering where is the gap in this logic?

I tried it on a circuit simulator website, and the device blew up everytime from the bigger voltage source even though the currentwas the same with the lower voltage source (by adding resistors). (The lower voltage source works just fine)

Unless of course it's not just the current that matters, and  that voltage matters more than just producing a certain amount of current


texts: What microcontrollers with programmable logic built in (FPGA/CPLD like) are available on the market?

texts:
Inspired by question I would like to ask what microcontrollers with CPLD or FPGA-like functions build in are available? The most interesting would be low-cost ones in friendly packages (non-BGA). The CPLD/FPGA portion should be big enough to allow implementing fairly complicated state machine (10+ states), fairly big logic function (10+ inputs), fairly big counters and shift registers (8+ bits) and be able to run at tens of MHz frequencies. Preferable method of design input for programmable logic function should be HDL based (Verilog or VHDL).

So far I have found two examples:
1) FPSLIC from Atmel
2) PSOC3 and PSOC5 from Cypress (those are not available yet, except in samples volume)


texts: Altium connection to multiple devices with same pad-to-pad trace len for each path

texts:
I am currently tring to route a SoC to two DDR3 chips.

Length matching is required for the signals SoC->DDRA and SoC->DDRB. Altium is able to measure a nets length by building the sum of all trace-object's lengths that are part of a net. But this doesnt help me, as the signal lanes will split up and partly be routed to just DDRA or just DDRB.

Does Altium allow to measure the length of a trace between two pads?

If not, I'll add net ties and split up all the signals but I'd hate this approach, as the schematic gets really messy + I got netTie components all over the PCB.

Altium Version is Winter 09.


texts: Bench power supply "Issues that rouse during build"

texts:
I'm building a power supply, based on this instructable
and this one

I am  using
24volts DC power supply, 7+ amps
circuit is based on LM338 / 7805 / 7812
Circuit is working although few things that I'm not sure off.

I've faced few issues:

First, when running low voltage, too much heat will be generated, what's the best method to reduce voltage before the voltage regulator? The schematic I linked shows 18+ diodes in a row each diode reducing .7 volts, the author and logic says this is not a good idea,
Zener diode would consume too much wattage I guess,(it would be in parallel no?) voltage divider is a good proposal but I'm not too sure, if someone can kindly point me out.

Secondly, let's say I'm charging a lipo battery, limiting current will be using a current limiting resistor (1 ohm 10 watts for example), but won't that reduce the voltage? was thinking of a high wattage potentiometer (10 ohms, to make it a variable voltage variable current Bench Power Supply) but something doesn't seem right there, I've tried simulating the circuit using LTspice but output current is off by a lot.


texts: Designing a down counter using Xilinx ISE design

texts: We are trying to design a circuit that counts down from 9.99 to 0.00. Could you give us some tips?


texts: DC current gain in complementary transistors

texts:
In Class-B amplifiers complementary PNP-NPN transistors are used, e.g. TIP2955 and TIP3055. https://www.electronics-tutorials.ws/transistor/tran_3.html says that

  They both have a DC current gain, Beta, ( Ic/Ib ) matched to within
  10% (...)

Is this really matched only to within 10%? Is this so difficult, would be expensive, or for what other reason accuracy is just that? What are the reasons that it is matched only to within 10% in TIP2955/TIP3055.


texts:
Here is the first schematic that I created : .

The Vcc is at 5.1V and I a self made using the LM317, Works Fine.

When I checked the Output with the Multi-meter I use., I was getting a high state of around 3.9V(Which I guess was fair enough.), but the Low was was giving an out of 2.5 ~ 2.6V, which to me seems a concern because the NE555 datasheet shows low state going to 0V in one of the .

I even tried simulating the circuit afterwards and this is what it looks like in simulation and even in the hardware set up :
.

And what am I supposed to make out of this?

So now I am getting a High state of 3.6V(seems fine), but the low state is still around 2.6V.

How do I find out the root of the Issue and how should I debug it?


texts: Rising Pitch Siren Electronics Circuit Explanation

texts:
Can somebody explain me how in detail what is going in this circuit? I tried it and it was working but I cannot understand how this works.

http://startingelectronics.com/beginners/start-electronics-now/tut6-rising-pitch-siren/

Also how to know the polarity of a loudspeaker and does this polarity really matter in this or any circuit?

And what is the role of the non-polarized capacitor?


texts: Converting 10 bit (2:8) value to 14 bit (6:8) result

texts: My C skills are seriously lacking, and I haven't come up w/ a good way to do this on 8 bit architecture.  I've tried shifting by 4, but then I lose digits, I know I can just multiply my 10bit result by 16, but then how do I get the unsigned int into 2- 8 bit registers??


texts: In which CPUs will write-after-write and write-after-read dependencies cause a hazard?

texts:
I've been studying the MIPS single cycle architecture for pipeline. I noticed that read-after-write dependency causes a data hazard but two other write-after-write and write-after-read dependencies won't cause any hazards.

So i was wondering if there exists processors with hazards because of this WAW and WAR dependency?

If there are, please can you name some of them. Thank you! (I searched google but found nothing useful)


texts: n-channel JFET: importance of gate drain voltage (Vgd) and validity of negative drain source voltage (Vds)

texts:
We always consider the gate source voltage as this determines the Vgs,off. But how come the Vgd doesn't have the same effect?

Following from this (and more importantly) why can't we have a negative Vds for an n-channel JFET??
I get that we need to prevent forward biasing between the diode, but that only means that Vgs < 0 and Vgd < 0, it does not mean that Vds < 0!


texts: Is there a version of the 74HC154 with active High rather than active Low?

texts: I'm looking for a 4-to-16 decoder IC, but I'm looking for an active High similar to the 3-to-8 decoder M74HC238. Seems all the ones I'm finding are active High.


texts: What is the closed-loop gain in this op amp circuit?

texts:
For the op amp below

Open-loop gain is \$A=2\times10^5\$
Input resistance is \$R_i=2\,M\Omega\$
Output resistance is \$R_o=50\,\Omega\$

I am asked to calculate the close-loop gain \$Vo/Vs\$ and find \$i_o\$ when \$V_S=1\$ .

(Schematic diagram above from "Fundamentals of Electric Circuits" by Charles Alexander and Matthew Sadiku.)

Then I've redrawn the circuit and defined the currents as shown in the figure.

simulate this circuit – Schematic created using CircuitLab

Then according to those currents above I've applied KCL and also I've got these equations below.

\$I = I_1+I_2\qquad I_2=I_3+I_4\$
$$I_4=\frac{V_1}{5\,k\Omega}$$
$$I_3=\frac{V_1-V_o}{40\,k\Omega}$$
$$I_3+I_1=\frac{V_o}{20\,k\Omega}$$
$$A \times V_d=2\times10^5\times 2\,M\Omega\times I$$
$$I=\frac{V_S-V_1}{2\,M\Omega}$$

Then I've also written some equalities according to KVL in the closed loops but I was never able to find a relation between \$V_S\$ and \$V_o\$ or just ended up crosschecking the same equations. It all got tangled up.

How would you solve this?


texts: How can I keep a momentary button low long enough for microcontroller to read it?

texts:
I'm using an ESP-12F to fire off mqtt messages when a button is pressed. The circuit works as expected; the physical button resets the device which boots, runs the code and deep sleeps indefinitely. I want to add more than one button (or external trigger) but I want to know which one woke the device up. I attached multiple momentary buttons to the circuit and they all do the job of reseting the device but I was unable to capture which button was pressed.

The yellow line is my button press (drives reset low), it takes about 150ms. The blue is a simple digitalWrite in the setup method of a blank program. It appears the ESP12 takes about 250ms to boot up into setup where I could read the pin but by then the button has returned to it's original state. Is there an easy way to extend the low so it can be read by the IC?

This is also an empty program, once I add libraries etc it adds another 50-100ms just to get to setup so I would probably have to extend the button state to say 400ms to be safe.

Edit: So an issue with this design is that if I hold the button low to try and capture it since it's connect to reset it doesn't actually reset. I need to "capture" the low and then release but then read it after startup.

Edit: Blue is connected to an LED on a GPIO. I'm using this to basically see when the program is in setup() by switching this high. The yellow line is the reset pin, the initial low resets the device and then when I release the button it returns to high via a pullup.


texts: Using Chassis as a conductor for DC Power Supply Return

texts:
Is it considered a good practice to use the chassis as a return path to a DC Power Supply?

I have been given a rack mounted device that switches 480 volt power on/off remotely. The remote feature is handle via a Raspberry Pi which is powered via 120v to 5v power supply (http://www.mini-box.com/OpenUPS).

I was surprised to find that the return pin on the 5v power supply is tied directly to the chassis and the GND on the Pi is also tied to ground and they are using the chassis as the conductor for the return path. There is only a positive 5v wire going between the power supply and the Pi. Is this considered good practice?


texts: Does the voltage on base limit the voltage on emitter?

texts:
I had some 2N2222 transistors and wanted to use them as a switch (to switch a 6V-12v from a 5V)
but when I apply 5V to the base the emitter only goes up to approximate same value (5V).

The same happen when I applied 3V on base - got 3v on emitter.

So, my question is, does the voltage applied on base limit the voltage on emitter?

simulate this circuit – Schematic created using CircuitLab


texts:
I can't figure out this issue.  In my test bench I am checking timing to make sure I have adequate separation of data/addr setup to the enable pulse edges in terms of clock delays, not logic delays.  I am finding a timing violation on this test.
      assert ((LCD_E_rise - LCD_RS'Last_event) >= ST7066U_tAS)
                OR (LCD_RS'Last_event > now)
        report Rgt_Lft & " tAS not met for LCD_RS, " &
          time'image(LCD_E_rise-LCD_RS'Last_event) &
          ", LCD_RS'Last_event = " & time'image(LCD_RS'Last_event)
          & ", LCD_E_rise = " & time'image(LCD_E_rise)
        severity failure;

The printout from this is:
# EXECUTION:: FAILURE: LEFT tAS not met for LCD_RS, -15228822 ps, LCD_RS'Last_event = 5030458392 ps, LCD_E_rise = 5015229570 ps
# EXECUTION:: Time: 5030488194 ps,  Iteration: 1,  Instance: /LCD_Drvr_tb,  Process: Disp_time.
# KERNEL: Stopped at time 5030488194 ps + 1.

The values printed out are saying LCD_RS is changing state 15 us after the rising edge of LCD_E_L (LCD_E_Lft or LCD_En in some procedures) which is one clock cycle before the falling edge of LCD_E_L which is what triggers the check.  The numbers add up just fine, but they say LCD_RS is changing and it is not.  Here is the code that updates LCD_RS.
  LCD_Out: process (Clk) is
  begin
    if (rising_edge(Clk)) then
      with Inst_State select LCD_RS <=
            '1' when DDData_Top | DDData_Bot | CGR_Data, '0' when others;
      LCD_Row   <= '1' when (Inst_State = DDData_Bot) else '0';
      -- Select the commands or data for the LCD data input
      with Inst_State select LCD_Data <=
            LCD_MData       when DDData_Top | DDData_Bot | CGR_Data,
            FuncSetCmd      when F_Set_1 | F_Set_2,
            DispOnCmd       when Disp_ON,
            EntryModeCmd    when Ent_Mod,
            DDRTopAddrCmd   when DDAddr_Top,
            DDRBotAddrCmd   when DDAddr_Bot,
            CGRAddrCmd      when CGR_Adr,
            DunCareCmd      when Cmd_Idl;
    end if;
  end process LCD_Out;

A screen capture of the time frame showing no transitions.

The entire program with test bench is over 600 lines, so too much to post here. I can perhaps provide it through another location where the various files can be downloaded.
The only thing I can think is there is a transaction at that time, but not an event and the simulator is screwing up, Active-HDL by Aldec.  My previous problems with this tool have been related to VHDL-2008 support.  I don't think that's the issue here.
Any thoughts?
Adjusted the assert code to show a time variable assigned to now on events of LCD_RS.
      assert ((LCD_E_rise - LCD_RS'Last_event) >= ST7066U_tAS)
                OR (LCD_RS'Last_event > now)
        report Rgt_Lft & " tAS not met for LCD_RS, " &
          time'image(LCD_E_rise-LCD_RS'Last_event) &
          ", LCD_RS'Last_event = " & time'image(LCD_RS'Last_event)
          & ", LCD_E_rise = " & time'image(LCD_E_rise)
          & ", LCD_RS_event = " & time'image(LCD_RS_event)
        severity failure;```

if (LCD_RS'event) then -- Check hold time to enable, tAH
...
  LCD_RS_event := now;
end if;

The reported time for an event on LCD_RS from this variable is 30 ns into the simulation which is the first clock cycle where it gets a '0' value rather than a 'U' value.  The 'last_event value reported is one clock prior to the current simulation time which is when it is updated with another '0' value.  Clearly a bug conflating event with transaction.

When I get both time to create a good test case and a means of accessing Lattice support I will report this bug.


texts: Sanity check: Routing high current traces (MOSFET relay circuit for 300W heater)?

texts:
This is the first time I've ever designed a power PCB/ a PCB that needed to take a high current, I'm looking to check that I'm doing this right and for any advice on how to improve? details below.

I'm using an arduino to control a 300W film heater in a PID loop kind of thing, and using a MOSFET to switch the high voltage which the arduino can't supply.

Given that it's a 24V supply and the heater is 300W, this trace needs to support 12.5 amps of current. If I have a PCB with 1oz/ft^2 copper thickness, this means a pretty manageable 5mm ish trace width - I narrowed the trace going into the MOSFET terminals because otherwise it wouldn't fit - is this going to be a problem? Image below:

Edit: The MOSFET I'm using is the IRLB8743PbF, and this is the circuit schematic:


texts: TTL output levels on SN75176 transceivier

texts:
I have a system that communicates between two subsystems over a distance with UART. The UART signals are converted to RS485 by using the SN75176 differential bus transceiver. A microcontroller on one side always transmits data from its UART pins to the SN75176 transceiver, and the other side also has an SN75176 transceiver that receives these signals and convert them back to TTL (UART) for the microcontroller on the receiver side.

Basically, the transceiver circuit on the transmitter side looks like this:

The transceiver circuit on the receiver side looks like this:

The communications work fine. However, I have noticed by analysing the UART signals, the output level on the receiver side is between 0.2 V and 4.2 V, as shown in the following measurement (this is the signal UART-MAIN-RX from the receiver circuit above. Note also that the string "Test123" was used in this case):

The SN75176 datasheet mentions that the output of the transceiver is TTL, and that the output signals should vary between 3.0 V to 3.7 V. Why am I observing even higher signal levels in my case? I am particularly afraid that if I connect this higher-level "TTL" output directly to the microcontroller UART pins, that it could damage the microcontroller.


texts: Determine the resistor required for a circuit

texts: If I want to supply power to a device that is rated for about 2V using a DC source of 12V. How can I find the resistor o should use.


texts: BJT Ic vs VBE graph in Proteus simulation

texts:
I'm trying to simulate the behavior of a BJT on Proteus.

The image below shows the graph that I got when I plotted \$I_c\$ on the vertical axis vs. \$V_{BE}\$ on the horizontal axis.

But according to the equation

$$ I_c = I_s \cdot e^{V_{BE}/V_T} (1+V_{CE}/V_A)$$

\$I_c\$ should always increase as \$V_{BE}\$ increases. As you see, the results I got from Proteus is different: \$I_c\$ keeps increasing until a certain value and then it stops increasing.

Did I do something wrong or there is some factors in real life that aren't presented in the \$I_c\$ relationship with \$V_{BE}\$ and \$V_{CE}\$?


texts: unconnected line (xx,yy) to (XX,YY) - Altium designer

texts:
Newbie in Altium designer here. I have read the online documentation from Altium, however, I still have a warning when trying to compile my schematic in Altium:

my schematic:

The warning says: unconnected line (xx, yy) to (XX, YY) and refers to the right and lower part of the bus. Strangely it doesn't complain about the left part of the bus. I drew the bus at once, in other words, it is not composed of two or more parts.

I have tried multiple things like inter alia redrawing everything, but the warning keeps being showed.
How can I solve this issue?

EDIT:

This is my current schematic that still needs modifications: http://www.imgur.com/a/Zy1nK

This is the schematic mine is based on http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=spmu365&fileType=pdf (starts on page 36)


texts:
I was looking at a friend's design for a simple PWM motor drive and I'm trying to figure out what's the use of some components. Here's the schematic:

I get what most parts are for:

power supply
fuse (not sure if needed when using a battery or a lab power supply)
PWM signal that drives the optocoupler
BJT acting as a switch (R4 to limit base current and R3 as a pull-down resistor when the PWM signal is LOW)
DC motor header with freewheeling diode (not shottky but should be fine)

I don't get why R2 is there... maybe to suppress noise/spikes together with the two capacitors?

Some more questions:

are C1 and C2 needed anyway?
should I add a capacitor across the motor leads?
should I expect voltage spikes even if there's a freewheeling diode?

It's a lot of questions so... please be gentle, I'm a newcomer :)

Edit:

I talked to my friend again and read some stuff. He still thinks R2 is needed and acting with C1 and C2 to suppress motor EMF and noise. I definitely think R2 is not needed and not useful for filtering - an RC snubber should be across motor leads and this is not the case.

I built the circuit but having no motor handy I just had a quick look on a scope using a resistor as load. I'll do some proper test with a motor tomorrow.

Thanks for all the people that helped here!


texts: Switching a Large Current with a Tiny Switch

texts:
I have a SPDT switch that can switch .3A @ 5V. I would like to use it to switch 1A @ 9V which will then be fed into a 7805 linear regulator.

This is the design that I have come up with.

I have run some simulations on this circuit and it appears to work. Is there anything else I should do? Should I toss in a resistor somewhere?

I'm planning on using this switch. I don't have a particular MOSFET in mind, but it should be cheap and SMD.


texts: How to detect Serial or TTL signal for a PIC?

texts:
I have a Microchip PIC with UART support. If i understand correctly, the UART is able to natively handle the TTL serial signal.

I'm expecting input signal that should be TTL (0/5V), but it could be RS232 (+/-13V).

What would be the best way to handle both different signals. Anyway to auto detect the (incoming) signal?
Or should i have a manual switch that allows for signal selection?

I was thinking of using a something like a MAX3232, but i'm not sure what would happen if that IC gets a TTL signal.

Thanks!


texts: Powering a MCU from a battery without a regulator

texts:
I have seen some development boards (for example. BL652 dev kit) for low power chips have battery power connected directly to the MCU without a regulator.

For the example case, the battery used is a 3V CR2032. The datasheet for the MCU defines the following parameters:

datasheet page 16.
Absolute Maximum Ratings            Min           Max
Voltage at VDD_nRF pin             -0.3           3.9

datasheet page 17.
Recommended Operating Parameters    Min    Typ    Max
VDD_nRF                             1.8    3.3    3.6

I'm interpreting this as "If your battery voltage drops to a value between 0-1.7 it isn't defined what will happen".

Why this worries me is because I've seen regulators having the Power Good pins and have found no explicit statements in the datasheet that the MCU from the example won't be damaged by the undervoltage.

How can I decide if a regulator is needed between a battery and a load, to guarantee there are no damages when the battery voltage starts dropping?


texts: What is the pin to light up colon in Basys 2?

texts: I am trying to make a clock in a Basys2 board but I can't find in documentation the pin to light up the colon of the 7segment display. Where is it?


texts:
I create a board with two bus: UART and I2C. Now I am expanding the connection terminal, which has the following contacts:
RX / TX / SDA / SCL / + 5V / GND.

The question is, do the I2C and UART buses affect each other? Should they be separated?

For example, UART / VCC-GND / I2C or UART / I2C / VCC-GND. What is the minimum distance I must observe? Tires are likely to be on the same layer.


texts: Decide P controller gain K so that phase margin is 50 deg

texts:
I need help finding the gain \$K\$ so that the phase margin for the system equals 50 degrees.
$$F(s) = K$$
$$G(s) = \dfrac{1}{(s+1)^2}$$
\$v\$ is a process disturbance sinusoid with amplitude 2.5 and freq 0.5 rad/s. Image below.

Now I need to find K so that the phase margin = 50 deg. I tried:
\$\varphi_m = 180\$ deg \$+ \arg G(i\omega_c) + \arg F(i\omega_c) = 50\$ deg
and solve for \$\omega_c\$ but I can't really figure out how to. Do I have to account for the disturbance as well? If so, why? why not?


texts: How to create rectangular holes in ARES?

texts:
I bought this three phase rectifier from local store and it has rectangular connectors,

Now I need to make its package on the ARES, but I cant figure out how to create rectangular holes in the package.


texts: Schottky transistor, Not sure I understand it?

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So I've been looking through and going through my Digital Computer Electronics book, and I came to this... It seems so simple and I understand the "point" of it, but I'm not sure I understand exactly how it works.

"In a Schottky transistor, the Schottky diode shunts current from the base into the collector before the transistor goes into saturation."

I guess this part confuses me above ^^^

http://en.wikipedia.org/wiki/Schottky_transistor

From what I gather the Schottky Diode has a forward voltage of .25 V... So it's taking .25 V out of the Input Line (coming from the left of the picture) and putting THAT into the collector... So it'll just take less time to switch... Because there is .25 V less coming in the base? Or is adding .25 V to the collector so when the Transistor turns "on" it'll already have a little bit flowing through it (since .25 V isn't enough to actually flow through when it's off?)? Wikipedia entry is confusing. I feel pretty stupid for asking such a simple question lol.


texts: Simulation performance of bitwise operators and binary arithmetic Operators

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In terms of performance if you have say two inputs a and with the same bit width say 64. If you apply a bitwise operator and binary arithmetic operator (verilog/system verilog), which one takes longer to evaluate and why?
For example, in terms of a parity circuit when the parameters are change I observed a big difference in terms of simulation time while for an adder, the difference in simulation time isn't much. Code for adder and parity circuits are shown below.
module adder #(parameter width=64)(input logic [width-1 : 0] a, b, input  cin, output logic cout, output logic [width-1:0] sum);
 always @(a, b or carry_in) begin
 {cout, sum} = a + b + cin;
 end
 endmodule

module eparity #(parameter width=128)(input logic [width-1 : 0] data, output logic p);
 logic [width : 0] i_parity;
 genvar i;
 assign i_parity[0] = 0;
 for(i = 0; i < width; i = i + 1) begin
 assign i_parity[i+1] = data[i] ^ i_parity[i];
 end

 assign p = i_parity[width];
 endmodule


texts: Arduino Uno: SoftSerial For Two Devices (em406a GPS and DS18B20 Temp Probe) Not Quite Right

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I am working on a prototype that requires use of an Arduino Uno, digital humidity sensor, heart rate monitor, temperature probe, and GPS unit. My issue, I believe is with trying to implement to the two serial devices (GPS and Temperature) with the software serial library. I've read in other posts that such issues may arise if the code tries to talk with both devices at once. I don't think I'm doing that, but might be mistaken.

I am achieving viable sensor output, but the Temperature output and GPS readings are inconsistent. Specifically, The GPS readings display often enough but not regularly and although the temperature data is mostly good, sporadically the code will print -1000. I can filter this nonsense data, but I'd rather solve the problem. Any ideas?

Main Code Loop:

 void loop(void) {

  //Read the serial port to see if GPS data is available
   while(uart_gps.available()){
     byte c = uart_gps.read();

   //If incoming data is GPS data, process it
     if(gps.encode(c)){
       Serial.println(F("Reading"));
       getgps(gps);
     }
   }

  int heartRate = getHeartRate();
  float temperature = getTemp();
  float hum_temp = getTemperature();
  float humidity = getHumidity();

  // ... print statements


texts: Using a transformer with 400 volt rated primary side with a 120 volt line

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Is it possible to use a transformer rated for 360 to 400 volts on its primary side on a 120 volt line? Will it still perform adequately? And I would assume the turns ratios still apply?

This is the transformer in question: WE-LLCR Resonant Converter.

Also, I understand that the saturation current is that which the inductance drops off; however, this datasheet says the I-sat is 4 amperes, but it's rated for 8 amperes output current. Why is this so?

I will be using this in an SMPS at 100 kHz.


texts: Can we apply maximum power transfer theorem to SMPS rectifiers?

texts: Thevinin and Norton equation simplifies BJT and MOSFET analysis leading to the hybrid pi models. Can we apply the same concept while analysing an AC-DC Converter with PFC and PSFB full bridge topology? For example, can I model a 100V rectifier having a thevinin resistance of Rth? If yes, how to calculate the Rth?


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Anyone know of a good type of electrical terminal crimpers from a reputable manufacturer?

The ones you find at Home Depot or Lowes are cheap, but they're simple lever systems for squishing the terminal collar, and don't do a particularly good job. (I just had a 12ga wire slide out of a ring terminal.)

I've seen more sophisticated ones with ratcheting linkage mechanisms where the force is nonlinear and increases towards the end of the crimp, but I'm not sure where to get one from a reputable manufacturer. The only one I could find from searching on line is this one from Neiko and I've never heard of them.