texts: Electric BLDC motor voltage and power limit factors

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Preliminary:
I know basic model of DC motor which depends of two electric parameters such as voltage/rpm and current/torque.
There are two models electrical - resistance, back EMF, and optional inductance of coils. On mechanical side there are torque, speed and optional moment of inertia.

Question:
What is the real limit for maximum voltage/frequency applied to BLDC motor if motor will be powered by high range current source ?
My presumption is that motor's mechanical construction is limited mostly for currend and torque and when higher rpms are needed then should be able to increase voltage/frequency of motor.

How it is with both case permament magnet or induction asynchronous motors?
Why some datasheets of similar motors have different both nominal/maximum rpm and voltage specified?

To summarize last talk thanks to  Gregory Kornblum

Some motors have ratings 24 V and could operate for higher voltages.
My assumptions:
Controller current source has filtered signals before output rails such that only envelope is driving motor's phases.
Bearings and mechanical construction of the motor is strong enough to handle high rpm.
There are fast mosfets to handle phases currents.

Any further explanation/ideas or confirmation to the subject?


texts: How do we get the negative voltage input value of this Op-Amp?

texts: This is an exercise we did in class about the linear limitations of an Op-Amp, I get how we get the conductance and the Current value. But I don't understand in this KVL how did we get the value of $$V_a = -R_3 I^+_{IB} - V_{IO} $$ It's at the right of R1 for those who didn't see it.


texts: where is the /models folder in the eagle directory?

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I am reading the EAGLE schematic to spice model tutorial here: https://www.autodesk.com/products/eagle/blog/spice-simulation-part-5-schematic-spice-mapping/
I got stuck on the section of loading a model from your computer:
"... In this case, we don’t need to go searching the web for a diode model. The Models directory in EAGLE already has what we need. ...."
where is the "/models" directory? I cant find it anywhere! please help.


texts: How can I rearrange the voltage divider formula for R2?

texts: Can I please have a step by step explanation as to how I can rearrange the voltage divider formula to find R2. I dont understand how I end up with R2 = R1 x Vout/Vin - Vout.


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I have a cermet potentiometer controlling the final gain of an opamp that I am using to control the amplitude of a 120kHz sine wave signal, about 2Vpp. What I have noticed, and it is a subtle effect, is that the noise in the signal is occasionally affected by the position of the wiper.

The questions are: what can I do about this? Is there a better material type? How do I test such devices for noise (which I assume comes from mechanical interface of conductor and wiper)?

Circuit diagram below


texts: Working principle confusion based on the photodiode, phototransistor and LED circuit

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I need help understanding the working principle of this circuit that I simulated in Multisim.
I'm doing this for my lab report.
When the switch is closed, the photodiode, phototransistor and LED are ON at the same time and they are in 2 different circuits. The LED is not ON when the photodiode circuit switch is open.
I need help ASAP, need to submit by tommorrow.


texts: What happens when we increase load on a motor?

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For engines when we increase the load on them while maintaining the rpm they start consuming more fuel.
But what happens for an electric motor when we increase the load on it.
Suppose 3 cases then:

What happens when a motor is running unloaded and we start increasing the load on it.
What happens when a motor is loaded with "x" load and running on 50% of its capacity and then we start increasing the load on it.
What happens when the motor is running on its full capacity carry a particular load and then we increase the load on it.

It would be of great help you explain current, voltage and resistance or any other factor involved in it as I am a mechanical engineer so I have little less knowledge about electric motors.


texts: I want to make a clock generator for Altera EPM240T100C5N using the CPLD itself as a Pierce oscillator. This CPLD has Schmitt trigger inputs so I guess this should be possible. What I`m not sure about is the reliability of this approach. Can I use a CPLD inverter to build an oscillator? If yes, how much influence will the supplied voltage have on the resulting jitter? Will there be much difference between 2.5V and 1.8V at 48 MHz?


texts: UM232H-B Breakout Module as a parallel port

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I want to build something like UM232H-B Breakout Module. This configuration uses an FT232H, to convert usb to serial/parallel. I don't know whether it works with FPGA parallel port programming cable or not.

Is it possible to use this configuration instead of parallel ports to program a XILINX FPGA? and Does this configuration work with XILINX's ISE?


texts: Sampling (reading) a digital data signal?

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I'm currently working on a project, where I have an external device (POCSAG pager - POCSAG protocol) that is giving out a digital (5V - 0V) square-wave signal. I have an ATmega2560 (Arduino) microcontroller and I want to read the signal so I can decode it to text.

I already finished this project where the external device works in perfect "lab conditions", which means that one bit is transmitted in exactly 833 microseconds (1200 Hz). I read all the bits correctly with a simple timer and decode them afterwards.

The problem is, when I try it on a real-world pager, the bit-rate varies a lot! From 750 microseconds to 870 microseconds, and each bit is somewhere in between this which means that I get a lot of errors when reading the signal since one message is up to 5000 bits long. Let's not forget that there is always noise on the data line when the real signal is not present, when there are no messages being transmitted.

I managed to make it work in "lab conditions" by measuring 3 bits, and if all bits match 833 microseconds I attached an interrupt that would trigger a timer with a period of 833 microseconds that samples the signal and saves it into a character array (yes, I know, bad solution). As I said, this works perfectly as long as the frequency is stable.

I tried measuring 10 - 20 bits which were between 750 - 860 microseconds and calculating the average bit-rate and sampling the signal with that rate afterwards... Didn't work either.

The digital signal always has a preamble of 576 alternating bits (0101010101...) so you can detect when an actual message is being transmitted.

Any ideas on how I should tackle this?

I'm sorry if I didn't explain it thoroughly enough... If you have any further questions, let me know!

EDIT: This is how the signal is encoded. In short, one bit is transmitted in 833 microseconds (supposedly) and the message starts bits 576 alternating bits, called the preamble (010101010101...). After that a 32-bit long Frame Sync codeword is transmitted (the FS codeword is always the same) that signals the beginning of the first batch of data. There are 8 frames (each frame holds 2 codewords, 2 x 32 bits) which hold 16 codewords of data. After those 8 frames, if the message continues, another FS codeword is transmitted and so on and on...


texts: In a NOT gate circuit, does charge not flow through both the transistor and output line when the transistor is "on"?

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I've tried to recreate a circuit from what I think would be a NOT gate, based on some other schematics and breadboard examples that I've seen.

simulate this circuit – Schematic created using CircuitLab

For this to be practical, I think SW1 would go away, and instead be substituted for some other voltage source as an input, but I've inserted SW1 and attached it to the same voltage source as everything else just to simplify the diagram...

Anyway, my assumption is that when there is charge going into the base of the transistor, the charge flows through the collector, out the emitter, and straight to ground (the negative end of the voltage source). So, in this case, does the charge not flow through R2 and through the LED, somehow? It seems to me that this conclusion must be correct, or else the LED would light up, right? But apparently, electricity does not take the "path of least resistance", so to speak.

Conversely, if the base of the transistor does not have any current, I assume the current stops at the collector of the transistor, but since the circuit must be complete, pressure moves the charge through R2 and the LED, then to ground.

I feel that I am missing some fundamental principle involved in this. Any thoughts?


texts: Calculating the constants of a permanent-magnet DC motor

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Based on measurements (current and angular velocity dependent on a given voltage from 0 to 12V) and force dependant on a given current (0 to 2A), I want to calculate the armature resistance, torque constant and the generator constant.
The rotor radius is given too.
My approach
Armature resistance

Using the method of least squares, I calculate a linear function. \$I = f(U)\$
The Resistance equals the reciprocal of the slope of the function (red).
$$I = \frac{U}{R}$$
I know that my calculated value for R should be correct.
torque constant

I calculate the linear function \$M=f(I) \Rightarrow F \cdot r = f(I)\$.
The slope of this function equals the torque constant. I don't know, if my calculated value is correct. Can you tell me if my approach sounds good?
generator constant
That's my main problem.
The idea was to use the equation \$ U_i = c \cdot \omega \$
Since \$U_i\$ wasn't measured, I have to calculate it.
\$U_i = U-I_R \cdot R \$ Where \$U\$ is the input voltage, R is the calculated resistance from before and \$I_R\$ is the measured current.
Plotting this, I realized that I am doing something wrong.
It seems that there is some major issue in my approach but I can't find it.

**Edit: **
I added the other plots.
The blue line displays the real data. The red line displays the "linearized" values, computed with the method of least squares.
The searched value was always expected as the slope (or the reciproce) of the (red) graph.


texts: Altium Designer: How to select different subcircuits in Schematic and on PCB?

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I've created three sheet symbol from the same sheet, and gave different designators to each of them. Update the PCB, and now I want to place components. But I can not select the components of each subcircuit separately. I don't know how?!

If I select any component from the sheet (That I've derived ARC1, ARC2 and ARC3 from) it selects the components of all three ARC's. How can I select the component of only ARC1?


texts: Explanation for Method of Monitoring Current from a Power Supply

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I recently came across an interesting way to monitor current, but was not certain exactly how it works. Likewise, I was hoping that someone might be able to explain how the device measures current.

The object shown in green is a High Voltage Electrostatic Precipitator capable of putting out a maximum of 30 kV and 10 mA (however, the designer stated that the load will usually only draw 1-3 mA).

Going from left to right, the first voltmeter is used for measuring the current off of the positive lead (the other voltmeter uses a voltage divider to find the voltage, but that section is irrelevant to the question). What is interesting is that the device is, in fact, a voltmeter rather than an ammeter. The voltmeter is set to roughly 3000 mV DC.

What's more interesting is that the readings (in mV) provided by the left-most voltmeter provide the exact number of milliamps that the load (shown as the box below the ballast resistor) is consuming.

Likewise, I was curious why this is and what math may be behind this effect?


texts: Help simply the resistor usage in this voltage summer and divider circuit

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Can someone help simplify the resistor usage in this circuit?

VS is a constant 5v supply. Flex is a variable voltage between 0 and 5v.

The resistors above have been brute forced to achieve this rough voltage range above. Could someone help explain how we could go about simplifying the circuit?

It is essentially a voltage adder and divider which has two possible modes of operation. We can only use resistors as it will be in a very noisy environment and needs to be something an auto electrician can easily add to a vehicle loom.

Mode 1. Low boost with the following voltage mapping.

0v -> 0v

5v -> 700mv

Mode 2. High boost with the following voltage mapping

0v -> 750mv

5v -> 1.25v

edit: Here is the multi sim project if that is of any help
https://www.multisim.com/content/ERRVHRCS93ekiEiXBNgbZH/flex-fuel-with-high-and-low-boost-1/open/

edit2: Here is the big picture, maybe someone can help design this better.

We have a single analog input into a vehicle PCM that accepts 0 - 1.66v

We have two inputs we would like to get into the firmware.

Ethanol 0-100% signal which is currently a 0-5v signal.

The state of a switch in the cabin, this is a logical 0 or 1. It is a switch so it can be anything.

We cannot modify the analog input logic as it is in low level firmware, as we are reverse engineering assembler code this would involve modifying the stack which is too complex. We can however use the signals at a higher level within the firmware and use a lookup table to infer the states.

We then have a lookup table that takes the voltage and infers ethanol content.

The lookup table looks like this:

Eg 0 to 0.7v is 0-100% ethanol low boost (eg switch off)

0.75 -> 1.45v is 0-100% ethanol high boost (eg switch on)

Lookup table of volts to % ethanol

Lookup table of high or low boost

What is the best way to multiplex this analog and digital signal into a single analog input?

We have a 5V source available however this needs to be a very simple circuit that can be put within a loom without a PCB at lost cost. Hence the resistor voltage divider/summer we came up with above.


texts: Wireless serial programming without the need to press a button to program it

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After a long play, I made this adapter to be able to program a Pro Mini wireless via BlueTooth. The long play wasn't the adapter but the settings of the BlueTooth module (baudrate is fixed and need to be changed to firmware upload speed).

It is working great however I need to press reset every time I want to update the firmware on the Pro Mini. That is a little pointless to be wireless, it would be great without the need to press reset every time I need to update the software.

The STATE to DTR seems to be doing nothing, get this from examples however doesn't do anything. Most of the examples use the HC-05 but I am using a SPP-C module (a different 'beast'), to be exactly, a JDY-30-V2.6, Bluetooth V3.0 .

The STATE pin (BlueTooh module) is to indicate a connection is established (HIGH) and when connection is refused (LOW). That is not very useful and the opposite the DTR pin requires (and is too slow).

What can I do to automate the programming feature? I have tried several things, connecting the STATE to the RESET pin, mess around with some resistors however doesn't work out to a solution.

Any directions or ideas what to do or is what I want impossible with this configuration?

Some datasheets

JDY-30
ATMega328p


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6I am a software engineer with a small amount of experience in electrical engineering that has been tasked with designing an embedded OS for a IDMT relay (uni project).

However, I don't understand why a protection relay would ever need a delay.

If a fault is detected shouldn't the breaker activate as soon as possible to prevent damage?


texts: First-order analog active bandpass filter with variable center frequency

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I've thought about designing an active first-order bandpass filter with variable center frequency and fixed bandwidth, using OpAmps, as a project for an Applied Electronics class.
My first try was to use the following topology, fixing the capacitor values and changing the frequencies by varying the resistances. But to do this without changes in the bandwidth, the bandwidth's derivative in respect to R should be 0. It happens that the only solution to this equation is to have equal capacitances, what would lead to equal frequencies to both low and high-pass filters.

Given this mathematical no-go, please give me some advice on how to proceed about this project idea.

Thank you.

EDIT: Thanks to the commenters, I've realised a fixed bandwidth wasn't really necessary for me, and using the State Variable Filter topology solved my problem.


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I am reading Chapter 12. Recommended Design Practices from the Quartus II Handbook Version 13.1
Volume 1: Design and Synthesis which states (p. 8):

  Ripple counters use cascaded registers, in which the output pin of one
  register feeds the clock pin of the register in the next stage. This
  cascading can cause problems because the counter creates a ripple
  clock at each stage. These ripple clocks must be handled properly
  during timing analysis, which can be difficult and may require you to
  make complicated timing assignments in your synthesis and placement
  and routing tools.

What is a ripple clock? Why is timing analysis difficult on a ripple clock?


texts: automatic bootloader without PC software

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I want to design a bootloader in AVR ATMEGA16 that when we reset the AVR, it receive hex file from some PC by serial port without run a program on PC
for example when we reset the AVR, it load .hex file from certain path to Flash on serial port
does it possible? and how?
thanks


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I created a lt spice model of my circuit which consists of an op amp in a unity gain voltage follower configuration which feeds a SAR ADC. I also included the flywheel circuit in front of the adc.   There are two models, each one having a different op amp.

The one labeled "bad" uses a TI 4111 which isn't really designed to handle the capacitive load my circuit has.  I originally designed with this op amp before I knew the capacitance values.  Thus I made a second circuit that uses an op amp with unlimited capacitance drive.

Using the analog suggestion on how to measure phase margin I plotted the following.

Not sure how to interpret these, it seems that the tlv4111 has more phase margin than the analog ada4807 which seems backwards to me given the load circuit.  Any suggestions?

Updated picture with the suggestion of adding DC source on + input, doesn't seem to have made a difference


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I am using the IR2110 IR2110 datasheet to drive a full bridge.
The datasheet says that Vss ( logic ground ) may be up to 25V less than the voltage that powers the driving side Vcc.
In my case I need to have Vss -25V.
The full bridge did work when the grounds between logic and driving side where connected between them.

But when I change that it does not work.

So I got a single IR2110 to test it.
I connected 0V to Vss. 5V to Vdd.
10V to COM and 22V to Vcc.
If you want to see the voltages differently, say: -10 to Vdd, -5 to Vss. 0 to COM and 12V to Vcc.
I connected also the Lin to and Arduino (connecting logic ground) and put SD to logic ground.

Result: The chip "exploded" and a hole exists in it! It is also dangerous because may injure the eyes!

What am I not understanding?


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I have a nodemcu that needs to turn on periodically (every 2 hours) to take measurements, send them to me and then go back to sleep. I need this to be able to last for at least a year on batteries, and so I chose the TPL5110 for this use (and it works perfectly). I have a sim module that uses a lot of power and this is also hooked up to the tpl.
Now I need to update the setup so that it can continually read from an accelerometer and wake up to take readings if the value reaches a certain threshold. Now I know that the tpl cannot do this, it's simply a timer, but I'm hoping someone knows of a way of doing it.

I've heard about the ATtiny, but I don't think it will work because

my sketch is too intensive for it and
I still need to be able to kill the sim module also.

Would it be possible to use the ATtiny as a kill switch, much in the same way a tpl works?

Thanks


texts: Why is Arduino Uno Rev3 input voltage specified up to 20V? OpAmp

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The Arduino Uno Rev3 has an OpAmp (TI LMV358IDGKR datasheet) where the non-inverting input ("CMP") is connected via a voltage divider to Vin. The OpAmp's supply is connected to 5V.

On the Arduino Uno Rev3 product page (click) they specify the recommended and limit ratings for the boards input voltage:

Looking at the LMV358IDGKR absolute maximum ratings i am wondering why having (in the case of say input voltage > 11.4V) a voltage above 5.7V at the OpAmp's input ("CMP") isn't a problem? For my understanding the OpAmp will blow up at say 15V input voltage?!
(Well voltage at barrel jack might be ok up to roughly 12.5V because there is a diode between power jack and VIN, but above?)


texts: Do I need USART1 to program the bootloader with STM32 - Or could I use SWDIO & SWCLK?

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I have heard that if I buy an empty factory made STM32, it will come with no bootloader at all. To program that STM32 with a bootloader, I need to do that through USART1. And later when I want to implement the program onto the STM32, I need to use SWDIO & SWCLK.
Is that correct? Or could I program the bootloader with USART1 and SWDIO & SWCLK, the same way I can program the STM32 with USART1 and SWDIO & SWCLK as well?


texts: Can a Current Limiter Power Thermistor be used in line to reduce the brightness of a 120v incandescent bulb?

texts: I have an application were I do not have the room for a dimmer switch but need to reduce the lumens of a 120v 25w incandescent bulb just a bit. There used to be a product called the Bulb Saver Button which was placed in the light bulb socket to reduce power consumption and increase the life of the bulb. It also reduced the brightness of the bulb. This would work for me but this product is no longer available. I'm wondering if I simply put, in line, a Current Limiter Power Thermistor, would it do the trick? I found on ebay this 10D-15 Inrush Current Limiter Power Thermistors 10ohms 5 AMP. Would this work like the Bulb Saver Buttons?


texts: Why can't my digital multimeter read resistance?

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My multimeter can read voltage (AC and DC), current, but it can't read resistance or diode.
When you set it on resistance it will always show 1, same thing for diode check. It was working fine until yesterday. I opened it but couldn't find anything blown inside. I really don't know what happened to my brand new multimeter.


texts: FPGA - Routing Diagram - what are the physical parts

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In Xilinx ISE I've generated a very simple piece of hardware and when looking at the routed design I'm unsure what some of the parts are and require some clarification on what some of these parts are. In this example a smaller device was chosen 'small' enough to view in ISE.

What are the parts shown by the arrows please. And are the yellow and orange bits the same?


texts: Will the High-Level Synthesis (HLS) design approach for FPGAs reduce the demand for RTL designers?

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I'm a senior electrical engineering student who's very interested in FPGAs and RTL design. But recently after learning what HLS compilers are capable of I had to consider the possibility that eventually the majority of RTL design will be done by computer science gurus using high level languages which will reduce the demand for RTL design specialists.

I understand that the need for experts in hardware description languages will never completely disappear as long and FPGAs still exist, so my question would be is it reasonable to think that the need for RTL/FPGA designers will be significantly reduced by the growing mainstream commercialization of HLS design tools?


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I am using a Pololu DRV8355 dual motor driver. According to the specs, it requires voltage between 1.5V and 11V to operate. I'd like to use two 3V motors with it, and also power an Arduino (Mega 2560) board through it. Since I'm a complete beginner, I am not sure about the input voltage I should provide to the driver. With my limited understanding, I came up with the following possibilities which I don't know how to verify (other than asking here):

Does the input voltage just need to be anything in the range 1.5-11V - in other words, can the driver adjust the voltage to whatever is needed? If so, would that mean that just two 1.2V batteries would work, and adding more wouldn't help in any way?
Does the input voltage need to be the maximum of needed voltages - 7V?
Does the input voltage need to be a sum of required inputs, which would be 3V + 3V + 7-12V? This clearly exceeds the driver's operating range. Would I therefore need to provide 6V to the shield and just power my Arduino directly with another power supply?


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I'm studying the space-state representation and I'm not understanding a simple situation that I created. I created the following system, on the frequency domain:

By writing the time domain representation of the bottom block, we get:

$$3y_1'+5y_1=u_1'+u_1  \,\,\,\,\,\,\,\,\,(1)$$

where y1 and x1 are, respectively, the output and the input of this block. Let's call the input and output of the integrator by x2 and y2.

We can see that:

$$u_1'=-y_2'$$ since u1=constant-y2

Replacing that in (1), we get:

$$3y_1'+5y_1=-y_2'+u_1 $$

But y2'=u2=2y1, so:
$$3y_1'+5y_1=-2y_1+u_1 \\y_1'=-\frac{7}{3}y_1+\frac{u_1}{3}$$

But if i replace the bottom block by the frequency domain of this equation:

$$\frac{y_1(s)}{u_1(s)}=\frac{1/3}{s+7/3}$$

we don't get the same result as the first situation (at least it is what my simulation shows). Can someone explain me why? Is that something about initial conditions? I created this simple system because i was trying to do the same thing to a bigger system (where there are some relations between inputs and outputs of subsystems), to manipulate state equations, but I was getting different results, like on this example.

(EDIT)
I simulated that last equation using the state representation and using the output as the state variable with initial conditions equal to 1/3 (just by guessing) and i got the same system as the first one. The step function value i used was 1. Does anyone know how i can derive the initial conditions i need for the output of this block so the system would be the same as the first one? By simulations i can see that it is the step value divided by 3, but i cant understand why.

Thanks.


texts: Does an analog filter with complex impulse response exist in application?

texts: Do we have in practice any analog filter that has a complex impulse response? Or they must have a real impulse response? Particularly, I am looking for a low pass filter that passes only a band in positive frequencies.


texts:
I am having trouble trying to convert the boolean expression A and B or Not C to an all nor gate circuit i have tried a couple of times but cannot seem to get the circuit right using ALL NOR GATES only. Any help would be appreciated. I think I need about 6 gates in total but i keep getting lost and confused

this is what i submitted i will go back and change the curve on them so they appear to look more like NOR but the circuit is correct to the truth table

Hoefully this image looks a bit clearer. Note this is how the software performs meaning i can only select and insert imgages i cannot really change the curve so much of the gate itself only drag it out ever so slightly

that is the expression i came up with and a hand sketch of the circuit instructor just went on to say my simulation were not NOR gates


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the Bessel filter transfer function is defined via bessel polynomials. If we consider for example a 2nd order filter, the transfer function is:
$$ H(s) = \frac{3}{s^2+3*s+3} $$
I wanted to build a simulation for such a filter with a Sallen-Key-Architecture. Therefore I consulted this design guide by TI.
They define the transfer function of a 2nd order low pass as:

Ao is 1 since I want the gain to be unity. I looked at the table below in order to correctly calculate the C- and R-values.

Hence the transfer function becomes:
$$ H(s) = \frac{1}{0.618*s^2+1.3617*s+1} $$

I ran the simulation and looked at the bode plot. It showed the desired result (the -3db cutoff frequency was as calculated).

However I do not understand why the transfer function looks so differently. Its definetely not a Bessel polynomial. I checked the step response and observed an overshoot of 0.4% as one would expect for a Bessel filter. Therefor I have 3 Questions:

How come that the transfer function in the ti design guide is not a bessel polynomial.
Should the pole location of a 2nd order Bessel filter be the same for any filter with a certain cutoff frequency?
Can a second order bessel low pass have a different Q factor than 0.5773?

Thanks!


texts: Sharing a single sprinkler system zone wire?

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Trying to share a five wire sprinkler system run to control five valves. I need a common wire, so now I have 4 valves. These are 24vac valves. I know this is possible because I have seen commercial products that are $50-$150.
(WireSprout, Doubler). That product has no requirement for power supplies and simply inserts on both ends of the wire run.
Seems To me there must be a simple circuit that does this and if it were DC valves it would just be two diodes at each end. Any ideas how the commercial product does this?
I wish to recreate it...
Thanks for the suggestions below.
Option #1: The diode approach seems most straight forward, but as jsotola said, the values may become magetized since they would be getting half-rectified AC rather than a full wave AC feed. I am not even sure if a sprinkler valve would operate with half rectified AC.
Option #2: The dual valve in parrallel approach suggested by vu2nan is straight forward, but runs the risk of reducing the actual water pressure too much. That said, if I reconfig my zones properly, I may be able to find the two zones that require the least amount of water pressure so when operated combined, would work fine. Interesting approach, and worth a try.
Option #3: Separately I heard from someone that suggested installing an ALTERNATING RELAY (something like the Macromatic Alternating Relay ARP024A3R) which would alternate which load gets power each time it is energized. I would simply have to remember that the zone alternates when I make my schedule and essentially turn the same zone on twice, once for loadA and then again for loadB.
I am thinking that the commercial WireSprout product is just the diode-only circuit shown above (not based on the HOLMAN AU patent above). $59 for a few diodes seems steep. I was not able to find a commercial product version of the HOLMAN patented approach. The 'Doubler' product is likely (based on the patent mentioned) the scenerio in Option #3, and for $150 seems to be a big markup for a $60 alternating relay.
I may try option #2 first. Its simple and may just work without extra 'stuff'. Will report back once running.
Thanks all.


texts: How to analyze Microcontroller input-logic-signal without ADC?

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I have a signal which is fed to one of the digital inputs of a microcontroller (PIC16F18326). The signal is shown in the image-1 below. This is during the normal operation of the circuit, that means when it has a load (array of LEDs). But when there is no load, or when open circuited, the signal becomes as shown in image-2.

Both the signals shown below were when the circuit is turned ON from an OFF condition.

Image_1:  Circuit Turned ON under load; 5V to microcontroller through out the operation. This 5V is considered as 1 for the µC. (and 0V or GND is considered as 0)

Image_2: Circuit Turned ON under no load or under open circuit. Approx. 4.5 V after 1 sec.

I have to distinguish between the Normal Operation and Open circuit just by analyzing this signal at the microcontroller pin without using an ADC!

Does anyone have a logic solution or idea, what feature of the microcontroller I can use to realize the circuit condition?

Update: For a better understanding of the circuit, I have attached below

image_1

image_2


texts: Best way to power sensor circuit from LiPo

texts:
I want to make small (~cigarette pack size) oscillometric blood pressure monitor (with arm cuff). The device will be powered by single cell 3.7V LiPo battery with USB charger circuit, without LCD display or physical buttons.

Main components:

ATmega32u4 microcontroller with Arduino bootloader,
single supply amplifiers,
5V or 3V pressure sensor (mpx5050 or mp3v5050),
3V air pump + 3V solenoid valves, powered directly from battery, controlled via transistors,
3.3V HM-10 BLE module (based on CC2540).

I'm not sure how to power microcontroller, sensor and filtering circuit. The current draw shouldn't be more than 250mA. It can operate on 3.3V or 5V, I would prefer 5V, becouse uC will run faster (16MHz vs 8MHz at 3.3V).
I think about TPS61232 boost converter as it offers undervoltage protection and over 90% efficiency. At 5V, p-p output voltage (taken from TI WEBENCH) is acceptable: value at 0.3A is 4.94mV, at 0.2A 3.52mV and at 0.1A 7.53mV.

Question:

Is using step-up converter in this case a good solution or are there any better options?


texts: Isolating an audio line connection with two capacitors

texts:
I've looked at several questions, such as:

Isolating audio ground between devices

I want to connect an input and output audio line signal of two different devices. The earth potential of their audio connectors is might be floating, connected to mains earth, or offset by some DC or AC amount, with some resistance and other complications - the usual real-life audio stuff.

Is a simple solution to connect them with two capacitors? The function generator is the line out, and speaker the line in:

simulate this circuit – Schematic created using CircuitLab

I'd rather not use audio transformers if this will do.

Edit - Additional details

The above values are a bit of a hack. The circuit too, so I'd expect problems like pops on power up at least


texts:
I have a 7 segment display that is driven by a TLC59281. How do I connect its pin to a Raspberry Pi in order to drive the display?
Edit: It uses SPI interface. The datasheet can be found here.


texts: Superposition principle and voltage division

texts:
I am looking at some circuit solving using the superposition principle and I came across this one.

We need to find \$v_0\$. My thought would be to use superposition and voltage division in the following way:

\$v_0=V_{ss}\cdot\frac{2R_a}{2R_a+R}+2V_a\cdot \frac{2R_a}{2R_a+R}\$

We in both cases find the voltage across \$2R_a\$ with the voltage divider formula. However, it turns out the solution is actually:

So my denominator and numerator should switch places in the second part of my solution, but I don't understand why this is. Aren't we then finding the voltage across \$R\$? And does that have an effect on \$v_o\$?

I hope someone can clarify this for me.


texts: How could landline telephone service cause fire alarms to activate?

texts: Someone I know informed me that their home’s fire alarm is occasionally triggered when he uses his home phone (landline). His alarm system company stated that they do not know why this occurs. They believe that it could be caused by short waves emitted by the telephone. Any idea as to how this could happen?


texts: Raspberry Pi driving a LED through a MOSFET

texts:
I need to control a LED with a Raspberry Pi!

The LED is a white one and it has to be PWM driven, in order to make it show a sort of "breathing effect".

Unfortunately I don't have the LED datasheet so I've empirically (using my bench power supply) found that the LED forward voltage is 3V approx. and that the brightness I want is obtained with 50mA approx.

So I can't drive the LED attaching it directly to a GPIO pin: Raspberry Pi is a 3.3V logic and I've read indeed that a GPIO pin can give a maximum of 16mA to them :(
I had to find another way.

I eventually come up with a circuit like the following one:

I'm using an IRL540N MOSFET (link) to drive the LED through the Raspberry 5V power supply pin.

The MOSFET gate is attached to the GPIO pin through a resistor to reduce the (theoretically minimal already) current required from the GPIO.

I've also added a pull-down resistor in order for the gate charge to discharge to ground when GPIO is LOW.

Resistor R1 and R2 have respectively 10k and 100k Ohm values (I put them empirically).

I chose a 2.2 Ohm R3 resistor for the LED, this way I've found current values are pretty near to the one I want.

MISURA CORRENI E TENSIONI

Now I have created 4 copies of the circuit mounted on a Raspberry Pi Adafruit Perma-Proto HATs (link).

Now I'm experiencing different behaviours for each of them. While two of them are working the way I wanted to be, the others are not.

Indeed:

In one case the LED has been burnt after working for a while;
The other last one showed a strange flickering pattern (not related to the PWM). It worked like that for a day then stopped working at all.

I'm supposing that in the first case, maybe the current through the LED was much higher than expected (maybe because of resistors, transistors tolerances?)

In the second situation, I'm not able to figure out what the problem can be. It seems a transistor problem but I not sure (I have only a limited knowledge of electronics).

What am I doing wrong?

Has someone already some experience in setups like that?

Any help will be much appreciated

Thanks


texts: How to find the transfer function of this first order active filter?

texts:
Going through Design with Operational Amplifiers and Analog Integrated Cricuits, in Chapter 3, problem 3.4 I am asked:

  The circuit of Fig. P3.4 is a noninverting differentiator.

  (a) Derive its transfer function.
  (b) Specify component values for a unity-gain frequency of 100 Hz.

I know that for a differentiator such as this, H(s) = -RCs

and for example, a resistor and capacitor in parallel, the impedance Z1 is equal to R/RCs +1.

The closest example I could find was that of a Deboo integrator, whose transfer function is H(s) = 1/RCs.

I am still struggling to understand how to extract the transfer function for Figure3.4. Any help would be appreciated.


texts: One sensor output gives voltage range within 5mv to 50v..I need to give this to an adc (analog to digital converter )..however the adc available is upto 10v.i need to stepdown hight voltage to low voltage(50v to 10V, 25V to 5V like this linear) to give it within adc input range..Any standard circuitry for this to reduce this high voltage dc?


texts: Magnetic locks with paramagnetic materials

texts:
Well I was wondering why magnetic locks are made of an electromagnet and a ferromagnetic material and not an electromagnet and a paramagnetic material.

The magnetic attraction between the electromagnet and material attached at the edge of the door will create a 2nd axis of rotation.

Ferromagnetic materials remain magnetized even after the electromagnet no longer exists.The magnetic field of the ferromagnet will magnetize the conductor.This wont destroy the 2nd axis of rotation meaning the door cannot be opened.

Paramagnetic materials don't remain magnetized after the electromagnet no longer exists.This will destroy the 2nd axis of rotation meaning the door can be opened rotating on the 1st axis of rotation.


texts:
I used LPM_RAM to store data and made read and write operations. But it seems like placing the data to wrong addresses. Here is screenshots;

Wave Result;

Memory Block;


texts: Arduino based digital to AC conversion schematic

texts:
I am trying to build an Arduino based system for sending electric pulses, of 24V, 40mA sinusoidal. Each pulse is in a burst of 5000 microsecond, and each pulse is about 20 - 800 microsecond. These pulses are grouped in a burst - which there are 10-15 in a second. So the logic that the Arduino could follow is as follows:

Send a 20 - 800 microsecond pulse of 24V, 40mA in a burst.
A burst is of duration 0.4 - 0.6 seconds.

The Arduino could easily help in this logic, and so the choice to prototype. Now, to achieve the logic above I plan to use a NE555 timer in the following schematic (see attached diagram).

To achieve the power requirements I am adding a 24V battery to a MAX533 (could use another digital to Analog chip too! - any suggestions welcome). To convert digital to analog, via the Arduino(send the sinus wave digital parameters via the Arduino to the MAX533-type DAC, and get a pulse + burst.

Is this the correct approach to the problem? Also, what Digital to Analog converter chips can give 24V, 40mA sinusoidal signals. In the diagram I have used MAX533 but that is for illustrative purposes. The MOSFET arrangement coupled with the NE555 allows the bursts to be formed.

Again, the schema I may have generated may be incorrect, any help + reference is appreciated, thanks in anticipation.


texts:
I am trying to understand a protocol (shown in figure 1) . For now this I have understood that data is transferred at high to low clock. as shown in figure. and the sync is for every 8-bit.

But then there is another data at the data line, as shown in figure 2, that is changing in the low of the clock. This does not happens at a particular instance but some time at 3rd, 4th, 8th etc. bit with respect to sync. Also this data is different every time.

After this the data is transferred at every low to high clock, still with 8-bit sync (Figure 3). So, I am thinking this may be sort of change of direction of data from read cycle to write(or vice versa).

Can somebody help me understand this.

Edit:
Its a probably a memory chip, canon is using in the protocol in there printer chips (Printer iP7230) to communicate the printer levels.

I saw this some days back thought I can try this. http://www.instructables.com/id/Reverse-Engineering-to-Emulate-Ink-Cartridges-for-/

I just wanted to be pointed in the direction of what sort of protocol it can be.


texts: Is there constant current flow in this circuit?

texts:
I am studying basic circuits, and have a very elementary question.
When the photoresistor is exposed to light in the following circuit, is there a constant drain on the power supply?
If this were used in a battery powered nightlight, the battery would eventually drain even if the nightlight were never in the dark?
Am I thinking correctly?


texts:
I want to get weight for load vehicle in Kg,
I Used this product  and I received like this output '1.361'
How I can calculate(convert) this value to Kg(Kilogram)


texts: Burn Micronucleus bootloader to use ATtiny85 via USB (AVRDUDE)

texts:
I am working on an ATtiny85 USB development board, and I need to flash the Micronucleus bootloader on it. I have heard that this bootloader allows the ATtiny85 to be programmed via USB from the computer, without the need of an external programmer.

So I decided to try to burn it, using the Arduino Uno as ISP. I downloaded the bootloader, AVRDUDE, opened the command prompt (I'm using Windows 8.1), navigated to the .hex file folder and wrote this:

avrdude -c arduino -b 19200 -P COM6 -p t85 -U flash:w:micronucleus-1.06.hex -U lfuse:w:0xe1:m -U hfuse:w:0xdd:m -U efuse:w:0xfe:m

Does that sounds right? That's what the prompt outputs:

C:\Users\Mohamed\Desktop\micronucleus-master\firmware\releases>avrdude -c arduin
o -b 19200 -P COM6 -p t85 -U flash:w:micronucleus-1.06.hex -U lfuse:w:0xe1:m -U
hfuse:w:0xdd:m -U efuse:w:0xfe:m

avrdude: please define PAGEL and BS2 signals in the configuration file for part
ATtiny85
avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.02s

avrdude: Device signature = 0x1e930b
avrdude: NOTE: FLASH memory has been specified, an erase cycle will be performed

 To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: please define PAGEL and BS2 signals in the configuration file for part
ATtiny85
avrdude: reading input file "micronucleus-1.06.hex"
avrdude: input file micronucleus-1.06.hex auto detected as Intel Hex
avrdude: writing flash (8162 bytes):

Writing | ################################################## | 100% 3.91s

avrdude: 8162 bytes of flash written
avrdude: verifying flash memory against micronucleus-1.06.hex:
avrdude: load data flash data from input file micronucleus-1.06.hex:
avrdude: input file micronucleus-1.06.hex auto detected as Intel Hex
avrdude: input file micronucleus-1.06.hex contains 8162 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 9.37s

avrdude: verifying ...
avrdude: 8162 bytes of flash verified
avrdude: reading input file "0xe1"
avrdude: writing lfuse (1 bytes):

Writing | ################################################## | 100% 0.02s

avrdude: 1 bytes of lfuse written
avrdude: verifying lfuse memory against 0xe1:
avrdude: load data lfuse data from input file 0xe1:
avrdude: input file 0xe1 contains 1 bytes
avrdude: reading on-chip lfuse data:

Reading | ################################################## | 100% 0.03s

avrdude: verifying ...
avrdude: 1 bytes of lfuse verified
avrdude: reading input file "0xdd"
avrdude: writing hfuse (1 bytes):

Writing | ################################################## | 100% 0.03s

avrdude: 1 bytes of hfuse written
avrdude: verifying hfuse memory against 0xdd:
avrdude: load data hfuse data from input file 0xdd:
avrdude: input file 0xdd contains 1 bytes
avrdude: reading on-chip hfuse data:

Reading | ################################################## | 100% 0.02s

avrdude: verifying ...
avrdude: 1 bytes of hfuse verified
avrdude: reading input file "0xfe"
avrdude: writing efuse (1 bytes):

Writing | ################################################## | 100% 0.02s

avrdude: 1 bytes of efuse written
avrdude: verifying efuse memory against 0xfe:
avrdude: load data efuse data from input file 0xfe:
avrdude: input file 0xfe contains 1 bytes
avrdude: reading on-chip efuse data:

Reading | ################################################## | 100% 0.01s

avrdude: verifying ...
avrdude: 1 bytes of efuse verified

avrdude: safemode: Fuses OK

avrdude done.  Thank you.

Is it flashed now? Because when I plug it in the USB port I get this error message: "USB device not recognized". Do I have to install some driver, or flash anything else on the ATTiny85?


texts: What is the difference between builtin voltage and cutin voltage in pn diode?

texts: I am little bit confused that how these two are different.


texts:
I'm trying to build a framebuffer using an FPGA and an external memory.  I have a soft core CPU running on the FPGA as well a small chunk of logic to output signals to an LCD.  My goal is to have the CPU rendering/writing a frame to a small chunk of external memory and then have the LCD write module read from that external memory.

My issue is that the LCD and write code is on a crystal-->PLL at 9Mhz and the CPU is on the original crystal at 50Mhz.  Do I have to put the CPU on the PLL as well or is there a way of interfacing the logic in such a way that it will work as is?

Specs:

Memory => SDRAM @ ???Mhz

CPU => NIOS II @ 50Mhz

LCD => Sharp 480x272 @ 9Mhz

FPGA => Cyclone III


texts: How do I calculate the supply current for a zynq 7010 chip?

texts:
I have a Zynq 7010 chip, and the current requirements in the datasheet confuse me a lot. Could someone explain how to determine how much current I'll need to supply to each rail?

http://www.xilinx.com/support/documentation/data_sheets/ds187-XC7Z010-XC7Z020-Data-Sheet.pdf


texts: Designing a pcb without components, only copper pads and copper tracks connecting each pad to pad

texts:
I want to make a pcb a bit like this one.

PLease guide me on how to design this kind of pcb, i plan on etching in on a rigid pcb board.
I find it hard because in CAD there are no pads or lines you can add easily to your design because components are needed first in schematics to proceed in pcb design.


texts: How can I read an large array of switches with some microcontroller?

texts:
I have been asked by someone whether or not I could do some programming on a large array (something like 18 x 16) of analogue switches.

I would want to wire up an array of analogue switches (you know, on-off toggle switches) that are in a grid pattern with rows and columns so that I can at a single moment understand the state of all those switches and do something with code on the basis of it.

I realize that microprocessors have limited GPIO's, I would need 288 ports to read that many switches. What is a circuit I can use to reduce the number of ports to something more manageable like less than 48?


texts: Converting an ADC value to equivalent Temperature?

texts:
I'm working on a humidity controller which also controls the temperature inside a   chamber.I'm done with the hardware (though i'm not the one behind the design)and which was originally designed with a 12 bit external ADC and an 89s52 uc  and I replaced both with PIC 16F877A uc and I use the  10 bit internal ADC.

Other hardware details are (I can provide the schematic though it seems cumbersome).

temperature sensor -PT100
humidity sensor - SY-HS-220 (datasheet)
+Vref for ADC - 1.235V and -vref =0;

I roughly checked the voltage across the 2 ADC channels by replacing the sensors with a 500 ohm pot (not concerned about the errors at this point) and got the following figures

proposed temp | voltage @ ADC

5 oC--------------1.650v
6 oC--------------1.660v
80 oC-------------2.480v

proposed humidity | voltage @ ADC

30% (990mV)--------0.098V
31% (1023mV)-------0.101V
32% (1056mV)-------0.104V
33% (1089mV)-------0.107V
34% (1122mV)-------0.110V
40% (1300mV)-------0.128V
90% (2970mV)-------0.29V

I want to use this hardware for the following requirements

Temp. measurement - 5-80 oC,  0.5 oC resolution
Relative Humidity - 30-90%, 1% resolution

And  my concerns are

Should I have to change the reference voltage to 2.5V as I can see the maximum voltage to be measured is 2.48? Or that voltage is out of a mistake since the original hardware is designed with 1.235V

is the voltage at the ADC in(of temp sensor) adjustable so as to make it within  1.235V (so I think better performance) by some minor hardware changes (like changing a resistance value to change gain of amp)

are my requirements achievable with a single ADC configuration as I'm concerned about the rough figures I got (ADC input values for temp and humidity are not comparable or that too a mistake?) ?

for the temperature I could measure only with 1 oC in steps as the RTD chart (For European Curve, Alpha = .00385, ITS-90)was provided with 1 oC increments. To measure 0.5 oC resolution is it OK if I divide the change in voltage for 1 oC increment by 2 (assuming the curve is linear, or not!?)

How to decide efficiently the sampling time of ADC  (considering the facts that the sensors respond slowly, transient voltage fluctuations in the line etc.)
Finally how ADC values are converted to equivalent process values.? (Excuse me if the title of question matches here only)

By a table look up? (in my case 150 values(for temp) + 60 values(Rel humidity) ) or can I use some calculation ? (if yes, how to get a linear relationship between the ADC values and process values) .which method is efficient in terms of accuracy?


texts: Voltage is reduced across chained breadboards

texts:
My Arduino is connected to the first breadboard. From there, I chained the positive and negative to the other boards. I have 6 breadboards connected right now. In the first board I see (with a meter) that I have 4.5V difference, and in the next board, 3.5V and in the last, I even get 2V.

Why am I getting this? I partially solved this (getting 3V to the last board,) by wiring every rail to every rail in the other boards, but it makes my design cluttered.

How do I debug this? What's causing it?


texts:
I'm trying to solve, for the voltage across the capacitor in the following circuit:

simulate this circuit – Schematic created using CircuitLab

The initial current in this circuit is equal to \$\text{I}_0\$. How can I find the voltage across the capacitor?

  EDIT: The initial applied current is equal to \$\text{I}_0\$, the initial voltage across the capacitor is equal to \$\text{V}_\text{C}\left(0\right)\$ and the initial current trough the inductor is equal to \$\text{I}_\text{L}\left(0\right)\$

My Work:

I thought that I can write:

$$\text{V}_{\text{R}_1}\left(t\right)+\text{V}_{\text{R}_2}\left(t\right)+\text{V}_\text{C}\left(t\right)+\text{V}_\text{L}\left(t\right)=0\tag1$$

Writing that in terms of the current through the components I get:

$$\text{I}_\text{in}'\left(t\right)\cdot\text{R}_1+\text{I}_\text{in}'\left(t\right)\cdot\text{R}_2+\text{I}_\text{in}\left(t\right)\cdot\frac{1}{\text{C}}+\text{I}_\text{in}''\left(t\right)\cdot\text{L}=0\tag2$$

And then using the initial conditions \$\text{I}_\text{in}\left(0\right)=\text{I}_0\$ and \$\text{I}_\text{in}'\left(0\right)=0\$ I can solve for the voltage across the capacitor. Is that right?


texts: Why don't we consider VCE voltage here when we calculate the current?

texts:
This is class B Push-Pull circuit for an amplifier.

The question says:

Calculate the maximum Icmax current of the resistance RL if you knew Rl = 8Ω

The book solved it this way:

Vcc - (Rl * Icmax) = 0

Then by solving the equation, we find Icmax = 3A

The thing is, how they used Kirchoff's law if they didn't count VCE's voltage of the transistor?

When you make a loop, you're supposed to get Vcc - (Rl * Icmax) - VCE = 0, right?

Then how the book here didn't consider it nor included it into the equation?


texts: How can i extend Bluetooth range at maximum?

texts:
I want to extend at "maximum possible" the range of my Bluetooth Low Energy chip, Nordic nRF51822. I have no limits of space, transmit power or energy requirements so i can use whatever i want.

I was looking for a signal amplifier like RFaxis RFX2411N, but what antenna can i couple with this amplifier?
A friend suggest me to use the Smarteq SmartDisc SD2.4W-02-01-01T but it this directional i think, and i need to have an omni-directional antenna to use on my project.

What products (amplifier, antenna or both) are best to use with this BLE SoC?


texts: How to consider diode leakage current in a voltage divider circuit

texts:
I am trying to derive an equation to calculate voltage at ADC pin for below circuit:

Initially, I have considered only ADC leakage current in my equation to calculate the voltage. During testing at high temperature, it was observed that for an input voltage of 48V, the SW measured voltage is around 49.3V because of diode reverse leakage current. As per datasheet it can go up to 2 µA at 125 C°.
Following equation I have used to calculate voltage at ADC pin.
Without diode:
$$V_{ADC} = V_{in} \cdot \frac{R2}{R1+R2} - I_{leak_{ADC}} \cdot (R3 + \frac{R1 \cdot R2}{R1+R2})$$
With Diode:
$$V_{ADC} = V_{in} \cdot \frac{R2}{R1+R2} - (I_{leak_{ADC}}-I_{reverse_{Diode}})\cdot (R3 + \frac{R1 \cdot R2}{R1+R2})$$
\$I_{leak_{adc}}\$ = ADC Input leakage current from datasheet
I am not sure my above formula is correct. Can anyone suggest a better way to derive a formula for the above circuit?


texts: How can I simulate TC4420 or TC4429 on proteus 8

texts:
I have to use TC4429 MOSFET driver for my project. However I couldn't simulate it on Proteus. Here are the errors it shows:

How can I fix these? I couldn't find libraries and models for this TC4429CPA device. Where can I find library and model files? Alternatively what device can I use instead?


texts:
I checked quite some ADC datasheets and am a bit confused regarding the actual achievable accuracy of an ADC.

Let's take this ADC for this example (ADC MCP3422):
http://ww1.microchip.com/downloads/en/devicedoc/22088c.pdf

The most important specs:

18 Bit ADC (for 3.75 SPS, no missing codes)
On-Board Voltage Reference (VREF): Accuracy: 2.048V ± 0.05%
INL: 10 ppm of Full Scale Range
GAIN ERROR 0.05 to 0.35% (PGA = 1, Includes all errors from on-board PGA and VREF)

An instrumentation amplifier will provide a signal in the range of 0-2V to this ADC (single ended). This ADC will not use the PGA (so: PGA = 1)
By only taking the spec 'Gain Error' it can be off up to 0.35%, so regarding the conversion table I attached below, would already yield only a 10 Bit ADC max.
I did not include all other errors from the specs i posted so far.
Am I looking at it the wrong way and could I still get a decent accuracy out of this ADC (actual useful bits 14=<)?

Thank you.


texts:
I am trying to design an LC input filter with the following requirements:

-The input current peak to peak value should be limited to about 1A because it will be connected to a PV panel

-The output of the filter will be connected to a full bridge converter (with output transformer for isolation with the load). I want the converter to be voltage fed, so this is why I need the capacitor.

The topology is shown in the attached figure. Because of the full bridge, I know that the output current of the filter will be some kind of square wave, so a lot of higher order harmonics compared to the rather flat DC current that I want to draw from the solar panel.

I managed to determine the value of L and C via simulation but I would like to under build this more mathematically. So I am looking for the transfer function I_out/I_in. It's easy to find if the full bridge is replaced with an impedance, because than you can use a current divider. But I cannot find it in case of a complex switching network, such as the full bridge. Any help or clues are appreciated.


texts: Questions regarding an upconverter topology (beating behavior, P1dB and compression)

texts:
This following diagram is taken from the textbook “RF Microelectronics” by Prof. Razavi.

The following points are my understanding about this upconverter topology:

There are two mixers in this topology. One mixer is composed of M1 and M2. Another mixer is composed of M3 and M4.

Each passive mixer generates a double-sideband output.

If a single baseband tone (a sinusoidal signal) is applied to XBB_I, then a beat with a large swing will appear at the gate of M5.

This beat with a large swing will drive M5 into the triode region.

Shorting the output of the two mixers can produce a single-sideband output.

If the output is a single-sideband signal, there will be no beating behavior at the gate of M5.

Now my questions are:

Refer to point 3. Without knowing the amplitude of the swing at XBB_I and  LO_I, how can we conclude that the signal at the gate of M5 has a large swing?

Refer to point 4. Whether it is the “beating behavior” or the “large” swing at the gate of M5 that drive M5 into the triode region? Would a beat with a small swing drive M5 into triode? Similarly, would a constant envelope with a large swing drive M5 into the triode region?

Refer to 5. Why shorting the output of the two mixers can produce a single-sideband output?

Refer to 6. Why a single-sideband signal exhibit no beating behavior?

Thanks.


texts: What is the meaning of Directivity and Reflection coefficient for a RX antenna?

texts:
it's known that the circuital models of TX and RX antennas are the following ones:

They are fine, but I find it hard to understand the meaning of some concepts when applied at the RX case. For instance:
1) INPUT REFLECTION COEFFICIENT
In TX case, the antenna input reflection coefficient quantifies the reflected power at the input port because of an impedance mismatch between the source impedance Zg and the antenna impedance Za. The reflected power goes towards the source, while the difference between incident and reflected power goes into the antenna and is radiated (or, in part, accumulated in antenna parasitic reactances).
But, what does it represent in RX case? Even in this case it describes a mismatch between the other circuit (here called ZL, but suppose it's equal to Zg) and the antenna impedance. So, I'd say that the difference between incident and reflected power goes to the load circuit ZL. But where does the reflected power go in RX case? In theory, it should come back to the surrounding space of the antenna... but it seems quite strange.
2) DIRECTIVITY
The directivity of a TX antenna is the ratio between the power radiated per solid angle of our antenna and of an isotropic antenna. What is its meaning in case of a RX antenna? Is it ratio the incident power (power induced on antenna conductors by the time-varying incident Electric and Magnetic fields) on the antenna? Is the directivity the same in TX and RX?


texts: Using pogo pins in a commercial product as contacts

texts: I've a question about possible usage of pogo pins in a commercial product. I've seen they have simply working principle and are easy to integrate in a case, some of that also have current rating up to 2-3Amps and gold finish. Is it possible to use them in this context? For example in an expansion board that don't require particular connection.


texts:
I'm having a problem making LPC2148 work with SRF10 sensor. LPC is 3.3v device with 5v compatible i2c (at least user docu claims that). On the other side there is SRF10 device which is 5v.
I have tried with both levels as pull-up lvl connected with 4.7k resistor (i have 3 devices on same line so i used higher value resistor).

Strange thing is that it sometimes read the value correctly but it fails to read values from 2 registers... Basically, it doesnt work.

Now, what is strange on this picture, is that logic lvl on SDA is 0 by default and it should be 1. That means that pull-up is not doing the job well ? Could that be related to logic lvl differences between uc and slave ?

EDIT:01.03

Here is my implementation of state 0x50, a_chn is i2c0 or i2c1

void slaveDataReceived (uint8_t a_chn)
{
uint8_t k;
volatile unsigned char *i2cConClear;
volatile unsigned char *i2cConSet;
volatile unsigned char *i2cData;

if (a_chn == 1) {
    i2cData = (volatile unsigned char *)(0xE005C008);
    i2cConClear = (volatile unsigned char *)(0xE005C018);
    i2cConSet = (volatile unsigned char *)(0xE005C000);
    }
else {
    i2cData = (volatile unsigned char *)(0xE001C008);
    i2cConClear = (volatile unsigned char *)(0xE001C018);
    i2cConSet = (volatile unsigned char *)(0xE001C000);
    }

k = *i2cData;
appendToDataBuffer (a_chn, k);
if (i2cDataRcv[a_chn] == i2cDataHead[a_chn]){
    I2CMasterState[a_chn] = I2C_IDLE;
    *i2cConSet = I2CON_SET_STO;
    *i2cConClear = I2CON_CLR_AAC;
    }
else {
    *i2cConSet = I2CON_SET_AA;
    }
*i2cConClear = I2CON_CLR_SIC;
}


texts: getting rid of little air wires in Eagle

texts:
I am just about done with a layout.  But Eagle says I have 23 air wires left.  It turns out they are little tiny ones, e.g. where traces overlap, like this one:

There is a tiny yellow dot where the two traces overlap pointed to by the arrow.  Is there a way to join these traces together to eliminate this?  Or do I have to delete one trace, and extend the other one?  I also have this happen where a trace is connected to a pin -- I will get a little air wire and can't seem to get rid of it.

If I verify that all my remaining air wires are of this type, can I just send the board out to fab as is, since all of the traces seem to overlap?


texts: What rules and tips make automated assembly easy?

texts:
What rules and tips make automated assembly easy, rather than unnecessarily difficult or completely impossible?

In particular, if I have a circuit board that works fine after hand assembly, some people imply that they may not be suitable for automated assembly:

  "The prototype-type PCB fabrication places will send you printed circuit boards, ... These boards are suitable to test your circuit, ... They can be used for HAND ASSEMBLY of your circuit. They will generally not be suitable for an automated assembly process."
  -- Scott

What things are Scott referring to that I might need to change before going to mass-production automated assembly?

After telling me "Always do A, and never do Z", please go on. Why you do that? What problem(s) does it avoid? Is there a book or website that discusses design-for-assembly tips?


texts:
Randomly searching for something else I found out about this strange communications scheme called data strobing.

It seems that instead of sending a data and clock line, you send a data and strobe line.  The strobe line is the data and what the clock would have been xored together.

So the real question is: Why would you do this (other than it is "cool")?  Are there any practical uses of this data sending method?


texts:
I'm having some trouble deriving this equation for transmission line theory:

From: http://www.antenna-theory.com/tutorial/txline/transmission3.php

When I sub the Telegrapher's equations into eqn marked 1 in image, I can't seem to get rid of the exponentials. See my attempt:


texts: How to find the schematic diagram of a component in Multisim?

texts:
Could someone please tell me how to find the schematic diagram of a given conponent in Multisim,  I've been trying to understand how does the IC 74LS729  (SR latch) work but coudn't succeed mostly because this component doesn't behave like a normal SR latch would and  it also includes another input called S3 whose function is also unclear to me.

Any help would be more than welcome


texts: Is a single wrist strap enough against ESD?

texts: I bought 2 anti-static gloves and 1 grounded wrist strap to protect the parts against ESD by assembling computers. I was wondering whether a single wrist strap is enough, because I use to touch parts with my right hand too.


texts:
I have a project requirement to use open protocol RFID tags to control doors handling of a light rail train (also called a tram in Europe). The application must sync and control 2 different doors: one at the train (normal train door opened by driver´s control) and other at the station, also called the platform door. Something as seen in this link here

The idea is, once the train stops at the correct position, when the train drivers commands the train doors to open, the platform door opens in sync. Once tha train driver commands the door to close, the platform door closes also in sync.

To do it, I´m looking for a Gen2 RFID Tag that is externally controlled by a switch or a power connection.

The idea behind the application is:
An RFID once in front of its pair antenna sends its data (code).
To sync doors, it need to "TURN ON" and "TURN OFF" the RFID reading by an external command to the tag. As the control is in the train, where the tag is located, then I need to control the TAG code transmission.

If I use a normal RFID in this application once the train approaches is position the RFID code is sent, the antenna captures it and command the platform doors to be open.

What I need is to sync the moment when the RFID code is sent with  the train door command, so that when the train stops no code is sent (the tag is "off") and when the door is commanded to open it "turns on" the RFID that sends its code that will be interpreted and command the platform door to get opened.

RFID usage is a requirement, not an option.

Advices welcomed.


texts:
this is my first time asked on stack exchange, please bear bare with me.
Anyway, I created portable monitor using multiple TP4056 as battery charger & protection circuit. But I'm not sure it's safe or not.

this is the wiring diagram :

why I wired this way? Apparently the monitor needs more than 5 Watt, and using 1 TP4056 can't give enough power. (the monitor needs 12 volt). So far my solution works, but I worried about the safety.

what I'm asking is this solution safe?

Thank you

edit 2:
To power up 12 volt monitor, I stepped up the output from TP 4056 (from around 3-4 volt) using XL6009 module to 12 volt. As you can see, the module located under the batteries.


texts: How to fix my simple MOSFET power switching circuit?

texts:
In my design the goal is to create a simple switch between power sources using a MOSFET.

J2 is just a connector for the main power source which remains connected
VDD is connected to a USB port
VREG is a voltage regulator that requires the Capacitor there for switching applications. It takes in 5 -30 V in and outputs 3.3 V
The LED should automatically light up if power flows through VREG that outputs 3.3 V
The MOSFET used is DN2450K4, an N channel MOSFET

The goal is that the main power source is always connected but if I needed to program my overall device I would plug USB in and the MOSFET should cut/redirect the main power to ground and the USB should be powering the regulator.
When I tested this application with no main source attached and the USB connected to power the LED wasn’t lighting up, so I knew my VREG wasn’t receiving power. The MOSFET was slowly heating up though.
Now my question is how can I change this circuit / MOSFET layout to better suite my application?
EDITED:
I believe this application will work better and not create the original short hopefully I'm correct

EDITED AGAIN: I changed MOSFETs. Now I'm using a P channel MOSFET AOD417 (DATASHEET) and switched some wires around based on the finds from this post HERE!
I also added another diode D4 to block the charging possibilities of the USB (VDD) to the other source MVOLT


texts:
I apologize in advance if my question is too naive or incorrect; I am still very new in the difficult domain of RF and antennas.
I know that at the first order, a resonant antenna can be modeled electrically as an RLC tank circuit, where more or less, R is the radiation resistance of the antenna.

Now, let us consider a non resonant antenna. To put flesh on bones, let us even restrict ourselves to horn antennas. This time, it is difficult to imagine there are both L and C components (for this would resonate). Hence my question: At the first order, is a non resonant antenna modeled by an RL or RC circuit? something else?


texts: Large amount of heat generated by AC to DC power supply

texts:
I purchased this power supply:

https://www.amazon.com/Yes-Original-Power-Supply-Security-Camera/dp/B078MN4XQG/ref=sr_1_3?ie=UTF8&qid=1530044862&sr=8-3&keywords=CCTV+Security+Camera+18CH+12V+15A+180W&dpID=51SEIcuz4xL&preST=_SX300_QL70_&dpSrc=srch

I am running about 15m of LED lights that are rated at a working current of 0.35-1.2A per meter.  In reality they seem to pull more like .6A per meter.

I estimate the total current drain to be between 8 and 10 amps.  This is well under the rated max for this unit.

The unit however gets very hot.  Outside of the metal case reaches 120-135F inside 180 to 195F.  These seems VERY hot for this small of a load.  I can only imagine how much energy is going up in heat.  The entire reason I purchased a more expensive supply would be for the advertised 89% effecenty.

I don't know electronics or physics well enough to know how much heat should be generated by the dissipation of an amp of current.  I was hoping someone could tell me if this power supply is broken, or if this is what is to be expected.

-----------------Update-------------------

I'm not sure what I did, but all of this is due to wiring.

I THINK this is what I had wired:  https://www.tinkercad.com/things/5FPIjvucQ46

However, the drain of each is screwed into the box, no guarantee that they aren't shorted against one another.

This: https://www.tinkercad.com/things/9SnoHMoNnBh Seems to be what I should have done.

I think the wiring was somehow causing an overload, and it to pull more current that just for the LEDs.  I have it re-wired and it is running at about 140F inside and 90F outside.


texts: Wiring up a AAA power toy to Pinball lighting supply

texts:
I'm trying to wire up a toy powered by AAA batteries (3vdc @ .09A) to the lighting circuit on a pinball machine (6vac @ 4A) and I was wondering what the best possible solution that I can keep small. I know I have to rectify it to DC Voltage but stepping it down to the 3vdc is where I'ma  bit fuzzy.
Any help would be awesome.

Thanks,
-M


texts: How can adding a reflector to a half-wave dipole (in a Yagi Uda antenna) increase the gain by more than 3dB?

texts:
I have been designing a Yagi Uda antenna using CST Microwave Studio.
For a half-wave dipole the directivity (at 1.3GHz) was 2.116dBi.

After I added a Reflector, the directivity improved to 6.074dBi.

This is an increase of 3.958dB - more than double!
I am trying to understand how this is possible?  How can the gain more than double?  If I understand correctly, the reflector reflects the fields from the dipole back to the opposite direction.  Thus in the best case scenario I will get complete super-position of the fields.  Therefore I should find a maximum increase of 3dB - not more!
Thanks!


texts: Would a high priority interrupt interrupt another high priority interrupt?

texts:
In the datasheet of the 18F4620 and others, section 9.0 (page 91), I read:

  The PIC18F2525/2620/4525/4620 devices have multiple interrupt sources and an interrupt priority feature that allows most interrupt sources to be assigned a high priority level or a low priority level. The high priority interrupt vector is at 0008h and the low priority interrupt vector is at 0018h. High priority interrupt events will interrupt any low priority interrupts that may be in progress.

I see that when a low priority interrupt service routine is running and a high priority interrupt occurs, the high priority ISR will be runt.

However, what happens when a high priority interrupt occurs during a high priority ISR? Or, when a low priority interrupt occurs during a low priority ISR?


texts: Using multiple white LEDs to obtain a unique CCT

texts:
I need to swipe between two white shades from one to another color temperature, let's say from 2700K to 6000K. Can it be done by simply mixing the intensities of two LEDs of respectively 2700 and 6000K? So that half of 2700 and half of 6000 will lead to a full (2700K+6000K)/2 of CCT?
I thought about this because I saw many table lamps that are somehow using this technique, or at least they seems to do this, but this does not imply that it is right.

I have also started to think about using a weighted average by adding intermediate temperatures by means of using more than 2 LED types, but if the starting point of this averaging technique is totally wrong, it doesn't make sense.

I also see some formulae from the CIE graph, in which you can find the quantity of each RGB color to obtain certain CCT and viceversa, but this is another story and I think that must not be misleaded with generating a CCT equivalent light from two types of white, which is the subject of this question.


texts: Buck Converter EMI simulation output LTSpice

texts:
I am trying to do an elementary EMI analysis on my Buck converter circuit by modelling the LISN circuit. I am using LTSpice for this. The buck converter works when I simply simulate this circuit alone:-
<img src="https://i.stack.imgur.com/HAeAd.png" alt="buck
" />
Here is the waveforms for this circuit:-

But when I try to add the LISN circuit with this I am getting wrong output voltages and thus wrong everything else. What am I doing wrong? I suspect it is something to do with the net labels but I cannot get it right.

Waveforms for this:-

EDIT 1:-
I made the suggested changes in the circuit and this is the waveforms I get:-

Is the Vpwm1 correct? I am getting a wrong switching waveform.
EDIT:2
After several comments, I have realized the problem lies with the LISN circuit, but I don't know how to set the inductors and capacitors of this module. As per Bruce Abbott's suggestion I lowered it to 5uH but still not getting the right common mode and differential mode voltages, although the output voltage is correct. This is a buck converter (12 V to 5 V @200 kHz):-

Here is the waveforms:-

How do I fix the C6 value and the LISN L & C values? [This is just for simulation on LTSpice, the real PCB is being simulated on ANSYS SIwave)


texts:
i'm very new to electronics and working thru an udemy course on an introduction to electronics.

I'm trying to get this air pump to activate in a simple DC circuit on a breadboard.

https://www.ebay.com/itm/DC-5V-6V-Micro-2-Position-3-Way-Electric-Control-Solenoid-Valve-For-Gas-Air-Pump/392190802553?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

The rating appears to be rated at 5-6v at 220mA.  Given nothing else in my circuit, I'd assume that I could just use ohms law to figure out the resistance I need for the pump to work. I'm using a 5v power supply so:

R = v / I

Or

R = 5v / 0.22

or 22.72 ohms resistance.

Is this correct?  I've tried a 20 ohm resistor but the pump won't activate.  Unfortunately, the pump I got was a cheapo from ebay so it doesn't have a downloadable manual or anything.  It just clicks once like its stalling when I power on.


texts: Do I need to duplicate the 4th "substrate" connection when building CMOS gates out of discrete transistors?

texts:
All CMOS digital integrated circuits I've ever seen connect all the nFET substrates together to GND.

In particular, the IC CMOS NAND gate has one nFET that has its substrate connected to GND, but its source pin connected to some other internal node.

If I build a NAND gate out of discrete nFET and pFET transistors for educational reasons, do I need to duplicate that substrate connection by using a 4-terminal transistor (with the substrate separately pinned out) to get it to work?
Or would that NAND still work just as well with 3-pin discrete transistors, with the substrate "incorrectly" connected to the source pin?

Is there something magic about a 4-terminal transistor that has a "source" pin not tied to its substrate, such as the ones inside an IC, that can't be duplicated by an individual discrete 3-terminal transistor?

(This question was inspired by some coments at Recomendation for a digital inverter made of discrete components ).


texts: Determining the percent overshoot, settling time, and peak time of a transfer function

texts:
I'm finding the percent overshoot, settling time, and peak time of the rotational mechanical system below. I'm worried that these variables may be undertermined.

I've found that the two equations are:
$$(2s^{2}+s)\Theta_{1}(s)-s\Theta_{2}(s)=T(s)$$
$$-s\Theta_{1}(s)+(s+1)\Theta_{2}(s)=0$$
Solving for the transfer function,
$$\frac{\Theta_{2}(s)}{T(s)}=\frac{1}{2s^{2}+2s+1}$$
Next, based on the transfer function above, I obtained both the undamped natural frequency and damping ratio to be 1. This gave me problems in solving for the %OS and the rest. The formula for %OS, after all, is \$percent overshoot=e^{-\frac{\zeta \pi }{\sqrt{1-\zeta ^{2}}}}\times 100 \$. The denominator would definitely be zero after substituting those values.
Furthermore, I think these answers support the following graph:
What do you think? Where did I go wrong?


texts: How to improve an elegant design for an LED dimmer, low-powered with LDO

texts:
I am building a sunrise alarm clock. The LED is supposed to get brighter over the course of 30 minutes, then remain fully lit for another 30 minutes, then switch off. I am using a digital pin on an Arduino Pro Mini 3,3V to feed a transistor. The Arduino board will sleep for the rest of the time, saving energy. The device is going to be powered by a single 18650 Li-ion battery, with an additional solar panel to charge the battery during the day (using a TP4056 with additional protection circuit).

This is the rest of the circuit. To protect the LED, I am using an MCP1825 LDO to regulate voltage input. I reason that with this small difference between Vin and Vout, it is efficient enough. I chose the MCP1825 for its low quiescent current and fairly low dropout voltage. (If I am lucky, I might obtain the version with shutdown mode). I might have to replace R1 which I have chosen based on an hfe of 30.

So far I have only tested this circuit without the LDO and battery with a stable 3,3V source (I don't have the other parts yet). It works.

I have these questions:

Given I am using a battery, I figured there is no input capacitor necessary for the LDO. Is that correct?
If I understand it correctly, an LDO fundamentally acts like a kind of resistor. Does this mean it does not produce any noise and can I therefore do without an output capacitor?
Would the TP4056 (and/or solar panel) introduce noise anyway, which I would have to filter out with capacitors (input AND output)?
Will the caps leak current all the time, wasting energy?
Do you see a way of forgoing voltage regulation or to save energy in any other way in this circuit?

I am trying to understand every single piece of this circuit, but I am still only a beginner. Please let me know of any major flaws in my design and also in the posting of this problem. Thank you.

(I did read the datasheet of the MCP1825 recommending usage of an input capacitor. That does not sound like a necessity though.)


texts: How can I evaluate the condition of used lithium ion batteries?

texts:
I am coming into possession of hundreds of 18650 batteries.  They are used, but initial checks indicate over 90% of them are good batteries.  I would like to discharge, charge, and measure capacity of them while logging their values.

I'm trying to find a cost-effective solution to measure as many as I can at one time, but I'm not coming up with much.  Are there any designs for what I'm wanting? Preferably open source.

The cells are 18650 Sony VT5.


texts: In HDB3, does a 1 have opposite polarity to the last 1, or to the last V?

texts:
I am trying to understand HDB3, and in particular trying to find out whether the picture below which shows the encoding of a bitstring in HDB3 is correct or not:

From what I understand, a 1 will have the opposite polarity to the last 1. So since the red 1 is -, the blue 1 should be +.

But in the picture, the blue 1 is -. Is this correct? Is it because the 0 in black is +?


texts: Understanding Block Diagram for Load Switch

texts:
I'm looking at the Vishay SiP32431 and am confused by the block diagram, copied below.

I understand the P-Channel at the top, but what are the triangles? What is the difference in level-shifting this way compared to an N-channel MOSFET or NPN BJT?


texts:
I would like to determine as accurately as possible (ideally within an error limit of +/- 0.25% or better, but I guess that's nigh impossible) the efficiency of a converter, using a simple method.

I need to have the instantaneous value of the efficiency, so calorimetric approaches won't do (Plus I don't have the equipment for that).

By 'instantaneous' I mean that since the switch operates at high frequency - in the upper tens of the kHz range - it will not falsify the results to average them over - say 10 cycles if need be, since the load is switched every few seconds or so; so the time resolution required is in the order of 100-1k measures/second.

Measuring the input and output voltages and currents would be another option, but this gives highly inaccurate results. (Partially because the instrument I use has a limit of 20 A and the current I measure is around a few 100 mA.)

What I have is: a very low power converter (P_rated = 5 W) with several load points in which to measure the efficiency at constant voltage V_out = 5 V. I have multimeters and digital scopes (with current probes). Theoretically I can measure on the PCB (I have access to the components and traces.)

Can anybody suggest a setting/method on how I could get some improvement in my measurement accuracy? Or maybe do I need to buy something else to get a better result?

EDIT: The converter is a simple buck (DC/DC) converter with a synchronous rectifier or a diode (both configurations possible). You can see the full specs here.


texts: Driving a solenoid with low voltage source

texts:
I have a 5V solenoid here, but my power source (battery) is only 3.3V . It's a pretty small solenoid, so it doesn't need huge amounts of power, but directly connecting it to the battery terminals wont move it. The battery will be a LiPo, so that shouldn't be limiting the current much.

A microcontroller will be present already in the system, so a boost converter could be implemented, but space is a bit of a premium, so if anyone has any better ideas to up the voltage it would be great to hear them. All that's needed is a pulse of high voltage and current, as the solenoid will be pressing a button (and no, the button cant be bypassed directly). The solenoid works well around 7-8V, so that would be the target.


texts: I've been using a full wheatstone bridge (4 strain gauges) to read stress on a steel bar, through a circuit mounted on an arduino breadboard. This seemed alright. I later used two strain gauges of similar (but not same) properties and similar size for a half bridge. As soon as I completed the circuit, one of the strain gauges' foil darkened but the other one was fine. Could this happen if I use the wrong resistances in the other half of the bridge?


texts:
I've been prototyping a circuit for a first year university engineering project and I've been running into some problems with one section of the circuit that has really stumped me.

Basically the flip flop and the decade counters I have are sometimes powering on with random values, not their default ones. As I understand it, the flip flop should start with Q = LOW and the decade counters should have Q0 = HIGH, but this happens only occasionally. I've tried putting a capacitor on the reset line that comes out of the right counter, connecting it to VCC, but that seems to freeze up the counter for some reason.

I'm not too experienced with ICs, so I'm not sure if I'm perhaps damaging them or trying to draw too much current out of them by using diodes. I'm also not sure if the pull-down resistors I have are important to have, or if I should have them on every chip. If anyone could explain what I'm doing wrong, or what can cause random values on power on, that would be really helpful, because I am completely stumped.

EDIT: Thank you to everyone for your help and answers to my problem. It seems that, with these specific chips at least, my assumption that they had a default power on state was incorrect, and that I need to implement a reset pulse that goes high when I first power on my circuit, by using a resistor and capacitor. Thanks again for all your support and advice.


texts: How to flip LTspice voltage controlled switch so that it opens at threshold voltage? (versus close)

texts:
I am trying to figure out how to tell the VSWITCH of the LTspice program to open after it crosses the threshold voltage and close when it is below (with hysteresis). Normal behavior is that with Vt and Vh defined, it'll close when the voltage is greater than (Vt + Vh) and open when the voltage is lower (Vt - Vh).

Unfortunately I can't use another component or edit my schematic since I am working off of a .lib file for an IC, and am attempting to edit the text commands so I can import it into MATLAB for Simscape simulations with physical components (torque, etc.). Basically, I want to ensure that my IC behavior is correct once I import it.


texts: increase the ADC resolution using oversampling

texts:
To increase the ADC resolution, oversampling technique can be used which must be followed by decimation (average) method.
Oversampling is just take several samples within time period. Unlike the normal averaging in which you might lose all the extra bits from oversampling, Decimation can remove only the lowest of low bits leaving some of the higher low bit to contribute to final result.

What is the lowest and higher low bit? And why the lowest low bit usually most noisy than the rest of the bits?

From my understanding is that the higher the extra bit can we get, a better ADC resolution can we have. In this case why can't we just use oversampling without decimation?
For example, a summation of 16 10-bit ADC result in 14-bit ADC and when we use decimation method (divide by 4) result in 12-bit resolution.

So why can't we just use oversampling and gain 14-bit resolution instead of 12-bit resolution with decimation?
Is that  to reduce the noise after the oversampling stage?


texts:
I'm working on a free-running circuit like the one here:
http://www.z80.info/z80test0.htm

The only differences are that I'm using a 4049 clock circuit with a 1 uf cap, and I've added an extra LED at Address pin #3. The resistors call for 470 ohm, but I'm using what  I have, which is a 1K. Now, I didn't pay attention the first time I inserted my Z80, and found it was upside-down, among other small but important wiring details, which have been fixed. However, the LEDs are not glowing at all upon power up and a few resets. And I've checked for power problems, because I have a power-indicating LED mounted for that purpose on the breadboard, to which it glows proudly. So is my Z80 fried, or could it be something else?


texts: Cheapest Raspberrypi (or MCU) power supply with both toggle *and* momentary switches?

texts:
TL;DR/main question:

How would one modify this PCB to add an extra toggle switch that does not just abruptly cut the power to a load and that still allows enough time for a clean shutdown of, i.e, a Raspberry Pi?

That is, two different buttons in the above PCB (one momentary, the other latched). I want it to be all passives, without involving MCUs.

Long version, see comments below too:

Together with a friend we tried to implement the following schematic we found online after a quick search for "simple raspberry pi on/off latch power supply":

Then we simulated the above schematic through our circuits.io breadboard:

Despite the simulator lagging a bit when pressing the momentary switch, it seems to work fine. This is similar to the simpler circuit that Dave Jones from EEVblog showcases in his "Soft Latching Power Switch" video, which we also implemented in circuits.io for comparison:

To be clear on what I'm asking, I would like to add a toggle (physically latched switch) to the circuits shown above in order to have both types of switches in one circuit.

A single push button for soft on/off behavior.
A toggle, physically latched, switch that respects shutdown times as in requirement "1" above.

All of it implemented in an analogical manner, without involving MCU's as featured recently in HackaDay and without 3 switches, which I think is unnecessary flexibility/complexity:

https://www.pi-supply.com/product/pi-supply-raspberry-pi-power-switch/


texts: Fast switching constant current buck output capacitor

texts:
I'm using a 1A constant current buck LED driver (the TPS92518 from TI), in order to implement "shunt FET dimming", where the load (1A LEDs) is short-circuited using a MOSFET in order shut-off a LED string very fast (but without ripple, hence the need for the output capacitor).
However, since an output capacitor will be problematic when shorting the LED string (because it will discharge through the Q2 switch when it's closed, and when Q2 will open it will sink current for awhile before any current goes to the LEDs again), I want to add a second switch, Q1, in order to disconnect the capacitor when the LEDs are shorted (Q1 OFF when Q2 is ON and vice-versa).

Ideally, Q2 needs to close a few nanoseconds after Q1 opens so that the capacitor doesn't begin to discharge through Q2.
However, I'm not sure what kind of switching topology to use. Q2 seems relatively easy, only a NMOS would suffice. However, for Q1 I'm lost. If I only use an NMOS for Q1 I won't be able to switch it because the body diode will conduct afaik.
I was wondering if anybody has a good suggestion for a fast circuit to implement Q1 (and make Q2 slower a bit). Basically, Q1 needs to be a few nanoseconds faster than Q2. Q2 needs to be able to switch for approx. 1us at worse.
There is in my circuit a voltage that is much higher than the voltage at the buck output, so this could be used to switch Q1, but since Q1 et Q2 must be triggered by an FPGA, there needs to be some kind of transistor arrangement. However I'm not too sure what to do to optimize the speed. Perhaps somebody has some clever transistor tricks?
Thanks!
EDIT: For those asking why shunt LED driving would even be a thing, see answer here.


texts: Why won't a 1.5V (or 1.2V) battery give an electric shock?

texts: Why won't a standard 1.5V (or 1.2V) battery give an electric shock when touching both ends (positive and negative) in the same time? Even if the battery is capable to provide a short-circuit current of 1-2 amps. It is only because of the human body resistance?


texts: High pitch sound coming from Low-Dropout Linear Regulator (1117 3.3V) setup

texts:
I am using the below schematic to drop voltage from 5V to 3.3V (1117 3.3V - http://www.farnell.com/datasheets/2100276.pdf?_ga=2.141255921.210515873.1532314816-790306462.1508240417) for a Wifi Micro-controller and after few weeks of usage it started producing some high pitch sound.

Upon evaluation I noticed that after few minutes of powering the circuit, the output voltage increases from 3.3V to 4.8V and keeps varying drastically. I have checked all component connections (dry solder, short circuit etc) and everything seems to be fine. The power supply is rated 5V 600mA and the MCU takes 300 ~ 350 mA max during peak operations.

I finally had to change the LDO 1117 and its output capacitor (changed C4, 22uF to 100uF) though I am not very sure if its the LDO or the capacitor which failed (during the LDO replacement, the output capacitor got spoiled and hence I couldn't test them separately). Now the noise is absent and output voltage seems to be stable (3 days continuous operation).

As shown in the schematic I am using multiple MLCC output capacitors (as required by MCU). Would this have caused any issue?

simulate this circuit – Schematic created using CircuitLab


texts:
I am trying to get this difference amplifier working, but it doesn't seem to be outputting what I want it to output.

$$
V_1 = V_{in}\qquad
V_2 = -0.5\mathrm{V}\qquad
R_f=R_i, \quad A=1
$$

I want the output to always be \$V_{in}+0.5\mathrm{V}\$. So,
$$
V_o = \dfrac{R_f}{R_i}\cdot (V_{in}-(-0.5))
$$

What to do?


texts: Impedance matching of USB device WITHOUT cable

texts:
If I understood correctly, when designing PCB with USB, the 90-ohm differential pair of D+/D- trace if for matching the USB cable differential impedance. Otherwise, there will be a signal reflection where the impedance is not continuous.
For those USB devices WITHOUT cable, for example,

USB storage
Wi-Fi module with USB interface, like this

Is it still necessary to trace D+/D- as 90-ohm differential pair?


texts: Impedance matching components with Ethernet

texts:
I’m designing a small switching circuit for 1000Base-T Ethernet and have a concern regarding impedance. The board design consists of 3 shielded Ethernet jacks and 4 DPDT relays (here) made for high frequency. 1 Ethernet jack will be the input and the relays will alternate between the 2 outputs.

I’m having the board laid out with 100 ohms of impedance but the relays I’ve selected have an impedance of 50 Ohms. After contacting the manufacturer, I was told that I should match the impedance between the board and relays.

If matching impedance is critical, what options do I have? One option I’ve found is using pulse transformers with a 1:1.414 turn ratio before the relay to drop to 50 Ohms and after the relay bump back to 100 Ohms. Alternatively, I found (here) that the impedance of a trace in RF circuits can be changed by simply changing the width of the trace with an abrupt step.  Is it really that simple and can I do the same without any issue?

The traces for each differential pair will be striplines and I believe the entire length of each trace will be less than 2 inches from jack to jack if it makes a difference.


texts: Power MOSFET versus regular MOSFET Silicon Layers

texts:
I am having some difficulties differentiating between a power MOSFET process and a regular MOSFET process.  Here is a regular MOSFET silicon layer stackup:

The n+ doped region for the source and drain connection is exactly as I learnt it in classes back in the days with the oxide layer between the gate connection and the p-type silicon as a substrate.  No issues here.  What I am confused about is the Power MOSFET process and why you would use this process to get lower RDS(on), higher voltage, higher current, and so on.  Here is a picture of the Power MOSFET process:

As you can see, the drain is connected to the substrate of the die.  The source is the top side of the die and the gate takes a very small area of the top side.  There is a N- dope region between the drain and source that is confusing me.  Also, the process seems to be working in a vertical fashion instead of horizontal.  So here are my questions:

1. Why would you want to use this process for a Power MOSFET?
 2. What are the advantages in terms of electrical characteristics?


texts:
I'm trying to build a small radio amplifier which will deliver around 15V at 1A at 250kHz from a 0.2V input of the same frequency. I have searched for and tried as many online circuits as I can which will fit on the breadboard (just no absolutely massive ones). I tried a push/pull circuit as shown:

but the simulation applet on this site http://www.falstad.com/circuit/ shows that it would never get enough current to the output.

Could someone please point me to a circuit which can deliver what I specified above?

I have AC/DC adapters which can supply 12V at 2A and the breadboard is roughly 11cm x 16cm.


texts: Transmission line simulation in LTSpice? How to model a CMOS input?

texts:
I am trying to simulate the effect of a PCB trace on a clock signal with LTSpice, see the following pictures:

In my quick and dirty setup, the clock receiver is the resistor Rin.
I the real world, it is a DAC with a CMOS input. Is there an easy way to model such an input in LTSpice? Is the resistor accurate enough?


texts: Is it acceptable to have A & B wire at same voltage in RS485

texts:
I'm trying to implement DMX with a Raspberry Pi after reading this page: https://www.element14.com/community/groups/open-source-hardware/blog/2017/08/24/dmx-explained-dmx512-and-rs-485-protocol-detail-for-lighting-applications

I'm using the "RS485 Pi" board.

I've plugged my oscilloscope probes on the UART TX pin of the Pi and get signal 1 (yellow), which lets me verify that timings are good. Next step is to convert to RS485, done by the board. Signal 2 & 3 are the "A & B" output. You can't see the "2" marker, it's under the "3". When UART outputs a 0, I get a nice difference between 2 & 3 (visible in red, which is 3 - 2). But when outputing a 1, I get 2 & 3 to be roughly at the same voltage, so no difference. That does not seem correct to me, I've probed a commercial DMX output and basically, a 1 is like a 0 with A&B signal swapped. Does the signal (2 & 3) below, especially when 1 is high seem correct to you?