texts: Can half-bridge current limitation in BLDC Motor controller cause MOSFET destruction?

texts:
I’m developing a motor controller based on a dsPIC33EP64MC504 from Microchip. The motor is a brushless permanent magnet synchronous motor of about 500W on 50V. The controller is based on an SVM algorithm from Microchip application notes. The bridge uses 6 MOSFETs SiR882ADP (100V) from Vishay. No speed nor current regulation is achieved meaning the motor is open loop controlled.

We‘ve first implemented a simple BLDC controller based on Hall effect sensors and it worked great.
We’ve then decided to improve the control using a 1deg resolution encoder to achieve a sinusoidal control (for a later Vector Control and current control). Here we are facing some problems of exploding/burning/blowing MOSFETs at middle range power. I will not explain all the design choices and issues : we are working on it but I would like to investigate one soft/hard choice: the hardware current limitation strategy we've changed between the 2 designs.

The current limitation is an hardware dsPIC embedded function which overrides the PWM commands normally driven by the SVM based on an analog signal from current sensor.

Here are the main differences between the 2 approaches:

The first strategy (version 1): the bus current value controls the 3 PWMs (all MOSFETs are open as soon as the current limit is activated and overrides the PWM signals out from the SVM).
The second one (version 2):  the low side current of each half bridge controls each PWM independently: the corresponding half bridge is open in case of a current limit.

I understand that in the first strategy, the body diodes of the MOSFETs turn the driving bridge into a classical 6 diode rectifier: current is recharging our battery is that right? Anyway, this strategy seems really safe!

But what happen in the second case? Could the opening of only one half-bridge be the responsible for voltage overshoot and MOSFET destructions due to current loop behaving in a different way than in the first version?
For example what happen in the case where the current limitation on PWM2 (the blue one) opens the corresponding half-bridge in the following condition ?

Thank you for your time and the answer you will give me (or not).

Regards,
MG.


texts: How to determine a Signal Generator's Marker (Event) output delay?

texts:
I am using an Agilent N5182B Signal Generator for modulating a 2-FSK waveform on a 160MHz RF carrier. For that, I am using a baseband waveform (I/Q mode), generated by a Matlab FSK modulator script.

The device allows for up to 4 markers to be associated with each sample. Those are essentially single bit values that can be output from dedicated digital output at the back panel of the device, and can be used to sync external devices/processes. According to the manual, the markers are in perfect sync to the associated samples in baseband. However, additional components in the RF path add delay, so the actual outputs are skewed.

How can I measure the time difference between the RF and EVENT outputs?

Note that the User Guide provides the information of how to compensate for a present delay, but there is no suggested procedure for measuring the actual delay.

Part of old description, removed for clarity:

I am using the 1st marker to signal when a preamble pattern is being transmitted in my repeating data packet waveform. The marker is set to "1" during the preamble and to "0" during the payload transmission. On my receiver, I am using the marker, as input through a GPIO pin, to sync the demodulator packet handler. Thus, I am waiting for a rising edge of the pin, then for a falling edge, and then decode the incoming data bits.

The problem is that the decoded bit stream is shifted (in time) by a random, small amount of bits relative to the actual transmitted stream. This means that the falling edge event, originating from the GPIO peripheral, is not in sync with the FSK demodulator and/or SERDES device events, that are originating from the RF front-end hardware.

I am trying to determine where this delay difference comes from. For starters, I want to verify that the N5182B's RF and Marker outputs are in perfect, or at least constant-shift, sync. How can I verify that, or measure the marker output's delay?


texts:
Can someone explain the math behind the following relationships between the equalities in a capacitor's reactance?

$$X_C = \frac{1}{2\pi f C} = \frac{-j}{\omega C} = \frac{1}{j \omega C}$$

For instance the second member, $$\frac{1}{2\pi f C}$$ It has no complex component, how can be equal to the others when
$$2\pi f = \omega$$
The complex component is missing right?

And the two last ones, they are alike, but the complex component is tossed around a bit. I don't understand what is happening there either.

The individual expressions/members is fine, but according to my textbook they are supposed to be equal but, I don't see how.
$$$$
EDIT: The two last equalities are from my textbook, the second one is from the Electronic Tutorials webpage. All under the X_C symbol.
Link: http://www.electronics-tutorials.ws/filter/filter_1.html

Alright. So what I've derived from the comments, is that different definitions of $$X_{LC}\ \ and\ \ Z_{LC}$$ are used in different places. I was under the impression that X, in a mandatory way, always had the complex unit inside it and was always a pure imaginary quantity. Not true though. The examples in my textbook now makes more sense now because it would seem it uses Z as the imaginary part and X as the mixed im. and real part.


texts: Why do we do right shifting in Booths algorithm?

texts:
I know the working of booths algorithm.

Suppose we have multiplicand M = 01011

and multiplier Q = 01110

We can write Q as (2^4 - 2^1).

So multiplication reduces to 2^4(M) + 2(-M)

Now booths algorithm rules are:-

If Q = 0 and Q(-1)=0 then do arithmetic right shift.

If Q = 1 and Q(-1)=0 then do A-M and arithmetic right shift.

If Q = 0 and Q(-1)=1 then do A+M and arithmetic right shift.

If Q = 1 and Q(-1)=1 then do arithmetic right shift.

Here A is initialized to 00000 and Q(-1) is initialized to 0.

If we see the algorithm then in every step we do right shifting. But as per the calculation shown above which is 2^4(M) + 2(-M) we multiply by 16 and 2 which requires left shift.

So how is booths algorithm working with right shift ?


texts: Li-ion power supply with a charger, a booster, and a pMOS high side switch

texts:
I am designing a circuit board for a small mobile robot and there is a problem with the power supply. The circuit is powered by a 1-cell Li-ion battery (VBAT) and includes a charger (MCP73831/2), a pMOS high side switch (SI2369DS), a booster (TPS61232) and a simple dual Schottky voltage selector because it can also be powered through USB (5VUSB). The relevant part of the schematics with all component part numbers is below.

The problem The pMOS high side switch does not close properly. When open, everything works as expected (green voltages). When closed (red voltages), the drain voltage is approx. 0.3V and the whole circuit is draining about 80mA. In all cases, the charger is off (jumper JP1 not present).

Things that I tried so far, without success:

Changed the pMOS to SI2399DS which has a lower Vgs, same behaviour.
Held a 330R resistor in parallel to the R14 pull-up, same behaviour.
Tried with both, a battery, and lab power supply, same behaviour.
Tried on 5 boards, behaviour is the same on all of them, so probably not a soldering problem.
Measured VON on oscilloscope and it is steady.
The pMOS footprint was checked and it is fine.

What could be the source of the problem?


texts: I have a battery pack consisting of 4 10 amp-hour 12 volt batteries wired in parallel. We recently bought a 2000 Watt rated HammerDown power inverter to run a 500 watt window air conditioner. The air conditioner is supposed to draw 5.6 amps. But when I connect the AC to the inverter the air conditioner always shuts off as soon as the compressor starts running. I measured the current going to the inverter and as soon as the compressor started it shot up from around .3 Amps a whopping 26 Amps before turning off! Now I understand there is a surge of current needed when starting an appliance but I didn't think it would be this much. I also noted that the voltage dropped a little too (from 13.5 to 12.9 v). Given all that though, I don't understand why the inverter failed to supply the power to the AC. With 40 amp hours shouldn't it be able to provide 40 amps of current at any moment (more than needed for surge)? Another interesting thing to note is that sometimes the inverter would read OVERLOAD after one of these tests.


texts: Why is the autorouter not reaching 100%?

texts: When I use the autorouter in eagle for creating simple traces (the more difficult ones I'm doing on my own) it stops at 98.2%, but no trace is left unrouted. Why don't I get 100%? How do I find out the problematic areas?


texts: Best way to detect horizontal vibration/shaking!

texts:
I need to detect shaking (not just vibration or small movements but significant horizontal rocking movement)! (its a long story)

I have an Arduino already in place, controlling some other stuff. I've tried a couple of simple methods with gyroscopes and pendulum like shake sensors and like, but they are either too sensitive or to hard to calibrate.

Mostly I need to detect horizontal plane movements.

Any suggestions? Anyone had done anything like this?


texts: measuring AC rms voltage of TMP36 using TDS Tektronix 2002C digital oscilloscope

texts: When measuring AC rms volt of TMP36 temperature sensor by TDS Tektronix 2002C digital oscilloscope, I got value of 5.97mV.What's the absolute error in my measurement (absolute error from oscilloscope )? I went through the manual but could not figure it out. It would be a great help.]


texts: For SCPI programming in python, Is it necessary to install a NI-VISA back-end if you are trying to iterface with a non-National Instruments device?

texts:
[background/context] hello, I am trying to learn to automate measurement devices using SCPI commands, but instead of using Labview I decided to go with python. I have played around with SCPI commands in Physik Instrumente (PI)-specific software in the past and It seems much more user-friendly to me than trying to work with complex flowcharts (plus I don't want my programs to depend on third-party licenses).

it seems from a rudimentary search that a common method is using PyVisa, in the second page of their instructions ("configuring the backend") they mention installing an NI-VISA library, which I assume corresponds to National Instruments (TM).

[Question] It mentions that "If no backend is specified, Pyvisa uses the NI backend". Will this even work for instruments that are not NI products? (e.g. I need to synchronize Agilent hardware to synchronize with various other instruments, including the PI hardware ).


texts: Using low pass filter for a differential ended receiver system?

texts:
I want to use anti-aliasing filters in different scenarios. Below is the topology for how to use a passive LP filter in the case of a single ended transducer and single ended data acquisition:

How should the RC the connection be:

1-) If the source is diff ended and the data acq. is also diff ended?

2-) If the source is single ended and the data acq. is diff ended?

Could you illustrate these two cases by drawing like mine above.

Edit regarding an answer:


texts: Massive Parallel Lithium Lead Wire Connection Point

texts:
I was wondering where the connection point should be on a "massive" parallel block of lithium batteries. Let's say there is a pack of 100 LiFePo4 18650 batteries all spot welded together with nickel tabs (1S100P). Nominal voltage is 3.2V and total capacity of 100AH (each cell is 1000mAh).

Where would the best place for the positive and negative wires attach to the pack? Is 4 gauge wire sufficient for the "short" run to the connector termination (assuming a 1C pull on the pack)?

My thought is if you were to connect the positive and negative leads to the single cell closest to the exit that it would receive the most abuse with the load becoming less and less until the furthest cell is reached, but this doesn't really make sense as they are all a single cell now that they are welded together.

Thanks!


texts:
While reading the guide of a chip I'm about to take in use (Intel Edison), I noticed the SoC is specifically not supporting multi-master.

  The SoC is always I2C master, it does not support multimaster mode.

However, as far as I know I2C is designed as a multi-master bus. Does this SoC violate the specification or is my understanding of I2C incomplete?

Why is it out-of-the-question for this SoC to be multi-master anyway?


texts:
I try to design a Chebyshev bandpass filter for 6 GHz as a coaxial cavity filter. I know that the filter can be designed with the aid of the coupling coefficients between the resonators and the loaded Q of the first and last resonator, and all resonators need to be tuned to the centre frequency of the filter.

First, I simulated the eigenfrequency of a single cavity, seen below:

I adjusted the length of the centre rod such that the cavity has its first eigenfrequency exactly at the centre frequency of the filter, 6 GHz.

Afterwards I tried to derive the coupling coefficients. For this, I placed two idntical cavities next to each other, as seen below:

I then do again an eigenfrequency simulation to find the even and odd mode eigenfrequency. Then I calculate the coupling coefficient as follows:
$$ k = \frac{ f_2^2 - f_1^2 }{f_2^2 + f_1^2} $$
where I use the higher of the two eigenfrequencies for f2 and the lower one for f1, of course. To vary the coupling coefficient, I change the width of the iris between the two cavities.

I always thought this is a possible approach for finding the coupling coefficients from simulations, but it's not accurate because the resonators get heavily detuned due to the iris. So it would be necessary to re-tune them as the iris width is changed, but I don't know the relation between the iris width and the resonator detuning.

I am also unsure about how I can actually determine the loaded Q of the resonators. If I tap the centre rod of a resonator with the inner conductor of a coaxial cable, the resonator gets detuned again, of course - then I should adjust the centre rod length, but this will affect loaded Q again.

At the end I try to design a filter as shown below:

So my questions are:
a) is my method of calculating the coupling coefficients accurate enough, or are there better methods?
b) how could I determine the loaded Q?
c) how I deal in the simulation with the fact that the resonators are detuned due to coupling or tapping?


texts: I'm wondering if there's a book that discusses resistors, capacitors, inductors, transistors, transformers, impedance, op amps, power supplies, and the general circuitry of a microphone pre amp. Thank you!


texts: Use an LA6500 to increase the current output of an MCP4725

texts:
I am trying to use an LA6500 to increase the current output from an MCP4725 that I am controlling with an Arduino UNO.  The LA6500 works well for voltages of 1 to 4 volts but but when I give it 5 volts, the output of the LA6500 is 4.63V.
What should I do to get a 5V output from the LA6500?


texts: Programming MSP430G2553 with Raspberry Pi 2

texts:
So, i want to program a msp430g2553 microcontroller with raspberry pi 2.
Since i don't want to use any IDE i would like to do it with clean C and terminal, without any external libraries like wiringPi etc. , just the microcontrollers one.

My questions are:

Can i do this with common interfaces like I2C or SPI?
Or should i use the JTAG interface to do this?

This is the first microcontroller that i am trying to program.I've seen that you can program an ATtiny85 with raspberry over SPI. Does all the microcontrollers have this functionalities or it is device specific.


texts:
Given current gain (hfe = 100), internal resistance (hie = 2000), reverse voltage gain and output resistance (hre = hoe = 0), compute input impedance for the following circuit.

The problem is that it is not a classic scheme and I don't know how to compute the input impedance (i.e. can apply formulas directly). My guess is that there will be some capacitor shortage in the circuit  but I don't know how and where. I'm looking for ways to transform this circuit into a simpler one in order to apply the formulas.


texts:
Is there any chance to read 2000A using STM32? I searched the Internet for low-value shunt resistor but nothing found. maybe some kind of current transformer could do the job!!
any help will be usefull.


texts: How is the gain controlled in a class B/AB amplifier?

texts:
I have tried simulating a simple class B amplifier, and I can't seem to get any gain (in fact, due to the crossover distortion, the gain is less than 1)

For example, in this diagram the resistors are biasing the input signal, but I see no control over the gain. Is a class B amplifier only for current amplification?


texts: What references cover DDR3 layout considerations?

texts:
I'm looking for succinct yet correct guidelines for evaluating a DDR3 memory PCB layout.  I know that trace length matching, via style and back-drilling, and signal grouping all matter.  I know that each group of 8 data bits plus two associated control lines need to be length matched.

I'm seeking a good summary of all the issues, or people's experience, especially if it covers both multi-chip modules and single point to point (one CPU and one memory chip) layout.  How critical is all this stuff for small single board CPU's?

I have read DDR1 Layout Considerations - DOs and DONTs and Compensating for unbalanced via count in DDR3 routing


texts:
I found it in my parts bin.
I can't find anything about it when I Google on the number on the back.

Not visible on the picture but behind the net it looks like a speaker.

Am my assumption that this is a speaker correct?


texts: Choosing series resistors for zener diodes

texts:
I'm planning to clamp an AC 12V volt signal with two 8.2V zeners (1N5344B).

After the zener couple the signal will be fed to an opAmp as in the figure below.

Do I need a resistor (Rz in the figure) before or after these zeners? What value would be suitable?


texts: If I were to discharge, recharge, discharge, recharge,..., an electronic equipment, would there be any negative effects?

texts:
Would there be any damage to a laptop or another electronic equipment if I use the internal battery supply till it has been completely depleted, then I recharge it to maximum, then wait for it to become completely depleted again, and then repeat.

If so, what would be some of the long term effects?


texts:
Unloaded power transformers consumes very little real power. Similarly, will an empty microwave oven consumes very little power too compared if it is loaded full with food?

If this is true, can we deduce the microwave oven is more efficient in cooking food compared to the conventional oven with resistive heater?


texts: Dimming all layers other than the active in Altium

texts:
I know single layer mode (shift + s) but it hides too much.
I really like highlight mode (right click on layer tab -> highlight, or ctrl+click on layer tab) where the all other layers are just slightly dimmed.
But when you switch layers it stays only on the layer you activated it. Also with shift+c it goes away and you need to activate it again.
Is there any option where all layers except the active one are displayed slightly dimmed (like in highlight mode)?


texts: Led reactive to bass preout from headunit

texts:
I am stuck with the following problem. And please keep in mind that my understanding of electronics is not the best, I am simply asking for advice on building my project.

I have created a circuit where the leds will flash accordingly to music from a headphone input. Everyone has seen these, using tip31c transistors. However I am planning to put this to use in my car. I have decided that instead of using headphones (because i can only get it to work on aux on this current circuit, not fm, usb, bluetooth ect,) I will use the sub pre out on the back of the headunit as the input in place of the headphones. (See circuit in link)

Now here it is, the leds will only flash when the volume is turned up very loud. The tip31 transistor is obviosly not receiving enough voltage to activate the leds. To my understanding I will need to up the voltage recieved by the transistor base pin. According to the headunit specs the pre outs are max 5v.

[Edit] I would like to know how I can boost the signal from the pre out to the tip31. The signal would be very very small, half of a volt probably (on low volumes). I am looking at a way to increase this so my leds are driven on low volumes. Currently (no pun intended) the output only reaches a level that can activate the leds once it is, probably, at about 2 - 3 volts. Can anyone provide me with a solution to increading the recieved signal to base pin of the transistor.

This is essentially what I've done:

This is my headunit. Google it to find an image of the rear. I want to use one of the black preouts instead of an aux. http://www.sony.com.au/product/wx-gt90bt


texts:
Recently reading about Linux and its folder /lib/firmware, I read that firmware is not needed to "live" on the device, that some network devices dont have any ROM to store a firmware. How is this possible if its definition is that is software that is present on the device and it software that runs on the device? Or maybe its called firmware buts its some kind of driver?
I understand that software drivers are the ones which know the "api language" of the device and what data or instructions send to this to do something but its needed a firmware on the device because its a software "listening" to these instructions from a physical port on the device and executing some code after these instructions are received. I dont know if I got it wrong
Thanks


texts:
I have removed the battery from an old portable dust cleaner. The acid has oozed out, and that is the reason the device does not work anymore. I want to replace the batteries, but their voltage is not indicated.

The only hint I have is the charger output. Is there a univocal way to determine which kind of batteries is meant to recharge (like a phone's 5V charger feeds 3.7V Li-ion batteries)? In that case, the charger is 3.9V and 0.5 VA (better, W).

Edit: Added photo. It was a pack of 2 batteries like the one showing in the picture, with my hand holding it for size comparison. Size is similar to a C battery, but not equal (approximately 4.5 cm height x 2.3 cm diameter - 1.77"x0.91")


texts: How does adding a capacitor change the frequency response of this inductive LPF?

texts:
I know that a simple circuit like this in an ideal case will have a frequency response of a single pole LPF, where the cutoff frequency is given by:

cutoffFreq = 1/(twoPi*L*2R)

This is reviewed here.

But what would the frequency response look like if you add a capacitor in parallel to the inductor like this:

Would it still be a low pass filter? What would it look like? How would it change based on the capacitance?

I tried running this on circuitlab for simulation but it is giving me an error and I don't know why:

It gives info on this error here but I don't understand it: https://www.circuitlab.com/docs/faq/#q_bode_opsolve_failed

No matter what I do it won't simulate with the inductor in there. But if I replace it with a capacitor it will simulate. Is there something else I'm supposed to be doing?

If it's not hard, what would be the transfer function of this circuit? Thanks.


texts: What are the implications on vibration measurement from decreasing Pulse-Width Modulation (PWM) frequency of a 9V electric motor?

texts:
What is the effect of a PWM (or other duty-cycle variation method) frequency change on the vibration of an electrical motor (9V, DC)?  I plan to measure the (surface-) vibration with acceleration sensors.

Thanks in advance.


texts: How can I protect LDO NCP1117 from overheating due to short at output?

texts:
I use NCP1117 to supply voltage to various chips, such as the STM32 and buffer driver, voltage sensor, digital insulator ect. But if any of these chips fail, the LDO will heat up. What should I do?

This Circuit diagram is taken from the datasheet.
Can I use this circuit? What values are R1 and R2? 100R?


texts: Adding voids underneath analog signal for improved impedance matching

texts:
Using a snapshot of an eval board design below as an example, voids are added to the ground plane on layer 2 (green) right underneath the analog signal path on layer 1 (yellow). This causes the analog traces to reference the ground plane on layer 3 instead. I understand that this increases trace width, hence improved impedance matching and decreased signal loss at the trace-to-pad junctions.

What is the best way to determine the minimum width of the voids that guarantees that the signals do not reference layer 2? I assume this is based on the trace widths and the layer separations.


texts: I'm trying to design an ac to dc conveter (230V ac to 12V dc). Haven't decided on the current yet. It's likely to be around 2A. I want the circuit to be compact and hence I think it is best to follow what's found in ordinary wall adapters. I haven't noticed wall adapter circuits much, but as far as I can remember, it is not an smps. I don't have a broken one lying around to take a look. Can someone help me with it?


texts: 3s 25p li-ion battery pack charging parameters

texts: I'm having a LG HG2 18650 3s 25p battery pack.To charge the pack i planned to use EPEVER mppt charger controller. But for that  i have to set the Float charging voltage,boost charging voltage and equalization charging voltage.Can anyone suggest the parameter values?


texts: Can you fully charge a super capacitor at a lower voltage (than its max rating)

texts:
Is it possible to fully charge a super capacitor at voltage lower than its listed max rating?

Example: could I charge a 5,5V or 6V super capacitor using only 5V.
In case it matters, two example super capacitors that have a higher than 5V maximum rating.

VEC6R0 255QG; 6V, 2.5F
http://www.farnell.com/datasheets/2149089.pdf
DDL105S05F1JRR; 5.5V, 1F
http://www.farnell.com/datasheets/2368882.pdf

Gut feeling is that it's not, but I have not been able to verify this as of yet. It's probably too obvious and thus not stated..


texts: How many shields can I plug into Arduino?

texts:
I'm going to buy an Arduino Uno/Duemilanove and I would like to add a couple of shields like an LCD and a WIFI shiled.

How do I know if I can plug them both to Arduino?


texts: Why is overflow error in two's complement addition represented by XOR-ing the last two carries?

texts:
The first chapter of my textbook on microcontroller theory has the following paragraph.

Here is one of the examples provided.

The book shows three such examples, but provides no explanation for why this is true in general. Can anyone provide an explanation?


texts: Referencing DC Operating Points When Plotting Expressions in LTspice

texts:
I'm new to SPICE, and I have a question about SPICE commands and references.  I've been using LTspice to design a multistage amplifier, and I am interested in plotting out the outputs of each stage, normalized around zero, without having to manually construct test points (with capacitors to drop the DC component).  When I run a transient analysis, I can plot the output nodes as below:

The eagle-eyed among you may notice a bit of distortion in the waveforms from the original sine wave, and that is what I'm attempting to isolate.  As a diagnostic tool, I'd like to be able to plot each node voltage, minus the calculated DC operating point for each respective node.  Ideally, I'd like to see something like this:

Putting each wave on top of the other like this helps me see the progression of distortion through each stage.
What I would like to find is a built-in function in SPICE or LTspice that allows me reference the previously-calculated DC operating point of a node, so that I can just plot a function something like V(n007)-DC(n007), and have it plot about zero instead of about the operating point.  Is there a function in SPICE to reference the DC operating point of a node?  If not, would it be possible to write one?  As a bonus, is it possible to normalize the waveforms to compare them at similar scales, despite their different amplitudes?


texts: Is it possible to make some selected via's exposed in KiCad? Although the option "Do not tent vias" is helpful but it is a global setting. Is there any option so that some vias will be left unmasked?


texts: How does Digi-Key make Digi-Reels (or Mouser make Mouser-Reels, or whatever)? That is to say, given parts in Cut-Tape form, what tools and additional materials are needed to add a leader to support spooling onto a tape feeder? The picture below shows some kind of foil that bonds the leader to the cut tape in such a way as to keep the pitch consistent through the join. Is it plausible / cost-effective to do this on my own instead of paying a reeling fee to distributors?


texts:
What have I done wrong in determining the transfer function for this RCL circuit?

(1) $$\dfrac{Eo(s)}{Ei(s)}=\dfrac{s^2R_2CL+sL}{s^2CL(R_1+R_2)+s(R_1R_2C+L)+R_1} $$
Regardless, of how many times that I try, I get the same result. However, my TF response doesn't match the circuit response, as can be seen.
Using complex impedance method
Defining $$z_1 = R1 $$ $$z_s=\dfrac{1}{sC} + R_2 = \dfrac{1+sR_2C}{sC} $$
$$z_p = \dfrac{z_sz_L}{z_s+z_L}=\dfrac{\dfrac{1+sR_2C}{sC}sL}{\dfrac{1+sR_2C}{sC}+sL} =\dfrac{\dfrac{s^2R_2CL+sL}{sC}}{\dfrac{1+sR_2C}{sC}+sL}$$
Multiplying numerator and deniminator through by sC
$$z_p=z_2=\dfrac{s^2R_2CL+sL}{s^2CL+sR_2C+1} $$
Therefore, we have that
$$\dfrac{Eo(s)}{Ei(s)}=\dfrac{z_2}{z_1+z_2}= \dfrac{\dfrac{s^2R_2CL+sL}{s^2CL+sR2C+1}}{{R1}+\dfrac{s^2R_2CL+sL}{s^2CL+sR2C+1}}$$
Simplifying
$$\dfrac{Eo(s)}{Ei(s)}=\dfrac{s^2R_2CL+sL}{{R_1(s^2CL+sR_2C+1)}+{s^2R_2CL+sL}}$$
$$\dfrac{Eo(s)}{Ei(s)}=\dfrac{s^2R_2CL+sL}{s^2CL(R_1+R_2)+s(R_1R_2C+L)+R1}$$


texts: How to combining EMI capacitor and ferrite bead change filter characteristics

texts:
Suppose I want to suppress the noise at around 100Mhz on a signal line. I can do that using a EMI filter capacitor or a ferrite bead. The frequency characteristics for both show suppression of noise at around 100 Mhz:

Left fig.: EMI capacitor
Right fig.: Ferrite bead

If I want to combine these two to have more attenuation, how does putting them in series change the frequency characteristics? Can I expect higher suppression of 100 MHz noise?

Should ferrite bead follow capacitor or other way round or doesn't matter?


texts: Mixing Lead acid and Lithium ion in series, after charging them separately

texts:
Can I connect a Lithium ion battery battery pack with a Lead acid battery bank; in series. I will charge both separately cells strings separately (not to mix the chemistries) before putting them in series and will use it just once to start a vehicle and drive it back to garage.

Each Lithium ion battery(LFP) cell is 3.2 V and 105Ah in capacity
--> 3 in parallel is 315Ah and
-->30 in series will 96V for the Lithium ion pack.
And Lead Acid bank is 12V and 100Ah.

Is there any fundamental disadvantage to this solution?


texts:
My circuit with an LM324 is malfunctioning.

I want to build a very simple charge full indicator as well as a low battery indicator (sensor) using an LM324.

But it is not working.

Below is the diagram, and as well some write-up.

Please help me figure out what could be wrong with the circuit.  Everything seems right to me.

Is it that I have not powered the LM properly, or is it that some specific voltage is needed at the input of the LM324?

I have tried using about 3 LM324 ICs, but the results are all the same.


texts: What does 'resist' mean in this IC datasheet?

texts:
In the lower right corner on the first page of this datasheet (https://support.epson.biz/td/api/doc_check.php?dl=brief_SG-210STF_en.pdf), the recommended footprint layout shows a hatch pattern with an arrow saying 'resist'.

What does this mean? Is it trying to say 'use a solder mask'?

Thanks,


texts: PIC:how can we get 1 ms interrupt using 16bit timer?

texts:
I am using PIC24FJ256GB106 controller.I am setting configuration bit for internal frequency to FNOSC_FRCPLL.

I have confusion to this configuration bits that Am i getting 8MHZ or 16MHZ or 32MHZ ?

if I want timer(16bit) interrupt at every 1 ms then which frequency i have to use ? FOSC or FCY?

When i am setting FNOSC_FRCPLL configuration bit then what is FOSC and FCY?


texts: What are the d and q axes for induction machine?

texts: What are the d and q axes for an induction machine (physical meaning)? I understand them for a synchronous machine but how are they defined for an IM?


texts: How to power an arduino controlled string of RGB LED's from separate power source

texts:
I'm new to electronics and working on a hobby project that will have an arduino board running 5 separate strings of RGB LED's. I'll be using a PWM chip (TLC 5940) so I can independently control tho color's of each of the 5 strings of lights. My question is how do I power the LED's. I know they can't be powered from the arduino pins and I highly suspect that they can't be powered from the PWM chip.

I think what I'll have to do is run the PWM output to the base of a transistor and have the string of LED's powered through the transistor with an appropriate power source. Can someone please confirm that and if it is incorrect correct my mistake in layman's terms?

A couple other questions related to this:

1) Is there any "lag" with transistors? i.e. if I run PWM to the base of a transistor will the emitter of the transistor produce an identical source (but amplified)?

2) I saw in an answer to a previous question than I need to look into constant current for the LED's. I still need to do that research but what does a constant current device look like? Is it just an IC you can buy? Can someone provide a part number or link to a page that has one so I can more effectively research how to use them.


texts: How to simulate the SCT2450KE Rohm SiC mosfet model in LTspice

texts:
I am trying to simulate the SiC mosfet in ltspice of ROHM.
I am using the spice model provided by the company https://www.rohm.com/products/sic-power-devices/sic-mosfet/sct2450ke-product/tools
But still, I am not able to do the switching properly. What is the problem.

What wrong I am doing, Kindly tell me.


texts: Are pull-up resistors needed when connecting buttons to a IO expander?

texts:
I'm connecting many momentary switches to a IO expander, like the MCP23017:

.

I read that I need to put pull-up resistors for each switch connected to the MCP23017. On another place (datasheet), I read:

GPA1 Bidirectional I/O pin. Can be enabled for interrupt-on-change and/or internal weak pull-up resistor.
GPA2 Bidirectional I/O pin. Can be enabled for interrupt-on-change and/or internal weak pull-up resistor.

Question: do I really need to add resistors myself between the IO expander and the switches or not?

Note: Here is how I would connect the tact switches to MCP23017 (which is then connected to a Raspberry Pi): will this work, without any external pull-up resistors?

simulate this circuit – Schematic created using CircuitLab


texts: How to design an RC snubber for a solenoid relay driving an inductive load?

texts:
I read up that switches driving inductive loads need to be snubbed and an RC pair seems to be the best (cheapest?) option. I have a large-ish AC induction motor (for a refrigerant compressor) that is being switched by a solenoid relay (about once every 30 minutes). Motor specs are like this:

Power:1500W (Input power. As read out on a watt meter.)
Max. Current: 10A
Rated Voltage: 230VAC/50Hz.

I came across a solution like this:

How do I select a suitable snubber? A very common combo seems to be 0.1uF - 120Ohm. But I couldn't justify it.
Should it be in parallel to the switch or the load?


texts: Relationship between power angle and real and apparent in ECO dataset

texts:
I am trying to parse the ECO dataset, which includes 1-second electric data collected from residential houses.
Link to dataset: http://vs.inf.ethz.ch/res/show.html?what=eco-data

But the relationship between the power angle and the real and reactive power do not always make sense to me. Here is an example of 3 rows, each representing a second:

                               57168     57169     57170
--------------------------  --------  --------  --------
powerallphases               19.506    19.724    42.936
powerl1                      19.506    19.724    42.936
powerl2                       0         0         0
powerl3                       0         0         0
currentneutral                0.1127    0.1125    0.3519
currentl1                     0.2039    0.2046    0.4279
currentl2                     0.1061    0.1072    0.1084
currentl3                     0.0645    0.0645    0.0645
voltagel1                   239.6     239.48    239.48
voltagel2                   239       239       239
voltagel3                   240       240       240
phaseanglevoltagel2l1       240       240       240
phaseanglevoltagel3l1       120       120       120
phaseanglecurrentvoltagel1  300       300       326
phaseanglecurrentvoltagel2  270       270       270
phaseanglecurrentvoltagel3  270       270       270

I am interested only in phase 1, so let's look only at rows that are related to it:

                               57168     57169     57170
--------------------------  --------  --------  --------
powerl1                      19.506    19.724    42.936
currentl1                     0.2039    0.2046    0.4279
voltagel1                   239.6     239.48    239.48
phaseanglecurrentvoltagel1  300       300       326

Here is the meaning of the fields:

* powerl1: Real power phase 1
* currentl1: Current phase 1
* voltagel1: Voltage phase 1
* phaseanglecurrentvoltagel1: Phase shift between current/voltage on phase 1

Apparent power is current * voltage.
However, I would expect that apparent power * cos(power angle) = real power
But if I add it to the table I get:

                               57168     57169     57170
--------------------------  --------  --------  --------
powerl1                      19.506    19.724    42.936
currentl1                     0.2039    0.2046    0.4279
voltagel1                   239.6     239.48    239.48
phaseanglecurrentvoltagel1  300       300       326

apparentPower               48.8544   48.9976  102.473
cos(θ) * apparentPower      24.42     24.4988  84.953

In the first two rows, apparent power * cos(power angle) is close enough to the real power to be explained by a measurement error. But in the last row, it is completely out of scale. And it's not a single measurement, all the following rows keep being in error:

                               57170     57171     57172     57173
--------------------------  --------  --------  --------  --------
powerl1                      42.936    30.469    36.452    42.268
currentl1                     0.4279    0.2309    0.2607    0.2856
voltagel1                   239.48    239.48    239.48    239.48
phaseanglecurrentvoltagel1  326       318       323       328
apparentPower               102.473    55.2959   62.4324   68.3955
cos(θ) * apparentPower      84.953     41.092   49.860     58.002

Am I missing anything in my calculation? Thanks in advance!


texts:
So I know that almost all i2c EEPROM ICs use 0xAh (or 1010) as the top four bits of the slave address. I currently have a 16 kbit EEPROM on my i2c bus that uses the lower 3 bits of the slave address for block addressing. This means that it co-opts all addresses starting with 0xAh.

I need to put a second EEPROM on the same bus, but I am having an extremely difficult time finding one that will not conflict with the existing chip (for design reasons, that chip cannot change). A smaller capacity EEPROM is fine, but I can't use any of the myriad 8 kbit/4 kbit/2 kbit devices out there because their slave addresses all start with 0xAh.

The only thing I was able to find was this chip from NXP, which uses 0x2h as the top four bits of the slave address. But it does not work in fast mode (400 kHz) and only comes in DIP or SO packages, both of which are much too big.

Does anyone know of an i2c chip that operates in fast mode, comes in a reasonable package, and, most importantly, uses a slave address not starting with 1010/0xAh? I would be extremely grateful for any help pointing me in the right direction!


texts:
I am using esp8266 the with atmega32a, the modules operates on 3.3V . However, when I use the voltage regulator Lm317 and adjust the voltage to 3.3V and then I connect the module to the output of the regulator the output voltage of the regulator decreases to 2.6v, why is this happening?

Is this normal as the esp draws a lot of current? or is there other problem? and the module is not responding to any AT commands.


texts: Unsolder large TO-220 or TO-247 packages

texts:
I'm aware this question may be construed as asking for advice but I'm going to venture to ask anyways. Does anyone have a good method for removing larger TO‑220 or TO‑247 packages? I typically end up cutting the legs off and trying to remove one at a time without damaging the through hole pad.

While this often works one or two times, on boards that need repair often, I end up destroying the solder pads. Maybe this could also be caused by the holes being to small to allow proper remove of solder via solder wick?

Any Advice?


texts: Cheap and small alternative to optoisolators: is there any?

texts:
Typical opto has several kV isolation voltage (which is not always needed), has relatively big cases (TLP291 in 4-SOIC is one of the smallest as I know) and typical price up to 1 USD in small amounts (not cheap in my case).

In my case I'd be satisfied if I'd be able to transmit a signal with as low as 350VDC (250Vrms) isolation. There are no safety reasons (I just need to transmit the signal from neutral to line).

At the receiving side the signal should be something similar to a switch (like collector-emitter of the opto): "on" or "off". This signal will drive MOSFET driver. The speed is pretty low (1 ms would be enough).

Capacitor can be cheap and small solution, but it will not work on DC.

So if I don't need such big isolation voltage is there any alternative to optoisolator?


texts: What are the mechanisms at work in a pull-up or pull-down resistor circuits with a push-buttons and a GPIO?

texts:
I have a question regarding the GPIO (from a Arduino board for example). How does it work exactly when you use it as an input pin? What are the mechanisms at work when you use it in a pull-up and pull-down resistor circuits with an push-buttons? I have read a few tutorials but they don’t give a deep explanation of the mechanisms, or I completely missed the points they were making. Most tutorials say things like (in a pull-up example), “When the button is pressed, it connects the input pin directly to ground. The current flows through the resistor to ground, thus the input pin reads a low state” (https://learn.sparkfun.com/tutorials/pull-up-resistors ). But in a pull-down resistor circuits with push-buttons, the input pin is also connected to ground when the button is pushed and the input is high in that case.

Also a baseline explanation would not work seem to work, because in case of a the pull-up example how does it know what the high/low value is when you have pushed in the button before connecting the power supply.
Even a threshold explanation doesn't seem to explain it entirely, the voltage on the circuit as a whole seems to me to be above 2.5 V in both pushed and non-pushed state, when a 5V Vcc and 10kOhm resistor is used or is there an error in my thinking about this?

Explanations of electrodes that only travel through  the pathway of least resistance also does seem to be right. Even if this was true this doesn’t explain the behaviour in the pull-down circuit, because there would never be any input when you would connect a 10 kOhm resistor to the ground (before the push button). Since this is lower than the impedance of the input pin (100k-1MΩ). Components divide the current according to their reciprocal resistances (I1 / I2 = R2 / R1). You can even see it when you connect a LED to the ground site of the circuit, which is on when you push the button and the input reads HIGH.
Does in the pull-up case I1 / I2 = R2 / R1 explain the behavior, because there is no resistor in parallel to the resistor of the GPIO and because the connection where no resistor is present the resistance is neglectable (at least over a short distance), all current flow goes to the ground directly?

It seem to me it got something to do with the fact that the connection that has no resistor between the input pin (and the ground or power supply pin) determines the state when both have a closed circuit with it. But what is the mechanism. Does the GPIO unit (in input state) contain a sort of capacitor that “transmits” the charge to the power supply when it is directly connected to it (larger pull with larger voltage), and contains the charge longer (or replaced charge quicker) when it is directly connected to ground, and so influences the internal circuit? Or does it have something to do with the potential difference between the sides of a resistor, and if so how does the input pin read this?

I understand the fact that in you use a ground connection to the input pin (in a pull-down circuit) because otherwise the input pin would be influenced by noise (static) and a resistor because otherwise there would be a direct connection between the Vcc and ground, and this would result in a short circuit. So this part can be skipped in the answer. Of course you can add this in your answer for other users looking for an answer regarding this.

I hope that somebody can give me an (in-depth) explanation of how these circuits work.


texts: Controlling multiple inputs without a common ground using semiconductors

texts:
I have a processor with GPIO outputs. It uses 3.3v logic outputs which share a common ground. (In particular, it has internal pull-up resistors, but I  could turn on open collector mode)

A device I need to control does not share common ØV grounds between inputs. (In particular, a number keypad on a handheld device.) The device only looks for a short betweeen the two points, and has no continuity between the "ground" of each switch. If I do attach grounds to a common point, the device will begin to false trigger and loose it's ability to determine which input is closed. Because it is designed for pushbuttons, not electronic triggering, a common ground does not matter in it's case.

Using discrete semiconductors (not relays, they are way to big and overrated current wise), how can I control many devices that do NOT share a common ground?

I do know of optoisolators, but I would really like an alternative semiconductor solution circuit (basic transistors, diodes, etc...) if it is possible.


texts: Altium Designer 16.1 Can't find Pin in Place Menu

texts:
I am new to Altium, so this is probably a stupid question. I want to place a pin in a schematic, as described here.

But I cannot find pin in any of the menus.

No pins anywhere... What am I doing wrong?
Thanks!


texts: I'm currently working on some simple circuits to learn about circuitry, and being a Physics major I have a pretty good grasp of the mathematics and concepts, but I'm a little confused about capacitors. I understand how they work, but am curious about their placement in a circuit.i would like to know the purpose using capacitor(1uf/400v) in parallel with resistor in this circuit


texts:
I am wondering what effect a coil before a DC motor has.

It's a 3 AA battery powered (4.5V) small RC car. I cut off the cables going to the motor and connected the motor to the battery directly (I soldered connecting cables first). I also did experiments with a Raspberry and a L293D motor controller always using the 3 AA batteries. All works fine, however, I believe that the motor was more powerful in its original state with the coil.

I unwound the coil. Each cable was spinning 8 times around the small metal hull. I think the coil was responsible for somehow making the motor more powerful. I just don't understand the logic how.

(photo shows the original state as I bought it)


texts: Is it ok to keep rechargeable batteries in an unplugged charger?

texts: Is it ok to keep rechargeable batteries in an unplugged charger considering possibility of discharging the batteries via the charger's circuitry, etc.


texts: How to use both RTC and RTC alarm on STM32?

texts:
I've got a board with STM32F103C8T6 and a 32.768 kHz external crystal.

The RTC module of STM32 is used as a calendar as I set the prescaler to 32767.

But, to reach the minimum power consumption, I also want the RTC module to wake up my MCU alternatively(about 10ms per time, high accuracy is not required), how can I do it?


texts: Why does my Brother labeler say both 9.5V and 12V?

texts:
First time poster on this SE. Thanks for existing!

I have a Brother PT2600 labeler and it says 9.5V DC IN on the adapter socket. I tried with a 9V adapter and it doesn't power on. 0.5V shouldn't make a difference, right?

On the back of the device it says DC 12V 12W. And it also accepts 8 AA batteries, with 8x1.5V = 12V.

Why would it list two voltages? Is there something about battery voltage that is different than adapter voltage? If it really takes 8 AA batteries in series then I should be able to use a 12V DC adapter, right?


texts: I was thinking of making a carry handle for two microwave oven transformers in series, and also so that they can share a common ground without having to split the ground wire. I thought about bolting an H type handle to the frame (The base of the transformer comes pre-drilled for mounting inside the microwave), but can I weld the handle to the transformer? I heard that it can cause eddy currents which may affect performance.


texts: Will this circuit work containing 2 transistors?

texts:
My gran keeps turning her internal light on in the car and then forgets to turn it off again. She has flattened the battery 5 times in the last few months.

I've been looking at how integrated circuits work and am hoping to go to university next year and study computer science. I was thinking this could be my first project!

The light has 3 switch positions:

always on
on when door open
off

What I want to do is fit a buzzer in the light that will buzz if the light is on and a door is open. I've come up with a circuit that I think should work. It's the first time I've attempted anything like this so I was wondering if you can see any problems with it or if it will actually work!

If you think it will work what type of transistors do I need to buy? Are there different types?

The 'from switch' wire will be live or not depending on what position the switch is in.

Also if there's a better way feel free to tell me!


texts:
Inductors, when applied as inline power filters, need a parallel snubbing diode so that when the load opens, the current can be safely discharged.

In certain contexts, ferrite beads such as the Laird 28L0138 series can be used as inline power filters. These have nonlinear, mixed inductive/resistive properties dependent on frequency.

Since there is some inductance in ferrite beads, should they too have a snubber, or is their internal resistance adequate to discharge current after an opened load?


texts: Stop position circuit for pwm regulated DC motor (bi-directional)

texts:
I'm building DC motor blind movement. I've paired motor with bi-directional PWM controller but so far I need to stop/start manually or time it...temporary I have USB relay configured to open blinds every morning. I'd like to add some automatic stop position circuit.

First I've been tinkering with magnetic/reed switches (3 contacts), but I've smashed those delicate glass tubes in the process. Plus, they were switching reliable only 2-4 cm from neodym magnet. Now I'm thinking about voltage comparator with IR led transmitter & receiver and some reflexive sticker/paint to mark my end positions. The circuits I've found is outputting logic signal, but probably I could connect that to small 5V dc relay to shut down the motor (12 volts). But with these I'll need to put up something like 8 wires. Or maybe less if I'll use diodes & step-down regulator to supply stop circuit.

Any thoughts/ideas, how to solve this better? I might end-up with some arduino at the end, but I wanted to do this "the old way" first


texts: USB keyboard unplugs and plugs itself when a human approaches or steps away

texts:
My computer makes the USB disconnect/connect sound whenever I stand up and walk away from the desk or sometimes sit down at the desk. I tracked down the source, which is the keyboard, by testing with it enabled and disabled multiple times. I also confirmed it using the software USBLogView to track USB device activity.
When looking up this problem, I've found that other people have also experienced this issue. Examples:
https://www.sevenforums.com/sound-audio/283251-my-computer-knows-when-i-go-walk-away-7.html
https://forum.quartertothree.com/t/my-computer-is-haunted/78433
Video included in the 2nd link: https://www.youtube.com/watch?v=V0ksE7g8nkA
In my case, I haven't had any loss of functionality of the keyboard because it immediately plugs back in after unplugging itself.
What could be causing this and how would I fix it?


texts: What is reducing the NOISE when probes are connected to a circuit?

texts:
When the oscilloscope probes aren't connected to anything, the following waveform is observed:

The oscillations are more then 1.5mV.

When the probes are connected to measure the voltage on a 27Ohm resistor with 30uA current flowing:

the big oscillations are gone and the new ones don't oscillate more than 200uV. Given that the probes are physically in the same location, and the circuit is battery powered (no earth grounding), what reduces the big oscillations?

Motivation

I came to this problem while trying to understand how much noise in the second graph is due to the probes. Wasn't expecting to get a larger error.


texts: How to convert 220V AC @50 Hz to 400V @ 20KHz?

texts:
Sorry, I may be asking simple question but I'm not specialized in electronics.

What I want to do is to increase the voltage from 220V AC to 400V AC. Also I want to increase the frequency from 50Hz to 20KHz. If I can adjust the voltage and frequency, that would be a privilege (I mean the output voltage could vary from 300V to 400V and the frequency from 15KHz to 20 KHz).

I know I'm supposed to use transformer to increase the voltage and rectifier/inverter to increase the frequency, but I was wondering if there are any other simple solutions? And how to design and built the circuits?

The current here is not important since I'll be using this voltage to generate electric field.


texts: I'm looking for the correct pcb footprint for the MAX1979 IC by Maxim, supposedly in a TQFN-EP package. While the land patterns are available on Maxim's website, there are apparently several 48 lead TQFN packages with different footprint areas, and the only information on the IC datasheet is that the area is below 0.93 in² (not very helpful). Where can I find the exact dimensions of the package?


texts:
I was buying a AC powered RV/Marine cord reel from outside USA. The cord has 2 lines, 1 neutral and 1 ground. The colors of the cores in the cord are red, yellow, blue and green. I need to use this cord reel in an electric charging station for vehicles in USA. Is it compulsory for us to US color codes for the wires ?
Also, I was wondering if this could cause any issues with any certifications like UL, etc for the product in the future.


texts: What models and brands can I find for logic fuses?

texts:
I'm trying to find logic fuses like the ones found here.
As I'm new user, I couldn't comment there, so I created this new question.
That fuse, in my case, is on a Clevo P170EM battery. This battery model is P150HMBAT-8 (6-87-X710S-4273).
I would also like to ask if these types of fuses can be replaced at home with a simple ersa i-Con Pico soldering station.


texts:
I have bought some ATSAM4E8C chips in LQFP 100 package. The datasheet shows that the IC should have a dot indicating the first pin, but mine have two dots. One larger in the corner, and a smaller white dot diagonally. The upper left side of the name painted on the chip is not aligned with any of them.
Where should the first pin be located?


texts:
I have a 8051 micro controller ,it has timer0,1,2,3 with different modes.

in timer0,mode0, i got a sample code (as shown below).

datasheet 8051

from that code

TH0_INIT=0xFC          //5.0ms@XTAL=12MHz, Period = (10.85/2) ms@XTAL=22.1184MHz
TL0_INIT=0x0F

both TH0,TL0 load with hex values..but could not derive  these values from equation below .      (website)
Could you please tell me, how these hex values derive?

tick = (1/(Fosc/12)
tick = 12/Fosc$$ For Fosc == 11.0592Mhz, the tick time will be
tick = 12/11.0592M = 1.085069444us = 1.085us

Delay = TimerCount * tick
        Count = (Delay/tick)
        RegValue = TimerMax- Count RegValue = TimerMax-(Delay/tick) = TimerMax - (Delay/1.085us)
        RegValue = TimerMax-((Delay/1.085) * 10^6)$$

source code for timer0,mode0

#include "N76E003.h"

#include "Common.h"
#include "Delay.h"
#include "Function_define.h"
#include "SFR_Macro.h"

#define TH0_INIT                                                               \
  0xFC // 5.0ms@XTAL=12MHz, Period = (10.85/2) ms @XTAL = 22.1184MHz
#define TL0_INIT 0x0F

void Timer0_ISR(void) interrupt 1 // interrupt address is 0x000B
{
  TH0 = TH0_INIT;
  TL0 = TL0_INIT;
  P12 = ~P12; // GPIO
  toggle when interrupt
}

void main(void) {
  TMOD = 0XFF;
  Set_All_GPIO_Quasi_Mode;
  TIMER0_MODE0_ENABLE;

  clr_T0M;
  clr_T1M;

  TH0 = TH0_INIT;
  TL0 = TL0_INIT;

  //    set_ET0;                                    //enable Timer0 interrupt
  // enable Timer1 interrupt
  set_EA; // enable interrupts

  set_TR0; // Timer0 run

  while (1) {
    TH0 = TH0_INIT;
    TL0 = TL0_INIT;
    set_TR0;
    while (!TF0)
      ;
    clr_TR0;
    P12 = ~P12;
    TF0 = 0;
  }
}


texts:
I am currently implementing a pulser for an ultrasonic device.  I need to supply it with ±100V and a current of 0.5A.
My first approach was with two NMT0572SCs (with ±72V) but I could not get them to work properly.
Now, my next option is to use the MAX1771, a usual suspect in boosting 12V at voltages above 100.
How can I invert the output? That is, how to get -100 volts?
Can it just be by inverting my +/- reference?


texts: Can I use 220V inverter as 12V power supply?

texts:
I have a pure sine wave inverter, it charges a 12V battery and converts 12V from battery to 220V during a power cut.
Since it can output 12V to charge the battery at quite a high current I was wondering if I could use it as a 12V power supply.
I connected the 12V output to a multimeter and it seems to be jumping from 6.xx volts to 13.xx. I reckon it automatically selects 6V or 12V battery.
So is there any way I could bypass this jumping from one voltage to another to use it as a power supply?


texts: Providing Schematics to a Contract Manufacturer?

texts:
A contract manufacturer mentioned the types of the files that they need in order to build and assemble boards. He indicated that they need the schematics along with gerbers, drill files, bom etc..

Is this common practice for CMs to ask for schematics ?

Is it common practice to bundle schematics with a fabrication+assembly package ?


texts: What is the difference between regular FPGA boards and FPGA boards for ASIC emulation?

texts:
I'm considering to buy a FPGA evaluation board for ASIC prototyping(makes HDL codes for designing chip that will be manufactured as real chip).

On the market, there are not only regular FPGA boards, but also FPGA boards that specifically says it's for ASIC emulation.

What is the difference and can I just buy regular one so that I can save money for it?


texts: Designing a test instrument to be connected to an oscilloscope

texts:
I'm working on a piece of test equipment that is intended to be hooked up to an oscilloscope to measure the waveforms it produces. Since that's its reason for being, I figured it made sense to provide some form of dedicated connection, rather than hooking up probes to test points, and so forth.

The obvious solution is BNC jacks on the test instrument, and a BNC cable to the scope, but I've been told there are subtleties embodied in a scope probe that simple BNC cables won't encompass.

Is this true? If so, what would I need to with my test instrument to ensure that it can be hooked up cleanly to a scope and give accurate measurements?

The signals to be measured will be pulses on the order of 1us long, with p-p voltages of between 100mV and 5v.


texts: Accuracy of a multimeter over 10 years period

texts:
Datasheets of multimeters contain accuracy specifications.
One parameter is usually accuracy over period of 1 year. I understand that it means multimeter can be off by the specified value.

For example Keithley 2000 for 100mV range:
1 year accuracy = 0.005% (of reading) + 0.0035% (of range)

or Siglent SDM2055 for 200mV range:
1 year accuracy = 0.015% (of reading) + 0.004% (of range)

But question is what accuracy I have to consider over period of 10 years?
Do I have to multiply "1 year accuracy" by 10? Or it is not nearly that easy (and not that bad)?

No hobbyist is going to do calibration of his equipment every year. It would be useful to know how does the accuracy shift in longer period of time.


texts: Communication between two STMs over 2 meter with small latency

texts:
I want to send messages back and forth between two STM32s. Probably STM32F407VET6, but it would be nice if I can try already something for a simple one (STM32F103C8T6).

My requirements:

round trip delay time: preferably 1 ms max (excluding processing), for messages with a payload of around 8 bytes.
distance around 2 meters
speed: pure data: around 128 kbps (excluded overhead) so probably around 200 kbps

I checked between SPI and I2C, and seems that SPI is easier (to setup) and I have enough GPIO pins.

However, I read that 2 meters and fast data rate might be a problem. Also I cannot find info about the round trip delay.

Of course I can check all this myself, but it saves me a lot of effort to set this up.

For the cabling between the two STMs I am intending to use an RS232 connector (and probably cable), but if there are better alternatives, please let me know (UTP cable maybe and internet connector?). Or are there more appropriate cabling/connectors for this?

(update, link to MCP2551 according answer remark)
MCP2551 adapter: adapter


texts: Can I use only 4 wires of an 8 wire serial port with hardware flow control?

texts:
I'm looking to connect a Telit UE910 cellular module to a microcontroller. The module uses an 8 wire RS232 style serial connection for the main serial (USIF0). I'd rather not tie up 8 IO pins, but I would still like to use hardware flow control. Is it possible to only use 4 of the 8 wires (RX, TX, CTS, RTS)?

The module also supports using only 2 wires with software flow control. The datasheet states that you should tie RTS to ground when not using hardware flow control. I believe this is just to prevent RTS from floating, but it's possible it uses this to switch between HW and SW flow control mode. Is this likely?


texts:
Given multiple possible powerful charge sources without adequate over-current protection, and a very large (say 500 AH) depleted battery bank, using a very low resistance / high acceptance rate chemistry.

50A is just an example, the goal is to "stack" more powerful charge sources in parallel until the user knows that the peak current demands of the bank are satisfied; the next step up would be 100, then 150 amps, etc.

If resources were unlimited, we could start out at say 5C (say 2500A) and work down, but they are not.

What are some components, circuits I could use to limit the source current to these power levels, starting with the 50A example?
If a single off the shelf device exists, that would be ideal, but I suspect not.


texts: Why must flash memory be written/erased in pages/blocks?

texts:
Title says it all.

I'm trying to understand the workings of flash memory technologies, at the transistor level. After quite some research, I got good intuitions about floating-gate transistors, and how one injects electrons or remove them from the cell. I'm from a CS background, so my understanding of physical phenomena like tunneling or hot electron injection are probably quite shaky, but still I'm comfortable with it. I also got myself an idea about how one reads from either NOR or NAND memory layouts.

But I read everywhere that flash memory can only be erased in blocks units, and can only be written to in page units. However, I found no justification for this limitation, and I'm trying to get an intuition about why it is so.


texts: ADuC812 needs DAC value written twice. Is that normal/common?

texts:
A while ago I had a project that involved Analog Devices ADuC812 microconverter.

Amongst assorted on-board hardware, the device had two very helpful DAC converters, that could source 0-5V on their respective pins and even maintain a respectable amperage.

There was one problem though. While the manual said all you had to do was writing a specific value into a specific register, and voltage corresponding to that value would appear on output, the reality wasn't exactly that simple.

One write could move the voltage value by about 3.5V. If you wanted to switch from 0 to 5V you had to perform

 MOV DAC0H,#00fh
 MOV DAC0L,#0ffh

twice. (reversing the order wouldn't help.)

First write would increase the voltage to some 3-and-something volts, and only the second would get it to the right value. If I started from 2V, it would achieve the target 5V in a single write. It's not a big problem, 4 cycles instead of 2 for rapid jumps, no impact for smooth "slides" at all, but it's a weird quirk.

I'd like to ask anyone who worked with that chip - was that just my chip's problem or is this common to all ADuC812? Does it appear in other ADuC family chips? 814 etc?

As a bonus, could someone with electronic knowledge explain how that happens? What internal mechanisms can lead to such behavior?


texts: Type of terminal/connector to use for CAN bus on Arduino MKR CAN Shield

texts:
Probably, this is obvious to everyone, but since I am a newbie to electrical engineering I am stuck. I have two wires of a CAN bus, (CANL and CANH), and I wish to connect them to the Arduino MKR CAN shield.

Which types of connectors do I need to buy and then crimp to the end of my cables in order to make this connection? I cannot seem to find any documentation as to which terminal is used on that shield. I suppose the terminal is the green one to the left of the board?

More generally, what types of connectors/terminals are usually used in such applications? What is the best way to go about finding such stuff out?


texts: Buck-Boost converter not working right when fed by dynamo

texts:
So my plan is to charge a powerbank with a bicycle dynamo. I have got it to work with a full bridge rectifier and a linear regulator, it just isn't very effective. I used the following circuit:

(The hatched box is the circuit that comes with the powerbank).

After some research I found that using a buck-boost converter is way more effective. So I ordered the following from AliExpress:
https://www.aliexpress.com/item/Boost-Buck-DC-DC-adjustable-step-up-down-Converter-XL6009-Module-Solar-Voltage/32661520979.html?spm=a2g0s.9042311.0.0.36774c4dvUq5VL

I connected it to my DC voltage generator to set the voltage to approximately 4.5 V, since that's what the power bank would need. Until here it all worked fine.

Then I connected it to my circuit instead of the linear regulator. When I started spinning the dynamo, the output-voltage of the buck-boost converter would rise quickly to 20 or 25 V (probably even more, didn't want to try that though, in fear of breaking it) with only 3 to 4 V input. I also tried it without the capacitor (1500 μF), hoping that would solve the issue, which it unfortunately didn't.

I know there are different types of buck-boost converters and I might have picked the wrong kind...
Could someone please help me to get this working?

Any help is appreciated.

Thanks.

Edit: The linear regulator I used is a L7805CV, which has an output voltage of 5V.

Here the schematics of the circuit I used with the buck-boost converter:

The Capacitor should be big enough. I measured it with an old oscilloscope and it looked fine as far as I can tell (by that I mean it was a more or less smooth line).


texts: Divide Sequencial Parameter Step in Spice

texts:
I've been designing a (very) simple MOSFET op-amp for school, and one of the things I need to do is determine the CMRR from my simulations. For the assignment, I'm just going to use the value at 1kHz, which should fulfill the assignment requirements. However, thinking about it made me wonder if there is a way to make LTSpice (or any other version of Spice) plot the CMRR over multiple frequencies?

I won't show the circuit, as this question is relevant to differential amplifiers in general, but here are the directives I'm using to run my current simulation:

.ac dec 100 1 100Meg
.step param vi list 0 1

vi is an AC voltage parameter for the non-inverting input, and the inverting input has a fixed value of AC 1.

Here is the result, measured at the output:

The black line (vi=0) shows the open loop frequency response with a differential input and the blue line shows the response with a common-mode input. In other words, it simulates these two circuits:

simulate this circuit – Schematic created using CircuitLab

I am wondering if there is a way to divide two instances of the same parameter. In other words, I want to divide the output voltages corresponding to the differential and common-mode gains so that I can do something like this:

$$ CMRR = \frac{v_o|_{v_i=0}}{v_o|_{v_i=1}} $$


texts: What's wrong with this IR2110 pulse transformer driver?

texts:
I'm trying to drive two MOSFETs through a pulse transformer. I'm using the "Power Supply Cookbook – Second Edition" book from Marty Brown. According to the book the formula to calculate the number of turns of the 1:1 driver is:

  N = Vcc/(4×F×Bmax×Ae)

In my case Vcc = 15V, F=200KHz, estimated Bmax to 0.1T (I'm using a 15mm toroidal core from a PC power supply) and Ae=0.000123m^2 so this gives me 10 turns. The book recommends toroidal cores from 10 to 15mm of diameter. This is the core I built, 10 turns on primary and the same turns on both secondaries in opposite directions:

I tried using a Push-Pull driver using BC548 and BC558 but at 200KHz it works really bad, a duty cycle on base of 80% gives me between 10% or 20% on the output, this doesn't happen at lower frequencies like 50KHz. So I'm using an IR2110, I know it's a high-side driver too but I'm using it as two low-side driver. This is the schematic:

And this one:

But when I connect the output of the IR2110 to the pulse transformer I get a current consumption of about 400mA to 600mA and the output on the secondaries are very distort, far away from a square pulse. The IR2110 inputs are driven from a microcontroller that generates a half-bridge output.

Is there anything wrong with my design? What do you suggest?


texts: How can I generate a signal and sample it simultaneously in STM32F407?

texts:
I was able to generate a signal using DAC periphery and a HAL_DELAY.
I want to sample this signal using ADC by connecting DAC output to ADC input for FIR filter purposes.
But there is a logical problem, because the code is sequential after generating DAC commands value I can sample with ADC commands but there will be only one DAC value to sample.
Is there a way to simultaneously generate signal with DAC and simultaneously sample it with ADC in STM32F407?


texts: Can't control DC motor with PWM on Raspberry Pi

texts:
I recently bought a 24V brushless DC motor from ebay (link: https://www.ebay.com/itm/392320171299).

I've been able to connect it to a 24V power source and it runs. I've been trying to control it via the connected PWM cable (white one, see link) but it doesn't work.
I'm using a raspberry pi and the https://docs.golemparts.com/rppal/0.12.0/rppal/pwm/ library to setup PWM. I've even measured the output pin and the voltage seems to change with my settings. However the motor still won't respond, it just runs at full speed.
Does the raspberry pi not provide the PWM voltage required (3.3V) required for this 24V motor?


texts: Full Bridge Rectifier Oscilloscope Reading

texts:
I am trying to read the output wave of a full bridge rectifier circuit on my oscilloscope, but the waveform looks really funky. I've set it up as shown in the spice simulation where resistor R1 represents where I have connected my probes:

When I breadboard it, I get this waveform:

I'm pretty sure its just a matter of me being an idiot and not setting up the scope correctly or something. I've tried using different diodes, probe resolution, and coupling settings but they all produce the same shape.
Thanks.


texts:
I need to make a cable run of approximately 150 feet. The source is a security camera box and the destination is a large ~42" television with all the basic hookups.
The source box is in a room right next to a cat5 ethernet wall jack and so is the destination television.

Is there a way I can use the existing ethernet cabling to transmit the signal from my security camera box to my television 150' away?

The security system box itself has these 'balums' which connect to it by bnc from the camera so could the same 'balum' be used to send the signal out to my television?

What kind of special adapters will I need in order to run it over bnc -> ethernet -> coax?

How much signal degradation should I anticipate?


texts:
can someone help me in here.
Find the V(t) when t = 2,5ms and knowing that i(t) = Icos(wt).
R= 50ohms, L=100mH, I=2A, w=100π rad/s

Like I know that Z = 50 + j10π = 59,05∠32,14°
And v(t) = Z*i(t) = 59,05∠32,14° * 2∠0° = 118,10∠32,14°
v(2,5ms) = 118,10cos(100π2,5m + 32,14) = 99V
But the answer in my book is 26,3V so I don't know what i'm doing wrong


texts: External clock with Arty Z7 FPGA development board

texts:
I have a digital audio source that is basically I2S. I need to run the FPGA at the exact clock as the I2S provides. I've got four such inputs required, but I am assuming that the clocks are the same.

Is there an input on the Arty Z7 board that works as an external clock? If not, is there a dev board for zynq that does? Any pointers to how to configure that in the vhdl?

Update: maximum sample rate is 384Khz. maximum bits per channel is 32. maximum channels is two. Consequently, maximum clock is 24MHz. Max z7 clock is ~100Mhz? I do not believe that this is a high enough multiple to avoid clock inaccuracies on the output (but would be happy to be wrong). This is an audiophile application and avoiding jitter is very important.


texts: Is it possible to program AVR microcontrollers using USB-UART converter instead od USBasp?

texts:
Is it possible to program an AVR microcontroller (e.g. Atmega328P) using a USB-UART converter like this one:

Instead of a usual USBasp ISP programmer:

?

If yes, is the procedure the same as in the case of USBasp programmer or are there some additional steps required?


texts: How to measure Common Mode Range and Output Swing of a CMOS Differential Amplifier in LTspice

texts:
I'm designing a CMOS opamp in LTspice here is my current design.

The amplifier obtains a DC gain of roughly 50dB and has a phase margin of 70 degrees at a ω (unity gain frequency) = 250 MHz. I'm also using a 32nm process technology with this BSIM library file.
I'm wondering specically how to calculate the input common mode range and the peak to peak output swing of my amplifier. My guess for the output swing would be to step in input value and see the possible range of outputs.

Running a DC operating point simulation I see the ouput can vary by around 0.87V

Would the input common mode range then be the range of inputs that bring the ouput from it's min to max i.e

(about 0.5V)
Normally I would compute input and and output ranges based on the saturation contion of the devices in the circuit. I don't have much experience working with spice and I'm wondering how I can do it exactly in my simulation.
Thanks


texts: What is "Pointer" in DM14 at J1939 CAN-bus standard? Can it be the memory Address[DEC]?


texts:
In my application, I need to transmit data between two arduinos, one as a master and the other as a slave using 485. The arduinos are connected to these modules, which have a Max485:

Schematic:

With these modules everything is working fine (38400 bps).
Next, I want to use Max13487 so I don't have to care about the direction control lines.
As I understood, Max13487 is the automatic direction control version of Max485, and their foot prints are compatible.
I took these modules, desoldered the Max485, and soldered the Max13487. RE and DE (now RE and SHDW) are tied together and pulled high.

What happens next is that communication is not working. I can see data going out from the master driver, but the slave receiver is not converting it back to 5V.

The voltages on the data lines are different for the 485 and the 13487:

                   Low   High
 - MAX 485:  -A    3.3V  2.3V
 - MAX 485:  -B    1.3V  3.3V
 - MAX13487: -A    2.3V  1.3V
 - MAX13487: -B    2.3V  3.5V

What am I missing? Thanks.


texts:
I'm new the the FPGA world. I was wondering if anybody could tell me the Altera equivalent of the Xilinx Zynq UltraScale+ MPSoC?

I'm looking to buy a development board but it needs to be from Altera.

Thanks
Tom


texts:
I'm trying to send some data through UART using DMA. I'm also using DMA to control ADC and DAC. When ADC is enabled and I try to send data I get a HardFault error. The HardFault occurs exactly during execution of HAL_UART_IRQHandler(&huart2) at the line: uint32_t isrflags = READ_REG(huart->Instance->ISR);  . When I stop the ADC the problem disappears but I can't understand why?
void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart)
{

}

void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{
    if (i<2048)
    {
        FFT_buffer_in[i] = (3.3*analogInput)/4095;
        i++;
    }
    else
    {
        i = 0;
        doFFT();
    }

}
int main(void)
{
      uint8_t MSG[] = "yo waddup ";

  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_DMA_Init();
  MX_ADC1_Init();
  MX_DAC1_Init();
  MX_TIM2_Init();
  MX_TIM1_Init();
  MX_USART2_UART_Init();

   arm_rfft_fast_init_f32(&fft_handler, 2048);

   HAL_ADC_Start_DMA(&hadc1, &analogInput, 1);
   HAL_DAC_Start_DMA(&hdac1, DAC_CHANNEL_1, (uint32_t*)Wave_LUT, 128, DAC_ALIGN_12B_R);
   HAL_TIM_Base_Start(&htim2);
   HAL_TIM_Base_Start(&htim1);

  while (1)
  {
  //HAL_ADC_Stop(&hadc1); -- only if I uncomment this, the UART_Transmit works

  HAL_UART_Transmit_DMA(&huart2, MSG, sizeof(MSG));
  HAL_UART_IRQHandler(&huart2);

    HAL_Delay(500);

  }
 ```


texts: Measuring soil moisture and using a vintage DC ammeter as the indicator

texts:
I have a vintage Weston Model 506 DC ammeter (it has a range of 0 to 20 amps) that has been sitting in my office and I think it would be interesting to use it as a soil moisture indicator for a (long suffering) potted plant. It would be more of a curiosity than something critical, so neither precision or accuracy is a big requirement.
One design that I saw uses an Arduino to indicate the moisture on an ammeter.  While interesting, I was hoping for a design that was not microcontroller based--trying to stay in the vintage theme.
Most of the circuits I looked at recommend an AC based design to mitigate corrosion on the moisture sensor.  Plus, the designs indicate the moisture level as a voltage, so I would need to put some sort of voltage to current conversion. Given the 20 A range on the ammeter, I probably would need to drop the voltage going to the ammeter to reduce the power demand.
Ideally I would like to avoid having to plug in a wall wart as power source or changing batteries (rechargeable AA) more frequently than once a month.  Are there any recommendations for a circuit design or should I go with the microcontroller design?


texts: Serial port adapter reads 5V data but not 3V data

texts:
Each time I wanted to hook up a micro-controller UART to my computer via serial port, I make an adapter with the following schematic:

For the capacitor, I use 47nF and for the diode, I use 1N4001. VCC is 5VDC regulated. The rest of the part values shown are self explanatory. Resistors are all 1/4 watt.

With this setup, If I deliver 5V to the TXDA net (aka output to PC), then the PC will recognize that bit as logic high. If however, I deliver only 3.3V then the PC doesn't want to recognize the bit.

The PC is able to output data to the micro through the RXDA pin just fine in all cases.

In my circuit, I connected pins 4, 1, and 6 of the serial port together and pins 7 and 8 together to make it compatible with all computers and to try to eliminate EMI.

Is there a way I can get this circuit so that it recognizes data at low voltages?

The reason I'm making such a circuit is because I'm simulating an HM-TRP wireless data module (that refuses to work at more than 3.9V) and I want to see and control the data on my computer so that later when I actually use the module instead of the computer, everything will then work.

And for those who ask, the voltage regulator I used to generate 3.3V from 5V is LM1117-3.3


texts: What are the terminals of a 6 wired step down transformer?

texts: I'm having a Transformer with 2 input wires and 6 output wires(in pair).I dont know it ratings also.Please help me to find what the terminals are?


texts: How to identify pinouts in an Hp Server Front Panel

texts:
So I found some old server front panel and want to re-purpose its LEDs and buttons for some custom PC. How do I begin to identify the pin-outs without burning down the circuits?
Image gallery


texts: Determining the voltage and charges across each capacitor

texts:
Since someone edited my question and asked me to post a new question instead with the edits I did, so here is the new schematic for this question:

Can someone help me find the voltage and charge across each of the capacitors? This is not just a simple/ parallel circuit so I am having a problem in formulating the right equation on how to find the voltage and charge across each capacitor.This is actually one branch of a charge pump wherein capacitors pump charges to the load capacitor, CL. I also want to know how charge transfer occurs between capacitors.

Below is the original circuit:


texts:
I am designing a device with USB OTG that has some power-hungry components that should run only from an external supply, but the device still should be configurable from a PC via USB. I have come up with the following scheme:

simulate this circuit – Schematic created using CircuitLab

USB data lines and capacitors omitted for clarity.

The firmware can detect the state of the ID pin, disable the load switch to prevent backfeeding the host from the 5V line.

When an OTG cable is connected the ID pin is grounded, MCU reads ID as zero and enables the load switch feeding the device.

When a device cable is connected the ID pin is floating, MCU reads the ID pin as high (internal pullup) and disables the load switch.

The MCU is powered from either the 5V line or VUSB.

I don't need exact current limiting in host mode (the load switch has internal limiting) nor any kind of battery management.

Is such a scheme viable or am I missing something?


texts:
Suppose, I have data which is stored in some EEPROM memory.

The EEPROM is connected via an I2C interface to a microcontroller, and this microcontroller is connected to an RF receiver circuit.

Assume my RF receiver circuit receives a code of information, and I want to check whether this RF information (after demodulation) is the same as the one present inside my EEPROM. The data is then fed to the microcontroller. After this, how does this comparison or validation of data happen between the received information and the stored information in EEPROM in rlectronics?

Say, how does the comparison between 2 codes, happen in electronics, and produce an output meaning "SAME" or "NOT SAME".

I just want to understand how the comparison happens in electrical terms.


texts:
Glad to found an "electrical engineer"-version of stackoverflow, I greet you all.

I am working on a MPPT projects, using 5V solar panel, and MCU ATTiny24 (for its ability working on a low voltage).

The solar panel output is used for MCU voltage source and load.
The problem is, PWM signal generated is not square if its on low duty cycle (see pics)

I also attach my schematics (sorry for the hand drawing, but I cant access the schematics right now)
Now I am using PNP transistor C9012 for switching.
My first guess is error caused by the transistor, anyone knows a P channel FET to switch low voltage? or maybe a P-channel substitution equal to MPF102?

When the duty cycle is higher than 60%, the signal is square.
I use load ranging from 1 ohm to 50k ohm.
Thanks in advance :)
Ps: sorry i can only post 2 links because of lack of reputation

EDITED--------------------------------------------------------
I have try to modify the circuit as the suggestion, but still got the same result (and I'm sure the oscilloscope works).
*sorry have to remove the former circuit, cant upload more than 2


texts: TPS61090 LBI Pin-->frequency compensating capacitor for voltage divider?

texts:
I was reverse-engineering some PCB to gain knowledge how to apply a TPS61090 Boost Converter (see my schematics attached, sorry for the unusual "arrangement" of the components). Input VBAT is about 4.2V from a MCP73871 charger, which in turn receives the voltage either from a 3.7V LiPo battery or 5V USB plug.
I stumbled on C14. It seems to be some kind of capacitor for frequency compensation of the voltage divider. Even with greatest parasitic capacitance I see no reason for this, as LBIs only purpose is to deceide if voltage is below or above 500mV to switch the LBO. I could only imagine, that there will be some kind of delay, until the voltage at LBI reaches its maximum, what would be negligible I think. Or would it perhaps prevent a "flickering" LED, when VBAT ist near the defined region for LBO?
Thanks in advance!
Edit:
I've been adding a picture of the switch, which pulls the EN Pin of TPS61090 high to start up. Another question came up there regarding to C3, which is counterintuitively connected to VBAT instead of GND. As far as I understand, the switch works as follows:
Connecting PIN1 and PIN2 of S1 (momentary switch), EN gets pulled high. Releasing it, LED_POWER overtakes the task of supplying EN with voltage (EN_POWER is connected to a GPIO of a Raspberry Pi, which in turn gets powered, when TPS61090 starts up). For this small transition time between both conditions, the capacitor stores the charge to keep EN pulled up. But wouldn't that be the case if beeing connected to GND?
(Further, by switching S1 a second time, "SHUTDOWN", which is connected to a GPIO as well, gets pulled high to shut the Raspberry Pi down via script).


texts: Why DC potential at output of diiferential amplifier limits output voltage swing (peak to peak)?

texts: Why DC potential at the output of differential amplifier (or any amplifier) limits peak to peak voltage swing?I have read that because of direct coupling, dc level increases and this tend to shift the operating point of succeeding stage and therefore limit the output voltage swing and may even distort the output signal.Why this happen?


texts: Simulate STM32F4 brownout reset using STM32F100

texts:
The STM32F4 MCU has a brownout reset feature. According to the manual, section 5.2.2, when the supply voltage VDD drops below the selected VBOR threshould, a device reset is generated. After reset, I can check the BORRSTF flag in register RCC_CSR (see section 6.3.21 of the manual) to see whether the reset was due to a brownout.

I'd like to simulate this behavior in the STM32F100, which lacks a brownout reset feature. My idea is to use the programmable voltage detector (section 4.2.2 in the manual) to generate an interrupt in EXTI line 16. When the interrupt handler is called, I'll generate a software reset; I can verify, after reset, that the reason was a software reset by way of the SFTRSTF flag in register RCC_CSR (see section 6.3.10 of the manual). Since I don't generate a software reset anywhere else in my code, I can be certain it was due to a brownout.

Here's what I'm looking to know:

Can anyone see a flaw in this idea?
Would an actual brownout wipe the SFTRSTF flag in question?


texts: Why can an AC circuit breaker not be used in DC circuits?

texts:
Let's assume that I want to use a 20-amp GE AC circuit breaker in a DC circuit. So, after testing it in a DC circuit with some loads and ammeter + clamp DC amp meter I find the current at which the breaker trips. Let's assume as an example this is 45 amps. So, is it possible to use the AC circuit breaker in the DC circuit on a permanent basis? I've seen a YouTube clip where a person is using an AC 6-amp 230V breaker with a DC circuit and it tripped at 13 amps when loaded.

Are there any significant safety hazards with this technique? I mean I was thinking since it's the current that matters maybe these breakers can be used with 6V/12V/24V circuits where the currents are generally going to be drawing only under 20 amps in the above mentioned case while using, but in a short circuit scenario, the current will be in 35A to 55A range thus causing the breaker to trip.

Update: I had these two breakers from the old panel in my storeroom. What you guys said is very true. It seems to be quite dangerous to use them in DC too. I have a high-current 12/24V supply capable of 35-amp output. But I’ll only be using it under 20 amps mostly. I build these supplies from UPS transformers. So, I tried to connect the three supplies and I had built to the GE breaker, in short, to see its response only 2 seconds power ON. The first one was with the biggest transformer from a 2000VA UPS. It had very thick low voltage windings (10AWG likely) and shoutings the AC low voltage caused the breaker to trip in 39-41ms. With another transformer from a 700VA UPS from low voltage AC side, it tripped at around 1.17s and finally from a 300VA UPS transformer low voltage AC the breaker did not trip. Now trying the first two transformers I’m dead short on the breaker via a 50 Amp rectifier (Imax peak 400A briefly) I was surprised the breaker didn’t trip even after 2 seconds and I immediately gave up the DC breaker idea. I’ll put the breaker on the  AC low-voltage high-current side for safety and add a 400-amp rectifier to protect in case of a dead short.


texts: Is this protection circuit designed properly?

texts:
I designed this protection circuit to avoid reverse polarity and over-voltage.

Here is the circuit:

simulate this circuit – Schematic created using CircuitLab

Is the circuit designed correctly?

Specifications:

conditions:
$$-20<V_{in}<20$$

requirements:

$$
\text{if }\  0< V_{in} <15  \qquad \text{then }\  V_{out}\approx V_{in} \\
\text{if }\  15< V_{in} <20 \qquad \text{then }\  V_{out}=15 \ \text{and } \color{Red}{LED } \text{ will light.}\ \\
\text{if }\  -20< V_{in} <0 \qquad \text{then }\  V_{out}=0 \ \text{and } \color{Yellow}{LED } \text{ will light.}\
$$


texts: Collpitts Oscillator; A Simulation and its problems

texts:
So i have been trying to make a metal detector and got it working.
I used a collpitts Oscillator from a simulation page (Circuits->Transistors->Oscillators->collpitts) to tune it to the frequency i have.

I want to increase the current that flows inside the coil to make a stronger magnetic field using a higher voltage at the input. In the simulation it works, however in reality when i tried this out the output voltage only decreased. Why is that? (the amplitude decreased)

EDIT1:

This is a rough overview of the whole build. You won't be able to make out the oscillator from the photos as its a big cable salad. I can assure you however that the oscillator is exactly the same with the Parameters (except the inductance which is just a rough assumption based on some online calculators).
The frequency of the wave according to oscilloscope is at about 80kHz to 100kHz.


texts: Power Metal Oxide Resistor - Maximum pulse voltage

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I am looking for a suitable series resistor (220k) for a 230VAC optocoupler input.

The device must meet requirements from EN60664-1. I am still trying to understand the final requirements, but from what I figured out so far, it must withstand a transient over-voltage of at least 5000V.

I was looking at some data sheets like the PO Series from VITROHM. For short transients, there is a maximum pulse voltage of 2000V specified.

Is using this resistor really a no-go or what exactly happens when this voltage is exceeded? If it was just about power dissipation, it would depend on the resistance.

I was not able to find any resistor with a higher rating. I have kind of a reference device (no schematic) and there are just some power resistors (unknown type) placed on the opto-coupler input as well, without any other protection/components.

Any suggestions how to design this?


texts: Main power input section P-CH MOSFET connection confirmation

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In our Design we are using simple P-Ch MOSFET connection to protect reverse current flow direction.

Gate connected to ground so Source to drain current flow will happen through Protection diode as well. If its reverse current flow Protection diode will be reverse bias.

Q1. Is it in reverse current flow Source to drain reverse current will allow because Gate always connected to ground?

Q2. Is this MOSFET connection will blow the device once reached High spike voltage and current?

Thanks in advance

Regards,
RK


texts: How do i solve a circuit when a capacitor is between in op amp inputs?

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I am quite confused with this circuit. Most circuits I have seen don't have a capacitor between the op amp inputs. I tried to write out the differential equations using nodes, but I can't find enough equations to solve the system.
*The circuit showed in the picture is used for humidity measurement by measurement capacitance \$C_x\$, it is an old design but it still works for a range of humidity, i dont have the values of \$C_s\$ and \$C_x\$,but it seems that \$C_x\$ can range from \$0-20pF\$
My goal is understand how this circuit works, and find the mathematical relation between the output volatage of the op amp and \$C_x\$ , frequency and duty cycle of \$S_1\$, then calculate the values of each component in such a way that this relation more or less linear.
I didn't consider that the voltage between the inputs is zero, because I think capacitor \$C_9\$ takes time to be charged or the op amp takes time to make it zero. Do we have to always consider that the voltage between op amp inputs is zero?
Could someone suggest some steps to calculate the components of the circuit?, maybe I shoud remove \$C_9\$ at the beginning, calculate the component's values , and implement the circuit and then check which value of \$C_9\$ give a better performance.
thanks in advance


texts: What wire to buy to extend the legs of SMD components?

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I am attaching some neopixels to an art project. Rather than buy the breadboard style neopixel which is 4x as expensive, I am buying the SMD style and just soldering legs on. This worked well for a few test neopixels, however, I was just using legs snipped off resistors.

This is a bit of a waste, and the resistor wire I think is roughly 26 gauge, I would prefer something a little stiffer.

I would prefer to purchase some 22 gauge wire and use that for the legs.

So what composition exactly are component legs? Just steel? I know it probably doesn't matter too much but I'm just curious if there is a standard. Is it possible to buy just component legs? I could buy a spool of bare wire but straightening it out could get annoying.


texts: What is the function of the two diodes and the resistor? Why does not the SET coil  have resistor?


texts: How do I use the Z-input on my oscilloscope (full range of contrast / brightness)?

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I guess all scopes are a little different and don't provide any adjustment knobs for the Z-axis input. Mine is a Protek 6502A and it's Z-axis spec says

Z Axis Modulation:

Sensitivity: 5V P-P (Intensity increases with a negative going input)
Bandwidth (-3dB): DC to 2MHz
Input Impedance: Approx. 33 KΩ
Maximum Input Voltage: 30V (DC or AC peak)

The input is the normal BNC probe plug and no separate GND. So I am already apprehensive that I will need a second voltage supply. My setup is TTL digital and I don't have a bench PSU, just drive everything off 5V DC cell phone chargers.
So, I just went ahead and added a second charger and connected GND of first to +5V of the second, and now I have a +5V - GND - -5V setup. Then I plugged a 1 MΩ trimpot between the two extremes and lead the middle to the Z-input.
I have hooked this up to my brand new 256 x 256 raster scan generator that I built with counters, buffers and R-2R resistor network (and it comes out pretty flawless, I'm happy to say.)
Now if I have the intensity knob just past the middle, say at 1 o'clock I can get the screen to go blank if I turn the pot over to the +5 V rail. When I turn the pot over to the -5 V, I get the brightness maxes out before the full brightness I can get by turning the intensity know further up.
I'd like to have the full contrast range on the Z-axis, but the specs seem to tell me that 5 V peak-to-peak is its range, but I doubt that. It also says 30 V max, so I guess that means beyond 30 V I would destroy it. But will I benefit from +/- 9V? Or +/- 12V?
And what if I were to build myself an auxiliary power supply with +/-15V, would that mean that I am then pushing the 30 V absolute maximum specified?
Here is a photo of what I'm getting if I hook the Z-axis into my X-axis ramp output (which goes from 0 to +5 V). It's not bad, but I like more brightness on the bright and more contrast range, with the black still black.
UPDATE: I bought a pair of 9 V batteries and with the pot between -9 V and +9 V I get about the full range. I suppose +/- 12 V would reach the full range. So, now I need to figure out how to convert the TTL > +2 V to -9 V and < 0.5 V to -9 V. A comparator / op-amp comes to mind. But it wouldn't work, not yet.