texts: Homemade EEG Circuit Common mode feedback

texts:
https://sites.google.com/site/chipstein/home-page/eeg-with-an-arduino/assembling-the-arduino-eeg-circult

Hi, I am currently building a DIY EEG circuit using the guide above. This guide is for when there are two inputs. However, how can I modify this so that I can also input two EMG signals too.

It is common knowledge that EEG's carry weak EMG signals with it. My idea is to
obtain a clean EMG signal from the source, and also obtain a EEG signal (with the EMG noise)
I would use the differential amplifier with both the EEG and clean EMG signal to effectively cancel out the EMG signal and get a more pure EEG signal.


texts: How would I go about finding the datasheet for an outdated IC?

texts: I picked up a digital frame and I want to salvage the screen for another project so I'd like the IC sheet to tell where video input is. The IC in question is CT952B. How could I find a datasheet for an obsolete IC?


texts: Power effeciency of Zener diode regulator

texts:
How to calculate the power efficiency of zener diode regulator?

Is it correct to calculate it as the ratio of power delivered to load to the total power drawn from input source?

If I am correct, would the efficiency of circuit shown in the schematic below is 0.5% ?

EDIT

The maximum current zener can handle in this case is around 240mA.

Based on this,

$$ \frac{Vin - Vz}{Imax} = \frac{12-3.9}{240} = 32 Ohms $$

Am I correct?

Is efficiency Vout/Vin or Pout/Pin ?


texts:
My reference text introduces the MOFSET as follows:

The text says the induced channel has uniform width as long as \$v_{DS}\$ is small, because in that case \$v_{GD} = v_{GS} - v_{DS} \approx v_{GS}\$, and if this is violated, then the width of the channel near the drain decreases. I don't really understand why, nor how this is relevant to the width of the channel. Shouldn't \$v_{DS}\$ be uniform across the drain? Then wouldn't all components of the electric field be horizontal?


texts: Altium Designer - Parameter for the current day of the week

texts: I am currently using the value "=CurrentDate" as one of my parameters, however I would also like to include the day of the week as well. I checked Altium's documentation but couldn't find anything for displaying the day of the week. My current display shows in the form of "mm/dd/yyyy" but I would like the display to show "day_of_the_week, mm/dd/yyyy"


texts: Can not get the IC version of some gates to show up in KiCad

texts:
I don't know if this is a problem with the software i am running, or the way i am trying to go about doing this. But every time i try to place the 74LS04 IC in Eschema it only shows the option to place the symbol for the inverter gate instead of the actual chip. i have tried re installing the 74xx library multiple times but no dice. i also tried typing ic after the chip name , because i know other programs run it that way, like Multisim but it did not work either.

If it helps to know i am running a Debian system with the 4.0.5 version of KiCad.


texts: 4-20mA Potentiometer to arduino questions

texts:
I've recently been messing around with the Arduino Uno and potentiometers. I got a potentiometer from where I work but I'm not sure how I should hook it up so I don't mess anything up! There are 3 markings on it that are as follows:

simulate this circuit – Schematic created using CircuitLab
I'm guessing the middle pin means it needs between 10-30 Volts to work, and the Out would be the signal output of between 4-20mA? How would I have to wire the signal pin so the Arduino can recognize it as an input? Sorry, this may be a very easy question but I am very new to the electronic area so any help would be greatly appreciated!


texts:
I was reading through this and was a bit confused. What do they mean by
"took forever to settle to 10-bits (0.1%)"?

How is 10-bits = 0.1%


texts:
I am using eeprom emulator which writes a page of flash of 60 bytes at once. Data to be written to that page is first stored in a 60 byte buffer (array of 60 elements) in ram and then transferred to flash at once.
Now I want to make my own function  above that library which will take address as well as data and store it in  page buffer accordingly. That is, if the data is 16 bit long then it should store it in two consecutive location in page buffer array, If it is 8 bit long then it should store it at single location pointed by address.
My query is how can my function determine size of data, I want to store, just from the data variable


texts: Using just one output of a J-K flip-flop

texts:
If I am using a J-K flip-flop, but only need one of the outputs, what should I do with the other?

Leave it disconnected, or tie it high/low (via a resistor?) Why?


texts: What limits the number of addressable LED strips that can be controlled?

texts:
As the title suggest, what limits the number of "pixels" I can control in an individually addressable LED strip such as SK6812. Most controllers on the market I see are only up to 2048 pixels.
If I were to make my own controller I can simply circumvent this by assigning another signal pin to the next line and just time it in code. Is it the  driving capability of the digital pin ? I thought each pixel in the LED strip will act as a repeater after it recieves its color. I can also just use a MOSFET to increase the current capability of the data pin if that's the problem.
So why do they stop at 2048?


texts: Detecting state of a button when in parallel with LED

texts:
I am using an Arduino to try to update an old lighting system in my house. The previous solution was a 20-30 year old Lutron Lumaster system. However, it was struck by lightning last summer and is no longer in commission.

Part of the lighting system are several low voltage switches distributed around the house. Each switch contains an LED (this indicates if the overhead lights for that switch are on or not) and a push button.

Because I couldn't find much info about this system online, I have been trying to reverse engineer how it works to put an Arduino in its place.

What I need to do is:

Be able to toggle the LED in the wall plate on and off.
Detect if the button in the wall plate is pushed or not.

The only issue is, the button and the switch are wired in parallel. Meaning at the electrical panel there are two wires. One marked "COM" and one marked "A". If you put a ohm meter across COM and A, you'll find pushing the button toggles it from something like 500K Ohms to 10K Ohms. Also, if you were to put 12V across COM and A (with + on COM) you would light the LED.

Is there a way to both drive the LED and detect the button push? I can figure out how to do or the other, but not both at the same time. Not entirely sure its possible.


texts: Ground connection between local and global GND in oscillator layout

texts:
I'm designing a PCB using the STM32F103CB, and have a question on the oscillator layout.

I've learned that I'm supposed to do a local GND plane for the oscillator circuit, and that the local GND plane should connect to the global GND plane in a single point. However, when I look into ST:s Oscillator design guide, it says the following (on page 42): "The oscillator ground plane should be connected to the nearest microcontroller ground."

I've implemented this as follows:

It's a 4 layer design, and C201 is decoupling for the 3.3V supply that's next to the oscillator pins.

The connection between the local oscillator GND plane and the global GND plane is now through the MCU, instead of using a via down to the adjacent global GND plane on the next layer. My question is, is this a bad idea? Am I misinterpreting what the ST design guidelines says? Should I have a connection both to the MCU GND and a via down to the global GND plane?


texts: Using two voltage regulators (780x) in series to prevent heat sink

texts:
(updated due to remark of ChrisStratton).

I am wondering if it is a good idea to use two regulators in series.

What I want: using 2 12V Nema17 motors (using 12V, 1.7A each).
Using a microcontroller board (STM32F103C8T6 in most cases, 5V input voltage). However, I'm not sure what to add (except DMX possibly also a nRF24L01+ 2.4 GHz transceiver), multiple LEDs (5 mA each). So assume I need max. 200 mA.

Than my power dissipation if I would use a single 7805 would be (12 V - 5 V) * 0.2 A = 1.4 W

I heard above 0.8 or 0.9 W a heatsink is adviced. However, what if I use two regulators in series:

7809: power dissipation: (12 V - 9 V) * 0.2 A = 0.6 W
7805: power dissipation (  9 V - 5 V) * 0.2 A = 0.8 W

Would this work? And if so, should I place them with some distance not to heat each other?


texts: I'm trying to design an isolated LED driver using this IC. The problem is that when I turn on the driver the MOSFET heats up too quickly and it fails if it stays on for a few seconds. I have attached a moderately sized heat sink suitable for To-220 package to the MOSFET. I have tried changing the gate resistors and even shorted them because I thought the gate was not turned on fully but the result is still the same. I don't have a temperature sensor but the heat sink heats up to extremely hot to touch in just a couple of seconds (~5 seconds). Obviously the MOSFET shouldn't dissipate this much energy when I'm running a 15W LED. What could be the reason for this?


texts: how to calculate the signal-to-noise ratio from a transient

texts:
This is probably a dumb question about the signal-to-noise ratio (SNR). I know the SNR of a signal is defined as the signal power divided by the noise power. Now I have a noisy transient voltage decay V=V(t), and the voltage decays toward zero as time increases. How do I calculate the SNR? Someone told me it was simply

$$
SNR=\left[\frac{V(0)}{V(\infty)}\right]^2
$$

But I doubted it since I couldn't link this formula to the original definition of SNR. Can anyone explain?


texts: Confusion with non-ideal current and voltage source models

texts:
I have a confusion with the following explanation of non-ideal voltage and current sources:

These above doesn't look like the Thevenin or Norton models since the plots are non linear.
Can someone explain the meaning of these graphs in a simpler fashion?


texts: Control theory diagram for feedback circuit with compensation

texts:
An op-amp that drives a secondary gain stage might be given like this:

simulate this circuit – Schematic created using CircuitLab

Where it is important to note that FB1 is some impedence (unlikely to be purely real) rather than a resistor, and the same for FB2_a and FB2_b.

However, I'm unsure how to describe such a circuit using a control theory diagram.  The diagram that I naively believe to be correct is here:

simulate this circuit

However, The node between FB1 and FB2 doesn't seem correct (and I'm not sure how to deal with such a node).  I have seen structures where FB1 and FB2 go through a summing block, or where they go through two difference blocks in series between In and G1:

simulate this circuit

However, this seems to ignore the fact that the voltages after FB1 and FB2 must be the same, they are not added together.

How does one properly represent the circuit given above using control theory diagrams?


texts:
I'm using a Cortex M3 processor on an LPC1769 board. For this particular situation, all processes occur within interrupts. Therefore, within the main "loop" there isn't actually anything to be processed. I want to calculate the processor utilisation however I'm not entirely sure of the best method to do this.

My original idea was to have a variable that is incremented every clock cycle where an interrupt isn't run. I can then use the equation below once a second.

$$ processorUtilisation = \frac{totalExpectedTickets - countedTicks}{totalExpectedTickets} * 100 $$

However, I'm not entirely sure whether that is a suitable solution mainly because I can't see a way to have a variable increment on every clock cycle.

Any other suggestions?


texts:
We know that transconductance is defined as:

$$g_m=\frac{\Delta i_{\text{output}}}{\Delta  V_{\text{input}}}$$

My question is: why is such a quantity as transconductance defined in the way it is? How is it helpful to electrical engineers?

I ask this because I am having difficulty memorizing this formula. I always mess it up as  \$g_m=\frac{\Delta i_{\text{input}}}{\Delta  V_{\text{output}}}\$ instead of the correct one. I know conductance is inverse of resistance, so the current will always be in the numerator and voltage in denominator. But, I am not sure which one is output and which one is input. Perhaps, if I know the logic of this definition, I'll be able to recall better.

Sorry if this reason is apparent to you, but I am a beginner, and it is not at all apparent to me, so kindly explain in simple language. Thank you!

Note: Please restrict your answer to a Bipolar Junction Transistor only.


texts: STM32F401 failed the search for probes ensure that the usb drivers are installed

texts:
I have a stm32f401vc discovery card, I can't download and debug the code
you can find the error in this picture

when I connected the card to my pc here is what I found in Device manager

I worked on this card for a long time and this is the first time that I find this error


texts: MAx peak to peak of ES without clipping?

texts: This is an exam problem in which my instructor gave the answers but no work. Any one has an idea of how to solve it;FOM(figure of merit)= 25/125, RL=15 ohms, Rx=250 ohms, r1,r2,vee,vcc, are not given. There is more info in the table in the image about vbe, etc.? The answer is ES=161.052 volts peak to peak. OHH and at 42 degrees above ambient the transistors dissipates 25 watts of power I tried somethings regarding ES which is ES=vin/zin*(Rx+zin), however I am stuck at finding vin and zin(since r1 an r2 are not given), and obtaining the thermal model didnt help me. My professor said the key to this problem lies on realizing the relationship between the TA or temperature at ambient and some other value, which I forgot, and is why I am here.


texts: Altium designing connector with mechancial pins

texts:
Trying to get this component drawn into altium:
https://www.molex.com/molex/products/part-detail/pcb_headers/0039303035
It has 3 pins which are the electrical connections but then there is also the two additional holes for the mounting feature.
I have attached the mechanical drawing for ease of understanding:

My issue is that i am unsure how to make the 2 mounting holes? I previously added them as multi layer non plated, but then it gives me an error if i don't have a designator (missing pad designator). But of course it's not a pad.
Downloading the cad from octopart uses the same method (multilayer non plated hole), that is something i can't directly import in.
This is what the octopart import looks like:

Any suggestions?
Also i am finding different designs on octopart makes use of different mechanical layers. Is there any best practices for this? For e.g mech 1 for 3d only.


texts: How to get the transfer characteristics of power strip lines?

texts: I am trying to design the Powerline Communication (PLC) module JUST for the 5-socket power strip (for demo purpose). So, I only care about the powerline network for those 5-sockets only. However, I need to know the transfer characteristics of the power strip lines so that I can choose the optimum frequency band for modulation. What is the best way to conduct this experiment so I can have a transfer characteristics of the copper plates (Line to Neutral) in the power strip? What I want is the impulse response in frequency domain up to 500 MHz. How do I do that in lab? I have a frequency generator (square, pulse, sine, sawtooth) etc and 5Ghz BW agilent oscilloscope.


texts: Lost layers after upgrading cadence into 6.1.5

texts:
I was using an older version of cadence with LSW in a seperate window. After upgrading cadence into the new version, I am unable to access the layers like: met1, met2. I enabled valid layers, but they are only some useless ones.

How can I enable the old layers?


texts: Instantaneous and active power in an ideal switch powered by real source and squared wave

texts:
This is a somewhat theoretical question, but one that has some impact on power theory.

The circuit in the figure is composed of a real DC source (with non-negligible internal resistance) and feeds a non-linear load, composed of an ideal switch that switches every T/2. This problem is proposed in https://doi.org/10.1109/EPE.2019.8777983 by L. Czarnecki (a renowned power system engineer).

It seems clear that the instantaneous power is null, since the voltage is 0 when the current flows and the current is also 0 when the switch is open. It seems quite intuitive. Mathematically, the instantaneous power is defined by \$p(t)=u(t)i(t)=0\$ and the active power \$P\$ is the average value, so it should be also 0.  The problem arises if you use the Fourier series for a square wave. In this case (\$\omega=\frac{2\pi}{T}\$),

$$u(t)=\frac{100}{2}\left(1+\frac{4}{\pi}\sum_{n=1,3,5...}^{\infty}\frac{1}{n}\sin{n\omega t}\right)$$
$$i(t)=\frac{100}{2}\left(1-\frac{4}{\pi}\sum_{n=1,3,5...}^{\infty}\frac{1}{n}\sin{n\omega t}\right)$$

In this case, it can be seen that the power is no longer equal to 0, as there is at least one DC term

$$p(t)=\frac{100}{2}\frac{100}{2}+...=2500+... \quad \text{[W]}$$

What do you think about this? For me, it makes more sense physically the first proposal, but I think there's something that I miss...

Update: I update the summation index to reflect odd sequence.

SOLVED: Indeed, all the terms sum up to zero. The key is that the cross products between 1 and the summations cancel out and the product of summations is

$$\left(\frac{100}{2}\frac{4}{\pi}\sum_{n=1,3,5...}^{\infty}\frac{1}{n}\sin{n\omega t}\right)\left(-\frac{100}{2}\frac{4}{\pi}\sum_{n=1,3,5...}^{\infty}\frac{1}{n}\sin{n\omega t}\right)=-2500 $$

so \$p(t)=0\$ in both time and frequency domain


texts:
Male part on the board:

Female part in the casing, on the cable. Lockable.

What type of connectors are these?

Sorry for low quality photos, camera seems to be incapable to do macro job. But male image is lucky one, and 24 conductors are more or less recognisable on it. I examined a female part and can positively confirm, connector have 24 conductors (not counting outer casing, which might be used as an additional "ground" conductor).


texts: Measuring average current consumption in hardware

texts:
I'm working on a very low power budget, battery powered project.  This project is allowed to draw 15uA (average) at 3v.  The microcontroller we're using draws 4-10mA when active, and 2-3uA when asleep.  The micro spends the vast majority of its time asleep.

I'd like to have an on-board way to measure the average current consumption of the entire system for the past 5-10 seconds.  The problem is running the micro to read a shunt resistor requires, well, running the micro.  This device is intended to run for years off of a battery, and we'd like to be able to detect premature failures based on current consumption.

My basic idea is to take the typical current sense circuitry and throw a big capacitor across the output of the opamp.  The ADC input to the micro is high impedance (10s of megohms).

Is this something that could work?  I would be looking for +/- 2uA accuracy.  Ignore the actual component values.  I'm trying to figure out a general approach first.

simulate this circuit – Schematic created using CircuitLab


texts: Alternative to train current collectors (pantographs)

texts:
A current collector (or pantograph) is a mechanical system used by, for example, trains and trams, to collect current from an overhead wire.

When thinking about high-speed trains, e.g., the Shinkansen, but also with lower speed trains, there must be massive wear and tear on the current collectors and the wires.

Because changing the overhead wire is more expensive than replacing the current collector contacts, one chooses a softer material to make the current collector wear down faster than the overhead lines.

I am fascinated by the fact that such a "primitive" way of transferring current is used so successfully, and that it is even possible that a train goes many hundred kilometers without having to change contacts.

Are there any other alternatives to transfer current for high-speed trains?

Some trains are using magnetic levitation, but I believe the tracks are costly because they have to be fitted with strong electric magnets all the way.

Why are there no attempts to use a contactless transfer of current, for example, couldn't one design an antenna where current sparks from the overhead wire to the antenna?

Please suggest better tags for this question.


texts: Fluctuating ADC results - is it normal and characterized in a datasheet?

texts:
As I have been reading [1], there exist four different DAC error types, which contribute to the overall error:

Offset Error
Gain Error
INL Error
DNL Error

Is my understanding correct, that these are static errors?
So if I was to take a measurement of a stable analog voltage,
the obtained result by the ADC has a certain error.
However, If I am to repeat the measurement x times, I would still obtain the same result, no fluctuation?
[1] https://www.maximintegrated.com/en/design/technical-documents/tutorials/7/748.html
Background:
I am using a 10 bit ADC, and my voltage reading fluctuate all the time.
The ADC accuracy specs are:

Integral Nonlinearity INL ±0.5 LSB (typ) ±1 LSB (max)
Differential Nonlinearity DNL ±0.25 LSB (typ) ±1 LSB (max)
Offset Error ±1.5 LSB max
Gain Error  ±1.0 LSB max

I took multiple readings with a voltage divider formed of 2 1k Ohm resistors, sourced by 3v3 on a raspberry pi 3.
The results are (left column is the abs. frequency, right col gives the voltage value):
      4 1.633887
     14 1.637109
     57 1.640332
   7927 1.643555
   7585 1.646777
   9042 1.650000
    605 1.653223
      9 1.656445
      2 1.659668

With a better circuit board would I ideally only obtain the same value all the time, regardless of how large INL, DNL and other errors are?
Thank you!
Edit:
As suggested by @JRE and @JustMe the unclean voltage and breadboard setup was indeed causing all the fluctuations. I am still using the poor setup on a breadboard as before where I had the fluctuating readings.
For anyone else with the same problem, a capacitor next to the ADC on the breadboard (as it would have been suggested for PCB designs anyway)  fixed things nicely (used a Panasonic FR capacitor with 270 uF). My readings are now repeatedly 1.65 V without any fluctuations.


texts: CAN bus physical layer configuration for more than two devices

texts:
I am designing a CAN bus for a light electric vehicle, likely using an Arduino CAN bus shield or similar.

Using a single D-sub cable it's obvious that two devices could be connected together. The system I'm designing will have multiple CAN nodes and so I'm curious of the best way to achieve this.

I think the best option is to use a simple D-sub splitter. This will keep the branch from the main CAN bus line less than 30 cm as per specifications and thus minimising interference.

The only other answer I can think of is to hack the board a little and wire up another connecter in parallel to the existing one.

Will using a simple splitter cause me any issues? If so, can I solve them?
If not, is there another easy way I can use these boards to interface with a CAN bus with multiple devices using D-sub cabling?


texts: Altium Differential Pair Routing Via to Via Clearance

texts:
In Altium 14.3 how can one define via to via clearance in differential pair routing to produce a different spacing between via to via and track to track?

I defined a design Rule: Electrical->Clearance->ClearenceViaToVia[IsVia,IsVia] to 0.2mm

Because my differential pair routing rule is set to MaxGap 0.15mm Altium violates it in interactive routing mode, which is pretty annoying


texts: How does short length of transmission line approximate to a wire?

texts: Suppose I have a transmission line of length \$L\$ with characteristic impedance \$Z_0\$ and load voltage \$Z_L\$. If it is connected to a ideal sinusoidal voltage source \$V_s\$, then the voltage across the load \$V_L=V_s \frac{2Z_L}{Z_L+Z_0}\$. However, I think that when L becomes very small (compared to wavelength of the source) , the line essentially acts as a short and I should get \$V_L=V_s\$ across the load. I do not understand how this approximation can be obtained by reducing the length since \$V_L\$ got from transmission line model seems to be independent of the length (and of source frequency).


texts: What's the influence of noises when electromagnetic waves are used as a power source

texts:
I am relatively new to this field, and please understand if my question seems ridiculous.

As far as I know, the passive RFID tag is supposed to harvest energy from radio waves emitted from other devices. The radio waves are electromagnetic signals. The passive RFID tag has a coiled antenna that also serves as a filter, which selects signals of a certain range of frequencies (for example, from 13.46 to 13.66 MHz)

This is where my question rises. Even after filtering the signal received, the filtered signal may contain noises.
I am guessing that power source does not have to be as sensitive as data communication between two devices. However, even so, I wonder if having noises in a signal doesn't have any effect on its role as a power source.
Thank you.


texts: 256-point FFT, but only need 5-6 frequencies, is there a better way?

texts:
Due to the constraints of my system, I have a 256pt FFT.  However, I only care about the energy at 5 or 6 of the 256 bins.  256pt FFT is still faster than 5 or 6 specific DFTs, but it seems wasteful to compute 256 frequencies for only 5 or 6. Is there a better way?  Would downsampling be what I would want to do here?  If I reduce from 256 to 64 frequencies, I'd get a 5x improvement factor in the no. of operations --but I'm not sure I understand the concept fully (even after reading Oppenheim's Discrete Time signal processing" book) --ie, would this be a proper application of this concept.

Any suggestions on what to look into or further reading would be greatly appreciated, and some real world examples would help me understand is better. Thank you.


texts:
We are running FreeRTOS with CMSIS. Is it possible, using CMSIS on STM32F3 Discovery board, to have periodic tasks running with periods less than 1 millisecond resolution? We want to run tasks at 400 Hz, meaning the period should be 2.5 milliseconds. All functions pertaining to delays in CMSIS that i've found have millisecond resolution. Should we reconsider using CMSIS for our purposes?

EDIT 2:
A straight forward question now, hehe.
Could someone show me an example of how to setup a task to run periodically with a rate of 400 Hz with FreeRTOS, possibly using CMSIS but not limited to it, on STM32F3 Discovery board?

EDIT:
I will try to explain in more detail. The task is a PID controller that should run as fast as possible, but no faster than 432 Hz. So 400 Hz seemed like a round number. This means that 2 ms is a too short period. And the difference in task frequency between 2 ms and, say, 4 ms is quite dramatically. I don't quite know how much jitter we can accept, though. But it should probably not be in the millisecond range.

It seems more and more like we have to make use of the native FreeRTOS calls for the timing of tasks.

We would happily trade CPU utilization for greater timing accuracy since we won't probably make use of a great deal of the cycles in non-OS activity.


texts: Ni-Mh batteries, low capacity better performance?

texts:
When we take appart cordless things like drills, vacuum cleaners, telephones..., they often use small capacity (like 700 mAh) Ni-Mh cells. I've always thought that it was because of cost reduction, but now I'm wondering if they tolerate better the abuse of the common user that doesn't care much and plug the appliances to the charger after every use.

This question arises since I replaced the batteries of one of those devices for the ready available 2000 mAh Ni-Mh cells from a good manufacturer, and I have the feeling after some time that they have suffered an important degradation.

Anybody knows?


texts: Arduino program not incrementing loop counter

texts:
I am programming effects for an LED cube. The cube and the independent functions are working correctly. The problem occurs when I call turnon_layer function in a loop. The loop counter is not incremented.

for(i=0; i<4; i++)
{
  Serial.println(i);
  turnon_layer(1000,i);
}

The Serial monitor shows that i has a constant value of 0 throughout.

When I call the functions with constants, then the output is as expected.

turnon_layer(1000,0);
turnon_layer(1000,1);
turnon_layer(1000,2);
turnon_layer(1000,3);

My turnon_layer function is :

void turnon_layer(long time, int layer)
{
  boolean state = HIGH;
  long wait, start = millis();
  for(i=0; i<4; i++)
  {
      if(i!=layer) digitalWrite(levelPin[i], !LOW);
      else digitalWrite(levelPin[i], !HIGH);
  }

  if(time/2<10)  wait = time/2;
  else  wait = 10;

  while(millis()-start<time)
  {
    state = !state;
    //Serial.println(state);
    //First 8 LEDs
    for(i=0;i<2;i++)
    for(j=0;j<4;j++)
    digitalWrite(ledPin[i][j],state);

    //Next 8 LEDs
    for(i=2;i<4;i++)
    for(j=0;j<4;j++)
    digitalWrite(ledPin[i][j],!state);
    delay(wait);
  }
}

I am using the Arduino IDE.

What is going wrong ? Why ?


texts: I have been interested in coil guns lately, and see that they use coils. However, in every design I have seen, their have been capacitors connected to a charging circuit that is connected to a battery. My question is, why can't a higher voltage battery be directly connected to the coils to create that electromagnetic field that drives the projectile?


texts: Questions about the voltages of a lithium jump starter I purchased

texts:
I purchased an Audew jump starter based on several favorable reviews on youtube.

According to the specs, the jump start output is 14.8V, but when I check the voltage with my multimeter it measures 16.3V.

The jump starter also has a 15V/10A output for a cigarette lighter adapter. The actual voltage for this also measured 16.3 which I guess is no surprise. I tried to power a 150W inverter but the inverter wouldn't even power a 15W device - I'm assuming the inverter can't handle the 16V?

My bigger concern is if it is still safe to use this battery to Jump Start a car? I understand that a car needs greater than 12V to start, but is 16V too much to risk damage?


texts: How do I mix two audio tones from two 555s to make a polyphonic chord?

texts:
I have set up two 555 chips in astable mode to produce a tone each through a speaker.

However, I am not sure how to mix them together to produce a musical chord.

If I directly combine the two outputs from the 555s into a single output, it creates a third tone, but it is just a single tone being some combination of the two frequencies.

Instead I would like to hear each one independently, but on top of each other, just like a keyboard (or a hammond organ if you prefer).

I have tried using an op-amp but with the same result.

Is an op-amp the solution here? Or is there some better strategy?

I just need a push in the general direction.

UPDATE

Both methods below seem to work, but it turns out the main problem was that the two 555s need to be "decoupled" by putting capacitors across pins 1 and 8. That is, when one 555 was sucking power from the battery, it was affecting the frequency of the other one. This (along with the large resistors from the 555s to the opamp) has more or less solved the problem, although the sound quality is not that responsive or stable. Thanks for the help!


texts: Could metal powders replace metal wires?

texts: My headphones broke recently due to what I suspect was work hardening, and I was wondering, could a sealed tube of rubber filled with a powder replace wiring? Products would be more durable as the wires wouldn't break due to work hardening.


texts: How does the secondary coil affect the Q of the primary coil?

texts:
This is an LC tank circuit in which load resistor \$R_L\$ is link-coupled through the inductor:

My textbook stated that:

Link coupling is another way of coupling the signal to a small load resistance. Link coupling means using only a few turns on the secondary winding of an RF transformer. This light coupling ensures that the load resistance will not lower the Q of the tank circuit

What I don't understand is the bold context that implies that if I decrease turns of secondary winding, the Q of the primary inductor (or the LC tank as the whole) will increase.
My thoughts so far is that the reflected impedance on the primary when the secondary has fewer turns (step-down) is that:
$$R_{p} = (\frac{Np} {Ns}) ^2* R_L$$
\$R_p\$ will be very big and this will be in series to inductor of LC tank, but if the series resistance increases then won't Q decrease instead of increasing?
What point am I missing?


texts:
Today When I was seeing this page(Digital multimeters (DMM or DVOM) part) I saw this part:

What does "automotive timing"? and What's the dwell signals? are these electronic concepts?


texts:
I want to generate a random bit sequence using Verilog. i.e. the random bit sequence would be composed of 1 and 0. Can someone guide me as to how to do it? Does anything equivalent of rand() in C/C++ exist in Verilog?

Update-1: FPGA is Spartan 3E Starter Kit


texts: OP-AMP Flip Flop start up predictability

texts: A customer had asked for a circuit design which I felt would be fun to implement using a couple of OP amps. (Its always fun to see if you can do something with op amps instead of a small MCU ). Anyway my circuit worked fine, but of course the customer then requested "just one" additional function, and it warranted an S/R flip flop. So, wanting to stay with the original design philosophy, I found the Op-Amp based SR flip flop circuit below. I implemented it and again everything worked fine. The circuit needs a "high" on either the SET or RESET inputs to toggle its state and conveniently (for me anyway), the circuit always powers up in the reset state. I've tried this with an LF353 I had handy, as well as a spare op amp in a TL084 in the customer's circuit, at a variety of voltages. For me this works out well, but I'm usually paranoid about start up "maybe" states. I suppose I could add a little RC network to the reset input (to force a little pulse on start-up). But if there is a good reason why its likely to be unnecessary, it saves me a couple of parts. :-) Can anyone see a good reason why this circuit reliably powers up reset?


texts: Is there a way to download a firmware from an stm32f103c8t6?

texts:
We have a prototype that uses an STM32 chip, however our software guy went off the grid since COVID-19 and we have only 1 out 5 working prototypes with the software uploaded and working. Now we cant contact him to retrieve the code, he just sended the pcb files and schematics but forgot the firmware. So is there a way for us (we handled other parts of the proyect more hardware related) to "download" the main code of the only prototype and put it in the other 4?
Thanks


texts:
Can anyone recommend a low cost or DIY buildable logic analyzer?

Mostly, it would be for debugging serial protocols (SPI, I2C, RS232) at low voltages.


texts: Did I get this BJT configurations correct?

texts:
I'm trying to learn what kind of BJT transistors are this:
Did I get them right?


texts: Linear potentiometer for suspension travel

texts:
I am working on a project for university measuring the extension of a cars suspension.

I have a potentiometer available to me, but have a few questions regarding how to use it. I understand that it acts as a simple variable resistor, however, how is the changing resistance used to measure extension?

I was told a voltage reading was used in some way to give an extension (unsure of this) but if V=IR, will V not be constant due to battery, and will I not decrease as R increases as it resists the current?

I need a way to collect this data and then transmit it 50m and display it. I'm unsure of how to collect the data (and what data I'm collecting, resistance/extension) and transmit it. But I'm thinking of using an Arduino to receive the data and display it on a monitor.


texts: Where in the instruction pipeline is machine code to microcode translation?

texts:
In my computer architecture courses on the N-stage pipeline, I never encountered the concept of microcode. I was surprised, then, when in a performance analysis course assignment, I discovered that division of certain floats on certain processors became substantially slowed, as the instructor described, because the division needed to take place in microcode because of underflow.

Where in the instruction pipeline does microcode translation take place, and how does it fit into the N-stage pipeline as taught in undergrad coursework? Does microcode translation take place for all instructions, or only complex instructions?

To be concrete, let's focus on modern Intel architectures.


texts: Current limiting in simple blocking oscillator HV generator circuit

texts:
Im planning to use a simple blocking oscillator with a CCFL transformer and Cockcroft-Walton diode multiplier to supply HV for a Geiger-Muller tube. This requires 1600V but at miniscule current.

I wish to make this draw as low a current from the supply as possible, ideally below 1mA from a 9V supply.

What is responsible for limiting the current (other than the load) in such a circuit? Is it just the back-EMF in the transformer primary?


texts:
This board has been very helpful to me, I am stuck with a small problem again. The datasheet is here.

Part name: SMDJ series.

I have a pulse train coming from an ignition system, the power I calculate is about 4 Watts of Pavg. When I refer to the datasheet above, we can see it can withstand about 6.5W of Pavg. But when I calculate the Tj, it exceeds, I get \$75C\times4 = 300C\$ above ambient. Which spec should I rely on: Pavg as stated by manufacturer, or Tj as calculated?


texts:
I am helping to build a costume prop that has four LEDs lights on it (1 white and 3 amber).

This device is worn on the wrist, so space for power is limited- a 9V battery or something that will fit in that space will need to power the four lights.

The device would work on a 4-position rotary switch. Here is how it needs to function:

position 1: off
position 2: white light on and left yellow light on
position 3: white light on and center yellow light on
position 4: white light on and right yellow light on

My long-ago electrical experience tells me that this should be pretty simple, but I just don't recall enough to make this work correctly. I also wonder whether the LEDs needs any circuit help since one of our folks only managed to burn them out connecting directly to a 9V.

UPDATED

Thanks for the feedback WhatRoughBeast and Sphero Pefhany! I appreciate the LiPo suggestion and safety feedback.

I'll take a closer look at the circuit diagram- it looks helpful. I reckon I'll need to do calculations on the resistors now that I have LEDs in hand.

There are more specifics for this case if any of y'all are still following this...

The rotary switch is a 3-pole 4-position switch. The 3 poles (labeled A,B,C) are in center of the switch, with 12 posts (labeled 1-12) in a ring around them.

The LEDs are:
white- Vf 4.1V max, If 25mA max, Vr 4V max, Pd 120mW max, Iv 4000mcd Typ
amber- Vf 2.4V max, If 25mA max, Vr 5V max, Pd 100mW max, Iv 5500mcd Typ

Thanks again for the help!


texts: Appropriate float voltage for SLA battery in 120°F+ environment?

texts:
I've read that the float voltage for lead-acid batteries needs to be adjusted based on the ambient temperature that the batteries are charged in; that lower temperatures merit slightly higher voltages, and higher temperatures merit lower voltages on the battery for float charging.

I have had trouble finding a reference that breaks this out based on the ambient temperature, in a chart or table for example.

I live in the Phoenix, Arizona region, where the temperatures in the summer are easily above 115-120°F.

I have a 12V, 50Ah sealed lead-acid battery in the back of my vehicle, that is currently being used to power some accessories that are in the back of the vehicle, separate from the car's battery and electrical setup.

This battery is charged from a flexible solar panel that's mounted to the top of the vehicle.

The charge controller for this allows me to specify a float voltage, and the default value is 13.7V.

I'm sure, since it's frequently 120°F+ outside, and likely 130-140°F inside the vehicle while it sits in the sun, I need to adjust the floating voltage for this, but I don't know what level would be appropriate for this environment.

To summarize, What would be an appropriate float voltage for a sealed lead-acid 12V battery, in ambient temperatures of 120-140°F?

Update: Asked a separate question regarding the cut-off voltage when discharging and whether similar compensation is needed / how it should be calculated here


texts: How to calculate how long a 9V battery will last based on schematic?

texts:
So I made this schematic for a little bathroom light I made. I would like to figure out how to calculate how long the 9V battery I connected will last with this specific schematic. The diodes are LEDs.

Here is what the Terrible Product looks like for reference:


texts: Compensation for op-amp difference circuit

texts:
I have a difference amplifier built with an op-amp (specifically, I'm using the LT6237) with 10dB gain:

simulate this circuit – Schematic created using CircuitLab

As it is, without external compensation, the frequency response has a bump of more than +12dB at approx. 15MHz (as per an LTSpice simulation).  This is undesirable, so I add a compensation capacitor in parallel with RF1 (approx. 2pF as per LTSpice simulations).

My question: do I need to exactly match this modified feedback network by placing an identical capacitor in parallel with RF2?  The rationale in favor is that this difference amplifier requires ZF2 / RG2 to exactly match ZF1 / RG1 (where ZFn is the impedance of RFn || Cc --- Cc being the compensation capacitor).  The rationale against could be that the mismatch occurs only at high frequencies that are in principle of no interest (where the frequency response starts to fall anyway). LTSpice simulations show that the bump in the frequency response goes away with just the one compensation capacitor; placing the same Cc in parallel with RF2 changes the frequency response making the bandwidth a little bit lower (this is consistent with the intuition --- Cc in parallel with RF2 introduces a low-pass filter in that branch).

Notice that this relates to a modification I need to make to a circuit where the layout is already done, and I'm struggling to fit additional components in it (that's why I'm looking for "excuses" ( :-) ) to avoid having to place the additional capacitor with RF2)

Any suggestions? Should I just place the one Cc in parallel with RF1 and be done with it?


texts:
Inverter circuit

I am trying to replicate the project on this website: https://electricalfundablog.com/make-simple-inverter-home-circuit-step-by-step-method/
 but the recommended transformer is a 9v 0v 9v 5A transformer, can I use this old UPS transformer: ratings on the input side is 7.5v, 0, 7.5v, 17.5v while on the other side(output) it has ratings of 0v, 170v, 195v, 220v, 250v? Do I use the 7.5v 0 7.5v as the input or 17.5v?


texts: How would one classify this transistor based amplifier?


texts:
I have seen a lot of projects that use a tape head, but there is very less information about how to build one yourself. Is this possible?
I know that basically it is a metal core, with a coil around it and a very small gap. I guess the challenge in creating this at home would be to create that gap.
Note that I am not looking for quality, it is just an experiment i would like to try.


texts:
I am using ATmega8 with 16 MHz clock and use Timer2 as PWM with this code:

DDRB |= (1 << DDB3);
OCR2 = 0;
TCCR2 |= (1 << COM21);
TCCR2 |= (1 << WGM21) | (1 << WGM20);
TCCR2 |= (1 << CS21);
OCR2 = 0;

But after this code 0 PWM my led was start with low brightness. So please give me solution.


texts:
I created a module that first sorts a byte array then choose last element as minimum.(just for practice). When I moved sort to the task block, it doesn't worked as well as before. How can use task block properly for sorting ? thanks.

Sort without task:

    module sort(input clk, input nrst, output byte choose);

    byte sorted[0:3];

    assign choose = sorted[3];// output must be minimum after sort (12)

    always@(posedge clk, negedge nrst) begin
        if(nrst == 0) begin // initialize to something
            sorted[0] = 17;
            sorted[1] = 12;
            sorted[2] = 23;
            sorted[3] = 21;
        end
        else begin
            int i, j;
            byte tmp;
            //sort
            for(i=0; i<4; i=i+1)
                for(j=0; j<4; j=j+1)
                    if(sorted[j] < sorted[j+1]) begin
                        tmp = sorted[j]; // swap
                        sorted[j] = sorted[j+1];
                        sorted[j+1] = tmp;
                    end
        end
    end

endmodule

Sort with Task:

module sort(input clk, input nrst, output byte choose);

    byte sorted[0:3];

    assign choose = sorted[3];// output must be minimum after sort (12)

    always@(posedge clk, negedge nrst) begin
        if(nrst == 0) begin // initialize to something
            sorted[0] = 17;
            sorted[1] = 12;
            sorted[2] = 23;
            sorted[3] = 21;
        end
        else begin
            sort_task(sorted);
        end
    end

    task sort_task(inout byte list[3:0]);
        begin
            int i, j;
            byte tmp;
            //sort
            for(i=0; i<4; i=i+1)
                for(j=0; j<4; j=j+1)
                    if(list[j] < list[j+1]) begin
                        tmp = list[j];
                        list[j] = list[j+1];
                        list[j+1] = tmp;
                    end

        end
    endtask

endmodule

Testbench:

module tb();

    byte choose;
    reg nrst, clk;

    sort sort(clk, nrst, choose);

    initial begin
        clk = 0;
        forever #5 clk = ~clk;
    end

    initial begin
        int i;
        nrst = 1;
        #50;
        for(i=0; i<4; i=i+1)
            $display("50 : %d", sort.sorted[i]);
        nrst = 0;
        #50
        for(i=0; i<4; i=i+1)
            $display("100 : %d", sort.sorted[i]);
        nrst = 1;
        #50
        for(i=0; i<4; i=i+1)
            $display("150: %d", sort.sorted[i]);
    end

endmodule


texts: NE555 delayed monostable timer with discharging capacitor after poweroff

texts:
I'm using the following circuit to try to simulate a button press in a speaker:

This is supposed to wait 2 seconds, set the output high for ~500ms and then set it to low.
The output of the NE555 is connected to a transistor that is actually driving the switch's contacts, when the transistor switches on, for the duration of the 500ms, the button is "pressed", as if I did it manually.
This is the transistor stage:

Note: AD_KEY is an ADC input on the speaker's MCU, it checks for a certain voltage provided by the voltage divider when the button is pressed.
I get 5V from the 5V pin of an USB connector somewhere inside the speaker.
The problem is that the circuit only works in certain conditions.
I have made an equivalent circuit using an Arduino, the arduino project works 100% of the time without a doubt.
This circuit is problematic since the first time I power on the speaker, it doesn't work, although the output of the NE555 is properly generated - using a voltmeter I can see the voltage going up after 2 seconds and after ~2.5 seconds I can see it quickly going to 0V.
If I turn the power off and measure (again, using a voltmeter) the output of the NE555, then I can see it slowly going from 1V to 0V, although after the 2.5 initial seconds have passed it was always 0 while the speaker was on - as you'd expect.
Then if I turn the speaker on when the output is still in the 0.1V - 0.2V range: the circuit works every time. So power on during 0.1-0.2V window, power off, wait, again power on while the NE555 output is in that range, it works!
However if I wait for that output voltage to drop very close to 0V and power on the speaker, the circuit no longer simulates the button press (on the voltmeter I can see that after 2 seconds the output voltage doesn't rise again). The same goes for quickly powering on the speaker after powering it off.
So a capacitor is discharging on the out of the timer IC?
Why does it work if I power on the speaker in that 0.1-0.2V range of the output pin?
And to add to the confusion:
A similar situation happens on a breadboard with an LED instead of the MCU, but this time, the circuit only works if I allow the out voltage to completely drop to 0V.
PS:
This is related to: Pressing a physical button, but digitally using an Arduino in an existing circuit


texts: How can I simplify my design for a Surge Protection Device (SPD)?

texts:
I have found a basic design for a SPD and I would like to simplify it. However, I have little experience designing SPD circuits.

This is my parallel type SPD circuit with embeded LED indicator:

In this case:

Can I remove MOV3 and TCO F3 between N and E? Will this still comply
with IEC61643-11/UL 1449?
Do I have to add a normal fuse(5A) at the input side of parallel type
? I will add it for serial type but not sure for parallel.
I will make a direct contact between TCO and MOV on my PCB. This
system will be inside in epoxy. How will this effect the thermal
performace? (I know, this is an experimental question)
I've chosen a 10kA surge MOV for 10kA protection level. Should I
overrate the MOV as you would overrate a fuse i.e. using a 5A fuse
for 3A normal current?


texts:
I have a bunch of motors that I collected from different places. How can I figure out which ones are stepper motors? I have access to the datasheet for most of them, just not sure what to look for.

Links to two pdf datasheets motor 1, and motor 2


texts: How do current spikes effect component lifetime?

texts: My Master's thesis project works with a system that mechanically prevents a DC motor from stalling and effectively thresholds the amount of current the motor draws and removes large current spikes from sudden loads.  It seems intuitive to me that removing these spikes will extend the lifetime of the components in the system (motor, motor controller, battery, etc.) but I need some sort of reference as to why this should be true; ideally some type of study or journal article that I can reference in my thesis.  I am also open to personal explanations.  Thank you!


texts:
I have 4 DC powered electro magnets which I am currently running at 16 Volts @ 5 amps using a variable DC power supply. I want to build a programmable controller that would allow me to control the following functions:

Polarity for each magnet independently of each other (need to switch polarity)
time on for each (duration)
order (8 different options 4 magnets by 2 polarity options)
controlled by my laptop.
fairly simple programming language

What would you recommend?


texts: Boost converter voltage drop when charging battery

texts:
I made a 4s battery pack made of 18650 LiFePO4 cells that I'm planning to use for a mobile computing hobby project.

My plan for charging it is to use a salvaged power supply from a computer along with a boost converter on the 12 V rail to push the pack pack to around 14 V at "full" charge. Max charging voltage according to spec is 14.6 V (3.65 V/cell) but I've read that slightly under-charging dramatically increases lifespan, which is desirable in my use case.

When initially assembling the pack I charged it on a bench power supply directly, until the pack was 13.3 V. Thanks to the power supply's gauges and dials I felt comfortable manually dialing in the current, etc for the initial charge.

After that, I finished the pack by hooking up a 4s protection circuit (https://www.amazon.com/4Series-Protection-Balancing-LiFePO4-Battery/dp/B07511RJ9S) and connecting all of my sensor wires and load-bearing wires according to the diagram pictured here. Now that I'm trying to charge through the protection circuit, nothing seems to be happening.

I've set the open-circuit voltage on the boost converter from 14 V to 14.6 V and no matter what I do I'm always seeing 13.3 V (pack's current resting voltage) across the boost converter's terminals. Waiting a while doesn't change anything, and I'm paranoid that I'm going to fry something just letting it sit powered too long or without supervision.

I don't have anything connected to the BMS load terminal. The charge terminal of the BMS is connected to the Vout- terminal of the boost converter, and the battery pack's positive lead is connected to the Vout+ of the boost converter. The boost converter's Vin- and Vin+ are connected to the PSU's GND and +12v rails, respectively.

I haven't tried going back to the hobby shop and directly charging through the BMS with the bench power supply. Would that be a good step to eliminate some problem with the BMS board? I'm not sure how often those come out bad, and I'm pretty certain I've got it wired correctly. If nothing else it would let me see if I've got any current flowing. The ammeter setting on my tester is finicky, and I don't trust it.

Is this inherent to how a boost converter would work ordinarily? If being connected to a power source causes the boost converter to freeze at that voltage then I'm going to have to figure out some other way of putting together a charger. I was under the impression that by pushing a higher voltage than the battery had, it should cause current to flow back into the battery.

I realize I'm going about this the hard way, but building it from scratch is part of the fun. Please no "buy a charger" replies. I may end up going that route, but until then I'm here specifically to troubleshoot my efforts at making one myself.

I can try some different things, including hooking up a 12v fan as a load, if anybody needs me to in order to eliminate potential issues.


texts:
I have recently seen a rechargeable LED emergency bulb on Kickstarter and I  was wondering how it is working.

In the event of a power failure, the LED bulb will turn ON automatically. That is, when the switch is ON and mains power goes off the bulb will detect that and turn ON. If the switch is OFF bulb will not turn ON. When mains are ON and the switch is ON the bulb will start recharging again.

It is just like a normal bulb. See the Youtube video

My question is, how the bulb will detect the event of mains failure?
Can somebody give me a hint on this?


texts:
I am a pure physics guy, so I understand the fundamental processes behind the generation of electricity, but I'd like to know how to apply it. I was wondering what kind of methods were used in the industry in terms of the generation of electricity.

Is DC generated using a sort of faraday disk generator? How is AC generated? Are there any good books on the subject?

I am capable of handling technical writing and math doesn't scare me.


texts:
I'm building a circuit that sends TTL level signal to uP whether AC signal exists or not. The schematic is as follows:

Actually, the circuit almost works as I expect; however, there occurs some coupling effect on the emitter side of phototransistor; which cause a delay at the output signal. I also added SPICE simulation of Vout and Vb of BC847B.

Green is Vout, and blue is VbQ1. Vout of the circuit is directly connected to I/O pin of my uP. Two questions arise here:

1) How can I prevent this coupling effect? (I've already tried to couple Vcc to emitter pin of optocoupler.)

2) What is the reason of periodic 90mV increase observed on the output signal? I don't think that it will affect the low-level sensing of uP (Vol = 0.3Vcc); however, it is better to supply a clean zero volt to the uP, I suppose.

Thanks in advance.


texts: Help Me to Identify What I did Wrong with this Circuit

texts:
This is the Circuit I Built

Circuit Source

I Assembled this circuit and once I connect the battery, it has to turn on the Relay and supply the Current to charge the battery.

but in my circuit nothing happens. So I checked with multi meter by putting one lead to Ground other lead to Coil terminals of relay and found that two coil leads of relay is receiving 12V.

as I Understand, Relay needs 0-12V to two ends of coil terminals to activate it.

I'm not sure whether i wired 50k preset correctly or not.

this is how I wired Preset

What could be the reason, My circuit not activating Relay?

Regards


texts:
I have been reading up on LED bulbs and it seems power factor correction (PFC) is quite needed in most designs.

My goal is to achieve a PF greater than 0.9. I am considering using an LED Driver with built-in PFC like Fairchild's FLS0116. From the datasheet (and attached photo), it's easy to see that the IC ensures that the LED current follows the shape of the input voltage waveform as closely as possible - including where the voltage crosses zero.

My question is: because the LED current is zero every 10ms, will there be any visible flicker?


texts:
I have several ESPWROOM32 based modules that connect to a far away access point with an RSSI of -70 (it's about 50 feet away through several walls) and a close by access point with an RSSI of -30 (about 10 feet away, free space).  Both of the APs are connected to the same subnet via the wired building Ethernet.  The near AP is on channel 4 and the far AP is on channel 0.
I have found that when the ESP32s are connected to the far access point, incoming port connection attempts occasionally time out.  In other testing, similar timeouts were caused by losing the ARP packets that were looking for the ESP32s IP address.
Is it likely for interference from a nearby AP on a different channel to cause packet loss on a connection to a farther away AP?  If so, is there any way to mitigate the interference?


texts: Adding two signals and finding the RMS and Peak to peak value of the output signal

texts:
I would like to start by saying I have been solving exercise related to Op amps and how to find RMS values and Peak to peak values. But I got stuck on this exercise.

Basically, two signals has to be added.

U1= 4v
U2= 2vsin(2*Pi*f*t)

and after those signals are added using op amps the result should be

Uout=2(U1+U2)

Before I have solved question where both U1 and U2 had some certain value without sine part, and I was able to solve it. But when sine is introduced on one of the signal generator it just got confusing.

My first question is how can two signals be added if one of them has sine part in it and the other not.(May be I am missing some basics, Sorry on my part then.)

Now Second question is how to find the RMS value and peak to peak value of Uout.

What I did for finding the RMS value was

Uout=8v+4vsin(2*Pi*f*t)

than just using RMS formula.

(UoutRMS)²= 1/T * Integration from 0 to T * Uout(t)².dt

Is this correct what I am doing, Need help my finals are coming?


texts:
I'm repairing an ECU board from a SCANIA generator.

It works with 24Vdc, and on the last maintenance the technician powered it with 220Vac, so it blew up some components.

I've managed to replace the burned components, and the board communicates with the controller and PC, everything looks good, except for a "small" problem.

There's a P-Mosfet circuit at the input that blew up, which is heating up a lot on normal use (it reaches at least 80Cº, can'ts say for sure, i don't have a good temp. sensor).

It's really difficult to reverse engineer because i only seee one side of the board and it's very dense (too may components), here's what i could follow:

simulate this circuit – Schematic created using CircuitLab

Some components that where affected: Q1 shorted, M1 shorted, C3 and C2 (tantalum rated at 20Vdc) shorted, and R2 open.

I replaced all those components and the board now "works". The replacements i used are the same components, not some
aproximated equivalent.

Point A is where most loads are connected, and is controlled by an input pin, where 24V on Pin = ON, 0V on Pin = OFF.

The curious thing about the circuit that i cant figure out:

When ON: Point A measures 7Vdc! So the mosfet is dropping 17V, so to me the fact that it's heating up a lot makes sense. (also makes sense that the tantalum capacitors at the output C2 and C3 are rated at 20Vdc)

Even though everything is working, it worries me that this mosfet doesn't seem to be working on normal specs.

This is leading me to think that there has to be a closed loop between "unknown circuit" in point A and "unknown circuit" in Q1 base, and somehow use the mosfet in it's linear region to drop voltage as a function of the load (maybe?). Maybe some other part was destroyed that i can't find, and it's driving the mosfet to a very high voltage of 17V drop instead of maybe 10V or less

If the mosfet was being used as a simple switch, the voltage across draing-source would never be 17V, no matter the load.

Anyways, my question here: Is there any "typical" circuit that uses a mosfet like this, to drop voltage AND turn on/off? Something like a "voltage dropper" perhaps.. If so can you give me example circuits so i can keep searching inside the board to find what the problem is (or if its a problem at all).

Keep in mind that this device is working fine on my bench, with nice temperature. The ECU goes mounted next to a generator where the temperature is at least 50-60Cº, so even if this works here heating up so badly, i don't think it will survive much on it's working conditions. Any ideas would help here.


texts: In this Foster Seeley discriminator, what is the purpose of capacitor C3?

texts: I understand the whole circuit, except for the use of capacitor 3. What's its purpose in here?


texts: MSP430G2553 WDT ISR compilation error - GNU v4.9.1

texts:
I'm using GNU v4.9.1 compiler, and I'm just trying to work with WDT timer:

void __attribute__((interrupt(WDT_VECTOR))) WDT_ISR(void)
{
    P2OUT ^= BIT1;
}

When trying to build it, I keep getting these errors:

section __interrupt_vector_11' will not fit in region `VECT11'

region `VECT11' overflowed by 2 bytes

Do you have any idea, what could cause this?

Thanks.


texts:
I'm being vague about part of my project, but please ask me to fill in critical details I'm missing.

I need to power a 24V @ 20A device for 5 hours (one time), within a weight budget of 700 grams, at a distance of 500ft from the ground.  A 500ft tower is impractical in this instance.  Nobody will die if the device fails, and since it's a hobby project I am OK with some serious liberties in terms of normal safety devices to drive the weight down.

The highest voltage I can realistically attain is 310-340 volts DC (rectified & smoothed 220), which is then raised via a pair of 26awg cables 500ft in the air, and transformed back into 24V @ 20A.  My initial plan is to hack apart a COTS power supply, and strip out the AC rectification side (doing that on the ground), remove as much cooling as I can (because I will have ample airflow), and other hacks -- but I wonder if another topology can be made simpler and still handle a 15:1 reduction ratio.  I'm assuming a fair amount of weight is being taken up with the full transformer inside the power supply, even though it is a high-frequency design.

I can live with high ripple and poor regulation (0.5v P-P, 10% regulation), I don't need mains isolation.  Am I better off chaining 3 buck regulators?  Should I go for a custom-wound transformer and a flyback topology?


texts: How to prototype with Jennic JN5148/001M00T Modules

texts:
I am fascinated by these all in one microcontrollers/zigbee radios from Jennic.  They seem to have done a much better job opening up their platform tools than say Microchip for example.  The SDK and API stacks are all freely available.  You can get a module pretty cheap too, less that $15.  Now comes the rub:  I can't seem to find any modestly priced solution for getting started with development.  To actually use the module you need some sort of carrier board that would have a USB/JTAG interface, a crystal, and a power source.  All these things are accomplished with what Jennic calls a "carrier board" which they freely provide the schematic and gerber files for.  Sadly, it seems there is no way to actually buy this board.  The only way I can find to obtain it is by buying their $1300 evaluation kit.  I'm sure it is really nice, but I don't really want all that stuff.

I could just take their gerbers and have the board made for a couple hundred bucks, but I feel like I must be missing some simple solution.  Why would a company that seems to have gone out of their way to make development simple make this one part so hard?  Is there a better/cheaper way to program these devices?


texts:
I'm browsing through the specs of Arista's Stratix V FPGAs. The first row of Table 1 is labelled "Equivalent LEs".

What are "equivalent logic elements"? What "logic element" do they use as a baseline? I'm assuming the number given is computed from the number of Adaptive logic modules (ALMs) and the number of registers. Is that correct? What is the formula?


texts: Arduino and Ethernet Shield Power Supply

texts:
I have Arduino Uno and Arduino Ethernet Shield. I have four sensors. I am reading sensor values and post it to an ip address. Everything works fine. But my problem is about power supply. When i plug usb cable from any PC to Arduino Uno usb port as power supply, everything is fine. But i want to feed my boards with adaptor that outputs 9V, 1A and available for Arduino Uno. When i use adaptor as power supply, my http post method is not working. I measure all the outputs and inputs of all components, then everything is fine again. The problem is about Ethernet Shield i think.

What is the difference between feeding from usb and feeding from adaptor? Codes are the same just the feeding is changed.


texts: What connectors should I use with 5V DC current?

texts:
In a personal project, I need to power several 5V appliances which, together, use up to 12A.

I want to use a 60 inch cable between a case to which those appliances are connected, and the transformer with 230V AC in and 5V DC max. 30A out.

When I look at the specification for the cables and the connectors, they are all rated pretty low in terms of maximum amperage allowed. For instance, standard C13/C14 connectors used for personal computers are rated 10A.

I suppose that those ratings are likely to be for 250V AC.

Is it safe to simply scale the ratings down to 5V, so 10A for 250V would mean a power of 2500W, and so a maximum of 500A at 5V?

If not, what calculations should I use to determine the required AWG size of the cables and the type of connectors that I am allowed to use?


texts:
I have a custom board with an ESP32 (Wroom-32U) module and JTAG connection for flashing and debugging. While attempting to flash software, I get a timeout. I measured with oscilloscope and found out that GPIO15 (TDO JTAG pin, which is also a strapping pin) is always high (also without programmer connected). I also measured GPIO0 and is it also constantly high. It seems to me that ESP is kind of stuck in a "reset loop" as strapping pins kind of "freeze".

What I have done so far:

I checked the 3.3V power supply, it is stable
I rechecked schematic several times, it appears to be correct

Here is the schematic:

Any idea how what this is or how I could find the bug?

EDIT:
GPIO15 (TDO) also always stay high during flashing.


texts:
I noticed that when using gps in mobile phone, I am positioned away from a wall if I stay very close to it. For example on a street with buildings on both sides, I usually get my location fix on the opposite side of the street than I'm actually on.

I'm guessing that can be explained by the building close to me resulting in a signal delay from satellites behind it (low-frequency microwave spectrum will not penetrate it that well), rather than signal from the front being reflected (this would result in locating me inside of the building instead).

Is that right or is there some more precise explanation?

Additionally, if I wanted to maximise the error for a single device using common materials, is there some simple solution that would achieve good result?


texts: Connecting unbalanced parallel battery strings to a common DC bus

texts:
We are currently researching a system in the design phase which will use 2 parallel 48V lithium battery strings.

Each string will have a battery management system ensuring the cells are balanced.
Each string will have individual charging circuits
The strings will be connected to a common DC bus via a string isolator, probably a high current relay.
The load can be run off a single string, but system performance would be better if both strings are run at the same time.

The question I have regards connecting to the common DC bus if the strings are not fully equalized.  We are considering options such as precharge circuits, connecting the higher string first and then switching the lower string in as they equalize.
Would appreciate input from the community on possible methods, which will allow me to research further?

Thanks,
Suze


texts: MCU sinking current from a higher voltage source

texts:
In previous designs, I have used an MCU digital output to drive the lower side of a resistor ladder to the supply voltage, to prevent power consumption when the ladder is not being sampled:
Schematic 1:

simulate this circuit – Schematic created using CircuitLab
This led me to wonder (in the schematic below):
If the MCU supply (VCC) was 3.3V, and the supply on R3 was 5V, driving the output HIGH would still result in current flow into the MCU. Would sinking current (through M1) when the output is driven HIGH be a problem? My understanding is that typically, when it is desirable to sink current, the output should be driven low (for current to flow to GND through M2).
Does this present a fundamental problem with how CMOS digital outputs are meant to be used? Can current be "sunk" to VCC? Would this cause problems with the intrinsic body diode of the P-Channel M1 always conducting some current, and is that an issue?
Schematic 2:

simulate this circuit


texts: BCD - Karnaugh Map-Logic Diagram-Logic Array

texts:
hi there my english is bad its not my nature language so i translate some words i hope you catch the meaning,i study informatics and i can confess i have trouble with an exercise on the  lesson electronics.I try solve a lot of exercises but i dont know, i stuck i cant solve ,i hope you guys help me with it,i see a lot of this on my book exercises but i didnt find similar exercises not theory spesific to this.I hope here i am in right place you can help me solve an exercise because this exercise i have trouble.I did a work on it but i failed.I know how to to do Karnaugh and etc but i stuck on this.
The exercise is:

  Create detector Binary Decimal Voting (BCD),Multiples with 2,meaning
  2,4,6,8.It given in binary intregers,with 4 bits,b3,b2,b1,b0.

1.Logic Array
 2.Karnaugh Map
 3.Simplified logic function
 4.Logic Diagram


texts:
"simple circuit"

I'm trying to find vout as a function of v1,r,c, and v2, but I'm i'm kind of stuck on what to do.
I'm pretty sure you need to do nodal analysis, but I've never really encountered a circuit like this where I need to find the voltage when it goes to ground.

My initial attempt looks like
(v1-vx)/R+(v2-vx)/Zc=0
where vx is the voltage at that node.  I'm not sure if there's more to the equation or how to find bout.

Any help would be appreciated.


texts: Moving a capacitor in a time varying or non-time varying magnetic field?

texts:
1) If a simple parallel plate capacitor connected to a circuit, and discharging, were to move in an exterior magnetic field, what would happen to the interior region?

Interior region components:

Positive & Negative plates.
Dielectric material.
No dielectric material(vacuum)

2) That same moving capacitor (while discharging) is exposed to a time-varying magnetic field. What effects could occur?

Ideas that come to mind:

Eddy currents
Time-varying induced electric field
Lorentz force(Highly doubt it can contribute anything, in the case
of vacuum gap between the plates it does not interact with
displacement currents, in the case of a dielectric material the
polarization would not yield to a net-positive force in any
direction... they should cancel out).


texts: I have come across Flip-Flop memory elements & it seems really cool, So far i have only did Set, Reset Using Flip Flop, I am eager to know that Is there a way to create a 2 bit / 4bit memory element using Flip Flop? I mean using NAND/NOR gates?


texts: Combine voltage divider with shunt for solar monitor

texts:
I have a basic 12V solar panel system set up with a basic (non-PPT) charge controller(anode/cathode for Panels-Battery-Output). I would like to monitor/control the system with an arduino-based external controller.

Specs on the panel system (let me know if I left anything out)

12V DC -
20A Max current -
12V 35Ah lead-acid -
Panel output: 100W

I am looking for Wh left in the battery and W currently being used.

To achieve this:

Voltage divider on battery
Shunt on charge controller output line.

Can I combine these circuits into one?


texts: If voltage determines the brightness of a LED, how does amps affect it?

texts:
I keep reading different sources and have little understanding of the vocabulary of resistors and LEDS.
Let's say I have a LED that uses 3v and 30mA, if I use a resistor to give it 1.5V at 30mA it will be half as bright; what if I give it 3v, but give it 15mA. Will it be half as bright? Please explain, and maybe add a little meaning to the vocalbulary like 'load' etc. Thanks!


texts: Midband output voltage of cascode BJT amplifier in PSpice not right

texts:
I made a cascode BJT amplifier. \$V_{AC}\$  = 10e-3 V (ACMAG)

From an AC sweep at the output, \$R_L\$, I need to get a voltage between 200 mV and 250 mV. However, I got 0 V.

Why is this so? Do I need to change the biasing?

EDIT

\$R_L\$ = 1M was changed to

\$R_L\$ = 1Meg (instead of milli)

Should the gain be negative?


texts:
I have a microphone cable with 2 conductors in shielded twisted pair in the center. Material is copper.
Each conductor is made of 28 strands x 0.10 mm thick.

They're covered in braided shield with 84 x 0.10 mm.

Outer diameter of the cable is 6 mm.

What is the AWG of the cable?

(28*0.10)*2+84*0.10 OD:6 mm


texts: Would a 9V alkaline power a 12V DC motor?

texts:
I am thinking about buying a 12V DC motor but want to keep everything, including the motor, battery, and power switch somewhat compact. I am not very knowledgeable about these kind of things and am curious whether or not my 12V DC motor would run at all on a 9V battery.

This is the motor


texts: High Step-up Ratio DC-DC Convert (12V-to-150V) - Boost, Flyback, Coupled-inductor Boost?

texts:
I am trying to design an on board DC DC converter that generates 150V from a 12V input.  I'd like to design it to handle at least a 30-50mA load, but in reality the load will most likely be smaller.  The output does not need to be isolated - it can share a common ground with the input.  The other circuitry on the PCB is relatively sensitive to noise, so conducted and radiated emissions are a concern with whatever design I end up choosing.

My first idea was to use a simple boost convert topology, but the step-up ratio seems to be close to the upper end of what most off the shelf boost controller ICs can handle.  For a boost converter, DutyCycle = 1 - (Vin/Vout) = 1 - (12V/150V) = 92%.  Some controllers might be able to produce a 92% duty cycle, but I'd like to have some more margin in the design, so a simple boost probably won't work.

I've looked into some alternatives, but I don't have enough experience with any of the more complicated switcher designs to really understand the pros and cons.    Here's a list of potential options:

-Flyback: Flyback seems like the most straight forward way to generate the 150V.  I've designed a 24V to 70V flyback using a dedicated flyback controller from Linear Tech with an off the shelf transformer designed for flyback applications.  I would imagine I could pretty easily design a flyback circuit for my application assuming I could find a transformer with a high enough winding ratio.  My concern with using a flyback is the noise that it generates.  I know there are ways to suppress some of the noise in a flyback, but, from what I understand, a flyback is inherently pretty noisy.

-Coupled-Inductor Boost Converter: There are some application notes out there that detail using a coupled inductor in a boost setup, which allows higher step-up ratios with smaller duty cycles (https://www.fairchildsemi.com/application-notes/AN/AN-5081.pdf).    I am also concerned with noise in this topology, since it seems like any leakage inductance would cause unwanted emissions that would be difficult to contain.  The switch and diode would need to be rated for a relatively high voltage, but that's not really much of a concern for me.

-SEPIC: To be honest, I don't know much about SEPIC converters, so I can't really speak to the potential pros and cons.  I don't even know if it can product the step-up ratio that I need, I just wanted to get it on the list anyway in case someone has more insight.

-SEPIC Multiplied Boost: I found an app note from Analog Devices that describes a topology that they call "SEPIC Multiplied Boost Converter" (http://www.analog.com/media/en/technical-documentation/application-notes/AN-1126.pdf).  I could not find any other information on the internet about this topology, so it's unclear if it's been widely adopted, or still just exists as a curiosity in some random app note, but it looks like a good candidate.  It would not suffer the effects of leakage inductance, so there would be less noise.  I am a little hesitant however, since it seems like a moderately novel and complex design with not a lot of documentation out there.

-Others?

My question is, for someone with more experience in designing switchers and power electronics, how would you approach this problem?  What topologies would you use?  Are my concerns over noise and high duty cycles valid?


texts: If you have multiple small pcbs in a single chassis, what is the naming convention for components?

texts:
ie, on board 1 do you name resistors R1-R10, then on board 2 name them R1-R10 also?

Or do you name resistors R1-R10 on board 1, R11-R20 on board 2, etc?

What is the convention or best practice?


texts: Is it possible to change the position of arrow to be a little more to upper winding or right winding? If we supply different values of voltage to two winding what will happen to arrow?


texts:
I'm looking at making a BLDC controller with an MCU, and have be reading through the atmel guide AVR444 which steps through a design and software needed for a sensorless back-emf timing controlled driver.

I'm broadening my understanding of the subject. The application I am looking at is for a RC quadcopter, so the level of speed precision isn't critical as long as the overall thrust can vary with a pretty quick response. The load isn't going to vary much either. The motor will be 3 phase (Y windings), around 5-10V, <10A I imagine.

I understand the concept of back-emf in the floating windings to sync up rotating the electrical field. However, my understanding is also that the torque experienced at the rotor is proportional to difference in rotation between the electrical field and the permanent rotor field. So the rotor usually lags slightly behind, causing torque to force it to try and catch up.

The AVR444 app note designs the software to drive the motor blind (using a fixed timings) to begin with, and speed it up to a point then let the back-emf control software to take over. This makes perfect sense to me, but what I am curious about is what is the limitation of driving the motor blind?

As long as there isn't a huge difference between the rotor rotational speed and the electrical field rotational speed, the torque will speed up the rotor and force it to match the electrical field. Since the electrical field is controlled by the software, what would be the issue with blindly driving the electrical field and assuming the rotor keeps up? It is likely to slip rotations every now and then I imagine, but at reasonably high speeds (1000 to 5000rpm) and with some degree of inertia, surely this will average out? If the speed varies by say 100rpm back an forth, I'm not too fussed.

Using a fixed voltage for the motor drive, and a fixed rotation frequency, I expect the current in the windings to vary with the amount of torque needed for the rotor to match pace with the electrical rotation. A current limiter on the power supply could stop anything too crazy.

Thoughts? I realize the preferred method is to use back-emf in a control loop, but I'm looking for an idea as to what the limitations of not using a control loop and blindly driving a BLDC motor would be.

EDIT:
In addition to being an interesting research point, it also has practical use. Blindly driving BLDC motors is a fairly trivial task, that a single control MCU could perform. The current design I'm looking at requires small, separate MCUs to run tight control loops per motor. In a design with 4 motors (possibly more), it's the difference between 1 and 5 MCUs on the board.


texts: series charging three 18650 batteries with three chargers off the same 5V supply

texts:
being from a CS background I am a complete noob at this. I'll keep this short. I have a couple of 18650 batteries that i salvaged from an old laptop battery. I want to make a balanced 3S charger with over-discharge protection. I know that I could use a 3S BMS, but BMS aren't good at charging as they dont balance the cells properly.

I've seen many YouTube videos, regarding DIY balanced 18650 chargers and most of them uses this schematics
this works perfectly for charging only and also does the cell-balancing.

But i wish to obtain the output from the charging modules as they also features a over-discharge protection IC in them. And embedded them into a project, without any hassle.

So, the question: will this work? those are TP4056 with over-discharge protection.


texts: Understanding multiple devices on one surge protector

texts:
This question will demonstrate my ignorance, but hopefully also my desire to learn:
If I just need to make a difficult to access power outlet more available by attaching a power strip or surge protector to it, or if I need a single outlet to be made multiple, is there a spec I need to look for to know that the splitter in question can handle having things plugged in? How does this work? Some questions to help you understand my confusion...

when you plug two items into one socket does it make it twice as "hot"?
are dual outlets wired, intended for two separate items and that's it? Are you overloading one when you put a surge protector on it?


texts: What does "Not recommended for new designs" mean in an ATtiny datasheet?

texts:
I am making my own circuit and I am using ATtiny10-TS8R (I couldn't buy any another type for now), but I found (6) in the datasheet on the part I want to use:

As noted in point (6), it says "Not recommended for new designs".
I used it already and the circuit worked very well, but I am willing to go to mass production, so, is it safe to use that one (TS8R) or may my circuit face problems in the future?


texts:
So, I'm struggling to understand what the S-parameter is in real-life terms; I mean, what does the S-parameter tell us about an antenna?
I have designed a microstrip Wi-Fi antenna that should work at around 2.4 GHz
I have simulated it and as the image below shows, the S-parameter seems correct to me with its down peaking at 2.4 GHz

My problem is, practically speaking, what shows me the S-parameter?
I know that the parameter describes how voltages or currents behave in bi or quadripole but I can't understand how to mirror this theoretical description in my specific example with an antenna working on a certain frequency


texts: Altium: How can I edit a component from a library

texts: I downloaded a library from the internet and I want to create a new  PCB component using the ones in the downloaded library with little editing/changes (such as the footprint). Is that possible? How?


texts:
I have half bridge load cells similar to the ones in the image below. While I understand the circuitry and hooking up the differential output of the load cell to an INA, I am not sure how these are physically mounted to create strain and give a differential output. So far I have used only beam load cells which are easy to mount.

Any help on this would be appreciated.

@Nedd Thank you for the reply. I have the part without the bracket and I was trying to figure out how to 3D print a part that would act as a bracket. Your answer gave me a lot of insight. I guess I need to make sure of the following points

"Inner E" shape does not have a firm support below it and it displaces when a load is placed on the bracket.
The bracket is mounted in such a way that the pressure is applied to far end of the inner E shape.

Thanks


texts: Need a level shifter, is there an IC which does what I want?

texts:
I need to change 3 signals (I1,2,3) which will be at around 2V to get shifted to 5V (in one direction only to O1,2,3). This schematic should do the job, but does anyone know if:

a) there's a better way to do it?

b) there's an IC which does this in a single package?

The way it works is: to set an output (O1-3) to low, the pin connected to the corresponding input (I1-3) should be pulled to anything below about 3.5V, to set it high, the pin should be floated. It works on a breadboard and seems to be the simplest way I can think of to do it.

The power consumption will be very small, a few milliamps. Oh, and these are P style MOSFETS.


texts: Build a breathalyzer like device but for testing liquid or semi-liquid subtances

texts:
As a recovering alcoholic, I know for a scientific fact that alcohol will altogether evaporate from boiling water after sufficient time, and nearly all alcohol from boiling food, which would have a much higher boiling point, but it is harder for the alcohol in a gas state to escape the mixture.

I would like to develop a means of testing for presence of alcohol in cooked food, tea with added alcoholic tincture, and just about anything my less scientifically informed fellow alcoholics are afraid to eat or drink. There are probably several purely chemical means at my disposal, but they are all invasive, and could only be used on a sample of the substance under test.

I would prefer to harness the power of whatever alcohol sensitive transducer (I ignorantly assume) that is used in most breathalyzer machines, and would like some explanation of how these devices work, and how I could apply that technology to a non-gas based but very similar sensor, say a porous rod that one would stir around a while in the substance under test, or be advised if there is any other sensor that I could acquire, or even build, and use.

My electronics knowledge and skills are at tradesman level, and my chemistry is good at high school level, so building the device and understanding explanations is no problem, although building the sensor might prove a greater challenge.


texts: Output current of op-amp of following circuit

texts:
i'm trying solve one question of question paper.

so from figure
I can say that
(1) Iout is Ib and i have equation Ic =BIb. but i have not Ic.
(2) Ib = Vcc-Vbe/Rb. but i have not Rb.

Anyone have another hint??


texts:
So I am solving this exercise. The problem given is to calculate the Voltage between ab. I calculate to 16V but the answer is 4V. I found out that they did not include Voltage between eb. I wonder why is that?

Edit: I applied KCL to calculate I.

The current to node c, I call it Ic

  Icd = Ucd/Rcd = 6V/3ohm = 2A

  Icd = Iac + Ic -> 2A = Iac + 3A -> Iac = -1A

  Icd = Ide (as the current to node e isn't interact with the circuit based according to the picture).

  Ie = Ue / Re = 12V/4ohm = 3A

  I = Ide - Ie = 2A - 3A = -1A

Secondly, I use KVL to find Uab

  -Uab + Uac + Ucd + Ude - Ue(U at the node e) + Ueb = 0

  Uab = -2V+6V+12V-12V+12V

  Uab = 16V


texts: DSP board TMDX5505EZDSP potentiometers and switches

texts:
I have to do a project for school that is an audio effects processor but I'm not experienced with dsp. I'm using the Texas Instruments TMDX5505EZDSP. I've programmed some audio effects based on some example codes, but now I would like to set some of the variables with some potentiometers and switches. How do I read the value of a potentiometer/switch and use it in real time as a variable of the program? Is this even possible?

Thank you


texts: How can the test pen light up when touching your fingers that doesn't have or have very little electricity current?

texts:
I saw this video: https://youtu.be/KiJH1lgaHrY?t=1m49s (at 1:49) where the guy touched the test pen with his fingers and the test pen lights up.

How could it possible? I tried that on my test pen and it doesn't light up. Is it a special test pen?


texts: How to operate a lower power thermistor power circuit?

texts:
I would like to like to create a temperature circuit that connects to a wireless module (e.g. Bluetooth) to transmit the signal. My challenge is that I have a limited power supply (200 mA - 3.5V) to power both. Therefore, I would like to use as little power as possible for my sensing circuit.
Sensing circuit:
For my circuit, I would like to use a thermistor. Since thermistor resistance change with the change of temperature leading the sensing of the thermistor to draw more current. I was thinking of adding a large resistor in series to keep the current draw low since the voltage will be regulated.
Is that a good approach? what problem might it cause? Is there a better alternative?


texts:
Lets have a look at the following circuit:

(Input waveform is sinusoidal and Vpp would be ~32V)

The input waveform should represent an AC Source from a transformer (230VAC/12VAC).

The circuit should automatically disconnect the load (between the two open points in the schematic) if the load draws more than 500mA.

As you can see, there is a relay which does the job.

Now imagine a short circuit in the load. Let's say the resistance of the load is 1mOhm:

Since RL is practically a dead short, the voltage across the shunt resistor will be the full waveform. And since the shunt resistor voltage is amplified by an op-amp, there is a problem because the op-amp supply is +/-5V! (The input voltage should never exceed the opamp's supply range!)

But since I never allow the load to draw more than 500mA, the voltage across Rshunt should really never exceed 0.5V. But since the circuitry has a lag, there will be a short voltage spike on the op's input.

Now, how to solve this problem? I don't want to rely on my circuit behind the op.

One "quick and dirty" solution which came to my mind was using two diodes antiparallel like this:

The voltage across Rshunt should now never exceed +/- 0.7V which is fine by me, because 0.5V is the detection limit. (0.5V = 500mA through RL).

But is there a better way to "cut off" upper voltage limits?
For example let's say I want to cut off an AC frequency to an upper limit of 5V and a under limit of -5V, is this possible with diodes too?

As said, 0.7V is okay but not perfect because it's very close to my 0.5V limit...

BTW: Here is a small illustration of what I meant:

(Left: input voltage, right: desired "clamped" voltage)

EDIT:

As two gave me also feedback on the "Overcurrent Protection" Subcircuit, I'll poste it here:

(UB+ of opamp here is 5V and UB- is 0V)


texts:
We buy a board which has been designed in Germany specifically for us, the board is manufactured in China and delivered straight to our manufacturing plant (not in Germany).

There is a ESD label on the board that likes to come off and potentially get stuck in not so suitable places inside our products (we remove them by hand before mounting the boards instead).

Are there any regulations in Germany that requires that such labels be mounted on all PCBs?


texts: Proton current? and its potential effects in cars and circuitry

texts:
Is this statement true:
"Within the (lead-acid) battery, the electric current is primarily due to proton (hydrogen ion) current which is in the same direction as the electric current."
What are the implications of this statement?

Does proton current exist at all in the rest of the car circuitry, outside of the battery?
And what effects does it have, if any, on the wiring, components, fuses, connectors, circuitry, etc. in cars?

References:
How the Current Flows in a Car?
answer mentioning different flow types: https://electronics.stackexchange.com/a/95049/66759


texts: Implementing a good connection for pogo pins in eagle

texts:
I'm currently working on my very first SMT PCB, and would like to connect a number of PCBs to the main PCB using spring loaded pogo pins like these:
http://uk.farnell.com/harwin/p19-2221/probe-convex-1-90mm-pitch/dp/9960171

My question is in 2 parts:

1)

What kind of connection would you use for the 'female'?
I wanted to use some small pads like the ones shown here:         https://www.harwin.com/product-highlights/pogo-pins-pads/
Somebody suggested leaving plated through holes where the pins would connect but I am skeptical about the long term durability of this method.

2) How would I best go about implementing that type of connection on an eagle schematic / PCB?

Must add that I do not literally mean those exact products, just included the links as an example


texts: Equivalent Circuit based on Current Response

texts:
I am attempting to model a real-world device that I have built. I want to develop an equivalent circuit that I can then tweak to understand its expected behavior in different situations. The image shows that when I supply a voltage with a long slew (green), I get a capacitive response (red). I can model this portion of the response quite well as an RC circuit (white). But you'll notice there is a wave in the current response.
Does anyone have some ideas on what could create this type of wave in the current response?
Edit1: Time axis is in seconds
Edit2: This was built out of raw materials, not electrical components, so I can't share the schematic. I am effectively trying to develop an equivalent schematic.
Thank you for the help!


texts:
The unified diagnostic services (UDS) protocol in ISO 15765-4 seems to be specifically designed for bus systems with a message length of eight bytes (for example, CAN). Now, new transport layers like FlexRay support messages with more than eight bytes.

Is it possible to adapt UDS for those layers? If so, how? Is there a planned update for that standard?


texts: What do small red lines in ActiveHDL waveform window signify?

texts:
Here is the waveform. In a few places for an input signal I can see that there are a few vertical red lines around some rising edge of clock.

What do these lines mean? I have not synthesized this yet and ActiveHDL does not seem to have a built-in option to verify if a design is synthesizable. Please let me know if there is one.


texts: How to test a crystal resonator in board?

texts:
I have 2 quartz crystal resonators in my pcb board: 32.768 kHz & 20 MHz. They are connected to a Freescale MC12311 transceiver IC, which has an HCS08 micro-controller embedded in it. I want to test if these crystals are working properly or not.

Available tools: Oscilloscope, Frequency-Meter (Digital Counter), Digital Multimeter.

How should I use these tools to test the crystals in board?

Note: The capacitive load-effect of probes should probably be considered. If not, the measurement would not be accurate, or even worse, the crystals would not work at all.

Edit1: I used both the oscilloscope and the frequency-meter (with x10 probes), but unfortunately there was nothing monitored at all.


texts: Lowest temperature for a microcontroller

texts: A microcontroller from TI (TMS570LS0432) has a minimum temperature of -40°C according with its datasheet. I would like to test whether it can work also below (e.g. -55°C) by climatic chamber. What would it be a good test scenario to setup to evaluate at that temperature the MCU still survives ?


texts: Influence of a Capacitance Matrix of a voltage measurment

texts:
I am having a problem in understanding how, in a multiconductor system, the Capacitance Matrix influences the measure of voltage between two electrodes.

In the case that interest me we have 4 electrodes, 2 emitting ones and 2 receiving ones. We transmit a known sinusoidal current into the the emitting electrodes and we measure a voltage on the receiving ones.

We calculate the impedance of the quadrupole :

$$
Z= \frac{V_{r2}-V_{r1}}{i}
$$

Where \$Vr\$ are the electrical potentials on the receiving electrodes, and \$i\$ is current emmited.

It is my understanding that the measured voltage is influenced by any conductor present in the medium close-by, therefore we have to determine the Capacitance Matrix to obtain the real voltage measured.

$$
V_{real} = V_{measured}  \alpha  C_{ij}
$$

What I don't understand is the relation between the measured voltage \$V_{measured}\$, the capacitance matrix \$C_{ij}\$ and the real voltage\$V_{real}\$.

If any of you could help understand this I would be very grateful.


texts:
I am reading in a book about the forward bias of a diode. It mentions that in order for a diode to be in the forward mode and its current to rise exponentially:

$$V_{D}\geq + 4V_{T}=0.1V$$

where \$V_{D}\$ is the diode's voltage and \$V_{T}\$ the thermal voltage (approximately 0.025V as a typical value).

My problem is that from what I know and from what I read in another section of the same book and also in other books, then for a diode to be in forward bias:

$$0.5V\leq V_{D}\leq 0.8V$$

If we use the equation of a diode with \$V_{D}=0.1V\$ then:

$$I=e^{0.1/0.025}\approx 53\cdot I_{S}$$

where \$I_{S}\$ is the reverse saturation current.

But with \$V_{D}=0.5V\$ then:

$$I=e^{0.5/0.025}\approx 485165194\cdot I_{S}$$

Clearly with \$V_{D}=0.1V\$ the current through the diode is very small compared to the current that will pass if the voltage is \$V_{D}\geq 0.5\$, as most sources mention as the necessary threshold for a diode to be in forward bias.

Am I missing something?