texts: How to get stereo and mono signals simultaneously?

texts:
I have PAM8403 circuit module to drive my two 3W speakers. I want to drive a subwoofer with a different amplifier. I have a 3 inch subwoofer, and I'll get an amplifier for that. My question is how do I get stereo and mono (both) from my source simultaneously? Because if I short the two signals (L and R), or use a resistor and get mono signal, I lose the stereo signal, and signal from the wires becomes mono. I have tried using just L or R after merging the signals, but they do not stay stereo as they were before, so output from the stereo amplifier sounds mono. So what do I do to get separate mono signal from my stereo signals?

I am a beginner at electronics and speakers, so I request you to please construct your answers accordingly so I can understand better.


texts: STM32 - cannot properly send UART response because EXTI frequently interrupts UART handler with higher priority

texts:
I'm using STM32F4 with HAL. It is configured as a simple counter as it counts pulses via EXTI interrupt. I want to asynchronously ask for the current number of impulses via UART.
Highest frequency of EXTI pulses is 250kHz, uC clock frequency is 180MHz. I think the problem is, sometimes the frequency of pulses on EXTI input is so high that a single UART Rx callback is unable to complete before a new pulse arrives on EXTI input. EXTI has a higher priority, so it interrupts UART Rx interrupt and the UART's response is rubbish.
I'd like this setup to work in a way that EXTI indeed has a higher priority, because it cannot skip any impulse. But the UART should, on rx interrupt, grab the value of number of pulses (global variable) and send it's message 'Pulse counter = <pulseCounter>' without TX buffer being filled with rubbish values. Doesn't matter if another higher priority interrupt arrives or not.
Is there a flaw in my understanding of this problem, or is there a way to fix the code?
Here is an example of UART response:

Here is the code initializing interrupts
HAL_NVIC_SetPriority(EXTI9_5_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(EXTI9_5_IRQn);

HAL_UART_Receive_IT(&huart1, &uartMessage, 1);
HAL_NVIC_SetPriority(USART1_IRQn, 1, 0);

Here is the code of interrupt callbacks:
EXTI:
void getCounterValue()
{
  *pGatePulseCounter = __HAL_TIM_GET_COUNTER(&htim6);
  pGatePulseCounter++;

  if (pGatePulseCounter == &gatePulseCounter[SAMPLE_TABLE_SIZE]) {
    pGatePulseCounter = gatePulseCounter;
    __HAL_TIM_SET_COUNTER(&htim6, 0);
  }

  pulseCounter++;
}

UART:
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
  uint8_t data[50] = {0};

  if (uartMessage == 'p') {
    sprintf((char*)data, "Pulse counter = <%d>\n\r", pulseCounter);
    HAL_UART_Transmit_IT(&huart1, data, sizeof(data));
    pulseCounter = 0;
  } else if (uartMessage == 'f') {
    sprintf((char*)data, "Current frequency = <%d>\n\r", pulseFrequency_Hz);
    for (int i=0; i<SAMPLE_TABLE_SIZE; i++) {
      gatePulseCounter[i] = 0;
    }
    HAL_UART_Transmit_IT(&huart1, data, sizeof(data));
  } else {

  }

  HAL_UART_Receive_IT(&huart1, &uartMessage, 1);
}

global variables:
int gatePulseCounter[SAMPLE_TABLE_SIZE];
int* pGatePulseCounter = gatePulseCounter;

int pulseFrequency_Hz;

unsigned long int pulseCounter = 0;
unsigned long int pulseCounterBuffer = 0;

uint8_t uartMessage;


texts: I'm considering starting a project that would require me to transfer data onto a keyboard ribbon in such a way that it mimics typing. Would it be possible to do this through wires connected to the ribbon itself with some kind of conductive glue? My understanding is that pressing down a key simply closes the circuit, so I realize this is a long shot... but it's one of the first ideas that crossed my mind and I'm not sure what else I'd do. Here are some pictures of the ribbon cable in question: http://imgur.com/a/LKAB0. It's quite old, this is actually a typewriter. Perhaps I could take the entire ribbon out and replace it with a new one which sends inputs from electrical signals? I'm not sure if something like this would be possible, though. Any ideas on how to approach this, or where to start researching?


texts: Load cell accuracy: rated output vs. full scale

texts:
I'm currently shopping for some subminature load cells for a research project. I've narrowed it down to two options, the FUTEK LCM100 and the Burster Model 8417. Problem is the two specify their accuracy in a different manner.

Futek gives the standard Nonlinearity, Repeatability, Hysteresis values but as a % of rated output:

Nonlinearity: ±0.5 % of R.O.
Hysteresis: ±0.5 % of R.O.
Nonrepeatability: ±0.1 % of R.O.

Whereas the Burster gives a single value as a combined % of full scale:

Combined value consisting of non-linearity, hysteresis and nonrepeatability,
in installation position: < ±0.9 % of F.S.

The rep from the Burster reseller says his are more accurate by 1.1%, but from what I can see the FUTEK cells are more accurate. Am I missing something here? Are rated output and full scale synonymous in this context or is there an important difference? Does "combined" mean a sum of all of the accuracy percentages or an average?


texts:
I would be thankful if someone could explain me what is the general formula used to calculate the gain of a common source jfet amplifier.

I have the fallowing circuit:

Since this circuit was taken out from a book, the author says that:"The voltage gain is equal to gm times the signal resistance in the drain leg. There are two paths to signal ground from the drain terminal.One is through Rd and the other is through RL."

If we make the small signal model we will realise that Rd is in paralel with RL so rd = Rd||RL hence the Gain = gm * rd

Okay, all nice and good but I don't understand that, since we use source degeneration resistor, why we bother ourself calculating the transconductance (gm) in order to calculate the gain, when we could calculate the voltage gain by dividing Rd with Rs ( Gain = -Rd/Rs ) just like in bjt..
Or this formula isn't available anymore at JFET?

Ps: The author of the book assumed a gm of 3mS which after calculating the gain it results a 4.5 voltage gain. If we divide Rd with Rs we will get a voltage gain of 6.6.

Thanks in advance!


texts:
If I want to use a Schottky diode with a forward voltage of 450 mV at 1 A. Is the forward voltage the same at 0.3 mA?

The diode is a 1N5817 and for 10 mA there is Vf=0 V.

If I put this diode in series with a 3.6 V lithium battery in a system consuming 0.3 mA under 2.5 V which is the Vout of an LDO, is my system going to work?

EDIT: This is the application :


texts: Voltage sweep circuit for non-linear voltage source

texts:
I am in a need of a simple circuit for sweeping a voltage of a solar cell and measuring the current.

I started with a simple voltage regulator, such as this one:

and adjusted it so it would work according to my purpose:

My colleague suggested to use closed loop compensation. But I am not sure how to approach that. Can I get some suggestions so the circuit will be stable ?


texts: An unwanted path with a microcontroller off

texts:
I made a prototype board of data acquisition and powered it like in the schematic below:

This is a simplified schematic.

There is a USB port that provides power for the whole board; a FT230 for the USB-UART conversion; a ST6600 for smart button functionality; a LDO-3.3V to power the microcontroller (PIC32MZ).

When I press the button, the ST6600 assert the signal that enables the LDO-3.3V and so the microcontroller.

But here I have a little trouble: if I plug the USB cable and NOT press the button, the LED on the output of microcontroller turns on feebly. So I noticed that the problem is due to the RX and TX signals which from the FT230 are connected to the microcontroller. These signals go to 3.3V when the USB is plugged and, even if the microcontroller is off, there is a current that flows inside it and goes out on the output of the LED; I can even read a 1.8V on the 3.3V net of the circuit.

Is this a normal behaviour (maybe I made mistake with this schematic) and if so, can anyone explain me why of the output current and the 1.8V?


texts:
Is decoder 2-4 a complete system?

My opinion: You can create OR, AND with D0-D3(For example D3 = X * Y). but you can't create NOT, because you do not have zero. for example {Dec 2-4,0} IS a complete system.

What do you guys think?

Edit: What I mean by complete system: it will be able to create "NOT" and one of these two: "OR" or "AND"


texts: Power Supply for Home Automation - SMPS vs Coil Based

texts: I need to design a power supply for my home automation products. I need +12V DC (1A) and +5V DC (500mA) respectively for two different products. One option is to use a circuit with coil based transformer; second option is to use an SMPS based circuit. Size, durability and cost are the key constraints of my product. Please suggest which option should I go with?


texts: How do I get a position from an encoder?

texts:
I have a motor that drives a rail which I need to know the position of.

I have an AM102 encoder attached to the motor. But am unsure how to get a position from it.

I have powered it up and attached the two outputs to my Teensy 3.0. In my program I can see the value changing as I manually move the motor. (Either 1023 or 0 if I recall correctly).

I am wondering how I can use this to determine position. I'm guessing that I can determine position by counting how many times the value changes from 1024 to 0 and then multiplying that number by a distance (not sure how to get that value). But when the system is first turned on, how will it know the initial position? Is there a way to get this from the encoder or some other device/method?

n.b. I also have an Atmega328P which I've been told may how me determine position how would I use this?

Question summary:

How do I get the distance multiplier?
How do I get initial position?


texts: How to "deserialize" a digital output to 4 digital outputs

texts:
I am working on a small test project for my Arduino and as part of it, I want to display a number on a 7-segment LED system. My first setup involved just direct links to the 7-segment display and controlling each segment individually with the Arduino by setting the output to LOW to activate it.

I then reduced the number of pins required to 4 (5 including the decimal point control) using a BCD to 7-segment High-speed CMOS chip (74HC4511) and connecting it as shown in the diagram below (the NOT gates are achieved through using NOR gates with one input connected to ground):

simulate this circuit – Schematic created using CircuitLab

I can then control the 7-segment display using the following snippet:

digitalWrite( 1, iVal & 0x0001 != 0 ? HIGH : LOW );
digitalWrite( 2, iVal & 0x0002 != 0 ? HIGH : LOW );
digitalWrite( 3, iVal & 0x0004 != 0 ? HIGH : LOW );
digitalWrite( 4, iVal & 0x0008 != 0 ? HIGH : LOW );
digitalWrite( 5, bDPRequired ? HIGH : LOW );

However, this isn't ideal as it still requires 4 pins; ideally I would like to reduce it to 1 pin which outputs the data serially. My first thought was to use some sort of 4-bit shift register; however, this would require another output pin to control the clock pulse, and would result in spurious displays during the transition from one number to another.

I'd be grateful for any potential ways I could minimize the number of pins!

PS: I am  aware that it is somewhat bad practise to have the current-limiting resistor on the 5V output rather than on each of the cathode pins on the 7-segment display as it will result in less light emission the more segments are activated.


texts:
I am looking for a under water wireless communication, distance up to 3000 meters. For this I quickly did some research on it and found out that Acoustic communication would be the best solution since they travel longer distance under water. I found these modems from EvoLogics (link)

I would like to know what are the things I need to keep in mind before I start making such communications. What can be the major problems on these type of communication or during the communication setup? I can already imagine of something that can cause problem which is the wave of the water if the water is not still, this can carry away the wireless modem which will result in lost of communication. Is there more things that can make the communication difficult?


texts: digitaly controlled voltage divider for picky audio recording enthousiasts

texts:
I want to replace expansive multi-deck rotary switches with a micro-controller and digitally controlled (i2C or ISP) analog switches.

It will be used in a vintage (1972) discreet transistor microphone preamplifier design (Neve 1073).

The original used "noizy" carbon resistors dividers to attenuate signal between stages.  I want to keep the signal as "clean" as the original, wich should be easy as far as I understand it.

I wonder if there are any drawbacks in using cheap ICs like the new Vishays DG series Analog switches IC. Distortion? Noise? Etc...

I need to pass low (100mVac) and hi(15Vac) level audio signals through the switches. A ROn of 120Ohms or less is ok (I guess) with this design.

serial communication would be great (I2C or ISP)

I'm not an expenrienced EE and I'm lost among the available choices. I have no experience passing audio signals through this kind of ICs.

My big vintage console is an important selling argument. ICs have a bad reputation among audio enthousiasts so I must be carefull if I break the "discreet rules" as I will need good arguments to convince my clients no harm will be made to their music.

Here is a simplified shematic of the circuit. The divider switches are symbolized by pots.  I Hope I gave enough info.
Thanks for your insights.


texts: Split output of one temperature sensor to two independent signals using an op amp buffer

texts:
First off I am a car guy, if I have a schematic or details I can solder what I need.

I have a client that fitted a digital temperature gauge to his car, he also wants to have the gauge on the instrument cluster to work. Now from experience, I know this can not be done by just splicing wires and I need to make an op-amp buffer from what I have read.

All I need are some examples of what wire goes where to the gauges and power and signal wire from the sensor. Also, what are the part numbers of components needed?

The sensor that is fitted is fairly common and from what I found is it decreases in resistance as the car warms up, unfortunately, there are no numbers on the sensor.

Hope this is enough information thank you.


texts: Strange Waveform at high frequency from transimpedence amplifier

texts:
Using a simple transimpedence amplifier setup, I was able to measure noise from the output waveform by applying a small signal to the non-inverting terminal, while the inverting terminal receives dark current. Once the frequency hits 100kHz the nearly perfectly sinusoidal output changes to the following waveform, and I am not sure what exactly is going on.

If anyone can help explain exactly what is going on at this high frequency it would be appreciated.  Some extra info about the circuit, the Rf used is 1Mohm, and the op-amp is AD795.


texts:
If I have a copper wire and a nichrome wire of the same gauge (e.g. 30 awg) with the same current passing through them. why does the nichrome heat up significantly.

Also, the length of the wires are the same (e.g. 1 foot), the voltage is the same (e.g. 12 volts). The current is being varied by PWM.

Question: What is it about nichrome that causes it to heat up so much?


texts: How to convert an existing design from USB Mini/Micro to use USB Type-C connector?

texts:
What does it convert a design from USB Mini or Micro connector to a USB type-C connector?

To have a more specific question, take for example FTDI Basic (schematic below) which is USB/Serial converter based on FTDI232RL and has a USB Mini connector. Converting this design a USB Micro connector is trivial, just rewiring the 4 connections to the USB Micro connector. What about a USB Type C connector, is it just a clever rewiring? Does it requires additional ICs and functionality to be type C compatible?

All I care about is modifying my existing custom PCB designs to have a functional USB type C connector. Having additional Type C features such as higher speed are non goal. Also, I am not looking for an off the shelf Type C USB/Serial converter but am more interested in converting existing designs to Type C. This is for a hobby/one-of/open-source designs if it matters.


texts:
Arduino Fio with XBee radio.

I have read the XBee manual (pg. 24-25), trying to figure out how to put it to sleep, but what I tried did not work. Then I found an example sketch using XBee sleeping, and I have condensed the code into this:

#include <avr/sleep.h>
#define XBEE_sleepPin 6

void setup() {
  Serial.begin(57600);
}

void xbeesleep() {
  Serial.println("sleep");
  pinMode (XBEE_sleepPin,INPUT);    // put XBee to sleep
  digitalWrite(XBEE_sleepPin,LOW);  // Setting this pin to LOW turns off the pull up resistor, thus saving precious current
}

void xbeewake() {
  Serial.println("wake");
  pinMode(XBEE_sleepPin,OUTPUT);   // Set the "wake-up pin" to output
  digitalWrite(XBEE_sleepPin,LOW); // wake-up XBee
  delay(1000); //make sure that XBee is ready
}

int i = 0;
void loop() {
  if (i==0)
    xbeewake();
  else if (i==5)
    xbeesleep();
  Serial.println(i);
  i = (i+1) % 10;
  delay(2000);
}

I have connected a wire from the digital port 6 to the DTR port on the Arduino, which I believe is connected directly to the DTR/SLEEP_RQ pin on the XBee. According to the manual, when sleeping the XBee should ignore all input via the serial connection. But it still transmits in the periods where it is supposed to sleep. Here is the output from the console monitor:

wake
0
1
2
3
4
sleep
5
6
7
8
9
wake
0

Any idea what is wrong with my setup? Or just advice how to make the XBee sleep?


texts: Importance of 2nd or 3rd order RC Low Pass Filter in noise/ripple filtering

texts:
I dont quite understand what importance does having a 2nd or 3rd order RC Lowpass filter do to filtering power rail noises. If the first stage filter only allows frequencies below 15.9 Hz arent the other stages unnecessary? Adding more series resistance to the rail will always not benefit the load since it would be receiving slightly less voltage.
Does adding more stages equate to less noise than the previous one ?

simulate this circuit – Schematic created using CircuitLab


texts: Comparing differential-ended and isolation amplifier outputs for an "unbalanced" source input

texts:
I tried to simulate the effect of common-mode interference on unbalanced sources for three different inputs: single-ended, differential-ended and isolated. Below I inject a 1V common-mode voltage to three identical unbalanced sources(1k Ohm source impedance for positive lead and 0.1 Ohm for negative lead) with identical cables but coupled to three different receiver types:

And here is the AC analysis for the common mode voltage between 1 Hz to 100 kHz:

The above plots show that the single-ended inputs do not reject the common-mode related noise as expected.

But if we compare the differential input receiver's output(the green plot) and the isolated receiver's output(the blue plot), for example at 50Hz the isolated output is 130dB better than the differential-ended one.

Does that make sense? Can we say based on these plots that isolation actually acts as a differential input? Does that mean an isolation amplifier can be more immune to common-mode related noise than a differential amplifier?


texts: How to characterize a wideband RF ferrite transformer

texts:
Transformer models incorporating intrinsic and parasitic elements are well known:

The mutual and leakage inductances are calculated from measurements of the primary and secondary winding inductances at a frequency where the parasitic capacitive reactances are high.
$$M=k\sqrt{L_P L_S} \text{ for } k=\frac{v2}{v1}\sqrt{\frac{L_S}{L_P}}$$
$$\text{in which }{v_2} \text{ and } {v_1} \text{ are measured at a "mid-band" frequency.} $$
$$L_{l1}=L_P-nM \text{ and } L_{l2}=L_S-\frac{M}{n}$$
What happens for transformers wound on ferrite cores whose permeability drops dramatically with increasing frequency? The primary and secondary magnetizing inductances may drop enough that their reactances no longer "disappear" in favor of the parasitic capacitances. Does the "direct" measurement of primary and secondary leakage inductance by short circuiting the secondary and primary, respectively, give better results?


texts: simple communication between two XBee modules

texts:
I searched and couldn't find this question in the forum. Maybe because it's so novice:)

I have a pair of XB24 modules. I have connected them both to my laptop through USB adapters. one of these for each of the modules:

This is the function set I've flashed into one of them (router AT) and its firmware version.

And this is the function set (coordinator AT) and its firmware version for the other

These are the settings for the coordinator:

and these are settings for the router:

They both have their power level set to 4 (highest) and they are both turned on. But as you can see, router's network address is 0xFFFE which to my knowledge means it's not joined a network. And the communication doesn't take place when I open up two serial connections in XCTU. What am I doing wrong? Is this setup even supposed to work? Any help would be appreciated.


texts:
I have an industrial breathalysers that outputs its status via a USB 2.0 OTG port. What might be a suitable combination of processor and perhaps Ethernet chipset. I have not played with the modern PICs and ARMs only the old old Z80s, 8051, 6800 and a few special custom chips.

Or is there a website "symptom checker" where one can specify ones needs and it will suggest a chip. I believe that most modern chips (including FPGAs, not that I intend to use one of these) have devices as added blocks so that the modern designer can keep his or her chip count down.

As the breathalyser is 12 volt I will provide 12 volt to this board with a suitable regulator. I am not sure if Ethernet has any funny voltage or current requirements.
It would be better if whatever chip is suggested has a loadable library of an Ethernet stack (DHCP) and USB driver as no one will pay me to write these. Don't have the time or knowledge yet anyway.

I know that the "Internet of things" is becoming a thing! So there may be new chips or even SOC that I don't yet know about that is suitable.

I will need a programmable chip as some filtering of the status stream will be required before broadcasting the results to servers etc.

The breathalyser transmits its status as a continues stream of cr lf terminated strings. As I don't know different future requirements on filtering, the worst case scenario is a 4800 baud stream of characters that has to be sent to a server. Latency is not a issue. It is to record the value of the alcohol test with a date and time.


texts: Help understanding the TI TPS22917 load switch

texts:
I'm playing around with a TPS22917 load switch on its own (not in a larger circuit), and there are two things that don't make sense to me:

When the ON pin is set to low, I see ~0.9 - 1.0v on VOUT. Shouldn't VOUT be 0v when the load switch is disabled (low)? Here is how I have it wired (my test circuit doesn't currently have the 1uF cap on VIN that the datasheet specifies):

I removed 5v from VIN and hooked up my multimeter to VIN + GND. Then I connected 5v to VOUT to see if I would be able to measure any backflow voltage. This fried the chip (smoke and all). Why does this happen? The behavior that I would want would be for this to work like a manual switch where nothing conducts when the switch is off. Am I doing something wrong here? Is a different type of part more appropriate for this sort of application?

I have read through the TPS22917 data sheet multiple times now and I'm clearly missing something. I'm a newbie so please forgive my ignorance. I specifically bought this part to test the scenario where someone puts voltage on VOUT. Trying to learn more about how to protect my circuits. I thought this part would successfully ignore anything on VOUT when the load switch isn't powered. Guess I was wrong! Any insights would be really helpful for my learning.


texts: Why do we need galvanic isolation with low power components?

texts:
This is an analog to digital converter with I2C communication from a project (350W power supply) by ti instruments. it senses line and pfc voltage and communicates with the MCU. I don't understand what is the purpose of the digital isolators as we are dealing with low power components? Am I missing anything here?.

Also, what is the purpose of the inductors?


texts:
I'm not sure that this is the correct place to ask, but I have had great success with questions on the other stackexchange sites, so I'll try my luck :)

I need a device, which can press a button on a given time, which I should be able to set. It's meant for turning on my washing machine in the middle of the night. So I would want to put the device over the turn-on button before I go to bed and then have it press the button at a time, I've set it for.

If anybody knows a place to get something like that, I would love to hear about it else I would be willing to build it myself, if I know what to look for.

Thanks!


texts: How are the field patterns for magnetic and electric field obtained using the field equations? What is the intuitive way of understanding and drawing them? I searched a lot regarding the method for drawing field patterns but at most places there were just figures saying - "The field patterns obtained from equations are as follows!" Plus, what is the practical use of these patterns? How are they useful?


texts: 800khz digital signal amp, transistors and biasing, opto-isolator

texts:
Basically I am trying to send serial data from a Atmel to a string of ws2812 LEDs.  I need to provide some isolation from the output pin to the LEDs located in a seperate place. My plan was to convert the data string to 12V and then back down at the LEDs in hopes of providing some noise immunity. WS2812 LEDs have their own 5V supply.

WHYThe environment is very electrically noisy and the atmel is on a good 5V supply and shielded along with a PLD that is controlling logic functions. The atmel only handles the lighting but is connected to many of the PLD inputs for data and a diagnostic function, but also on the same 5V supply. The main is 12V from a automotive type system.  Very large loads are being switched on it. Transients of 8V to 30V are expected. Logic circuit is tested and everything else can handle the conditions.END_WHY

Originally I tried using 4n25 and 4n35 optos, but they don't switch nearly fast enough. The data string is 800Khz, which I didn't realize in the beginning, and uses a short pulse for a 0 and a long for a 1.  Next I built a amp driving a 3904 with the atmel output and it drove a 3906, just like the attached circuit but with a 3904 instead of the 2n7000. I tried bypass caps and getting the transistors out of saturation, no luck there. The attached circuit works and I've played with values, but afraid I'm on the edge of it not working. I attached a screenshot of the scope output. So my questions are.

Am I making a mistake turning the current back to a voltage for the LEDs with the resistors and zener(3.9V)
What through hole opto can handle this? This is the preferred route since with an opto the whole 5V circuit can have an isolated ground. At least the transistors and mosfet should slow down anything nasty, maybe only blow the atmel.
Is my mistake selecting a 3906 for this, or something else.

PS. I went to school for electronics and have lots of practical experience, just not in this area.

Thanks in advance for any input.

simulate this circuit – Schematic created using CircuitLab


texts: Battery pack with 12 NiMH 1.2 V AA batteries

texts:
I have been doing an experiment with a battery pack I have been building as a hobby for remote use of a simple low power DC device.

For this purpose, I put together a battery pack with 12 AA 1.2 V NiMH batteries in series (DC).

The load on the device itself is just a 5 W - 20 ohm resistor to keep things simple. I calculated the estimated resistance of 7 ohm for the battery holder (boy, are those cheap units) and 3 ohm for the wires, connectivity and unknown. Meaning a total resistance of 30 ohms in the circuit (not counting the battery resistance).

I am using 2000 mAh batteries or greater. After a full charge, I put the batteries in the unit and run it.

For my latest test, the voltage at the combined battery starts at 15.27 V (with load) and over one hour drops to 14.39 V. After the second hour it drops to 12.64 V. It typically does not make it to a third hour based on my test so far.

Incidentally, the power supply for the unit is an AC-to-DC 12 V 1000 mAh unit. When I check the voltage on this power plug it nears 14-15 V for the power supply.

Is there a way to efficiently limit the power with a switching device to 12 V (or something else)? I would like to extend the life of the battery power if possible.


texts: Easiest way to read a large bank of LED's

texts:
I have a pretty straight forward question but every answer I come up with seems over complicated or just plain wrong.  I'm designing a data logger/fault detection system to be used for a large piece of industrial equipment.  The gist is that the only output for the current status of this machine is a large bank of LEDs (>64) either lit RED, GREEN or a BOTH (Common cathode or anode led lights) and we would like to make this output remotely accessible.  I have no access to the control system of the machine so I cannot tap into the signal that controls which lights are on or off but I do have the ability to read the voltage drop across each LED with respect to either the cathode using a microcontroller.  Imagine the circuit for the LED's is just a common cathode connection of all the LEDs and then >128 wires coming in connecting the anodes (no access to the current limiting resistor).

My question for you is how would you go about determining if each of the LED's has either RED, GREEN or BOTH lights lit so that it could be read by a microcontroller?

My current thought is to take a massive bank of analog multiplexers and then just multiplex the voltage of each LED (>128 different voltages to read) into an ADC and use a software threshold to determine if its on or not however this method seems way to complicated and expensive and I'm sure there is a better option.  I know daisy-chaining a bunch of IO expanders together and connecting the voltages w.r.t. the cathode would work but the voltages seem too low for TTL (1.65V and 2.5V) and probably wouldn't work to produce a '1' when the LED is lit.

Could you suggest a circuit or IC or a combination of both to make this work?  Thanks!


texts: i2c over 1m shielded multi-core cable with 0.5A load at the same cable is possible?

texts:
I'm using an I2c sensor (Time of flight, VL6180X breakout board with voltage regulator onboard) at the end of a 1M cable. An arduino controls it.
As I2c was not meant to be far away from the PCB and the MCU, I used a 6 core shielded wire to connect the sensor to the Arduino Leonardo. I grounded one side of the cable mesh to the sensor. I'm using an USB 8 pin plug to connect the cable to the arduino control box.
I also added two 10k Pull-ups from the SDA and SCL lines to 5V, close to the MCU.
But, in the same cable I use the two other cores for powering a 2W led, at 500-600mA max. (4 cores for the sensor - 5V, GND, SCL and SDA and 2 for the led driver).
The sensor works normally when the led is off, 100% of the times. But when I turn the led on, mostly when the pwm duty is close to med-max, it makes the sensor fail almost everytime.
Am I adding capacitance to the whole cable when the led is on? Why does it happen? I measured the 5V VIN to the sensor with a multimeter and it doesn't change with the led on or off.
Is there a workaround for it? Having I2c working normally in a cable where 0.5A load is applied? Is there another type of cable that would make it work?
I could make the cables separate, but it wouldn't be the best option for me, for I would need more connectors, and a bulkier setup.
Edit: For testing purposes, I separated the cables. One for the led and another one for the sensor, on the same connector. It works much better, but it's not a solution I'd like to use for good....
Thanks for reading!


texts: Splitting a 5V digital signal in two, for two different ICs

texts:
I have an application where a hall-effect switch's digital 5V signal needs to be read by two separate ICs, a motor driver and a microcontroller. Can I simply route the signal to both inputs, or do I need to effectively 'split' the signal and repeat it to both inputs? If so, is there a simple circuit to accomplish this?
Both the microcontroller and motor driver have a built in resistive pull-down.
Probably a very simple answer, but I want to clear my thinking on it.


texts: How many ohm is the ADC port internal resistance of the atmega8?

texts: I am trying to link a digital pin to a pad that's already wired to an ADC. I was wondering how many ohm the ADC port internal resistance is.


texts: Ltspice running but gives error log. Ignore?

texts:
When I run my simulation it works fine but this log file appears when I close out the simulation. It started this when I changed a third party part that was not working with the model of that part from the mfgrs. list of models. Here is the contents. Can I ignore it and proceed on?

R26: both pins shorted together -- ignoring.
Error on line 1843 : .model m6:bsim3 nmos (level=7 version=3.1 mobmod=3 capmod=2 paramchk=1 nqsmod=0  tox=970e-10 xj=1.4e-6 nch=1.7e17 ua=1.6e-9  u0=700 vsat=1.0e5 drout=3.0 pvag=5  delta=0.10 pscbe2=0 rsh=1.0e-3 pdiblc2=1e-7  vth0=3.50 voff=-0.1 nfactor=1.1  lint=5.90e-7 dlc=5.90e-7 fc=0.5  cgso=1.12e-9 cgsl=0 cgdo=1.05e-14  cgdl=1.68e-9 cj=0 cf=0  ckappa=0.20 kt1=-2.07 kt2=0  ua1=1.02e-9 nj=10 )
    * Unrecognized parameter "fc" -- ignored
Error on line 1843 : .model m5:bsim3 nmos (level=7 version=3.1 mobmod=3 capmod=2 paramchk=1 nqsmod=0  tox=970e-10 xj=1.4e-6 nch=1.7e17 ua=1.6e-9  u0=700 vsat=1.0e5 drout=3.0 pvag=5  delta=0.10 pscbe2=0 rsh=1.0e-3 pdiblc2=1e-7  vth0=3.50 voff=-0.1 nfactor=1.1  lint=5.90e-7 dlc=5.90e-7 fc=0.5  cgso=1.12e-9 cgsl=0 cgdo=1.05e-14  cgdl=1.68e-9 cj=0 cf=0  ckappa=0.20 kt1=-2.07 kt2=0  ua1=1.02e-9 nj=10 )
    * Unrecognized parameter "fc" -- ignored
WARNING: Less than two connections to node NC_01.  This node is used by R:SV1PSPOT:1.
WARNING: Less than two connections to node N003.  This node is used by V2.
Warning: Pscbe2 = 0 is not positive.
Warning: Pd = 0 is less than W.
Warning: Ps = 0 is less than W.
Warning: Pscbe2 = 0 is not positive.
Warning: Pd = 0 is less than W.
Warning: Ps = 0 is less than W.
Instance "m:m3:1": Length shorter than recommended for a level 1 MOSFET.
Instance "m:m3:1": Width narrower than recommended for a level 1 MOSFET.
Per .tran options, skipping operating point for transient analysis.

NOTE:  Since output waveform compression is enabled and not all nodes(currents) are
       saved, it is possible to have compression artifacts in the output data.

Heightened Def Con from 0.428853 to 0.428853

Date: Thu Jul 06 07:04:21 2017
Total elapsed time: 5.890 seconds.

tnom = 27
temp = 27
method = modified trap
totiter = 36564
traniter = 36564
tranpoints = 14814
accept = 10157
rejected = 4658
matrix size = 269
fillins = 417
solver = Normal
Thread vector: 107.1/66.2[2] 23.7/13.8[2] 12.2/7.0[2] 3.6/91.3[1]  2592/500
Matrix Compiler1: 43.39 KB object code size  23.1/12.7/[12.9]
Matrix Compiler2: off  [6.5]/7.1/7.6


texts: Basic Series/Parallel connection understanding

texts:
I am just starting out with electronics and I have understood that there is something fundemental I just cant seem to figure out about parallel and series connections. I am having a lot of trouble figuring out the connection type between resistors in some circuits.
Here is the example from which I base my question:

After too much time I figured it might be correct to redraw said network as such:

which then is clear as per which connections are parallel and which in series.
So my question is:

Have I made any mistakes in re-drawing my network?
Is there any foolproof way of telling which connections are in parallel and which in series in any given network?


texts:
I'm doing my term project, in which I have a memory, which can be changed by the user. The specification is that whenever reset is activated, data on this register should be reset to all zeros.

I first declared the memory consisting of 128 addresses* 16 words as follows

    reg [15:0] memory [127:0];

Here is the code that I try to use for resetting purpose

    always @(posedge clk)
    begin
    if (reset)
   begin
    for (i=0; i<256; i = i+1)
        begin
            memory[i] <= 16'b0000000000000000;
        end
   end

This is my attempt to solution. I tried synchronus reset approach.

Now the crucial thing that I want to ask is, can I use for loop inside always ? I have made some research and I found that for loop is not synthesizable for the FPGAs, which are required during the demonstration of projects. Without using for loop, how can I make the 16 bits in all 128 addresses all zero? It seems impossible to me ? I am quite new to Verilog so it may be a noob question.

Any help is appreciated.
Thanks.


texts: Relation between settling time and natural frequency for a critically damped system

texts:
In an article by Wie et al. (1989), for the purpose of calculating the gains of a controller, the equations of motion are approximated by the expression for a damped harmonic oscillation:

$$\ddot{\theta} + d \dot{\theta} + \frac{k}{2} \theta = 0$$

where, of course:

$$d = 2 \zeta \omega _n \quad ; \quad \frac{k}{2} = \omega^2 _n$$

In the design example presented in the article, a settling time of $$T_s = 50 \text{ sec}$$
is assumed. Now, the article states that for a critically damped response, $$\omega _n = 0.158 \text{ rad/s.}$$

Indeed, using this natural frequency to calculate the controller gains yields responses that settle after about 50 seconds:

However, when using the relation between the settling time and the natural frequency for a critically damped system as presented in this answer, one obtaines:

$$
\omega_n \approx \frac{5.8335}{T_s} = \frac{5.8335}{50} = 0.117 \text{ rad/s.}
$$

So the question is, how was the natural frequency calculated in the article?


texts: How do I copy relays + diodes multiple times in Eagle 7.7 Pro?

texts:
I designed a board with 512 latching relays and uC + shift registers to allow changing each relay from NO to NC, or NC to NO, individually.  I had the end user wire up several relays on protoboard to make sure the design was working. Now I find out that diodes need to be added for additional isolation when larger quantities are added. That's another 1024 components to add.

I would like to design just 1 row of the 16 relays across array, add the diodes, do the placement, and then copy that row 32 times, then reconnect the control signals.

Is there a way to duplicate the schematic & placement so I'm not stuck dragging relays & diodes for days on end? That was tedious enough when I did the design with just the relays.

Thanks


texts:
I'm trying to set up a project in which the raspberry pi will turn on/off and on a 12V circuit. I've read that a MOSFET would be best but I can't seem to get the circuit to work. I'm using a 30N06 MOSFET, and this guide for reference. Before testing the entire circuit with a GPIO pin I wanted to test the switch itself, so I've connected the 5V raspberry pin directly to the gate of the MOSFET in an attempt to "turn on" the switch. My circuit looks like this currently:

I must be doing something wrong though, since there is no current flowing in the 12V circuit. I have troubleshooted by running the 12V circuit without the MOSFET, as well as measuring the voltage from the raspberry pi 5V pin, and everything seems to function normally, so I am sure the problem lies in how I am connecting/using the MOSFET. I have also also found this guide online which seems to agree with my circuit, so I am extremely puzzled as to why it is not "turning on" (http://www.robertcudmore.org/blog/?p=181).

Any help or suggestions would be extremely appreciated.


texts: PCB-To-Cable connector for power and bus line

texts:
My current design has

Power cable: 3 pair (max 2A)
Bus cable: 4 pair and shielded
Distance: ~1-20m between the slave PCBs

I am having trouble finding a suitable connector for the PCB and cable

For the power supply I am looking at

https://uk.rs-online.com/web/p/pcb-terminal-blocks/7901092/ and
https://uk.rs-online.com/web/p/idc-connectors/5066904/

with the screw I would be more flexible and I do not need a connector on the cable. With the 'Stelvio' I have a clean click connection.

How should I handle the BUS cable? Previously I used https://uk.rs-online.com/web/p/pcb-headers/7620872/ with https://uk.rs-online.com/web/p/pcb-connector-housings/8201478/, but the mounting on the cable was not as easy as I thought and after multiple connects/disconnects the contact was a little loose.
Alternativley I looked at https://uk.rs-online.com/web/p/pcb-headers/1650532/. I do not want to use a standard DSUB because of the size and the unused pins.

Are there standard header/housings for PCB-To-Cable? I filtered the RS and Mouser catalog, but was overwhelmed by the amount of connectors


texts: Which gate is better in building the Full Adder ? XOR or OR

texts:
So this is a question that was asked in one of the exams. As you know, there are 2 ways to get the boolean expression for the sum of the full adder.
Given X and Y are inputs, C0 is the carry from previous adder and C1 is the carry output and S as the sum, described as:
C1 = X.Y + C0(X + Y)
C1 = X.Y + C0( X ^ Y )
is the other expression with an XOR gate (^)
so which expression is better in building the Full Adder? Should we use the XOR or OR and what is the reason for the selection?
EDIT:
I previously mentioned it as sum which is a mistake, it's for the carryout.
Thank You


texts: Multiplexing 3 phase motor driver signals to drive a BLDC motor bidirectionally

texts:
I have this unidirectional 3 phase motor driver powered by a 3S LiPo battery and want to make it be able to switch direction of the brushless motor connected to it within software. The way to reverse the direction of rotation of the brushless motor is by switching two of the wires with each other. I've found that multiplexers or CMOS switches can help with this. Would my following setup be able to do this signal switching?
Ao/Co are motor driver outputs (PWM, max 1.5A output) and Ai/Ci are inputs to the bldc motor itself. L1 and L2 are the logic inputs to the multiplexer or CMOS switch.


texts: How much energy is stored in a AA battery when its voltage has dropped to 1.2V?

texts:
The general question is how useful it is to use weak batteries with a boost converter - say, boosting 3AA of 1V each to 5V?

According to this image it seems that only 5% of the energy is left when the voltage has dropped to 1.1V but about 50% when it's 1.2V and dead for most uses. Still this usefullness of boosting depends on its efficiency.

Is there a rule of thumb when boosting is advisable based on battery type, the remaining voltage and the required current?


texts: Maybe a daft question, but I am not an electronics expert. I have an old car that was originally 12v positive earth. It has been converted to negative earth by a previous owner, and everything works fine, apart from the clock (which has been disconnected and is ok), which is positive earth and is very difficult to convert internally. I understand there is such a thing as an isolated voltage converter that could do this, but cant really get my head round what I want. Would something like THIS do, and if so how would I wire it? Many thanks.


texts: Long vs Short Earth Connection for Single Phase Motor vs 3 Phase Motor Frame

texts:
What is the correct way of grounding single phase motor frame if I have to choose between two options:

(1) Short to earth connection: from the frame to nearest grounding rod. See below the schematic.
(2) Long to earth connection: from the frame to the ground bus power panel that the motor is supplied by (which could be just far away. See below.

I think (1) is not enough since it does not have a fault current path with the neutral if the hot conductor (s) energizes the frame.

I see the fault current path as a way to trip the breaker or the fuse

However, I just do not understand why this is not the case with 3 phase motors

In 3 phase motors, you don't usually have a neutral, and if the frame is energized, then how will the trip happen ?

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts: Not getting the correct output sine wave for the circuit built

texts:
I am trying to solve this lab for circuits class, but for some reason, the myDaq oscilloscope software is not showing the correct sine wave to find the question number 3 or 2 in the following image.I have also given the output i am getting.

Here is the image of the circuit, I made sure the connections are right almost 10 times now. The op-amp number is - TL082


texts: P-Channel MOSFET Drain-Source Polarity in Power Switch Application

texts:
I'm looking at using the LTC4412 power switch in an application. From the datasheet, here is the typical application circuit: :

In the application circuit, an FDN306P p-channel MOSFET is used.

I'm kind of new to this, but my understanding is that for a p-channel MOSFET, current flows from the source to the drain, and that the source should be at a higher voltage than the drain. Looking at the application circuit, though, it appears that the drain is connected to the positive battery terminal.

What am I missing?

Thanks.


texts: What is the best way to test the ISO 106 signal isolation buffer amplifier?

texts:
I need to test the ISO106 signal isolation buffer amplifier as part of my next task.  I went through the data sheet without getting any idea on how to test these ICs.
Basically, I need to test the functionality of this IC.
Can someone help me with this by explaining what it is and how to test it please?
Yes I already have boards which contains the ISO 106 and wish to check it. "GE COROMETRICS MEDICAL 11867FA REV 002 MODEL 122 ISOLATED UA/FECC ISO106" this is the board which has this ISO106 and would like to check the component with respect to this board.
I am going to remove the ISO106 and test it seperately.  Which parameters would be best to test it?
I know these are outdated products but it is part of my task so please help me out.
Datasheet of the ISO106.


texts:
I've recently done a Lab at the Uni to make a Mosfet 2 stage op-amp shown in the image below:

A lot of simulations were done to understand how the op-amp worked, and whether it works correctly. Such as DC analysis, AC analysis, finding a suitable Rc, common mode range, worst case offset, etc, which I have already completed in my report.

The lab has an additional bonus component (which I always attempt, but this one seems a bit hard). It asks us to consider the above circuit as low voltage where the MOSFET transistors cannot exceed 1.8V all around, Vdd is 1.8V (max) and is single supply. In the optional component it says the above circuit must be used as a buffer which has a ground to 10V supply and must be able to ideally output 0-10V hence, the input must be between 0-10V. "Higher" voltage MOSFET transistors must be used to replace some of the lower voltage transistors along with other optional components. I am to write a page length of what the best approach is to changing the circuit as little as possible with minor assumptions.

The question seems kind of tedious and hard to comprehend. I really have no idea how to begin here as high voltage op-amps aren't even covered in lectures or even low voltage operational amplifier for that matter. The only things that I could think of is voltage sensitive devices such as current source? Obviously the transistors themselves.

Q: I'm not looking for someone to answer this, but any input to articles with similar design problems is appreciated!


texts:
I have this MAX9278 GMSL1 Deserializer.
I have 3 below questions:

How to configure the CX/TP pin if I want to use the coax mode?

And how to arrive at the address of the deserializer if I connect both ADD0 and ADD1 as ground? I am not able to understand the table 10.

I have 800 * 480 TFT 3.1 inch.

I have arrived at the below PCLK calculation :
Vertical Resolution   =  800    Pixels
Horizontal Resolution = 480 Pixels
Frames Per Second   = 60fps
Blanking Percentage = 20%
Approximate PCLK    = (800 * 480 * 60 * 120%) / 1000000 = 27.648MHz
Is the above calculation for PCLK correct? What would be a good value to set for my above TFT?
And there is no provision to connect external crystal to the deserializer?


texts: Trigger two circuits with single SPST switch

texts:
I'm an electronics noob willing to learn.  So I have a door bell that looks like it is wired like this:

And I've bought a fancy 3V battery powered device that is intended to be wired simply like this:

Now I would like to trigger both with the same door bell push.  (The push is already in place with wires going where I wouldn't really want to disturb them.)

So how would I go about this?

I know enough that I can't just connect both together.  And I've learned that there is a way where a circuit with a transistor can act as a simple SPST switch (see https://www.electronics-tutorials.ws/transistor/tran_4.html, https://www.nutsvolts.com/magazine/article/may2015_Secura, and a number of similar tutorials/descriptions).

But that is how far I got.  What would possible approaches to this?

Thanks!


texts: Convert car stereo setup to run from mains supply

texts: I have a car stereo system that I wish to keep once my car is no longer running. I have thought about if I could convert it so that I can power it by a wall plug. I have three things to be powered; the head unit which has a 10amp fuse, a 4channel amp which has a 60amp fuse, and lastly another 4channel amp with a 50amp fuse. They all run off of one car battery currently and so I was trying to see if I could convert this setup to run off of a wall plug in or a few to be able to power them in a garage setting. And simply have to unplug them from the wall when not in use or plug in when I want to use them. Is this feasible, or would it require multiple car batteries chained together with a converter from the wall plug in and constant measuring of voltage on the battery to do the job.


texts: 900 MHz vs 433 MHz for urban environments

texts:
At ranges of a few hundred meters, will there be an appreciable difference in performance (ie range, bit rate) between 900 MHz and 433 MHz for digital applications in an urban environment?

Forgot to mention, I've read that some frequency ranges are more crowded than others, is that relevant here?

Also I live in the US.


texts: TVS Diode Array with EMI Filters on ADC Input

texts: Is there any problem with using this SP6002 TVS Diode Array/EMI filter to protect ADC inputs on a micro-controller? The ADCs will only measure DC voltages. I am a little worried that the filters will affect the ADC readings as I have never put EMI filters on an ADC input before.


texts: I'm looking for USB to serial FTDI cables. However, the cheapest I can find is $20 US each, which is way too expensive, given my price target for the entire product is $70. I'm hoping they can be found for $5 each somewhere, but even FTDI themselves has them for £16 (about $25) each. Anyone know of any other options?


texts: Arduino-like microcontroller with more ram for image processing

texts:
I want to build a device to perform image acquisition and processing, but I don't know which kind of board/microcontroller to use.
My idea is to use a low-res camera, take a shot, analyze it and return the results. These shots should be taken at most a couple of times per day, in an outdoor environment, in "controllable" conditions: no video streaming or elaboration, only single shots.

An Arduino-like board would be perfect, but a single low-res image wouldn't fit in the low amount of RAM available to any Arduino board available (quick estimate: 100x100 pixels times 3 color channels times 4 bytes for each float32 = 120 KB).

Therefore I was thinking about a Raspberry Pi Zero board, which mounts a Broadcom BCM2835 and 512 MB of RAM, but it's rather an overkill for my needs.

I don't have any high computing needs, since the interval between the shots is really long (hours), and the pictures taken don't need to be stored (so no need for an external SD memory). The microcontroller should process the image processing on its own; there won't be any laptop around to delegate the compute, and I don't want to transmit images over the internet since this thing is gonna stay outdoor in places with low network coverage. A small GPU chip inside would be great.

Moreover, power consumption is another "constraint": between the shots (hence, the 99% of the time), the system will go in sleep mode/next-to-zero energy consumption, or simply shut down.
I plan to wake it up from a "master" node nearby via wireless connection when it's time to take another shot. This requirement is set because there won't be power sources around, at most a solar panel to recharge the batteries the microcontroller will run on.
(The RPi doesn't seem to have a real sleep mode: from a very quick search I found this discussion, where they suggest to shut it down completely and wake it up using an external device - which is what I'm planning to do anyway.)
Moreover, I think running an entire OS is useless: my application is a single program, and I don't need a kernel using my precious CPU clocks.
I won't use any peripherals such as usb/hdmi/sd available in a RPi, but having them on a prototype is fine; if I'll ever build any production-level board I'll use directly the Broadcom chips.

To recap, I'm looking for suggestions for a board/microcontroller with the following details:

A couple of MBs of SRAM/DRAM, to store a shot from a low-res camera to be immediately processed.
Low-power consumption: it will need to run on a battery pack. A sleep-mode is not needed, I can turn the device on at each iteration (using an external wireless module).
GPIO pins to get the picture from camera and use other stuff.
A decent CPU (maybe with a GPU?) to run OpenCV or other image processing tools, in a decent amount of time (I'd say at most 1h to analyze a couple of shots).
No need for a complete OS: an Arduino-like board or microcontroller, with more RAM would be great.

What advantages could I get from using a RPi, instead of working directly on a CPU+RAM like the ones mounted on it? The board and the OS would not be of much help in my case, I think.
In case you think using a board to prototype my idea isn't useful, what kind of microcontroller would you suggest to use?

Similar questions:
In this discussion the OP requested a device with more RAM to perform image processing, but he wanted to install an entire OS on it: Embedded System for a image processing task
And here's a similar discussion: Embedded system for image processing project

Edit: I don't want a specific recommendation of a specific board/microcontroller to use (although it would be great), rather to point me to a "class" of devices that could suit my needs.


texts: CMOS circuit design: How to implement an interrupt circuit that detects minimum or maximum peak?

texts:
I have an input signal sine wave like but comes with a little distortion. I need to give an interrupt when it reaches to minimum or maximum value with an acceptable tolerance.

this graph is from a fading sine wave, what I want to do here is to detect the first minimum right before or right after rising again. So I can discharge or recharge it when it reaches its peak. But, as I told before there is a little distortion on the signal that may lead to false detection.

I can tolerate a little timing here, interrupt may give signal a little time after peak point.

So, how can I do this in transistor level? I know I can use an ADC but I need this to be a transistor level solution.


texts: a camera which records images at different wavelengths using optical filters

texts:
I need to create images at a certain wavelength range(around 850-900 nm). For this a frequently cited solution is using optical filters. However I am not being able to understand the concept behind those.
A camera has image sensors which store charges, and then convert it into colored images using RGB optical filters. Now if I am to put up an optical filter that transmits wavelengths of only 850-900 nm, then what kind of image shall be captured?

From what I understand, since there is no RGB based wavelength in 850-900nm light, so the pixels will all record values (0,0,0) and we'll have just a black image.

Am I right? If not, please explain what exactly will happen and why? And is this method to capture a specific wavelength based image using optical filters the best one or even a possible one or I will have to go to the basics of image sensor development itself?


texts:
I was poking around a video amplifier and — in its dual-rail power supply — saw a pair of inductors unlike any inductors I've come across before:

(These are the two sides of the same inductor; the other looks the same.)

What properties is this type of construction trying to achieve?

By the look of things, these sit between a switch mode supply and a 78xx/79xx-based linear regulator. (Happy to provide more details; just let me know of what kind.)


texts:
I would like to have an idea for a square wave inverter I am making.It would be a 48V to 415V in the final product, but initially I am trying it with a 24V to 207V with the same transformer.

I am implementing this with a PIC uC which will generate the 50Hz square wave,which will be used to switch the MOSFETs of a center tapped transformer in the push pull mode.

My query is how to get the feedback from the output to make a closed loop system.I am planning to wind an auxiliary winding for the feedback and assume the aux. winding will replicate the load winding.

The specific question is: Would it work if I calculate the RMS value of the output and then vary the input PWM to get the required RMS at the feedback winding?

Or would there be any simpler way to do this ?


texts:
A legacy product we are making uses this obsolete Frequency Sensitive Switch, Consumer Micro FX-301L.

The switch is setup such that it switches on (-12V) at 2000Hz +-100Hz and switches off at 250Hz. Packaged in a TO-100 can.

We need to replace this component, but there is nothing I can find that is even close to this type of operation. I've never seen a component like this before!

The IC uses a combination of amplifiers, monostable timers and comparators and has some extra logic to configure the setup.

In circuit, its output goes to a FET which is gated to the output of a 7412 flip flop which i believe is used to illuminate a status indicator lamp.

The diodes drawn on (D15 and unlabeled) are not fitted.

Are there alternatives? Do we need to design a daughter board to replace this?If so, what would be the smallest footprint circuit that we could use?


texts: Contactor rating with capacitive load, how to compute the maximum allowed capacitance?

texts:
Considering this:

simulate this circuit – Schematic created using CircuitLab

V1 is a beefy battery - it will happily provide 1000A or more;
RLY1 is a beefy contactor, the LEV200 series, rated for 500+A, 12-900VDC;
C1 is the capacitor in question.

When closing the contactor, the inrush current to energise C1 is capable of welding the main contacts. Of course if C1's capacitance is small enough the issue subsides to manageable levels. This amount of capacitance is what I want to compute, if possible. A crude/conservative figure is reasonable given that the datasheet does not mention anything about (non-precharged) capacitive loads.
Ideally there are many methods to avoid the welding even if C1 is large (precharging, adding series inductor and/or NTC resistor), but my question pertains to the above model only, I want to know when these measures are needed.
EDIT:
As per Macrus Müller's comment, the source impedance of V1 is very important, it is approx. less than 0.1 ohms.


texts: Datasheet LTC3892 - how to calculate Rc, Cc1 and Cc2?

texts:
I am working on building a DC/DC converter using the LTC3892 chip. I went through the calculations in their datasheet for the chip, but they don't specify any formulas for Rc, Cc1 and Cc2. I don't see any correlation between the values they used in their application circuits either. The only mention of these components are on page 27.

Does anyone know how to calculate these values, or at least how they got their values for the example circuits they provided (pg 31,32, 33, 36)?

Link to the datasheet: http://cds.linear.com/docs/en/datasheet/38921f.pdf


texts:
I need to switch off a 20V 60A DC current electronically. I don't want to use a relay, due to the environment (vibrations etc.).

It is not a switching supply, just a switch that turns everything off when given a signal.

I've been trying to design a circuit that basically passes the load current through a MOSFET which can be switched off.

I've been looking at power MOSFETs and IGBTs and am having trouble understanding their specifications. For instance this MOSFET has a Maximum Continuous Current rating of 100A, but when I look at the Safe Operating Area graph, at 20V DC it will only do around 1.5A. Similarly for other FETs and IGBTs.

Is the SOA graph what I need to be designing with, or can I use the Max current specifications?

Are there transistors made specifically for DC applications that can handle a large DC current, or am I using the wrong components/design approach here?


texts: I have this problem which is driving me crazy: I want a LED light to indicate when my motorbike is running on emergency fueltank. The system works with a normal halogen bulb, and the system is generating 13,5V whenever is runs on the emergency tank. When the fuel level is above the critical limit, it Will generate ni voltage which is just fine. But, whenever i change the halogen light bulb to s LED with an appropiate resistor it stats on forever and generate 13,5 V ni matter what the fuel level is. It's maybe Nice to know, that whenever the system start it Will turn on the fuel indicator for 2 sec, and turn off again, it's like it's testing for something. Best regards


texts:
I'd like to know how synchronization between the GPS unit and any other sensors is done in a typical system. I understand that the 1PPS signal plays an important role.

Could anyone give me a very simple explanation of the 1PPS signals role?


texts: Amplifier analog design - how to effectively do it when gain varies so much?

texts:
For example, I was thinking about building a small current sensing device that has an display to measure small current draws on some of my circuits. The design would be such that a very small resistance (~1m Ohm) is placed in-line and the voltage take across it amplified. However, I have always had trouble with amplifier circuits.

As you know, the gain constant of a transistor varies greatly even within the same batch of devices. I know that certain designs can be made such that their transfer functions depend only slightly on the gain constant, but are all gain applications implemented in this way?

Operation Amplifiers can be a bit simpler because their open-loop gain is so high - but similar to any amplifier circuit the gain is a direct function of the values of resistances (which vary largely!).

So how can amplifier circuits be used effectively in a particular application that requires the exact gain coefficient of the circuit (i.e. the current sensing design I mentioned earlier). Of course you can measure the resistance values before you implement them into your design - but what about commercial designs? The software edited based on the resistance values for every unit manufactured - at least it seems very impractical.


texts: Precisely determine the actual consumed watt of the device

texts: What is the actual consumed watt of the device stated a value of input watt and a value of output watt which we often see it?


texts: electric chewing gum prank circuit diagram

texts:
I'm new to electronics.
I'm trying to find out how this works out of curiosity.
http://www.amazon.com/gp/aw/d/B0050UNNQS
Does anyone have a circuit diagram for the circuit?
Is the current safe for such a prank?
Internal picture:

EDIT: Merged question from Trever Thompson
Help here would be greatly appreciated:
This question has been asked several times on this site and elsewhere, and it seems as if the posters became satisfied with inaccurate answers.
How on earth do the electric shock prank pens/bubble gum work?
I have no intention of shocking anybody or recreating this circuit, I am simply baffled by how it operates. I have verified that all purported explanations readily available online are inaccurate or incomplete.
The above image shows the only two components in the circuit. I do not know for a fact what the white component is, but I have to assume it is a high value capacitor.

The above image is a literal layout of the circuit. The 50k load is the user's hand. Both switches are closed upon pressing the button. The switch is before the capacitor. This is based on closely observing the circuit and is 100% accurate unless someone can prove otherwise. I tested this with varying capacitance and inductance values and was unable to induce a significant current in the load for more than dozens of miliseconds. When testing I moved the virtual switches from the ground to the positive wire. When I move the switch after the capacitor I can have a long lasting current through the load, but the voltage/current are very low.
Edit: It is beginning to appear as if the white piece (Shown as cap above) is an active component/IC. There may not even be a capacitor in this circuit.
What I know:

The device behaves as follows: When the pen is held and the button is pressed a mildly painful electric shock is felt. After about 3 seconds, the pain gradually decreases until it is not longer felt. Upon releasing and pressing again the full shock is felt once again, even if only released for the slightest moment. The button and grip are the electrodes.
It uses 4 1.5V button cells in series (with high internal resistance)
The shrink wrapped component is a tightly wound step up transformer. The   secondary uses extremely thin wire. It apparently is an autotransformer, as it has three leads and is wrapped around one ferrite column.

What I think I know:

I measured the frequency on the primary with a primitive oscilloscope. It was equal to a couple hundred hz, which is reasonable considering the pain of the shock.
If the frequency is ~200hz, the capacitor (if the white component is a cap) would have to be over 100uF non polarized. This may be possible as I have discovered high capacitance low voltage smd caps. The primary inductance would have to be several mH.
The turn ratio would (I believe) have to be at least 1:90. This surprised me because I read that most autotransformrs have a low ratio. I then encountered higher ratio custom ones (which is more reasonable if varying wire gauges are used).

What I want to know:

What the white component is. Is it merely a capacitor? Does it serve other functions?
How on earth does this circuit work. It seems so simple and then again I can't explain or emulate its behavior accurately in a simulator...

Help will be greatly appreciated, as this has kept me occupied for a long time.


texts:
I am trying to "read-while-erase" and "read-while-write" with my stm32f427 dual bank flash for firmware upgrade. what I need to know is how can the program dynamically figure out which bank it's executing from? so the code can calculate the flash address of the other bank where it need to start erasing from or write the new program to. Is there a bit or register I can check? Another question I have is..how do I move the vector table from one bank to another?

Thanks.

Link to the Refence Manual:
http://www.st.com/web/en/resource/technical/document/datasheet/DM00071990.pdf


texts:
I am designing a 6-axis robot arm, and I just finished tuning the control algorithm for a single BLDC using a STM32 MCU. The next step led me to wonder how such system usually works: I don't think my STM32 MCU can drive 6 motors, it simply doesn't have enough PWM timers and pins. I'm suspecting multiple MCUs will have to be used somehow, but I can't seem to find any such examples/tutorials on the web.
How can I use multiple processors if I'm lacking resources?


texts: How does the serial data input SDI for the MAX31856 (thermocouple to digital converter) works?

texts:
I want to communicate with a MAX31856 using SPI. Unfortunately, I have a basic understanding of electronics and only used SPI communication once.
Briefly, the thermocouple sensor (MAX31856) is connected via SPI to Arduino and the latter is connected to a computer. The temperature is read using LabView and the Linx Makerhub add-on. The MAX31856 works perfectly fine using the Adafruit libraries for Arduino.
The MAX31856 chip requires a serial data input (SDI) to set some parameters and simply to require a temperature value from the chip (From the datasheet: communication with the MAX31856 is accomplished through 16 8-bit registers that contain conversion, status, and configuration data). I do not understand what to send via the SDI pin. In the register memory map, I can see that the three addresses 0Ch, 0Dh and 0Eh respectively read the temperature bytes 2, 1 and 0. Do I have to send an array of three bytes with the value of 12, 13 and 14 (because in Labview the array is unsigned byte 0-255) to get the temperature back?
Maybe the difficulty also resides in my LabView code. In this case I will go on a more appropriate forum.
Thank you in advance for your help. If you have any question on my problem, do not hesitate.


texts:
When controlling a BLDC motor which has hall sensors, are the hall sensors always enough when combined with suitable logic in software?

Whether using Hi/Lo PWM block commutation or a sinusoidal wave with all 3 windings used at any time, it is possible to get a reasonable approximation of the current motor position with the 1st, 2nd and 3rd derivatives of the motor position with respect to time (speed, acceleration and rate of change of acceleration). With timings for the each hall state for the phase rotation of the motor this is fairly simply to calculate and to adjust based on changes in power levels. This does require the motor to be moving above around 60rpm but this is not generally a problem.

So given I have this... why would I want to consider measuring the back EMF or the current on each phase?

Both would add complexity to the circuits, and with sinusoidal commutation you are pretty much limited to the current sensing method as each winding is in use with possibly very minimal off time.

Am I missing something obvious where there is a distinct advantage in the calculation of rotor position based on current sensing?

For the purposes of this question I'd like to limit this to small, low voltage motors in the range of 25-500W, 12-48V.

Note: This is not looking to consider sensor less design which has specific reasons for needing other forms of measurement.


texts: UART in open drain causes mosfet switching voltage spikes

texts:
I'm using an ATMEGA3208 and I have configured the UART peripheral to open drain mode. I'm using an external pullup 1KΩ. I'm experiencing switching voltage spikes that goes negative. They are about 0.4V 500ns.

The spikes are only on receiver's side. The baud rate is 9600bps. The logic '1' is 3.3V.

I tried to increase the resistors to: R1 = R2 = 3KΩ. And R3 = R4 = R5 = R6 = 130Ω and the undershoot goes away. Of course that affects the logic '0' but it's still well below the threshold (0.3 x VCC).

They are exactly like this. However this answer doesn't help me as the mosfet is internal in the mcu. What can I do in this case?

EDIT: The undershoot is present even with 0.5m cables (multi copper standard wire 0.75mm)

Why does impedance matching matter in this case? Doesn't it matter only when the cables are much longer than signal's wavelength?

simulate this circuit – Schematic created using CircuitLab


texts: Looking for an inexpensive button that can withstand hits from a baseball bat

texts:
At work, we're decomissioning a pile of servers. However, they are all virtual, so we can't celebrate office-space style.

However, I was thinking - if I could hook up something that acted like a button to a keyboard, so it registered as the enter key, I could script the destruction of the effigy server with the launching of commands to destory the real one.

So, what can I use as a button here that will take a good 30ish whacks or so before breaking? Would a piezo sensor glued to a metal plate work? Would I need extra circuitry? Or is there a place I can find a cheapish, large button that I could hook up?

I can handle the soldering, but otherwise, my EE knowledge is fairly weak, so please consider added simplicity over absolute minimum price. Budget for this is probably around the $20 mark.


texts: How to explain the decrease in the voltage spike due to the resistor in this RL circuit?

texts:
In the below circuit simulations a 1V 100kHz pulse train applied to the base of a transistor where R1 is the output resistance of the function generator Vfun. R_load is the load resistor.

In the case of R_load is 100k Ohm, when the transistor switches off the node called Vobs rises to around 250V as shown below:

But if the R_load is reduced to 100 Ohm, when the transistor switches off Vobs this time rises to only around 18V as follows:

I'm having difficulty how to explain the decrease in the voltage when the R_load is decreased. Obviously the node Vobs does not act as a constant voltage source. But what model describes this behaviour? Can anyone explain this in a step by step manner along with the circuit laws? (Similar questions were asked but I guess I'm stuck more with this particular case.)


texts: Why are dependent sources not disabled with the superposition principle?

texts: I've been wondering this recently.  My intuition says that a voltage drop across a dependent source is no different than any other circuit element whose response depends on the inputs of one of the independent sources.  But I don't feel like that reasoning is rigorous enough.  How exactly would this principle regarding treatment of dependent sources be derived?


texts: There is a traffic light circuit that I have built shown above. It works on circuit wizard just as I want but when bread boarding both the astable and monostable work however my 4017 does not I have looked over and I am not sure what is wrong.


texts:
The company I work for is manufacturing a device with ARM processor and embedded Linux. At the time of the project (a few years ago) our consultants relied on NAND flash chips with UBIFS as filesystem, due to project constraints:

The device must always be bootable even after a power cut.
The boot time of the device must always be the same, even after a power cut.

Unfortunately, power cut is the "normal" way our customers shut down their devices.
Unfortunately, the flash chip is no longer in production, so we are reassessing other alternatives: MMC embedded or SATA SSD. Something, in short, that if it goes out of production, we can find a replacement while maintaining the same identical FW.

I wonder if today the hw (ssd, eMMC, etc.) and sw (mainly filesystems) technologies allow me to stay within the constraints with devices other than NAND flash chips.


texts: PIC12F675 Timer0 stops after a short while

texts:
Okay so I'm using MPLAB X and basically I'm trying to achieve a Software UART for this little PIC running at 4 MHZ. At first I tried with delays because it's been said that even at 4 MHZ, you could achieve 9600 bps (which is what I need, no less) but for some reason I couldn't even achieve 1200 bps. I've read that Timers are a lot more accurate so I started googling around and came out with this sample code to blink a LED:
#define _XTAL_FREQ 4000000

// Configuration Bits
#pragma config FOSC = INTRCIO   // Oscillator Selection bits (INTOSC oscillator: I/O function on GP4/OSC2/CLKOUT pin, I/O function on GP5/OSC1/CLKIN)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF      // Power-Up Timer Enable bit (PWRT disabled)
#pragma config MCLRE = OFF      // GP3/MCLR pin function select (GP3/MCLR pin function is digital I/O, MCLR internally tied to VDD)
#pragma config BOREN = ON       // Brown-out Detect Enable bit (BOD enabled)
#pragma config CP = OFF         // Code Protection bit (Program Memory code protection is disabled)
#pragma config CPD = OFF        // Data Code Protection bit (Data memory code protection is disabled)

#define LED GP2

#include <xc.h>

unsigned int count = 0;

void interrupt ISR() {
  count++;           // Interrupt causes count to be incremented by 1
  if(count == 18) {
   LED = ~LED;       // Toggle LED every sec
   count = 0;
  }
  TMR0 = 192;        // TMR0 returns to its initial value
  INTCONbits.T0IF = 0;  // Bit T0IF is cleared so that the interrupt could reoccur
}

void main(void) {
    ANSEL = 0;
    ADCON0 = 0;
    CMCON = 0x07;
    VRCON = 0;
    TRISIO = 0b111011;
    GPIO = 0b000100;

    OPTION_REG = 0x07; // Prescaler (1:256) is assigned to the timer TMR0
    TMR0 = 192;          // Timer T0 counts from 192 to 255
    INTCON = 0xA0;     // Enable interrupt TMR0 and Global Interrupts

    while (1) {
        // No code here
    }

    return;
}

I set TMR0 to 192 because that's 3/4 of 255, so the LED would blink every fourth of a second. When programmed and tested, I could see the LED blink a few times and then just stay on. Sometimes it would blink 10 times, some just 3 and then just stay on. Weird thing that it stays on cause it could also stay off. Maybe it has something to do with the problem. If you could point me anywhere on this I'd really appreciate it.
EDIT:
Here's a photo of the PIC setup. I left that 10k resistor from GP4 to ground because I was using it for another code now that I remember. There was also a wire coming from that pin that was floating around.

Maybe that resistor could've brought problems.


texts:
I will freely admit that I am mainly digital when it comes to electronics, so may help explain my confusion (that or just general incompetence).

I am getting review feedback on a design, and one thing that keeps bugging me is that placing a BJT below the LED keeps being labelled as 'wrong'. Is this a major issue or just a convention or is the reviewer just being annoying?

simulate this circuit – Schematic created using CircuitLab

NOTE: The circuit is a sketch, ignore actual part numbers or values.


texts:
I have a slightly ambitious project for my first PCB: I want to control a wall of WS2812 LEDs from an Altera CycloneIV. The LEDs are connected to a rail carrying the 5V supply, at up to 350W, and expect their control signals at 5V as well.

For the FPGA, I need 1.2V (core), 2.5V (PLL) and 3.3V (I/O).

I'm routing the I/Os (40 of them) to voltage converters to bring them up to 5V and get ESD protection.

My current approach would be a linear regulator for 3.3V, as I expect the current draw to be minimal, and there isn't much room to work with; for 2.5V and 1.2V I'd use a switching converter each and add large capacitors for stability.

For additional safety I could place reverse-facing diodes between the five voltage levels, although I'm not sure these are actually required.

Is that a viable approach, or can this be improved somehow?


texts:
Apologies if this is simple/rule breaking, it is my first electronics post and I am a newbie.

I wish to build an simple motion sensor / pir circuit, to control a relay. For controlling hard-wired heaters, this sensor to be installed "inline".

Timing to be user adjustable, so relay should stay on between 0.5 to 3.0 hours after trigger.

Question Is it possible / advisable to keep the whole circuit HV/110v?  (goal: small circuit size, and build simplicity) Or should I step down to LV?  I realise it is a very basic design question.

Thankyou.


texts:
I want to make a plug that I can turn on and off with a micro controller like a raspberry pi.

I picked up one of these http://www.radioshack.com/radioshack-15a-12vdc-125vac-relay/2750031.html
And the device I want to power is within the relays specs.

I don't know how to wire it up, and I'm hopeful that someone has worked with these before


texts: Shunt resistor choice for H-bridge current sensing

texts:
I'm trying to construct H-bridge using DRV8701 gate driver. This part expects you to attach low-side shunt resistor to measure current going through motor to limit your duty cycle if motor is stalled. In the example provided in datasheet they use 50mOhm shunt resistor with expected current chopping level of 3A. I want to set chopping level to 10A, so it seems that 50mOhm resistor is too big, then I have to dissipate 10*10*0.05=5W continuously through that resistor in worst case scenario.

I'm going to use 1mOhm resistor instead. But then DRV8701 sensor will see only 0 to 10A*0.001=0.01V voltage range, so is it reliable enough to sense current using such small resistor?


texts: 5V (analog) to 3.3V (analog) for current measuring

texts:
I want to use an ACS723 current sensor and I would like to transform that signal into digital using the integrated ADC inside a ESP8266 (Wemos D1 mini).

I'm not sure how can I do that.

I think maybe the easiest way is a voltage divider. Another solution maybe be usinag an op-amp, something like: Voltage translation: 5V to 3.3V analog

What are the different options I have?
Thanks in advance!


texts: Reduce amount of I/O required for automated switching

texts:
I got a device with a 16-pin connector. One of the functionality tests consists of shorting every pair of pins (the first with the second, the third with the fourth, etc.) and measuring the voltage between A and B (B is grounded). The device itself has multiple states. Every state has 2 measurements: one unshorted and one shorted.

The test goes like this:

Go to next state.
Measure voltage A-B
Short pins consistent with that state
Measure voltage A-B
Remove short
Goto 1.

So the setup looks like this:

Where the connectors X1-1 through X1-16 (not all are drawn) are available at the exterior of the device and the switches are added only during test. What they are connected to and how A-B is determined is quite irrelevant.

The important part is I want to automate this process. The current switches are hand-toggled. The easy solution is replacing every switch with a non-latching relay. However, this would require 8 relays and 8 I/O on whatever switches them. The current going through them is negligible and the most important part is the resistance is as low as possible.

I'm looking for a solution requiring less I/O. At all times only one relay will be active at a time, so I'm hoping a demultiplexer or something similar might make it less I/O consuming. Even better alternatives are welcome as well. Resistance between pins should be as low as possible, say below 0.5 Ohm.

Driving secondary test units with a low I/O solution like I2C is unacceptable unfortunately.


texts: Can we route using plated through hole in a Multilayer PCB?

texts:
Hi I'm designing a 4 Layer PCB for my project this is my first time using a ML4 Board. Layer Configuation are as follows.
-L1 [red]
-L2 (GND)[purple]
-L3 [light blue]
-L4 [dark blue]

My question is I have a through hole via or plated through hole running from L1 to L4 can terminate signals running on L3 on to that L1 to L4 (through hole via or plated through hole)


texts: Multiplex temperature signals through one conditioning circuit

texts:
I'm planning on designing a PCB that takes numerous analog temperature sensor input signals and convert them using an Analog to Digital Converter (ADC) to be read by a computer. The signals need to go through a conditioning circuit prior to being read by the ADC.
I need to read so many temperature signals that it would take up a ton of space and power to have conditioning circuits for each sensor.  Would it be practical to first route the temp signals through a multiplexer that then goes to a single conditioning circuit, then gets converted to a digital signal?  I don't need high time resolution for the temperature measurements so we could interpret the sensors based on some frequency.  I've attached a rough sketch of what I'm suggesting.  From searching online so far I haven't seen anyone try to do it that way.  I'm wondering if a multiplexer might distort the incoming signals too much and throw off measurements.
Thanks


texts:
I'm building a 12V parallel circuit to run some LEDs...I simplified it in the picture below but need some advice on wire sizing in a parallel circuit.
The combined amps of the 3 lights is ~11.25amps.  I had planned to use 18ga wire to wire the lights...and splice them together after the switches so I could control them individually.
Can someone coach me through gauging the wire?


texts: Can an oscilloscope add a frequency component to my signal?

texts:
I want to check the spectrum of a DDS signal ("pure" sinewave) for undesired frequency components. The way I am doing it is by storing the waveform from a 2GS/s oscilloscope (Agilent DSO81204) and then applying FFT (or Chirp Z) in MATLAB. I want to compare the results with the spectrum I see on the Spectrum Analyzer. Well, long story short, after the signal processing of the time domain signal in MATLAB I see two peaks on both sides of my desired frequency i.e. similar to AM.

When I feed the same signal to the Spectrum analyzer the peaks are not there anymore (even when using the smallest possible Bandwidth). So my question is - which spectrum is the right one? In MATLAB I tried using different windows including Rectangular (i.e. no window) but the peaks are still there. I filtered the signal with  a lowpass filter before measuring with the oscilloscope and the peaks became smaller but were still there. The only reason that came to my mind is that it is some higher order mixing product in the oscilloscope. Anyone any ideas?

P.S. I tried another oscilloscope but it is some low end model that can store only 1600 points which is far from enough for an accurate FFT.


texts: switching DC trolling motor to generator

texts:
Would like to drag the trolling motor prop while sailing to re-charge the battery.  The trolling motor is 12 VDC and the max amps at full forward speed is 50.  The sailing speed of the boat will turn the prop easily and at times will turn the prop 4 times faster than the full throttle speed of the motor.

My question is this, will the current crop of DC motor controllers with 4 quadrant control handle this amount of regen?  and what circuitry do I need to alert me that the battery is fully charged and to pull up the prop?

Thanks in advance for any help with this.  Answers from the Chesapeake Bay region can come aboard for a sail.


texts:
quick question, I am able to create schematics in EAGLE and other online based tools. But for the purpose of creating basic schematics, i.e. no model numbers, with basic stencil component outlines?

I have VISIO but it does not have all the required shapes, such as op-amps, or is it a case that there is no free option available?


texts: I want to make a program that will display color pictures (eventually video with sound too) on a small color lcd screen, I want to use an atmega 328 chip with an sd card to store the images. Any help that would point me in the right direction would be greatly appreciated.


texts: What is difference if Floorplanning for FPGA, ASIC (Standard Cell Based) & Gate Array?

texts:
Floorplanning is the step, in which functional blocks are allocated on chip area and total chip area, pins location are finalized.

Now what is the difference in Floorplanning for FPGA, ASIC and Gate Arrays?

I believe, FPGA & Gate Array both do not require floorplanning.

Kindly comment on my view.


texts:
Is any kind of (human) input/signal possible using one wire?

Maybe a coil and button with a magnet?

Maybe measuring the capacitance of the wire somehow?


texts: converting nand to nor (boolean expression)

texts:
I can make the expression using nand gates but how can I rewrite as products of sum because of making with nor gates.
$$F=S'X+SY$$

I try to take not of not but I can't.

How can I make the circuit just using nor gates.

I get it


texts: How much ripple current is safe when charging Lithium Polymer batteries?

texts:
I am looking to design and build a LiPo charger using a switching DC supply. This results in ripple current to the load, and I am wondering what ripple current is acceptable when charging LiPo cells.
When asking Google, all the results relate Li-ion, not LiPo, however the chemistry is fairly similar and a lot of what applies to Li-ion can be applied to LiPo. For example, this suggests that ripple current has little impact on Li-ion cell life. However LiPo chemistry is more dangerous, and that is obviously a much bigger concern.
Cost of the project is no real barrier, so just adding an excessive output filter is likely what I will go with. However, I would still like to know if there is any tangible information regarding LiPo charge ripple current.
Thanks :)


texts: Do consumer high temperature RF ASICS exist at 200C?

texts:
So at lunch I was browsing Indiegogo projects and I saw this one here  It's a wireless meat thermometer, I've seen it in some permutation or another a few times on sites like this.   Apparently no one can handle wires coming out of their oven or BBQ.

I'm skeptical that this could be built cheaply, do ASIC and RF components even exists at 200C temperature ranges?  I'd never thought about it so I did a little searching and saw the main market is oil drilling and probably military.  The one little MCU I found from TI is $359 on digikey :)

This project claims their thermometer's communicate via bluetooth!  Based on my experience I find it hard to believe such a chip exists, but maybe I just don't know any better.   So anyway just trying to expand my knowledge if something exists or fuel my skeptacism of this project

Oh I also read this SE article which more or less says what I expect, but maybe things have changed.


texts:
I was trying to change the laser diode in one of our broken OBIS Lasers (640nm, 40mW). Thus I thought I would buy this Thorlabs HL6362MG diode.

If I connect the diode to a power supply directly at 2.6V then it works. The old diode also works (just weak) with the same pins connected to the power supply. Therefore I assume that the pin code of the diode that I bought, matches the original one.

However, when I place the diode into the laser itself, it doesn't work. The old one, however, does work (just that it emits way to weak).

Any ideas?

Thank you.


texts: Unidentified Component in an AC motor speed drive unit

texts:
I opened by curiosity an AC single phase motor speed driver unit to understand how it works, however, i found an unknown component that i don't know what it is.

Its the first time i see this kind of component. It looks like a 9 pins black box without any reference on it and it is inserted in the PCB with a label Ouf1 engraved on the silk.

1,2 : Input of variable resistors switch

3,4:  Output to the AC Motor

5,6:  230 VAC Power Input

The variable resistors that control the motor speed and the power MOSFET all of them converge to this black box:

Any one have an idea what it could be ?

UPDATE:

I removed it from the PCB, here is how it looks from bottom, it seems there is another mini PCB inside.


texts: hardware software co-simulation in HDL simulator

texts:
When we simulate (VHDL) RTL designs in a simulation tool like ModelSim or ActiveHDL e.t.c, we can have a complete visibility of all signals and variables in the design. This goes a great deal in aiding debug in simulation. Certain things like function calls and procedure calls are not easy to debug though, we would have to set breakpoints for that.
Now assume I have a soft-processor inside the design like a Nios II processor or something else which has a program written in high level language. This program will have its own variables and state-machine code implemented in a high level programming language like C. If I carry out RTL simulation, I would be able to see what is happening at the interface of the processor. However, if I want to be able to debug the system, I should be able to see into the software of the processor in real-time as the simulation progresses.
How is this problem handled in the real world? How would such systems be debugged? If I want to fix an error in the code, I would have to have a command-line method to compile the code, generate hex and put it in a place where the simulation tool can access it everytime.


texts:
I asked this question on stackoverflow and stackexchange mathematics, but on both sites my question was closed and suggested to ask here as mentioned in the comments to this question on mathematics.

I am developing an android app which generates beep sound with vary frequency and vary  dB. User can set frequency and dB and then corresponding beep sound will be generated.

The problem is in android the sound volume change by amplitude which  is in range of 0 to 1 where 0=min and 1=max. So users give dB and by formula of

  amp = 10^(dB/20)

I convert dB to amp ... but in this formula the dB should be negative so formula gives amp in range of 0-1 but users select +ve dB and in this case all calculated amp is above 1 which in android is always max.

I want to know if there is any way to get -ve dB equivalent to given +ve dB.

Note: This app is about hearing experiment.


texts: Circuit to generate a very short pulse from long pulses is not working

texts:
Here is a simple circuit I found recommended on here for generating a very short pulse from longer pulses (in this example from a switch)

However it isn't behaving as expected when resetting a CD4017. The switch only successfully resets the CD4017 if there is long delay between presses, 4-5 seconds, pressing rapidly causes nothing to happen no matter how long I keep repeatedly pressing.
I tried adjusting value of resistor up to 200K to see if maybe the pulse was too short, this made no difference. I have no idea what's causing this strange behaviour.


texts: What is a near IR blackout material for Lidar testing?

texts:
This question seems not a best best question for this place but still related. I am doing a project regarding to lidar that involves in testing lidar behaviour when beams get absorbed.
So, what is a good off the shelf material that is good on absorbing 850nm-1000nm bandwidth?


texts: OK To Use This Male/Female Jack Combo For 24 Volt DC?

texts:
I'm using 24 volt DC motors along with 12 volt solenoid actuators for a installation piece.  For ease of install and maintenance, I want to wire each motor with a barrel jack like the one below:

https://www.amazon.com/43x2pcs-Connectors-Security-Lighting-MILAPEAK/dp/B072BXB2Y8/ref=sr_1_4?keywords=male+female+pigtail+dc+jack&qid=1564592392&s=gateway&sr=8-4

The wire is 18 gauge which works great for me but I'm a bit concerned about the title apparently giving these a 12V 5A rating.

I expect each motor to draw only a few amps.  The loads are not too extreme, only a few pounds, and the motors are definitely able to handle the load.

I'm more concerned about the jacks being able to handle 24 volts.  Although, I may be overthinking this a bit.

Will these jacks be ok or are there other jacks I should use?

Note, I did find screw terminal barrel jack adapters but I like the ones in the link I posted since the jack is a bit smaller which would make routing my wires through the cable chase channels easier.


texts: How much can GaN components make powerbanks and chargers smaller and lighter?

texts:
There is a lot of talk about GaN circuits making chargers more powerful at the same size as traditional silicon-based chargers. But are there any benefits if the goal is to minimize size and weight with the some power, or do the advantages of GaN manifest only with higher power flows? Does this concern powerbanks, where this is also claimed.

1) I.e. let's say I have a charger outputting 18 W through USB-C PD or some equivalent USB-A. Something like this: https://www.axagon.eu/en/produkty/acu-pq22 weighting 62 g. How much would one expect to save from using GaN components?

2) Or let's say a typical powerbank at 20 000 mAh, input and output at 15 W, 3 A at 5 V as per USB-C PD, weighting around 360 g, like this: https://www.anker.com/products/variant/powercore-speed-20000-pd/B1275011
How much (if anything at all) decrese in size and weight can one expect from GaN components?

I hike a lot so weight is probably the most important consideration. I would like to know if I can expect any improvements in this area from GaN components. Of course, higher power is a nice bonus but if having to choose between lower weight and higher power, I would always go fo lighter weight.


texts: Ratio between RFID reader and tag antennas

texts:
If a tag's antenna (45mm x 75mm) is larger than the reader's antenna (20mm x 26mm), could this pose coupling problems when trying to read the tag?

The reader functions correctly with tags similar to its size.