texts: 2S Lipo charger circuit with Adafruit MCP73831 OR alternative?

texts:
I studied several topics and sources on the net, besides Adafruit's own, and decided to try designing my own circuit.

My goal is to develop the prototype of a robot/drone that does not require me to go into surface-mounting and soldering small parts like, for example, the Texas Instruments BQ**** series.

The prototype in question is a low-powered drone of sorts and I have to be conscious of weight. Therefore I am contemplating putting all the charging circuitry into the base-station, at the price of having to lead more wires to my custom charger plug.

The "must-haves" I identified are:

provide at least 5 V power to load while charging
have Lipo cells in series, to provide at least 7 V power when not charging
have high power efficiency while away from the base-station
the mobile part of this prototype should be reasonably light-weight

I am not restricted about what voltage the base-station could provide.

I simulated the part of my circuit that disconnects the batteries when a GPIO-pin is set to high and that seems to work (though I get about 2 V voltage drop, which is really not great).

My question is:

Do you think it is a good idea to keep pursuing this general design?
If not, do you see a more integrated alternative for charging that does not require me to go into surface-mount-soldering? Or should I bite that bullet?
Do you see any obvious beginner mistakes in the circuit shown here?


texts:
I am working on Subtractor circuits using Adder circuits. I have to do x-y.

Suppose x = 111111 , y = 100000
Using the 6 bit adder circuit I created the overflow flag is coming to be 0 but when I solve it using pen and paper the overflow is coming to be 1.

When x = 000000 and y = 000000
the Carry out flag is coming to be 1 but using pen and paper it is coming to be 0.

I have used the basic logic used to create Adder circuits and for evaluation of flags.

I created 15 test cases. Only these two test cases did not agree with these flags. The final answer they displayed was correct.

Calculation that I did on pen and paper:

x = 111111, y = 100000
y'+1 = 100000

x + y' + 1 = 011111 with Carry out = 1 and overflow = ex-or of 1 and 0 = 1

x = 000000, y = 000000
y'+1 = 000000

x + y' + 1 = 000000 with carry out = 0 and overflow = ex-or of 0 and 0 = 0

What mistake I might be doing?

I think it has to do something with 2s complements because 2s complement of 0000000 and 100000 are the numbers themselves.

I have created the circuit in vivado.

My code is this:
Full 1bit Adder:

module FullAdder( a,b,cin,s,cout ) ;
input wire a,b,cin ;
output wire s,cout ;
assign s = cin^a^b;
assign cout = (b&cin) | (a&cin) | (a&b) ;
endmodule

Code for 6 bit adder:

`timescale 1ns/ 1ps
module sixbit_ripple_adder
(
input wire[5:0] x,y,
input wire sel,
output wire overflow, c_out,
output wire[5:0] sum
) ;

wire c1,c2,c3,c4,c5,c6 ;

FullAdder f1 ( .a(x[0]) , .b(y[0]^sel) , .cin(sel) , .s(sum[0]) , .cout(c1) ) ;
FullAdder f2 ( .a(x[1]) , .b(y[1]^sel) , .cin(c1) , .s(sum[1]) , .cout(c2) ) ;
FullAdder f3 ( .a(x[2]) , .b(y[2]^sel) , .cin(c2) , .s(sum[2]) , .cout(c3) ) ;
FullAdder f4 ( .a(x[3]) , .b(y[3]^sel) , .cin(c3) , .s(sum[3]) , .cout(c4) ) ;
FullAdder f5 ( .a(x[4]) , .b(y[4]^sel) , .cin(c4) , .s(sum[4]) , .cout(c5) ) ;
FullAdder f6 ( .a(x[5]) , .b(y[5]^sel) , .cin(c5) , .s(sum[5]) , .cout(c6) ) ;
assign c_out = c6 ;
assign overflow = c5^c6 ;

endmodule

Value of sel for both the test cases is 1.

What am I missing?


texts: Setting up PWM on PA.3 of the STM32F091RC Nucleo board

texts:
I am using STM32Cube and the HAL libraries to set up the PWM.

For initializing Timer 2, I have:

void HAL_TIM_Base_MspInit(TIM_HandleTypeDef* htim_base)
{

  GPIO_InitTypeDef GPIO_InitStruct;
  if(htim_base->Instance==TIM2)
  {
  /* USER CODE BEGIN TIM2_MspInit 0 */

  /* USER CODE END TIM2_MspInit 0 */
    /* Peripheral clock enable */
    __TIM2_CLK_ENABLE();

    /**TIM2 GPIO Configuration
    PA3     ------> TIM2_CH4
    */
    GPIO_InitStruct.Pin = GPIO_PIN_3;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_LOW;
    GPIO_InitStruct.Alternate = GPIO_AF2_TIM2;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  /* USER CODE BEGIN TIM2_MspInit 1 */

  /* USER CODE END TIM2_MspInit 1 */
  }

}

and:

void MX_TIM2_Init(void)
{

  TIM_ClockConfigTypeDef sClockSourceConfig;
  TIM_MasterConfigTypeDef sMasterConfig;
  TIM_OC_InitTypeDef sConfigOC;

  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 0;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 800;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  HAL_TIM_Base_Init(&htim2);

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig);

  HAL_TIM_PWM_Init(&htim2);

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig);

  sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.Pulse = 400;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_LOW;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  HAL_TIM_PWM_ConfigChannel(&htim2, &sConfigOC, TIM_CHANNEL_4);

}

Both of the above were generated by STM32CubeMX.  In main, I added two lines to start the timer and the PWM channel:

int main(void)
{

  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration----------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* Configure the system clock */
  SystemClock_Config();

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_TIM2_Init();

  /* USER CODE BEGIN 2 */

    HAL_TIM_Base_Start(&htim2);
    HAL_TIM_PWM_Start(&htim2, TIM_CHANNEL_4);

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
  /* USER CODE END WHILE */

  /* USER CODE BEGIN 3 */

  }
  /* USER CODE END 3 */

}

The code compiles and downloads, but I do not see a PWM output at PA3 (I'm measuring with a logic analyzer).  PWM output also doesn't work at PA4. I've tried switching from TIM2 to TIM15 to check if that works, but there is also no PWM output.

To verify my code, I tested a few other PWM pins (PA10, PB3, PB5, PB4, PA8, PA9, PA6, PA5) and they all work.  Are there unique settings for pins PA3 and PA4 to get PWM output working?


texts: Use Raspberry Pi Gpio Header as Memory Mapped Interface

texts:
Raspberry Pi is really an interesting device for its support of so many features in such a small and simple formfactor. If the GPIO expansion header can be accessed in the same way as a normal memory-mapped interface, more projects will be able to use it as a development platform. A few questions regarding this:

Can the GPIO pins on the header be aggregated into a single memory access instruction in its hardward (chip)? If not (that I assume), can some expansion board/circuit be attached to the connector to modify the behavior such that it can have support to such an access method? How do you see such a design?
If all these seem to be impossible or too much hassle, I see a viable solution is to wrap the access into a library or abstraction layer. Has such kind of work existed? Is there any similar work? I'm not looking at the userland access, I'm thinking of some kind of kernel library that makes it easy to develop kernel level drivers based on R-Pi.

Thank you in advance for your comments.


texts: Does this sort of "multi lane" switch exist?

texts:
Does a component exist that functions as a switch for multiple connections at once, 3 in my case.

So power, ground, and data are coming in from the top. When the switch is in the left position (as pictured) they will get connected to the power, ground, and data lines on the left side. When the switch is flipped to the right position all 3 power, ground, and data are moved over to their respective matches on the right side.

Essentially it's like having a 3 switches, one each line and flipping them all at the same time.


texts: Sequentially driving multiple stepper motors with 1 driver and 1 controller

texts:
I am trying to control multiple stepper motors sequentially (only one at a time) with one controller, one driver a multiplexer and a dedicated "relay" circuit (shown in red). The idea is instead of having each motor have a dedicated driver, one driver is connected in parallel to all motors but with a "relay" circuit which lets the controller decide (via a mux) which relay to switch on and therefore which motor will rotate. For simplicity, the following diagram consists of only 2 motors:

I need inputs on the "relay" circuit (in red) since I built one and it is producing inconsistent results. Sometimes it works well sometimes it's constantly "on" with no way to influence through the "relay" circuit.

Any suggestions on tagging this question better are also appreciated!


texts:
I have a 12 V motorcycle battery hooked up to a buck-boost converter, giving me a constant 12 V supply. This buck-boost converter is then hooked up to a normal buck-converter giving me 7.5 V. I know I could vary the buck-boost to 7.5 V, but because I want to power other 12 V devices later on, I need to add another buck for the 7.5 V fan supply.
Question: When I hook my fan up to the out+ and out- of the buck converter, the fan spins. However, when I use the GND from my ESP32 instead of out-, the fan doesn't spin at all. Why is this?


texts: PCB design - paste coverage calculation for exposed pad (TL;DR version?)

texts:
I have created a Web tool for creating solder mask and paste mask for exposed pad:
  https://jsfiddle.net/d1wang/5t6urzwo/

The idea is get around limitation of DipTrace and help automate footprint design.

Currently, the tool only calculates the total area of the paste stencil apertures. For 3.15x3.15 e-pad with nine ø0.3mm vias, the paste coverage is calculated to be 44%.

I do not think the calculation is accurate (the ratio is way too low). I think we need to take account of the stencil thickness.

Does someone have a "too-long;don't read" equation for the paste coverage and also a standard stencil thickness?


texts: What is meant by Input clamp current/Output Clamp current in micro controller datasheet?

texts: While reading a PIC data sheet, I found the parameters Input clamp current / Output Clamp current. Where do I consider these specifications?


texts: In adaptive signal processing, what does it mean for an arrow to go through a block?

texts:
For example, in this case the FIR digital filter has an arrow going through it. This is common in the signal processing comunity but very unintuitive from a control perspective i.e. where is the arrow going to?

Can someone care to explain, thanks!


texts: What is the best modern replacement type for a metalized paper capacitor?

texts:
I have a couple of old power supplies in which Rifa brand metalized paper line filter capacitors (for 240V mains power) have failed - or may fail - like in this question here.

30+ years sounds pretty good for a capacitor, but researching replacements turns up lots of opinions about brands and references to different types and materials.

Similar metalized paper capacitors are still available (Evox Rifa is now Kemet), which though a bit pricey have the appeal of looking like the original part. One downside is their failure is messy!

Alternatively  there are cheaper metalized film capacitors with polypropylene or polyester.

Is there evidence for a best replacement type considering performance and reliability?


texts: Having trouble identifing this connector

texts:
I am trying to find a male component that will fit the female component described and pictured below. Unfortunately I do not have the male end to provide pictures of. Any help identifying this connector or any tips for identifying connectors are much appreciated.

40-pin
20.3mm long
3.2mm wide


texts:
My load is 48v
What I am trying to achieve:
I want to connect this IGBT module (SKM400GAL12V) by Semikron as a switch.
What I have tried:
I connected the negative side of load through 1 and 2.
"No connection so far"
Once I connect a 12v power supply to pin 6 (+) and Pin 7 (-).
"Pin 1 and 2 are now connected"
Once I disconnect the 12v power source.
Pin 1 and 2 remain connected until I short pin 6 and 7.
Question:
How to achieve this disconnection without shorting 6 and 7 after disconnecting the 12v power source.


texts: Sallen Key filter for audio applications (guitar)

texts:
I am building a custom guitar effects pedal.
This is a digital pedal where the microcontroller handles all the effects.
The guitar signal enters the silicon domain through the ADCs , the effect is applied, then the DACs take control to transform it back to the audio world.

Unfortunately, the DACs aren't very good so noise is introduced.
This means i get high frequency noise on my aplifier.
Provided, i do not have a spectrum analyzer to measure the spectral information of the output signal...

What do you think it is a good cutoof frequency, in order to maintain the audio information while cutting off the high frequency noise?


texts:
I would like to know the difference between Ambient temperature vs operating temperature?
In datasheets they specify operating temperature for IC's.
ex -25°C to +125°C, so does this mean even though the IC's generate heat and ambient temperature is 125°C it would work(with the die temperature being greater than 125°C as IC is generating heat), or is it the die temperature(ambient has to be less than 125°C with th junction temperature of 125°C)?


texts: For a LiPoly-accu driven device using the Olimexino-32u4 board (includes LiPoly charger) I want to measure the accu state (voltage?). How to measure the voltage without the need for a current increasing voltage divider?


texts: CORTEX_M4_0: Error connecting to the target: Frequency is out of range

texts:
I tried to burn my coding into the board TM4C123GH6PM using Code Composer v7 (Fedora Linux), it keep showing this error message: "Stellaris In-Circuit Debug Interface /Cortex_M4_0 Error connecting to the target: Frequency is out of range."

What should I do?


texts:
I have a 12v car battery, 12v led strip and a 12v 775 DC motor.
When I connect the led strip to the battery the strip shines like a star, but when I connect the dc motor, the strip start to flicker and the luminance goes down alot.
The dc motor came with a circuit of tow conductors (I think) and tow 104 capacitors but it's damaged so I took it off.
How to stop the flickering?


texts: Is there any thumb of rules how to determine optimum spacing (marked with S below) for a RF signal (@2.45 GHz) on Coplanar Waveguide with ground (CPW-G)?


texts: Why does my ADS simulation provide no gain?

texts:
I am utilizing the following spice model for a BS170 MOSFET:

  *

  *Zetex BS170P Spice Model v1.1 Last Revised 3/5/00

  *

  .SUBCKT BS170P 3 4 5

  D G S

  M1 3 2 5 5 N3306M

  RG 4 2 270

  RL 3 5 1.2E8

  C1 2 5 28E-12

  C2 3 2 3E-12

  D1 5 3 N3306D

  *

  .MODEL N3306M NMOS VTO=1.824 RS=1.572 RD=1.436 IS=1E-15 KP=.1233

  +CBD=35E-12 PB=1

  .MODEL N3306D D IS=5E-12 RS=.768

  .ENDS BS170P

15V, 120Ohm drain resistor, 0.25V input sine, and transient simulation. Bias at 2.5v

I have tried adjusting all the values, with and without the capacitor and so forth. If the DC bias is increased current starts flowing in the FET which decreases the Vout as expected, but at no point does it provide any AC gain.

The DC block, and the AC are outputting as expected. I am not sure how to troubleshoot any further. I am new to ADS so I might be missing something obvious. The parameters for gain are in the model. I did verify it has a transconductance parameter. This MOSFET is a very quick one so 1MHz should be no problem for it. I have an actual working model of it at 14MHz, too.

This has been solved by adding an inductor to the Vbias(gate)


texts:
I'm trying to draw a plot of a passive integrator circuit. I think it's not correct as it should look like this:

but mine looks like this (it's Vout/Vin on the right):

I also don't know what voltage source should I choose (Vac/Vsin/Vpulse?) - I used pulse (as I saw it in a tutorial).


texts:
I'm using this circuit to run a small device within my car (12V):

Now I need to consider the height of the PCB and C1 is currently 10mm height. Is there a way to replace this component either with an equivalent or with may be two/more capacitors?

Right now I use this guy: http://www.digikey.com/product-detail/en/EEE-1VA221UP/PCE3955DKR-ND/1838721

Thanks in advance
JB


texts: Difference between sectors used for Flash and IAP?

texts: Here is a picture of sectors on on-chip 512kb Flash memory on LPC 1788, and the question is what's the difference between sectors 0 to 19 and 20 to 29. Can 0 to 19 be used in IAP or not and vice-versa?


texts: Fourierspectrum of the output voltage of an real inverting amplifier

texts:
First a quick descripton of my circuit:

The inverting amplifier amplifies by 20dB, the input voltage is a sinus signal with the Frequency 10 kHz and the peak to peak voltage is 200mV or 10V. The used amplifier is a OP177G. I've measured the Fast Fourier Transformation (FFT) of the output Signal. The Bandwidth of the amplyfier is 60 kHz. The outputsignal gets altered by the Slewrate for frequencys greater than 477 kHz if the input voltage is 200 mV and 9,5 kHz if the input voltage is 10 V. I only look at frequenys lower than 60 kHz cause im only interested in the altering by the slew-rate.

Now to the interpretation and my question:

If the input voltage is 200 mV I get a big peak at 10 kHz in the Fourierspectrum and no other peaks, as expected. The frequency of the input signal is way lower than the critical frequency 447 kHz, so I get a sinus signal as an output signal.

If the input voltage is 10 V, the critical frecueny 9,5 kHz is lower than the frequency of the input signal so my output signal should be a triangular function an therefore there should only be peaks at 10 kHz, 30 kHz, 50 kHz and so on after the fourier transformation. But I also have peaks at even multiples e.x. 20 kHz, 40 kHz, ... . I dont get why this is the case, because there are none in the fourier transformation of a triangular function?

Here is my plot for the input voltage 200 mV:

Here is my plot for the input voltage 10 V:


texts:
I'm trying to interface with a 23K256 SPI RAM IC using an Arduino Mega 2560. I can't use the standard SPI pins, since I'm using an ethernet shield and it doesn't play nicely when SS is set high.

So, instead, I'm trying to bit-bang it. I've tried a few methods of my own, and eventually borrowed the code from the link in this video's description, but it doesn't seem to work at all.

// hold pin is wired directly to VCC (3.3V)
int RAMClockPin = 14;
int RAMInPin = 15;
int RAMOutPin = 11;
int RAMSelectPin = 12;

// These are hard-wired in the chip
int RAM_READ_COMMAND = 3;    // 00000011
int RAM_WRITE_COMMAND = 2; // 00000010

//================================================

// Send a byte into the chip's input, bit by bit
void RAMRawWrite(byte b) {

  // Cycle through the 8 bits in the byte
  for (int j = 0; j < 8; j++) {

     // Send MSB (Most Significant Bit) to chip
     if ((b & 0x80) == 0x80) digitalWrite(RAMInPin, HIGH);
       else digitalWrite(RAMInPin, LOW);
     // Send a clock pulse
     digitalWrite(RAMClockPin, HIGH);
     digitalWrite(RAMClockPin, LOW);
     // Shift the rest of the bits, one to the left
     b = b << 1;

   }

}

//================================================

// The whole procedure of sending a data byte
void writeToRAM(unsigned int wAddr, byte wValue) {

  // Pointer to a byte
  byte *bp;

  // Point to higher byte of address (wAddr is 2 bytes long)
  bp = (byte *)&wAddr + 1;
  // Start session
  digitalWrite(RAMSelectPin, LOW);
  // Send the "write" command
  RAMRawWrite(RAM_WRITE_COMMAND);
  // Send the address, one byte at a time
  RAMRawWrite(*bp); // Higher byte
  bp--;
  RAMRawWrite(*bp); // Lower byte
  // Send the data byte
  RAMRawWrite(wValue);
  // Close session
  digitalWrite(RAMSelectPin, HIGH);

}

//================================================

// The whole procedure of reading a data byte
byte readFromRAM(unsigned int rAddr) {

  byte b, currBit;
  byte *bp;

  // Point to higher byte of address
  bp = (byte *)&rAddr + 1;
  // Start session
  digitalWrite(RAMSelectPin, LOW);
  // Send the "read" command
  RAMRawWrite(RAM_READ_COMMAND);
  // Send address
  RAMRawWrite(*bp); // Higher byte
  bp--;
  RAMRawWrite(*bp); // Lower byte

  // Get bits, MSB-first
  b = 0;
  for (byte currBit = 0x80; currBit > 0; currBit = currBit >> 1) {

     // Clock signal start
     digitalWrite(RAMClockPin, HIGH);
     // Get one bit of data, put it in the appropriate place
     if (digitalRead(RAMOutPin) == HIGH) b += currBit;
     // Clock signal end
     digitalWrite(RAMClockPin, LOW);

  }

  // End session and return result
  digitalWrite(RAMSelectPin, HIGH);
  return b;

}

void setup() {
  Serial.begin(9600);
  pinMode(RAMClockPin, OUTPUT);
  pinMode(RAMInPin, OUTPUT);
  pinMode(RAMOutPin, INPUT);
  pinMode(RAMSelectPin, OUTPUT);
  digitalWrite(RAMSelectPin, HIGH);

  Serial.println("Writing 0xA3 to 16");
  writeToRAM(16, 0xA3);
  Serial.println("Reading back...");
  byte value = readFromRAM(16);
  Serial.println(value, HEX);
}

void loop() {}

The result of the read is 0x00 every time. I've double and triple checked my pin numbers and tried reversing SI/SO, but it still isn't working. Unfortunately I don't have a scope to test the data.

Any ideas?


texts: Resistor in series needed with LED string?

texts:
I have an adjustable 24VDC power supply.
I have 1W LEDs that I was planning on stringing 7 or 8 in series to get approximately 24V across all of them together. They are rated 3.3-3.8V each.
Do I need a resistor in series to maintain current? I was thinking so since a lit LED is basically a short? I can't find an answer to what it is really needed for, just that most people say to put a resistor in series to 'limit current'...
if so, it would be a small resistor, around 2 or 3 ohm?


texts: Why do laptops' chargers have coaxial cords?

texts:
The cord connecting my laptop to the charger is a coaxial cord. It seems to me that other laptops also have the same type of cord.

I get that coaxial cords are good for connecting my TV to an antenna, or to transmit other signals, but do we need coaxial cords to transmit DC power?


texts: Can someone please explain how to add an external potentiometer to a voltage regulator with a trim pot?

texts:
I'm building an LED light panel and I'm setting up the electronics according to this video.
As you can see, he uses a 22K potentiometer and a 6.8K resistor. I would like to understand why he uses those values. As in, why a 22K potentiometer and would any other value work? And why would a 6.8K resistor result in a minimum voltage of 5V? And how do the two potentiometers work together?


texts: Trying to find voltage v across resistor

texts:
I can find the equivalent Thevenin resistance, but am unsure where to assume ground/how to do nodal analysis (what is the rule) when the current source is passing through the voltage source.
When I do superposition, I find the Rt to be (1/(5+15)+1/5)^-1 + 10 Rt=14. Is it correct to assume then the I=20/14=1.43 then do voltage divider with the current source as an open circuit?


texts: Switching a 220VAC/20A Load with a 5VDC Coil Voltage?

texts:
I have a Rasberry Pi running inside a device, which I want to connect to a relay to switch a 220VAC/20A load. The load 'spikes' to 20A when the motor is starting up, but then runs nominally at 7.7A when the motor reaches it's max.

I currently have an electro-mechanical relay rated for 10A contact current and am afraid that the 20A peaks from the motor startup (~7-8 spikes each for ~1.0 second) will cause the contact to 'arc and stick,' if not cause a worse failure.

I do not want to use a SSR, bc of the heat dissipation requirements, if I can help it. I was thinking I might use the 10A-rated relay to drive a contactor switching the higher-power load, but Im not confident in that design.

Thanks!


texts: Twin T notch filter vs RC HPF for 120 Hz sinusoid

texts:
I am sending a data with On-Off keying over the air using an LED and receiving it with photodiode.
A figure below is a stream transmitted (blue) and a stream received (yellow). A symbol rate of this test is 2,000 Symbols/sec. It means, each duration of HIGH and LOW is a multiple of 0.5 ms, 500 us.

As I use the light as communication medium, interference from fluorescent light exists. And it is a sinusoid with a frequency of 120 Hz. And it appears in the figure as the upper and lower envelopes.
Therefore, I need to filter out that 120 Hz sinusoid from the received signal.
I have two choices:

RC HPF with 120 << cutoff << 1 kHz
(Passive or active) Twin T notch filter at 120 Hz

I used filter design and analysis tool to determine proper resistances and capacitances of each circuit.

RC HPF with R = 51, C = 10u

Twin T notch filter with R1 = R2 = 4.7k, R3 = 470, C1 = C2 = C3 = 1u

(source: okawa-denshi.jp)

I think both are sufficient to have a gain nearly -10 dB at 120 Hz so that the interference can be reduced significantly. In addition, it shows nearly 0 dB gain when frequency is higher than 1 kHz.
But I wonder that how phase distorts the received signal significantly or not. With my knowledge, different phase over frequencies are related with group delay as below:

(source: williamson-labs.com)
But, I'm not sure about phase and group dealy since I have little knowlege about it.
In short:

Which implementation would you recommend to reject f = 120 Hz and pass f > 1 kHz?
Will phase do something serious to the received signal in filtering out f = 120 Hz?


texts:
If I want to use feed through for my circuit, which has a high source impedance(500M ohm), what type of filter should I use?
(if C type is OK for my selection or I should use L-type? (also  I have an op amp with high input impedance in another side of feed through)
does inductor characterize is important if I want to use an L-type filter?


texts: Can I use a WLAN mini pcie card (half or full height) in USB WiFi/WWAN slot?

texts:
I have a mini PC which has an mSATA and a USB WiFi / WWAN slot.
Below is a picture with the board and its slots.

I want to know if there is a possibility to install a WLAN mini pcie card (half or full height) which supports 5Ghz AC standard into that WWAN slot or if there are any adapters/converters that can be inserted there to be able to use it as a standard mini pcie slot for WiFi cards ?
I have tried with two different mini pcie cards one Compex WLE600VX full height and another Mediatek MT7612E half-height and there are not detected.
Thank you


texts: Why is there a diode connected in parallel to a relay coil?

texts: In most electrical circuits with a relay, a diode is connected in parallel to the coil of the relay. Why? Is it always a good practice?


texts: Where can I fnd a header for this goofy chip

texts:
I got this chip and didn't realize the pins were not the normal spacing.

Anybody know where to find a header for it.

BTW the chip is a re-issue of the old sound chip SN76477


texts: What does 4xVDD and 4xVSS mean in STM32F302xB and STM32F302xC datasheet?

texts: This particular image is on page 56 and comes under Electrical Characteristics.


texts:
Why does Intel produce core i3, core i5 and core i7 processors; but not core i2, core i4 or core i6 processors?

What is the reason behind this?


texts: P-Channel vs. N-Channel in Buck Converter

texts: It seems in most applications, an N-Channel MOSFET would be more advantageous than a P-Channel, so what would be the use of implementing a P-Channel MOSFET in a buck-converter vs an N-Channel?? Or in other words, when and why would one want to use a P-Channel MOSFET to design a buck-converter?


texts:
hey guys i just got my ACS714 -5 to +5A IC i am new the current and voltage sensing i googled for tutorials on ACS714 5A but couldn't find a suitable tutorial with AC sensing.
I got the code below from the arduino playground but the output of the current is not proper. The Curernt reading while the switch is on or off is same. can some help us out.

Arduino Current Sensing Source

int AnalogInputPin = 0; // Define analog input pin
// --------------------------------------------------------------------------------------------------------
void setup(){
  Serial.begin(9600);
}
void loop(){
  double Current = currentSensor(analogRead(AnalogInputPin));  // Read  analog value
  Serial.print(", VariationFromNull: ");
  printDouble(Current, 2);                                     // display Current
  Serial.print(" A");
  Serial.println("");
  delay(1000);
}
// --------------------------------------------------------------------------------------------------------
// Print decimal numbers
void printDouble(double val, byte precision) {
  Serial.print (int(val));                                     // Print int part
  if( precision > 0) {                                         // Print decimal part
    Serial.print(".");
    unsigned long frac, mult = 1;
    byte padding = precision -1;
    while(precision--) mult *=10;
    if(val >= 0) frac = (val - int(val)) * mult; else frac = (int(val) - val) * mult;
    unsigned long frac1 = frac;
    while(frac1 /= 10) padding--;
    while(padding--) Serial.print("0");
    Serial.print(frac,DEC) ;
  }
}
// Read 1.1V reference against AVcc
long readInternalVcc() {
  long result;
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  delay(2);                                                    // Wait for Vref to settle
  ADCSRA |= _BV(ADSC);                                         // Convert
  while (bit_is_set(ADCSRA,ADSC));
  result = ADCL;
  result |= ADCH<<8;
  result = 1126400L / result;                                  // Back-calculate AVcc in mV
  return result;
}
// Calculate current with Allegro ACS714
double currentSensor(int RawADC) {
  int    Sensitivity    = 185; // mV/A
  long   InternalVcc    = readInternalVcc();
  double ZeroCurrentVcc = InternalVcc / 2;
  double SensedVoltage  = (RawADC * InternalVcc) / 1024;
  double Difference     = SensedVoltage - ZeroCurrentVcc;
  double SensedCurrent  = Difference / Sensitivity;
  Serial.print("ADC: ");
  Serial.print(RawADC);
  Serial.print("/1024");
  Serial.print(", Sensed Voltage: ");
  printDouble(SensedVoltage, 1);
  Serial.print("mV");
  Serial.print(", 0A at: ");
  printDouble(ZeroCurrentVcc, 1);
  Serial.print("mV");
  return SensedCurrent;                                        // Return the Current
}


texts: A basic question about voltage current relation for an inductor

texts:
Section below is taken from a text:

What does the author try to explain here? What is that to do with integration that sudden change is not possible? Why infinite voltage would be needed for a sudden change?

I think I lost the link between the meaning of integration and its manifestation in an inductor. Can it be put in a better way to explain what the author means here?

edit:


texts: Impedance calculation results between grounded coplanar waveguide and microstrip

texts:
I got the following question regarding the impedance of a grounded coplanar waveguide(gcw) and microstrip as shown in the image attached:
If I increase the spacing w in the gcw to large values I am expecting getting a similar impedance results for the microstrip if the other parameters remain the same since both geometries equalise. At least that both result converge.
Why is this not the case?

Thanks for any advice


texts: I am reading the following signal from an open drain output, and trying to read the signal frequency. However, I am getting short spikes in the wave as seen below, and this is messing with the reading of my microcontroller. Any advice on how to filter this noise? Thank you


texts: Write \$V_{A}\$ in terms of \$V_{in}\$ and the resistor values algebraically in a Op-Amp

texts:
Question

Consider the Op-Amp circuit in Fig. Q1(a). Write \$V_{A}\$ in terms of \$V_{in}\$ and the resistor values algebraically.

My Try

Case 1 :

I see wire(+) as opened since it draw almost 0 current ideally. So, we have

$$V_A=V_{in}\left(\frac{R_3}{R_3+R_4}\right)$$

Case 2 :

Transform the circuit as if the following one. Since wire(+) and wire(-) ideally have no potential difference, I shorted them together.

simulate this circuit – Schematic created using CircuitLab

$$
R_{13}=\left(\frac{1}{R1}+\frac{1}{R3}\right)^{-1}\space \space \space \space and\space \space \space \space R_{24}=\left(\frac{1}{R2}+\frac{1}{R4}\right)^{-1}
$$

$$
R_{eq}=R_{13}+R_{24}
$$

Therefore,
$$
V_A=V_{in}\left(\frac{R_{13}}{R_{eq}}\right)
$$

My Questions

For Case 1 and Case 2, which one is correct? Or, both are wrong?
How to find the current I from \$V_{A}\$ to \$V_{out}\$? Can I calculate it from the following equation?

$$
I=\frac{0-V_A}{R_1}+\frac{V_{in}-V_A}{R_2}
$$

Thank you for your help.


texts: Capacitor Storage Temperature vs Rated temperature

texts:
I have a device that contains this capacitor: https://search.murata.co.jp/Ceramy/image/img/A01X/G101/ENG/GRM21BR71H104JA01-01.pdf

The rated temperature range was listed as -55°C to 125°C. However, in the section "Storage and Operation condition", it states "The performance of chip monolithic ceramic capacitors may be affected by the storage conditions. Store the capacitors in the following conditions: Room Temperature of +5℃ to +40℃ and a Relative Humidity of 20% to 70%."

I'm wondering why there is such a huge discrepancy. Does this mean that if I needed to keep the capacitor in a 80℃ environment, I need to keep the capacitor powered at all times? Or maybe the +5℃ to +40℃ values are specific to the pre-soldered state?


texts: Verilog: Shift Register with feedback loop

texts:
I am trying to simulate a 3 stage shift register with feedback loop using D-flipflop and XOR gate.

main.v:

module main(
d0,d1,d2,
 clk ,
 reset ,
 q0,q1,q2);

input clk,reset;

inout d0,d1,d2,q0,q1,q2;

dff df1(.d(d0),.clk(clk),.reset(reset),.q(q0));

dff df2(.d(q0),.clk(clk),.reset(reset),.q(q1));

dff df3(.d(q1),.clk(clk),.reset(reset),.q(q2));
xor1 exor1(.a(q1), .b(q2), .c(d0));
endmodule

dff.v:

module dff(
d,
 clk,
 reset,
 q);

input d,clk,reset;
output q;

reg q;

always @ ( posedge clk)
 if (~reset) begin
   q <= d;
 end  else begin
   q <= 1'b0;
 end

endmodule

main_tb.v:

module main_tb;
reg clk,reset;
 //reg d0,d1,d2,q0,q1,q2;
 wire d0,d1,d2,q0,q1,q2;
 initial
 begin
    clk = 0;
    reset = 1;
    #15
    reset = 0;

 end

always begin
    #5 clk = !clk;
    end
    main U0(
 .d0(d0),
 .d1(d1),
 .d2(d2),
 .clk(clk),
 .reset(reset),
 .q0(q0),
 .q1(q1),
 .q2(q2)
 );

endmodule

Now ISim doesnt simulate this code. Where am i going wrong?

EDIT: edited the testbench code. ISim is stuck at 0ps.


texts: Powering ATtiny85 for temperature sensing

texts: I have been working on a miniature temperature sensing module which buzzes once the temperature crosses a threshold using ATtiny85, lm35 and a pico buzzer. When I power the whole circuit using an arduino board and take readings of the temperature sensor, they are consistent. But when I try to take the readings after powering the whole thing using 2xcr2016 3V coin cells, the readings are erratic. How do I solve this issue?


texts: LED Blink is not working but code can program with PIC18F4550 and MikroC

texts:
I tried to code LED on-off program for test PIC18F4550 microcontroller. The code can program to IC using Pikkit 2 but a program is not working. I code by using MikroC Pro for Pic 6.6.1. I am using 4Mhz crystal oscillator.

Why program is not working? is it IC not working?

Code:

void main() {
  TRISA.B0=0;

  while(1){
     PORTA.B0=1;
     Delay_ms(2000);
     PORTA.B0=0;
     Delay_ms(2000);
  }

}

This is my circuit diagram:


texts:
I recently found out about Nixie tubes, how to implement the decoder, microcontroller, as well as the power management.
I have one big problem. I don't really know if ground = ground.
On the schematic it is shown that all grounds are connected to one another (ground terminal) as if I could just draw a line and connect them, but I'm not quite sure if I understand that correctly.

Image and Schematics are by GreatScott


texts: Why is a voltage divider used when reading analog sensors?

texts:
So when reading sensors (ping sensors/light/pressure/etc...) I notice they always use a voltage divider with resistors before running the input into the ADC input of a microcontroller.

Why can't we just run the sensor straight into the ADC? I understand that if the "device/sensor/whatever" went to a really high voltage the MCU wouldn't be able to understand it, but what about smaller ones that don't really go past 5v?

Also what's the best way to calculate what resistor value I should use? I guess whatever gets it between 0 and 5v?

edit: Apologies, I wasn't very clear. I guess I meant both types of sensors but I think I was more-so thinking of resistive type sensors (LDR's/etc...), but I guess it makes sense because an MCU can't actually measure resistance (Which I now feel stupid for not making the connection lol)


texts: Can I connect two rechargable LI batteries of different specs in parallel?

texts:
More specifically, can I combine a high-discharge battery with a high-capacity battery if I want periodic high discharges combined with the higher capacity?

For example, if I wanted to pair a high-capacity Panasonic NCR18650B with a high-discharge Samsung INR18650-25R, where the capacities are 3350mah and 2560 mah, and the continuous discharge rates are 6A and 20A, could I hope for say 25A continuous discharge rates over a 10-15 seconds, with an total capacity of around 5400 mah? how can I calculate for other numbers as far as time/discharge rates for other combinations?


texts:
I have coded a simple timing check for my STM32F4 Discovery board.

#define IT_PER_SEC 100

int main(void)
{
   if (SysTick_Config(SystemCoreClock / IT_PER_SEC))
   {
      while (1){}; // error
   }

   initGPIO();

   for(;;)
   {
   }

   return 0;
}

void SysTick_Handler(void)
{
   static uint32_t csec  = 0;
   static uint32_t ctime = 0;

   ++csec;
   if(csec == IT_PER_SEC) // every second
   {
      // every second
      GPIO_ToggleBits(GPIOD, GPIO_Pin_12);
      csec = 0;

      // clock
      ++ctime;

      if((ctime % 10) == 0) // every 10 seconds
      {
         GPIO_ToggleBits(GPIOD, GPIO_Pin_13);
      }

      if((ctime % 60) == 0)     // every minute
      {
         GPIO_ToggleBits(GPIOD, GPIO_Pin_14);
      }

      if(ctime == 3600)         // every hour
      {
         GPIO_ToggleBits(GPIOD, GPIO_Pin_15);
         ctime = 0;
      }
   }
}

This seems to be working fine. I checked it with the stopwatch app on my android phone. But after an hour and something I noticed that the LED timing was about a second in advance and after two and a half hours I'm almost at two seconds.

I guess my app is not at fault here, or is it? The SysTick should be fine as well, I suppose. So it must be my code...

The schematics are the standard schematics of the STM32F4 Discovery board. They can be found in the user manual on page 32. There, one can find an 8 MHz crystal together with the two common 20 pF capacitors.


texts: STM32 custom bootloader: how to verify the firmware?

texts:
Using a custom SDIO/FAT in the application bootloader for a STM32 chip, is it possible to make the jump from the bootloader to the new firmware fail-safe?

I would like to verify the new firmware sanity before jumping to it and ideally do so in a sandboxed or safe environment to treat failures if need be. All examples and documentation I found verify the firmware has correctly been placed in the flash memory and then jump to it without a second thought.


texts:
At a given point of time, current in any wire in armature winding is either positive or in negative direction, then why there is a need of so many slots in commutator? doesn't a two slot commutator suffice?
Or Aren't the any given winding wire is not powered all the time? if so, Why?


texts: What is the reason behind transfer function representation valid for only LTI system?

texts: One of the major advantages of state space representation is the fact that it can represent non-LTI system as well. I tried searching a lot to find a reason but couldn't get a reason explicitly stating why tf method is not valid for non-LTI systems.


texts: Issue with HV boost converter using TL5001

texts:
I have a boost converter circuit that (should) convert from 12V input to 500V output with a TL5001 PWM controller.
The problem I'm having is that the TL5001 PWM controller doesn't seem to be doing anything. When I plug in the circuit the output spikes to around 450V and then falls down as the output capacitor settles.
Here is the circuit diagram I'm using, which is basically a power supply portion of the MIT's DIY Geiger Counter lab guide found on 6th page with the exception of different HV sense resistor values and other closest replacement parts that are mostly SMD.

I've measured the OUT pin of the TL5001 and it looks like that the OUT pin is only activated first 75ms of powering the circuit, after that due to OUT pin closing the output voltage spikes:

I've also checked the FB pin voltage and seems about right, reaching 852mV when the output is at 440V (TL5001 should be trying to reach 1V).
Any ideas on what could be wrong or what else to look for?


texts:
I have an EPEver 3210A MPPT connected to my solar panel and a battery to charge. I'm initially experimenting with a small size battery (12V, 7Ah) before I upgrade. The MPPT pulls 100mA from the battery to operate. There is no on/off button on the MPPT.

I don't want to drain the battery too much with the MPPT on inclement days (which happens often during this time of year), so I added a DC switch that kills the connection between the MPPT and the battery. I'm not sure if the manufacturer intended for the MPPT to be under constant use and I'm afraid that using the switch often would put too much stress on the system.

Will a switch that periodically turns the MPPT on and off damage it?


texts:
My ebike batteries use a 2 amp charger so I will be using two for a total of four amps
How long would my 100 amp hour car battery be able to run these chargers?


texts: creating artifical neutral point in delta connection

texts:
I am trying to measure 3 phase 3wire and 3 phase 4 wire  L_L voltage and L_N voltage.Circuit i am looking is common for both.
In star connection i will get an neutral point for reference to read the accurate reading
in delta connection i wont have neutral reference but i wanted to create virtual neutral point. can someone suggest me circuit that can interface to MCU with above requirement

How to create virtual neutral point for delta connection
how can i differentiate real and virtual neutral point
is it safe when actual neutral point connected to virtual neutral point.
i have seen some application using this kind of circuit,I could not able get operation / functionality.mainly used for star and delta connection.
Is there any other technique where i could use Y and delta connection as common
78m6631
MCP3914
ADE7880

but i have used this IC there is no issue while reading star connection. but when connected in delta it make huge difference.


texts:
I used to have a 3-coil cooling fan that would rotate slow or fast depending on what is powering it - the air conditioner "signal" would make it rotate slower than that of the engine heat sensor.

Now that since a compatible fan is impossible to replace (original one died), I've installed a single-coil 12VDC fan, the only one I could get that would fit perfectly, and combined the AC and engine circuits. The thing works ok, but at full RPM from either A/C or engine temp input.

Now what I want is to separate the two and introduce some kind of a voltage drop on the A/C line - I was thinking of a few high-current diodes, each dropping about 0.7V connected in series, but I'm afraid I will not be able to deal with diodes overheating. Is there a better solution to my problem, or diodes with proper heatsink are ok? We're speaking 15~20Amps here (+ on/off spikes)

here's a diagram explaining the current setup that I would like to modify (decouple the AC and engine temp sensor lines):

>- 12vdc from A/C ------------> >-+------3
                                  |      3
>- 12vdc from heat sensor ----> >-+      3 * (single-speed fan)
                                         3
                                 GND ----3

and the original (2 separate "inputs"):

>- 12vdc from heat sensor ---->  >-------3
                                         3
>- 12vdc from A/C ------------>  >-------3 * (2-speed fan, slower from A/C)
                                         3
                                 GND ----3


texts: Kirchhoff's Laws on Series-Parallel Circuit

texts:
Consider the circuit

The writing in red are my own additions (so let me know if it's wrong).

From Kirchhoff's Laws, I obtained

\$I=I_{2}+I_{1}\$

\$I_{1}=I_{3}+I_{4}\$

\$V=V_{C_{1}}=V_{R_{2}}=V_{C_{2}}\$

\$V=R_{1}I=R_{3}I_{4}\$

\$I_{2}=C_{1}\frac{d}{dt}V_{C_{1}}\$

\$V_{R_{2}}=R_{2}I_{3}\$

\$I_{4}=C_{2}\frac{d}{dt}V_{C_{2}}\$

Did I get it right? Again, I'm not really sure as I'm not entirely familiar with circuits and the sort, being a mathematician rather than an electrical engineer.

In the end I want to come up with a differential equation that links \$V\$ with \$V_{C_{2}}\$, but I imagine that I can reach that via elimination, provided I have these equations right.


texts: Replace bad voltage regulator with another one that have lower output current

texts: I need to replace a shorted TL750L05 +5V voltage regulator with a new one. The problem is I can not easily find a replacement part that has the same features. I found the LM2931M-5.0 but is rated at 100mA max output current instead of 150mA of the original TL750L05. How bad it would be for my smps (the regulator is used in the secondary circuit of the switched mode power supply as an output voltage) and how long it will last ?


texts: reactive power and battery drain(in inverter)

texts: if the load of an inverter(using a battery) is a pure reactive load, will the battery be drained ( neglect the efficiency of DC/AC conversion)?


texts: Why two seperataly doped semiconductors cannot be joined to form a junction?

texts:
My textbook says that when a slab of P-type semiconductor and another slab of N-type semiconductor are joined, they cannot form a junction because no matter however smooth the surface is, there will always be some irregularities present in it and hence continuous contact will not be possible.

Why is this continuous contact necessary? Maybe it is necessary for electrons to jump from one slab to another. But in case of two metallic slabs, we can make electricity flow in it. How is this happening?

In other words, how are electrons trapped at the interface of a semiconductor but are not at the interface of a metal?


texts: Is a screw or push-in terminal better for vibrating environment?

texts:
I need to decide what connector to use on my PCB to connect low power wires. Among the available options on Farnell/Mouser etc. The price and size are almost similar.

I wonder if using a screw terminal or a push-in terminal would be better for a vibrating environment?


texts: In a parallel circuit where a power wire goes all the way across, why is there still current going into the circuit?

texts:
Why does the electricity does not take the shortest path and just skip past all the bulbs?

Here is a parallel circuit with two sets of 3 bulbs in series. Notice at the bottom of the circuit there is a negative wire and a positive wire that goes all the way across.

Why does the electricity still enter the parallel circuits? Also is that power wire that goes all the way across really necessary?

See my illustrations below:

I understand now from the answerer that circuit 1 it is not connected to anything. But how about now?


texts: CAN transceiver interface with two CAN BUSES

texts:
I would like to use the NXP TJA1046/TJA1048 dual CAN transceiver to connect to two CAN BUS. I would like to mux the TX1/TX2 and RX1/RX2 and connect them to single TX/RX interface on the MCU. In order to avoid conflict, I can put one of the block into standby mode and vice versa. Please check the attached picture and see if my implementation makes any sense.
Thank you


texts: What are the possible causes of sudden extremely high internal resistances in Lithium batteries?

texts:
Not a duplicate, just to separated a good question from Does a crude Li-ion 18650 battery have internal thermal (mechanic?) protection?

Short history long: I extracted 6 18650 (Sanyo) batteries from an Acer battery pack. They had more than 3V each and accepted charge and load. Unfortunately a pair of them stood (unused) next to the hot air output of a laptop. When rescued from the heat they were, obviously, hot, maybe more than if they were just a piece of something else - not sure. Hours after that they had almost no more charge (0.8V and falling) and, strangely, extremely high internal resistance (a load of 100Kohm was sufficient to turn 0.8V into 0V). When trying to resurrect it, there was no current flowing through it, no matter how high the voltage applied.


texts: Make three respective LEDs blink with an LM3914 in dot mode

texts: I'm trying to figure out how to make in the below schematic, LEDs D2, D3, and D4 blink respectively while the LM3914 is in dot mode when their on state occurs. Basically this would act like a warning indicating that you should recharge soon, and D1 would just be solid on when it's respective on state occurs (dot mode). I would like to do this with no 555 timer or micro controller either, using as few components as possible. Edit: I'm using a 10 segment LED bargraph.


texts: Cutoff or Corner Frequency for Coax Cable

texts:
I'm trying to understand better what the significance of the cutoff frequency for coax cables is. I have a case where a cable is considered for use at frequencies up to 3% higher than the manufacturer's stated cutoff frequency. (It also happens to be about 11% higher than the specification for the connectors.) This is a microwave application, BTW.

What I think I know about "cutoff frequency" is:

It is also known as the corner frequency, which for other things would normally represent the knee in the insertion loss curve where the loss may increase more rapidly with frequency.
Something about the dominance of other transmission modes changes at the cutoff frequency.

Test data that I have shows the loss vs frequency of several cables (and their connectors) varies uniformly from the lowest frequency up to and beyond the cutoff, covering the range of frequencies that I'm interested in. There is no sign of a corner or knee.

How concerned should I be about this? I'm most concerned about the mode issue mentioned above, because I have less experience with that. I suspect the stated cutoff frequency is conservative, and I have more margin that I'm using.


texts: Designing a DVI/DP to VGA converter/converting 16bit bus to 8bit bus at 2x the frequency

texts:
as it turns out, new video cards no longer have analog video output. There are multiple converters available for sale, but I have not found one that can do higher resolution than 1080p at a refresh rate higher than 60Hz.

So, I though that maybe I should try making one myself, assuming I manage to get the DAC and other required parts for this. I mean, it should not be that difficult other than getting the high frequency signals behaving correctly (which would be a learning opportunity).

However, so far it seems that I am stuck with a chicken-and-egg problem - I do not know enough about the design of such devices to be able to find good information about the design of such devices.

Could anyone point me in the correct direction so I can learn about these things? Or maybe someone has a list of chips that would e useful to in converting video to analog?

EDIT to answer pjc50's comment:
I know how VGA (signals) work and I also know that the pixel clock is the reason that pretty much all converters do not support 1920x1200@85Hz. However, since video cards have 400MHz video DACs (well, all except the very latest), this means that someone makes those DACs and I would need to figure out how to feed data to one. Or use a fast general purpose DAC. The problem for me is that I do not know where to start learning about the DVI side of things. I mean there has to be a way to, say, take video from DVI input and put it in a frame buffer in a way that can be read and sent to a DAC.

EDIT2: after reading the example that rioraxe suggested (that was low frequency), I found a possible way to do this:

ADV7619 can take HDMI input and convert it to RGB output and it works for pixel frequencies up to 300MHz.
ADV7125 is a DAC designed for driving VGA and operates at up to 330MHz.
Both chips are not BGA, though they have a pad on the bottom which will probably be annoying to older, but not impossible. Both chips are not that expensive too.

Now I only need to find a way to interface those two. ADV7619 outputs two pixels at once (300MHz pixel clock results in 48bit 150MHz output), but ADV7125 expects the data to be one pixel at a time at the correct pixel frequency.

How do I convert a 16/48bit parallel bus operating at 150MHz to a 8/24bit parallel bus operating at 300MHz? Any logic chip family operates at these frequencies at 3.3V?


texts: How to calculate input resistance of a multiplxer

texts:
I am trying to measure the input resistance of the following multiplexer:

Multiplexer

The reason I am measuring the input resistance of this multiplexer is that I have a signal coming out of my source and upon the signal reaching the input of my multiplexer the signal is distorted. My guess is that the output resistance of the source is high compared to the  input resistance of the multiplexer. I want to be able to measure the input resistance of my multiplexer but I am not sure how. I have the following ideas but not sure which is correct:

I am using a push-pull circuit to model my input of my multiplexer:

Here VDD is 3.3V and VSS is 0V. To measure the input impedance of the entire multiplexer I tried the following:

Where the signal from my function generator was 1.8 Vpp, square wave, and I tried at frequencies from 1KHz to 8 MHz. This resulted in an decrease in impedance as the frequency is increased due to MOS gate capacitance. I measured V2 with respect to ground and V1 with respect to ground (V2 and V1 were measured peak to peak). Then Iin = (v2-V1)/R (in this case R = 4.7K). Then Rin = V1/Iin. Now i am not sure if this is the input impedance of my multiplexer or not? The reason I am not sure of this is I also wanted to add in a pull-down resistor to pull down my signal to ground. So I wanted to calculate the input resistance between the ground and input. Therefore I could add in a pull-down resistor to the input of the circuit.

That way this could help bring down my signal to ground (two resistors in parallel of about the same size would decrease the resistance in half) so i wanted to measure the resistance between the input and ground and then wanted to see what the resistance would be between the input and Vss(+) if I were to use a pull-up resistor as well (for another test). For input resistance between the input and VDD(+) I used a similar set-up as mentioned above expect instead of connecting my reference to ground I connected it to VDD(+) (3.3V). I am not sure if this is correct? Then for the resistance between the input and ground I realized that this would be the exact same as what I did for the input resistance of the entire multiplexer (first scenario). Therefore, I am confused as to how to measure the total input resistance of my multiplexer, the input resistance seen between my input and ground, and my input resistance seen between my input and VDD.


texts: Meaning of unevenly spaced data points in LTspice

texts:
When View --> Mark Data Points is selected on the waveform, LTspice shows data points unevenly separated along the time axis.

Does anyone know what do these points correspond to? It doesn't look like sampled points.


texts: Maximum voltages of an op amp comparator

texts:
If I have an op amp setup as a comparator, e.g. like this one:

I know that Vo represents the difference in the input voltages, but is there a maximum value these voltages can be? Is there a limit to Vo, V1, and V2?


texts: Why is there risk of overvoltage when jump-starting a vehicle?

texts:
Ford Focus C-Max manual describes jump-starting procedure as follows:

shut off everything, connect the jump cables, start the donor vehicle engine and let it run for a while, turn the ignition key on the disabled vehicle, the disabled vehicle engine should start, do not turn on any electrical equipment, headlights included - overvoltage can damage them.

Where could the overvoltage arise from? The goal of the procedure is to connect the batteries in parallel, so that the donor battery temporarily serves instead of the depleted one. Connecting a 12V battery in parallel to a depleted (less than 12V) battery should not yield more than 12 volts.

How could the overvoltage happen in this scenario?


texts: Generating a delayed pulse of 0,5sec with one 555 timer upon powering up the circuit

texts:
In the link below, this circuit I found is what I needed.
Only the length of the pulse and the delay are not what I want.

When I want just 0.5sec before pin 3 is up and the pulse duration I want is also 0.5sec, can someone tell me how big my resistors and capacitors must be? Or can someone tell me how I can calculate this?

My source power is 16 Volts
I have already found 555 timers that can operate with 16 Volts, so thats not the problem.

When someone has another idea with two 555-timers, or something else that does the same, it's also OK.

Thanks

Circuit I need with wrong delays


texts: Why is the verification of Thevenin's theorem more accurate than that of Superposition theorem?

texts:
In my first course on Electrical Engineering, we have an experiment in the Electrical lab that asks us to verify the Thevenin theorem and the Superposition theorem and cross-check our results with our calculations on paper.

Here are the circuit diagrams, straight from my lab manual.

Thevenin's theorem:

Superposition theorem:

Question:

I was asked, during my post-lab viva, to explain why the errors for the Superposition theorem were greater than those of Thevenin's. I answered saying that both theorems were dependent on the linearity of the circuits for their functioning, and the increased current in superposition theorem was heating up the rheostats and promoting non-linear behavior. However, she was dissatisfied. She said there was something more important that I was missing. I couldn't figure it out. This was months ago, and I still wonder about it but haven't been able to come up with an alternative explanation.

TL;DR
Why is Thevenin's theorem more accurate than the superposition theorem, experimentally?

Note: Please forgive the incorrect labeling of the DPDTs in the first schematic. I am redrawing them.


texts: What could cause a buck controller to regulate to half its set point?

texts:
I have had two buck converters (from different vendors) fail in very similar ways.

The first was blamed on electrical over-stress (i.e. too high of a voltage was applied to a logic-level pin) - the second is as-yet-undetermined but suspect the same.

Both controllers have weak internal current sources to pull-up their enable lines, so they turn on if EN is unconnected. The EN threshold is 1 V.

Both controllers failed and don't turn on. EN is ~0.64 V - suspicious Si diode level...

When EN is externally pulled up, OUT is approximately 1/2 the expected value, i.e. a 5 V rail regulates to 2.4 V, and a 12 V rail regulates to 5.8 V.

Obviously something in the controller is damaged. The question is what could cause this failure, and what subcircuit of the controller would cause it to continue to regulate, but at 1/2 its setpoint?


texts: Calculate current through a resistor attached to an ADC?

texts:
I have a resistor, R1 = 100 kΩ, connected between a:

DAC PIN_1 outputting 1.34 V
ADC PIN_2

At PIN_2 I measure 0.57 V.

Can i model the circuit as:PIN_1 -- 100 kΩ R1 -- PIN_2 -- R_ADC -- GND?

For V1 = 1.34 V we have ΔV= 1.34-0.57

I want to calculate ΔV if V1=1.8 V
If i coudl use the cirucit above, i could calculate R_ADC=0.57/I and find out what Δ would be with V1=1.8 V.
To calculate I through the resistor, I just did

ΔV / R1 = (1.34 - 0.57) / 100e3 = 7.7e-06  is this correct?

However, if I connect a current to digital converter on PIN_2, and measure current, I get: I = 1.8e-7 A.

Why is the calculated current (ΔV / R) different from measured current with current to digital converter?

simulate this circuit – Schematic created using CircuitLab
EDIT: Explaing my problem in more detail
What i am trying to do is use NHS3152 to caculate the resitance of my DUT. I am running some tests now.
The way NXP (the chip manufactures) say to do it is:
Give fixed Voltage output at PIN_1

Find V at PIN_1
Find V at PIN_2
Find I at PIN_2
R= (V(PIN_1)-V(PIN_2))/I

What is unclear to me is why when i test it wiht R1 = 100 kΩ, i calculate:
ΔV / R1 = (1.34 - 0.57) / 100e3 = 7.7e-06
but measure:
I = 1.8e-7
This here is the Datasheet of my device: DATASHEET 3152 PG34


texts: How do I wire up a 3 wire electric motor?

texts:
I bought an old Dewalt bandsaw. It had this motor attaced:

I initially thought it was just missing a switch, but in fact it has no capacitor and all the wires coming out of the motor are unlabeled. No wiring diagram is present. There are four wires in total:

I have identified the wire on the right as earth.
Using a multimeter I determined that
Green / black had a resistance of 8 ohms
Green / brown had a resistance of 16 ohms
Brown / black had a resistance of 23 ohms
I have found a replacement capacitor and wired it up like this (blue is neutral and brown is live):

Will this work? I have not yet turned it on and thought I would check here before proceeding. In trying to do this have watched plenty of youtube videos on motors and looked at wiring diagrams but am finding it tricky to match theory to reality.
Thank you in advance for any help you can give.
Will.


texts: How to make communication between microcontrollers

texts:
I want to make a project where it is necessary to communicate between several microcontrollers in the fastest way possible.

For that matter I have 10 micro-controllers whose names will be 1 ... 10:

I want 1 to receive a number as input (input from user), and send it to 2.
2 will receive the number and will add 10 to it, and send the results to 3.
And so each will add a number and send the results to the next micro-controller until it reaches 10.

10 will output the final output (the output should be the number 1 received as input + all the numbers that the other processors in the chain added).

I am looking to buy STM32F103C8 (blue pill) because they look both cheaper and also stronger (and they looked more supported) than Arduino (although I am open to suggestions for other micro-controllers including claims in favor of Arduino).

Now my question is how I connect the micro-controllers I have selected (or the suggested micro controllers) to each other in the fastest and most efficient way.

I'm not looking for suggestions like: add an Ethernet/Bluetooth module and communicate with it between the micro-controllers.

I'm looking for an explanation of how to connect them using a serial or I2C connection or something like that (and I would be happy if you could add a detailed guide on how exactly to do it, which legs to attach to etc., since I'm still relatively new at working with micro-controllers)

Thank you.


texts:
If you help to find out the right formula to calculate Balance Resistor and its power value( R1 and R4 ) as shown in Pic. because i have seen every one is using different different formuals.

Data given is
Vdc min=400Vdc
Vdc max=735Vdc
C6=C5=100uF/450V , 167uA leakage Current


texts: How to put "printf" on console Debug QEMU on Eclipse STM32F4

texts:
I create a blinky project to test a qemu simulator, but my printf`s not showing in the debug console. I create a project like official tutorial GNU MCU Eclipse.

int
main(int argc, char* argv[])
{
  // By customising __initialize_args() it is possible to pass arguments,
  // for example when running tests with semihosting you can pass various
  // options to the test.
  // trace_dump_args(argc, argv);

  // Send a greeting to the trace device (skipped on Release).
  trace_puts("Hello ARM World!");

  // The standard output and the standard error should be forwarded to
  // the trace device. For this to work, a redirection in _write.c is
  // required.
  puts("Standard output message.");
  fprintf(stderr, "Standard error message.\n");

  // At this stage the system clock should have already been configured
  // at high speed.
  trace_printf("System clock: %u Hz\n", SystemCoreClock);

  timer_start();

  blink_led_init();

  uint32_t seconds = 0;

  // Infinite loop
  while (1)
    {
      blink_led_on();
      timer_sleep(seconds == 0 ? TIMER_FREQUENCY_HZ : BLINK_ON_TICKS);

      blink_led_off();
      timer_sleep(BLINK_OFF_TICKS);

      ++seconds;
      // Count seconds on the trace device.

      printf("My printf");

      trace_printf("Second %u\n", seconds);
    }
  // Infinite loop, never return.
}


texts:
Am I correct that to disable the reset pin of Attiny85, and use it as an IO pin, I need to disable the reset fuse bit(RSTDSBL)?

If so, should my RSTDSBL bit be 1 (assuming 1 = yes, disable)?

I am a little confused, because it looks like my reset pin got disabled only after I set the RSTDSBL bit to 0 (which is reverse of the logic I expected).


texts: How to Design Binary Multiplier for 2 bits?

texts:
\$(X_1,X_0)*(Y_1,Y_0)=>(S_0,S_1,S_2,S_3)\$

What should I use here? Half Adders? Full Adders? MUX? What goes were?


texts: Why use RMS instead of the average voltage of half the cycle for power

texts:
In a AC sine wave, the RMS voltage value is \$\frac{V_{p}}{\sqrt{2}}\$ where \$V_{p}\$ is the peak voltage whereas the average voltage value over half the cycle is \$V_{p}\cdot \frac{2}{\pi}\$

If we take the average of the entire sine wave the result would yield 0, since both half's of the sine wave cancel each other out. In order to fix this issue we've come up with the RMS value.

What I don't get is why bother using RMS, can't we just use the average voltage from half the cycle to compute the power.

Use \$P = \frac{V_{avg}^{2}}{R}\$ instead of \$P = \frac{V_{RMS}^{2}}{R}\$

I've heard that the RMS voltage value is the same as the DC voltage for calculating power. But why RMS? And not the average voltage value for half the cycle.

Any help is grately appreciated.


texts:
I want to reproduce an LFO circuit where the author uses NE5517N OTA. So I started form looking for the LTSpice model of NE5517. Unfortunately with no success, I decided to make NE5517 simulation and use it as subcircuit. But getting into the schematics downloaded from On Semiconductor web, I have faced some questions that are "legended" on this picture:

What type of transistor is this (with 2 collectors going out of it)?
What value is this R1 of could be?
Where can I find the params of PNPs used in schematic.
Where can I find the params of NPNs used in schematic.

Please help!


texts: How should I make a generator-powered rectifier/regulator charge a battery?

texts:
In my bicycle, I have a hub generator which provides alternated current, at nominal 6V / 3W.

I have built a regulator/filter/rectifier, using a rectifier bridge, a 6800 uF electrolytic capacitor, and a 6V/5W zener diode, and it is working great.

Now I am considering, as commonly seen in vehicles, to add a battery in the system, but I wonder how should a battery be wired / specified so that:

The battery doesn't discharge through the regulator;
Every excess power produced by the system while in use is sent to the batteries;
Running devices take the power from the battery automatically when the generator is not running (that would mean the devices would "blindly" use the energy from the system, disregarding if it is provided online by the generator, or drained from the battery).

I guess this is a fairly simple and common setup, but I am looking for the theory involved, instead of just taking a ready circuit design for a random blog, without even knowing what I am doing.

EDIT for more context:

I am using a 6V regulated generator, so I am thinking about using 4 x 1.2V (4.8V total) rechargeables. That would be enough to keep my stuff (led lights mostly) running while the generator is not active. All the lights have series resistors, so their brightness is not severely affected by 1,2 voltage drop.

One concern is that, besides not discharging the battery through the generator (I don't think that would happen since there is a rectivier bridge there), I shouldn't damage the batteries through over-charging them if I keep riding for hours and hours...


texts: Potential difference between battery negative and battery cover

texts:
I built a 30P12S battery pack using 18650 cells (3.7V Nominal). To house the pack I made a frame out of square tube Mild Steel.

When I install the pack in the frame I get a positive reading on the voltmeter between the negative of the battery pack and the frame. The voltage reads 7 to 8 Volts. If I hold one lead of the voltmeter in my hand and place the other on the negative terminal of the battery, again I get a reading but of 3 to 4 Volts. Doing the same with the positive terminal results in a low voltage of about 0.5 Volts.

The reading between battery positive and negative is 48 Volts. So there is no voltage drop in the battery itself.

The battery is not connected to any other component.

I am using a non-isolated dc-dc converter to get 12 volts. When I connect the converter to the battery while holding the voltmeter leads (Black on battery negative and Red on frame), the reading fluctuates before settling down to about 5 to 6 Volts.

What is the cause of this potential difference between the frame and the negative terminal of the battery?

edit: Using the voltmeter to measure resistance between the battery and frame gives a 0 reading.


texts: Automating a Fluid Dispenser with an Arduino

texts: I would like to automate a process which will require applying force to the plunger of a 5ml syringe to dispense fluid at about 10ul per second onto a 25 mm by 75mm surface and I am thinking of using an arduino to control an actuator that will apply this force to the plunger. I am not sure if this is the best way to go or the best way to go about it . Any help would be greatly appreciated!!!


texts: Rule of Thumb When a Bleeder Resistor is Advisable

texts: New to building circuits, I’m trying to develop an understanding as to when a bleeder resistor should be connected across a capacitor for safety reasons. I’ve seen several references talking about how quickly the bleeder resistor should reduce voltage (usually 5T), under what threshold the bleeder should reduce voltage (either 50V or 60V, used for certification purposes), and how to size the resistor.  However, in my mind it wouldn’t be voltage alone that determines when a capacitor is "safe enough" – it would be related at least partly to the amount of energy/Joules remaining within it.  I certainly wouldn’t want a capacitor charged with “only” 12V but with the stored energy of a car battery being discharged when a metal object I’m holding touches it.  Is there a convenient rule of thumb people use to determine the threshold when one should consider adding in a bleeder resistor?


texts: adding a "power output button" to a cheap bench power supply

texts:
I've an old and cheap Atten TRP3005T Take a look at atten site

I have seen more expensive device that had a specific button that always disable the current emission every time you power off the device.

This is a security feature to avoid disastrous error when you attach a device to the power supply when the power supply is off and has been left to wrong settings (happen to me.. but without consequences... 15 volts on an Arduino when I want to use only 9 volts to test it)

  Is there a way to add the same feature to my power supply ?

I think that I need   to build a circuit with a dual mosfet but I'm not enough skilled to design it by myself...
Also I'm not sure if this option draws power from the power supplier and can make some strange side-effects to power output like wrong value for voltage.


texts: How should I sense the presence of current in Solar-Supercapacitor circuit?

texts:
I am trying to measure the presence of sunlight through current sensor circuit. I don't want to use LDR as it may give a false alarm if something occludes the small LDR window. Will using the board mount current sensor work given that I am trying to charge supercapacitors from solar panels? I want to use maximum solar power in my circuit.

NOT ACTUAL SCHEMATIC

simulate this circuit – Schematic created using CircuitLab


texts:
I am measuring Dc motor RPM using a rotary encoder(custom made).The input supply to the encoder is 3.3v and the encoder output(Sine wave) is given to the Schmitt trigger to get square shaped signal.
I read this signal through a microcontroller for controlling the motor.

I have few question regarding this.

The length of the wire which I use to transfer the signal from encoder to PCB board(microcontroller) is 5 meter.Is this a problem 3.3v signal travelling for 5mts?
If so, then I have a 5v supply in the board can I use that instead of 3.3v?

If I am using a 5v instead of 3.3v should I have to use levelshifter(Again Microcontroller uses 3.3v control)?What kind of level shifter can I use for this?

Additional information:
Encoder Signal Frequency : 2-5khz

Any idea??


texts:
I have two questions.  First, I've been staring at this problem for over an hour and I'm stumped.  To be clear, I'm not looking for the answer, just some hints to get going would be helpful:

1) Using only three 2-to-4 decoders with enable and no other additional gates, implement a
3-to-8 decoder with enable. The inputs of the resulting 3-to-8 decoder should be labeled
as X2 X1 X0 for the code input and E for the enable input. The outputs should be labeled
Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0.

I definitely know how to use a 2-to-4 decoder, and how to use a 3-to-8 decoder, but how to create a 3-to-8 decoder using only three 2-to-4 decoders is stumping me.  I don't know where to begin making the connections.

Second, I have this circuit:

My next question has to do with a specific gate from this circuit:

I have never seen this gate and don't know exactly what to do with it.  Professor didn't go over it in class.  what is it?


texts: Stepper motor power requirements and contraints

texts:
I'm looking to drive a bunch of stepper motors with some of Adafruit's Raspberry Pi motor HAT.

(This product: https://www.adafruit.com/product/2348).

I need high torque motors, and I've identified this one here: http://cdn.sparkfun.com/datasheets/Robotics/57BYGH420-2.pdf.

I'm a hardware beginner, but after looking at the specs it's a little mismatched I guess. The motor calls for 2A, 3.2V, while the shield is meant to provide 1.2A, 5-12V.

Will this work? I've read that there will be a torque reduction without sufficient current, but that's within acceptable ranges. The voltage difference concerns me, but I'm wondering if maybe it will work fine.

I've looked at higher current control boards, but those seem to invariably be geared towards CNC applications, which isn't what I'm doing here (it's a robotics project).

On the most general level, I am looking to understand the constraints on delivering power to a stepper motor via a control board.

Any advice? Will this pairing work or am I about to start an electrical fire? I apologize if this question seems basic, I'm trying to get a hold on the fundamentals here.


texts:
I'm trying to build my own MPP Tracker on Solar Cell, here's my schematics

Explanation :

PA6, PB0, PB1, PB2,PA3 : I/O Pin
PA 7 : PWM Pin
PA4 : Used to measure voltage
PA0 and PA1 : Differential ADC to measure current

The problem with this circuit is, voltage drop on solar cell is too big (about 2V from 5V solar cell). I am sure that there is no problem with the solar cell since it works perfectly using MPP tracker commercial module. I've try changing the transistor several times, and also change it into a P channel trench mosfet PMV65XP, which is the same transistor used by the commercial module (it took me 1 month to get it).

So my question is, what did I do wrong? My assumption is I am using wrong kinds of diode. If yes, what diode I should use? or perhaps did I do something wrong with this arrangement?

The solar cell output is on GND and VCC, used to supply MCU and load
Here's one of the test result :

Solar Cell V-open circuit : 4.91V - 0mA
Load resistance : 220 ohm (non capacitive)

Using commercial module :
V and A on solar cell : 4.20 V, 40mA
V and A on MPP output : 3.00 V, 45mA

Using my module :
V and A on solar cell : 2.60 V, 42mA
V and A on MPP output : 2.38 V, 37mA

I've tried to change both diodes from Fast Recovery diode FR104 into Switching diode 1N148, but still there's no significant change

Just for information, at first, I also doubt my algorithm and my code, that's why I put a potentiometer (on PA3) so I can manually adjust the PWM (works on 15kHz). And as for @Maximus suggestion, here is the graph (mine is on the left side, and the commercial on the right):

The graph data is taken by changing PWM duty cycle per 10% and observing the voltage and current of solar cell output (VCC) and MPP output (J1 on circuit). And here is some of the PWM output as suggested by @laptop2d:

It appears that the Vpp of PWM signal is increased along with the Voltage of solar cell (which used as VCC supply of uC)

----Edit----
These is the PV characteristics:


texts:
I have to design a 3 phase Reactive Power Compensation System with using only reactors, no capacitor is needed. Total capacity is 505kVAr, but 475kVAr will be done with contactors, rest (30kVAr) will be done with Static VAr Compensation (SVC). This 30kVAr reactors are established using 3 monophase 10kVAr reactors (because of the SVC driver manufacturer told as like this.).

For measuring the power line, an Energy Analyzer is used. It gives the VAr power and PF, rather then a measuring with a Reactive Power Relay (since some special request from the costumer). Rest of the system is an SVC driver which is connected to 3 monophase reactors and a relay which trigers the SVC driver.

Hence, I have to design a special Reactive Power Relay, which takes the data from the EA and triggers the driver via trigger signals. My relay is able to provide any different analog output signals in addition to PWM via DACs at very high speeds and 16bit resolution for ±12V, or ±24mA outputs whichever acceptable if needed.

First problem is, I see on the driver catalogues, SVC drivers are triggered via PWM signals (as opposite to contactors, it looks like a Pulse Train). These trigger signals are shown as consecutive sharp PWM pulses, looks like there is a 120° delay between the different phases same as VAC for three different phases (like a sawtooth or just a pulse rather than a square). Hence, I think my SVC relay must provide PWMs. However, SVC relay and driver manufacturers telling me I cannot make such a relay, it is not that easy! They say that the trigger signals are not PWM or any square waves with different duty cycles. Ok, than the first question is what is the format of the trigger signal? Is a trigger signal sequence needed for 3 phase? What is the format of this sequence and how it is determined?

Second problem is, I use only reactor banks, there is no capacitor bank on the system. Second missing point occurs here; some driver manufacturers tells that the relay have to follow the zero crossing point, however some tells not! Because of this reason, some tells I have to add a 3 phase 25kVAr capacitor bank to my system. Do I really need to follow the zero crossing point for triggering only the reactors? Should I add a capacitor bank?

You might check the attached pictures for the Schematic and Trigger Signal given on SVC Driver catalogue.


texts: Eagle Cad: change default drill size list

texts:
Eagle Cad specifies certain drill and hole sizes, for example, used for VIAs, when routing.

I know that I can enter the drill size in the combo box and it will be remembered. But all the other "incorrect" default sizes remain there as well, as tempting as they are.
I also know how to specify a minimum drill size in DRC settings.

The question: how to replace the Eagle list of drill sizes (for vias) with my custom list, as per PCB manufacturing house specs?
Do I really need to go into eagle configuration files, or there is another way, for example, using scripts?


texts: A question on pulse conditioning implementation

texts:
Here is the aim of the circuit from input-output perspective:
Below on the left side of the arrow are the possible input pulse train signals. On the right side are the desired sharpened output pulses.

input .............. output

0 - 100mV --> 0 – 5V

0 - 3V --> 0 – 5V

0 - 8V --> 0 – 5V

0 - 12V --> 0 – 5V

3 - 12V --> 0 – 5V

2 - 5V --> 0 – 5V

How is it possible to implement this without using a level-shifter? By using a single or maybe two opamps.

Any ideas appreciated.


texts: LM337 based current-limiting power supply

texts:
I would like to convert the LM317 circuit found in the accepted answer of this similar thread into its negative equivalent based on the LM337, in order to make a non-tracking +/- lab power supply.
Is it as simple as replacing the LM317 and swapping all polarities? I.e., starting from this schematic:

Update: Here is what I have for both positive and negative rails (including the generation of the +/-12V necessary for the JFETs). Is this correct?

I couldn't find the JFETs anywhere on Farnell or RS - I guess they're outdated. Could you suggest a suiting equivalent and why (so that I can learn from that)?
Many thanks
P.S: I am aware this is dissipating a lot of heat worst-case - I'll mount the TO-220 on a heatsink fan-cooled to get the Rth below 3°C/W and never touch the ICs. There is actually 0.5A out of those, 0.82R is supposed to be 2.5R.


texts:
I'm looking to read digital and analog pins on one arduino from another arduino. I believe that as long as they share a common ground connection this should work fine. I'm aware of I2C and I have used it for other projects, but for this I am more interested in just making the connections.

I was wondering

Has anyone had experience with this?
Will I damage anything if I do this?


texts: use of library files in verilog synthesis and decompile original rtl file

texts:
I am testing a tool for verilog synthesis.I need to test that tool by using a library file or a directory but i am unable to get any example for the same.I am very new to verilog. Can any one suggest me any link for the same.

I had read on google that in any verilog file if we are using a library file, that means we had used the content of that library file.Its quite similar to using library file in C.

Also what does "decompile the original rtl in file" means.When i use synthesis tool , it always generate a intermidiate rtl output.I save that output in a file.Is that file is rtl file or there is some other rtl file which is to be decompiled to get some useful information.


texts: Why FTDI and not AVR with built-in USB controller?

texts:
I made a simple program in Visual C# which communicates with AVR via FT232RL chip.

PC <-> FTDI <-> MCU.

I am using FTD2XX_NET.dll for direct access to USB Device.

I'm wondering, what's the difference between a pair of FTDI-AVR and a single AVR with built-in USB Controller? I think there must be some difference in communication speed. What else is different?


texts: Diodes in series to increase reverse voltage: why one need to add resistors?

texts:
Usually it is recommended to put resistors in parallel to each diode like this:

It is supposed that the resistors will equalize leackage currents and make the voltage drop more even.

However, I doubt that. And that's why: diode I-V curve looks like this:

All diodes will share the same leakage current. And if the voltage is low it CAN be distributed unevenly. But it is not a problem until any diode will aproach to the breaking point. At this point the curent will go higher for all of the diodes. And all diodes will have a voltage drop near to its breaking point (V1, V2 and V3 on my ugly drawing).

So even different diodes (like 200V plus 1000V to have about 1200V of reverse voltage) should work well in reverse without any additional resistors. The only thing should be considered is the reverse leakage current of the most leaky diode multiplied to the highest breakdown voltage which in turn can make the last one to melt.

So is there anything I missed?


texts: Help for PWM circuit for 12 volts DC up to 1.3 A

texts:
Is there a way to do a fairly simple PWM circuit that will handle 12 volts DC up to 1.3 Amps?
The 555 timers appear to fall in the 600 mA to 900 mA max power dissipation range.

Attached is the basic diagram that I have been working with.


texts:
So I have been trying to solve the problem below for quite some time but I can't seem to do it right.

I have mainly tried to do KVL in order to get iE.

For example:

15 = 3iE + vEC
3iC = vBC

I have used the fact that C is grounded so vEC is just vE and vBC is just vB.

I also used iE = ( Beta+1 ) iB and iC = Beta iB

However, I keep getting wrong answers.

Is there something I am missing to see?

Thank you!


texts: How does the Linistepper, open source linear Stepper Motor Drive work?

texts:
I have been trying to get the Linistepper to work, however I can't seem the understand the working of the circuit.

The circuit is here.

The issues that I'm unclear about are:

What are the diodes D1-D6 for?
How does one calculate the resistors R18 - R23 for setting different microstepping current levels? (It is currently set to 0, 25, 55 ,100 % respectively).
How does current regulation in the circuit work.
PWM is used to achieve 3600 steps, how is this done?


texts: Input and output array for CMSIS DSP Real FFT Q15 functions

texts:
The first question:

in the documentations for CMSIS DSP real FFT functions, it is mentioned :

  The FFT of a real N-point sequence has even symmetry in the frequency
  domain. The second half of the data equals the conjugate of the first
  half flipped in frequency. Looking at the data, we see that we can
  uniquely represent the FFT using only N/2 complex numbers. These are
  packed into the output array in alternating real and imaginary
  components:

X = { real[0], imag[0], real[1], imag[1], real[2], imag[2] ... real[(N/2)-1], imag[(N/2)-1 }

so an array of N samples, gives N parts (N/2 real parts and N/2 imaginary parts).

but in the description of arm_rfft_q15 function it is written :

  If the input buffer is of length N, the output buffer must have length
  2*N. The input buffer is modified by this function.

why is that ?

The second question:

the description of arm_rfft_q15 indicates that the input values should be in 1.15 fixed point values:

I understand the simple fixed point arithmetics, but  how I'm supposed to convert my real int8_t values to 1.15 format? and what to do with the ouput type (let's say 256 points FFT which outputs values in the 8.8 fixed point format)? I guess some scaling should be done but I don't understand the upscale thing.


texts: NPN Transistor common emitter calculation

texts:
I built the following circuit in LTSpice using the default NPN BJT model (beta = 100).

I calculated the Ib to be 115.754uA.
This is how I did the calculation:

  Equivalent voltage at base is:
  12V * (800/(800+1000+220)) = 4.75V
  Equivalent series input resistance = Equivalent Voltage / Equivalent Current:
  4.75 / (12v / 1220ohm) = 482.9V
  This turns the input into equivalent circuit like so:

  Use KVL to solve Q1 (assuming Vbe is 0.8V):
  4.75 - ib * 482.9 - 0.8 - ie * 330 = 0
  ie = ib + ic and ic = 100 * ib
  ie = ib * 101
  4.75 - 0.8 = ib * (482.9 + 101 * 330)
  ib = 116.82uA
  ic = ib * 100 = 11.68mA
  but the simulation shows:
  ib = 1.3mA and ic = 8.65mA

What is wrong with my calculation?


texts: The common base configuration has been well documented for the BJT .Small signal analysis shows better high frequency capability then common emmitter for the same transistor.I have seen common gate used on JFETs at VHF where the low input impedence would be a better match to 50   ohm.              Would  a common gate circuit arrangement which would be more complex on an orthodox SMPS give lower switching losses ?   Is there a definative statement about how much lower they would be ?   I did this on a small ZVs royer where the circuit complexity penalty for common gate was minimal  but the actual switching losses of ZVs are so low anyway when input volts are high and input currents are low .Is it worthwhile to look at common gate ?


texts: How to find the secondary inductance value in flyback transformer?

texts:
I try to design smps converter with flyback topology. Parameters are below:
Vin = 100V(dc) (constant)
Vout = 50V(dc)
D(on) = 50% (So, D(off) = 50%)
fsw = 70 kHz
Np/Ns = 2
According to my calculations inductance of the primary Lp = 236µH.
What is the value of inductance of the secondary? How to calculate it?
In my opinion:
Ls = Lp x (Ns/Np)^2
Ls = 236µH /4 = 59µH    (I'm not sure if this calculation is true for flyback topology)
Normally, Current changes (ΔI) on primary and secondary must be equal. Because of the D(on) = D(off), slope values of current ramps must be equal.
BUT !
(Sp: slope of primary current;        Ss : slope of secondary current)
Sp = Vin/Lp = 100V / 236µH = 423729 Ampere/seconds
Ss = Vout / Ls = 50 / 59µH = 847458 Ampere/seconds
Why are they not equal? I don't know my mistake
[UPDATE - 27.07.2020 - 13:28]

This image is at page 3 in AN4137 app note by OnSemi
If current changes is not equal, how can I calculate current change for secondary?


texts:
I have just begun with transistors and came upon the common base configuration.

There it's given that output current is less than input current which makes sense considering some electrons are lost during the recombination process in the base region but I don't understand this particular line:

  The base-emitter junction JE at input side acts as a forward biased diode. So the common base amplifier has a low input impedance (low opposition to incoming current). On the other hand, the collector-base junction JC at output side acts somewhat like a reverse biased diode. So the common base amplifier has high output impedance.

Therefore, the common base amplifier provides a low input impedance and high output impedance.
what does this exactly mean
it's a npn transistor btw
though if base-collector is reverse biased then it sould make sense that no electron flow to collector......

Source


texts: Batteries with same voltage but different number of plates

texts:
Why do some batteries have the same voltage with a different amount of plates? What is the specific purpose of that?

E.g. 12 V with 11 plates and 12 V with 13 plates.


texts:
I just got a new Hakko 888D for Christmas.  I have used it a bit since then, and I'm using the wet sponge, brass sponge, and some RadioShack tip cleaner to maintain the tip quality.  The issue I am having is simple, and I might know the source but I lack a fix.  The very tip of the tip, when new, looks like the first picture with the bag.  It has a different color, and presumably a different metal, at the end.  That part gets very hot, but the shinier parts don't, and solder will NOT adhere to them.  This is likely intentional by Hakko and I like this.  My issue, as shown in picture #2, is that the shiny part is getting oxidized.  It may be ineffectual due to the fact that the oxidized portion doesn't get solder on it anyway, but it's spreading.  It's now on the non-replaceable part of the iron in small quantities.  I can't remove it with any of my aforementioned cleaning "tools".  It could be oxidizing due to the flux in my lead free solder, but it uses resin which isn't corrosive like rosin.

**My question: why is this happening and how can I fix it?  I've had this for 2 days "


texts: How to use Butterworth Polynomials to determine RC components of a n-th order filter

texts:
I am working on a project to design a 7th-order Butterworth filter Sallen-Key topology. I am not sure how to interpret the Butterworth polynomials correctly to calculate each component. I mean how is the coefficient of 0.445 for instance applied into a calculation to determine the resistor and capacitor values? Has anybody done that before?
Butterworth Polynomial for 7th-order:
$$(1+s)(1+0.445s+s^2)(1+1.247s+s^2)(1+1.802s+s^2)$$


texts: Designing a 50Ω coplanar waveguide on 1.6mm FR4

texts:
I'm trying to design a 50Ω coplanar waveguide to connect the output of a LoRa module to a SMD metal antenna. The two images below show the top layer (red) and bottom layer (blue). Vias are green and both copper pours are connected to ground. C7, C9, C10 are tuning components - not all will be caps and not all will be fitted in the final design.

Board thickness is 1.6mm, dielectric is FR4 (which I know isn't ideal and doesn't specify exact performance - cost reduction is important to this design). Feed trace width is 1.5mm, gap between feed trace and copper pour is 0.3mm and copper thickness is 35um. Operational frequencies are nominally 868MHz and 915MHz.

Does this look like it has sensible dimensions for a 50Ω feed? I used a few different online calculators (each of which with varying degrees of variable control) and it seemed close - but I have no experience of any RF work so I wanted to run it past some more experienced eyes. Also any general comments on the RF section layout would be welcome.

EDIT: Following on from @ThePhoton's comments, I have shifted the antenna feed slightly - see updated top copper image below:


texts:
I'd like to measure the number of cycles a routine uses on a 8051. I'm guessing that I could toggle a pin on and off and measure the period with a scope and multiply it by the number of cycles the 8051 can do in a second. However, I'm not sure if it'd be prone to delays in toggling.

Are there better alternatives? If it's a good idea to use a hardware counter, which timer could be used?

Thanks


texts: Unable to read output of a joystick on a Raspberry Pi

texts:
I connected my joystick with this tutorial: link
However, it does not work. The code runs fine (after changing print "---" to  print("---") to support modern python), but the output values stay at 0.
X : 0  Y : 0  Switch : 0

This is my circuit. I checked it 2-3 times, seems fine.
Notes:

"+" and "-" are reversed on my breadboard. I decided to stay consistent with marks on my breadboard, not the tutorial.
pins on my joystick are different. (on my js, highest says "GND", second highest says "5W". bottom three output signals.


texts:
Normally potentiometers have three pins, but the Song Huei's SL-20V has four. According to the datasheet: 1, 2, 2', and 3

What is the fourth pin for?

Update

Disassembly shows that @jippie's assumption is correct. Pins 2 and 2' are interconnected, and there are indeed two sliders (barely visible on my photo):


texts:
I wanted to make a 3S li-ion battery pack. I also wanted to use an AMS1117 5.0 and 3.3, but when I read the datasheet, it said, that it can work with maximum of 12V.
Would I kill my AMS1117 if I supply a voltage of 12.6V (3S Li-Ion) to it?
EDIT:
Yes, it can work with 3s lipo batteries


texts: Calculate current in branch using Thévenin's theorem

texts:
E1 = 20 V

E2 = 5 V

R1 = 10 Ω

R2 = 20 Ω

R3 = 10 Ω

R4 = 10 Ω

R5 = 5 Ω

Calculate Ix.

It's obvious that the Thévenin's theorem should have been used, but the implementation is a bit confusing for me in this case. So far I even don't know how to find an substitute impedance outside of the branch with Ix.


texts: Should a trace be connected through multiple pins on a pin header?

texts:
I'm designing a modular board, where the two modules are connected through pin headers. For mechanical stability I have more pins than traces and my question is that which is the better: route each trace through one pin and leave the remaining pins free or route the traces through multiple pins?

In the case of power traces (e.g. ground) I think it shouldn't be a problem, but what about high frequency signals (e.g. gate drive signal)? Does splitting them on the pin header cause any problem (noise, signal integrity, EMI, etc.)?


texts: Why is outer turn of this smart card antenna wider than the other turns?

texts:
Here's a scan of a stripped MIFARE Ultralight smart card. Most of the wiring is the antenna which effectively consists of a single spiral track. The outer spiral turn clearly is a bit wider than the other turns while all the other turns have equal widths.

Why is the outer turn wider than the others?


texts: Approximate transfer function expression of this circuit

texts:
I have a generic circuit like that one in the first photo: 4 impedences, and an alternating voltage generator; I want to calculate its transfer function (the output voltage divided by the input voltage).
Now, if I use the mesh or nodal analysis I get the result in the first photo (I'm sure it's correct). But in some cases I know I can multiply the transfer functions of the separeted two circuits shown in the second photo. I'm wondering why and in which cases?

I think that this approximation si valid if Z_3 is much less than Z_2 and Z_4, as you can see in my calculus.
But is this the only case in which I can approximate the transfer function of a circuit like that one?

What do you think about it?

Thanks in advance