texts:
This might be a out of stand question.I am trying to understand a verilog netlist for 1 bit adder and make schematic out of it.But as i am very new to Verilog, though can understand some basic commands.I had preferred reading this, but it didn't help me out.Below is the required netlist

module test(in1, in2, out);
input in1;
input in2;
output [1:0] out;

wire  synth_net;
wire  synth_net_0;
wire  synth_net_1;
wire  synth_net_2;

wire  synth_net_3;
wire  synth_net_4;
ADD2 synth_ADD(.in1({synth_net, in1}), .
    in2({synth_net_0, in2}), .cin(synth_net_1), .out({synth_net_3, synth_net_4})
    , .cout(synth_net_2));
GND synth_GND(.out(synth_net));
GND synth_GND_0(.out(
    synth_net_0));
GND synth_GND_1(.out(synth_net_1));
BUF synth_BUF(.in(
    synth_net_3), .out(out[1]));
BUF synth_BUF_0(.in(synth_net_4), .out(out[0])
    );
endmodule

Well variable declaration is understandable.But i can't understand

ADD2 synth_ADD(.in1({synth_net, in1}), .
        in2({synth_net_0, in2}), .cin(synth_net_1), .out({synth_net_3, synth_net_4})


texts: LCD 18 (6 x3 ) Pinout without Datasheet AW -60i LCM V4.1

texts:
I have this (18 X 3) LCD Pins, I need help to find the Datasheet or the pinout for it.

AW -60i LCM V4.1


texts: Read 4wire pressure transducer via a differential amplifier

texts:
I have been trying to read a 4wire pressure transducer (M3021-000005-01KPG) with a microcontroller, but problems keep arising. First of all, I realized that the signal (0-100 mV) is differential, which means that we have to measure it between the 2 signal wires of the transducer, not between the ground of the circuit and a single wire. With lab instruments this is no problem, but I would like to read the signal with a microcontroller. In this case, the problem becomes obvious because not only is the signal too small (0-100mV), but also the microcontroller's ADC (ex. the ADC of an Arduino) compares a voltage with its ground, and does not read differential signals.
I tried to pass the signal through a differential amplifier circuit (an op amp with some resistors) with unity gain (i will add gain later) in order to convert it to a signal relative to the circuit's ground, but the signal was not correctly read. More specifically, I was reading 5mV without the sensor connected and 8mV with the sensor @6bar pressure. The sensor's signal @6 bar should be 9 mV, so I assume that i should read 5+9 = 14mV.
I know that the diff. amp. circuit is correct because I was measuring the expected results when I was sending a custom differential signal instead of the sensor (I was getting the signal value + the noise). I also know that the transducer's signal is OK beause I measured it with a multimeter, without the diff. amp. circuit.
So, I can't find out what is wrong. I dont have much experience with op-amps, so any help would be appreciated !!
P.S. : Some info about the transducer. The signal is 0-100mV representing values from 1 to 69 bar linearly. I know that the signal is almost at noise level, but I could consistently measure 9mV @6 bar with a good mulimeter, so I assume that the sensor works fine. Filters and amplification will probably need to be added later on, but for now I just need to be able to convert the differential signal to single-ended.

simulate this circuit – Schematic created using CircuitLab
Datasheet : https://eu.mouser.com/datasheet/2/418/6/ENG_DS_MSP300_B-1130121.pdf


texts:
I am having an issue with my ADC output.

I am using:
12-bit ADC integrated in a MCU
3.3V voltage reference.
Power supply of MCU, ADC and ADC voltage reference sharing the same voltage rail(3.3V)

The mean value of my data is ~20mV and I am getting mean value of approximately 20mV, 18mV, 16mV, 14mV, 12mV and 10mV throughout my PCB validation. I will get a random mean value but the mean value will be very close to either one of the values mentioned above.

1st& 2nd attachments are data from development kit.

3rd attachment is oscilloscope measurement for ADC input.

4th& 5th attachment is the data from my PCB which has mean value of 12mV.

6th& 7th attachment is the data from my PCB which has mean value of 16mV.

8th& 9th attachment is the data from my PCB which has mean value of 20mV.

I have 0.1uF tied to ADVREF, ADC power supply.

Is this problem caused by noise within my PCB?


texts:
I am struggling with the simple oscillator on the picture below.

My aim is to obtain system of ODEs or DAE at most for numerical simulation in Matlab. But few issues occured with basic circuit theory.
For a nonlinear current \$i_d\$ I suppose piecewise defined function
\begin{equation*}
i_{\mathrm{n}} =
    \begin{cases}
        0\quad \text{for } u_{\mathrm{gs}} - V_{\mathrm{T}}\leq 0\\
        \beta(u_{\mathrm{gs}} - V_{\mathrm{T}})^{n_2}(1 + \lambda u_{\mathrm{ds}})\mathrm{tanh}\,(\alpha u_{\mathrm{ds}}) \quad \text{for } u_{\mathrm{gs}} - V_{\mathrm{T}}> 0
    \end{cases}
\end{equation*}
for some given FET parameters \$\alpha\$, \$\beta\$, \$\lambda\$, pinchoff voltage \$V_{\mathrm{T}}\$ (it is VA approxiamtion used in Sussmann-Fort's MESFET model).
For the linear part I worked out these equations so far:
\begin{align}
\frac{\mathrm{d}i_{L}}{\mathrm{d}t} &= -\frac{1}{L}(u_{\mathrm{ds}} - u_{\mathrm{gs}})\\
\frac{\mathrm{d}u_{C_d}}{\mathrm{d}t} &= \frac{i_{C_d}}{C_{d}}\\
\frac{\mathrm{d}u_{C_g}}{\mathrm{d}t} &= \frac{i_{C_g}}{C_{g}}\\
\end{align}
Using KCL I obtain \$i_{R_{\mathrm{d}}} = i_L + i_{C_d} + i_{\mathrm{n}} + i_{R_1}\$. But how do I obtain \$i_{R_1}\$ and \$i_{C_d}\$ at the same time? Both branches with loads \$R_1\$, \$R_2\$ are giving me headache.
Second problem is that blocking capacitor \$C_\mathrm{b}\$. How we can tackle with floating capacitor while using ODE formalism?
Note: Somebody here suggested me MNA aproach which is not bad after all, but due to the lack of examples on use of inductor stamp with \$sL\$ rather than \$1/sL\$ (which would produce integrodifferential equation), I would like to ask for by hand solution.
Edit:
I managed to achieve these equations according to this thesis on MNA (pages 59-62). But it uses somewhat cumbersome notation so I am not really sure about the red current source if I understood it well. Can anyone check if it is legit to use my nonlinear current use on RHS like this? Sorry for the snippets, I was typsetting it for myself in overleaf.

It is clear after performing these opeartions we can obtain equations involving only derivatives of node voltages and inductor current. Currents through voltage sources are given without derivatives. But also I get \$u_R\$s which confuses me too.


texts:
Step response of system is

\$c(t) = 5 - 0.5e^{-2t} + 8e^{-t}\$

then find steady state gain. Answer is -7.5

Now in book solution is given as :

Since this is step response we will find impulse response by differentiating with time, then "new c(t)" = y(t)

\$y(t) = e^{-2t} + -8^{-t}\$

convert into s-domain

\$Y(s) = \frac{1}{s + 2} - \frac{8}{s + 1}\$,

by final value theorem taking s->0 DC gain is -7.5

I understood this much. But my doubt is that why can't I just use
\$\frac{C(s)}{R(s)}\$ where \$R(s) = \frac{1}{s}\$ as that is step response. Then by taking s->0 I get DC gain as 5 which is not the correct answer. Please illuminate!


texts: Reading a datasheet for power requirements - regulator vs positive supply

texts:
I'm trying to interpret the attached datasheet to figure out how much power to give this sound board from adafruit:

https://www.adafruit.com/product/2220

I was hoping that the sound board could share the same power supply as 3 or 4 of these Intel Tinytile Accelerometers (datasheet also below):

https://www.intel.com/content/dam/support/us/en/documents/boardsandkits/curie/intel-curie-module-datasheet.pdf

Which number do I use for voltage from these datasheets?

Sound board datasheet:

Tinytile Datasheet:


texts:
I have 6 parallel connected led "strips" each having 4 leds in series connection (see image below).

Those leds should be 3W each (2.4V and 700mA max each)
I have a LED drive as power supply (should be 12V and 6A max)

I tried measure the voltage and the current and I found out, that there is only 1/6A = 0.16A running through each LED with the voltage 12/4 = 3V each (rounded) thus having 0.16*3 = 0.48W.

I can't find what is wrong with my observations and/or calculations or if those leds are not really a 3W LED. I guess there is something wrong with my calculations or observations because the LEDs in this setup are bright enough and based on my original calculation it should work this way.

Thanks for help


texts: Minimize current draw in a section of a circuit

texts:
I'm making a circuit in my car that gets turned on when the blinker lights are activated.
I've already connected appropriate wiring from the positive wires just before the bulbs, with ground connected to the car battery. That circuit is connected to two Arduino microcontrollers, pulling approximately 12V 1A whene the circuit is closed by the blinker signals.
The blinker signal uses a 5A fuse and I cannot simply use a larger fuse due to the wires used in the circuit.
My proposed solution is this (forgive the tacky drawing):

The ESP32 will be directly wired to the car battery so that it can stay on until needed, and I will have it in a hibernation mode pulling only 0.15 mA, so that it can't kill the car battery.
The idea is that when the blinker turns on it'll send 12V to a converter which will send 3.3V to a GPIO pin, which wakes up the ESP32, so that it can run just fine. When it loses power to the GPIO pin (AKA the blinker turns back off,) it can go back to hibernation mode.
Now, I'm worried because the lowest current consumption I can find from a 12V - 3.3V buck converter is 800mA, which will still blow the fuse. The GPIO pins only need 40mA each, which is much more like what I need. So, my questions are:

If I only have the ESP32 GPIO pin connected to the buck converter, do I have any guarantee that it'll only pull 40mA from the circuit of the bulb?

If I can't affirm my first question (which I suspect I can't,) then how could I forcefully drop the current draw from converter manually? I hear about solutions like adding a resistor, but it sounds to me like that will not drop the current draw from the bulb circuit at all, and it'll only drop current going to my buck converter.

Any suggestions?


texts: Arduino Uno/Freeduino Serial Monitor reports that the connected WiFi Shield isn't present

texts:
I have connected my Uno (freeduino USB 1.1) to a wifi shield but when I run a program for network scanning, the serial monitor prints:

  WiFi shield not present

The code is here: http://arduino.cc/en/Tutorial/ScanNetworks

Shield is properly connected, LED named L9 lits up on powering up the board.

This is the wifi shield i'm using http://arduino.cc/en/Main/ArduinoWiFiShield


texts: I want to use the following command (PINC & B00000011) to read 6 different conditions from hall effect sensors

texts:
I need help with this code. I don't understand why it doesn't execute all 6 conditions. I am using PINC which is PORTC (A0-A5) on the Arduino Uno to read in 3 hall effect sensors from a BLDC at the same time. I am just putting print statements in the conditions for testing, however the conditions are not being executed. Can any one help please?

void setup()
{
  Serial.begin(9600);
}
void loop()
{
  if (PINC & B00000011)
  {
   Serial.println("1");
  }
   else if( PINC & B00000010)
  {
   Serial.println("2");
  }
   else if( PINC & B00000110 )
  {
    Serial.println("3");
  }
  else if( PINC & B00000100)
  {
    Serial.println("4");
  }
 else if( PINC & B00000101)
  {
   Serial.println("5");
  }
  else if( PINC & B00000001 )
  {
    Serial.println("6");
  }
 }


texts: BLE beacon 2.4GHz PCB antenna layout for SoC Nordic nRF52832

texts:
Schematic, suggested by the datasheet:

PCB is round with 33mm, FR4 1.6mm
Bottom side

Top side

Bottom+top

3d view

The antenna drawings is based on AN043 of Texas, HERE.
How about the question on the last picture? It is better to keep the solder mask open or close it? If open, which PCB surface finish is better? Tin, Nickel, Gold ENIG?
I wonder if my ground plane is ok, do you see something that could change on it in order to obtain good results with the antenna? I followed the spacing between antenna and ground according to AN043 drawings.
And also, you can see on schematic that there is an inductor in series (3.9nH) an a capacitor (0.8pF) to ground on the RF line. RF line is 8 mils width, with 8mils isolation to ground. I wonder if these values are the best to use as starting point. Can calculate them correctly? I'm not from RF area.
As said, PCB trace of RF line (4mm lenght only) is 8 mils width, 8 mils clearance to ground (coplanar waveguide). If an internal ground plane layer on the PCB is used, and between these 2 layers we have 0.18mm clearance, the RF line will have 50 ohms, I know this because I already used this before for other boards. So I wonder if I can make the PCB with only 2 layers and dont take care about the impedance that it will have in practice, because the trace lenght is only 4mm.


texts: Data transmission through multiple IoT devices

texts:
We are implementing a device which will have multiple sensors inside multiple houses in our local area.
Each house will have 1 device fixed at a place and data will be transmitted to one central location. But the problem is we cannot install WiFi on these devices, it should work with cellular network.i.e. 2G,4G Or NB-IoT.
What is the best approach to implement this? Please suggest some good IOT devices which support cellular network transmission.


texts:
So I'm developing a circuit to control charge, discharge and balance LiPo batteries.
Supply voltage will be ranging from 7V to 25V, but not larger than max. Voltage of charged battery. (If I connect 2 cell battery, say 3.5V/cell, supply voltage will be 8.4V) and max current would be 3Amps. The critical part in this circuit is a minimal voltage drop. The current in such circuit will flow in both directions, since batteries can be charged and discharged. That's why I decided to try modifying this schematic which is intended to switch AC:

My idea is to set one mosfet in saturation mode, while the second one would be operating in it's linear region. By doing that I'd have control over current, whether the LiPo is charging or discharging.
I also suppose that I have to add some kind of a current shunt to have a feedback for the control unit.

So here are my questions:

How I could control gates of the mosfets using MCU and/or op-amp?
How to control several independent circuits like this?


texts: How does having more antenna help in a networking router

texts:
When I look at networking routers on the market, those that provide external antenna connections offer at least 2 connections.

What is the reason for having 2 antenna? Most if not all, have their antenna virtually at the same locality since they are attached to the device itself, hence it does not seem to provide "greater coverage". Or, does it boost the total gain e.g. 2 x 18 dBi anntena gives 36 dBi, if so, why not just have a single 36 dBi antenna?

Long Story:
I recently had to buy antenna to try boost the signal strength going into my 4G LTE router. The router has 2 SMA female connectors on the back.
I bought a single antenna and connected to one of the connectors and tested the setup. There was no increase in signal strength and speed a according to the tests.
I am thinking of buying another antenna to connect to the router, but not sure if it will help at all.


texts: What components can I throw in the trash?

texts:
I did some repairs on a project of mine and replaced a handful of MOSFETs. It occurred to me that I don't know if I can just throw the old ones in the trash or if I should take them to a recycling station?

More generally, what classes of components can be thrown away and which need special treatment?

I live in Europe, specifically Sweden, but answers for other parts of the world might be interesting as well.


texts: SSD1306 I2C: Draw only changes works however on wrong position, how to set position (command)?

texts:
I create an OLED display class for the SSD1306 and how it works is pretty straight forward. The display is buffered (offscreen method) and at performing an update, it 'dumps' the buffer to the display via I2C, in this case a total of 512 bytes (128x32 pixels) but can be also 1024 bytes (128x64 pixels).
The offscreen method is to avoid flicker and performs faster because it only updates when I want it to update. Very usefull with animations for example.
Nothing fancy however on many updates, its an expensive operation and mostly not neccessary because of little screen changes. I'm also curious about the frame rate, with less updates needed, does it perform better.
So I want to be the class is smart enough to send only the changes, so I don't need to take care about speed/performing issues. This is partly working already (by a double buffer), to detect the changes and send only those, however, appear on wrong position. This is caused by previous method, with a simple dump, it is not required to specify each pixel pair location, it just pumping an array of values.
What kind of command/instruction of the SSD1306 do I need to set target position or am i able to skip values? I cannot figure it out using the datasheet.
Here is my code (AVR-C):

// Send start address
  if (useRegisters)          // Send TWI Start
  {
    // Send start address
    TWCR = _BV(TWEN) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA);
    while(TOD_CHK_WAIT((TWCR & _BV(TWINT))) == 0) {};
    TWDR = twiAddress<<1;
    TWCR = _BV(TWEN) | _BV(TWINT) | _BV(TWEA);
    while (TOD_CHK_WAIT((TWCR & _BV(TWINT)) == 0)) {};
    TWDR = TOD_DATA_CONTINUE;
    TWCR = _BV(TWEN) | _BV(TWINT) | _BV(TWEA);
    while(TOD_CHK_WAIT((TWCR & _BV(TWINT)) == 0)) {};
  }
  else
  {
    pinSendStart( twiAddress<<1 );
    pinWaitForAck();
    pinWriteByte(TOD_DATA_CONTINUE);
    pinWaitForAck();
  }

 // Dump buffer
  for (uint16_t i=0; i < cacheSize; i++)    // Send data
  {
     bool bUpdate = ((!doubleBuffer) || ( doubleBuffer && (displayCache[cacheSize-1+i] != displayCache[i])));

     if( doubleBufferFirstTime || bUpdate )
     {
      if( doubleBuffer )
       { displayCache[cacheSize-1+i]=displayCache[i]; }

      if( useRegisters )
      {
         if( !doubleBufferFirstTime && doubleBuffer )
          {
            // Set location must be here
            // /* X */ set( TOD_SET_COLUMN_ADDR, x ); //width-1 );
            // /* Y */ set( TOD_SET_PAGE_ADDR  , y ); //height-1 );
          }

         TWDR = displayCache[i];
         TWCR = _BV(TWEN) | _BV(TWINT) | _BV(TWEA);               // Clear TWINT to proceed
         while(TOD_CHK_WAIT((TWCR & _BV(TWINT)) == 0)) {};        // Wait for TWI to be ready
      }
      else {
             pinWriteByte(displayCache[i]);
             pinWaitForAck();
           }
     }

  }

  doubleBufferFirstTime=false;

  if( useRegisters )                                            // Send TWI Stop
    { TWCR = _BV(TWEN)| _BV(TWINT) | _BV(TWSTO); }              // Send STOP
  else { pinSendStop(); }

I tried to use the COLUMN_ADDR (21h) and PAGE_ADDR (22h) to set the offset, the device doesn't seems to like it (lock up). What can I use to change the offset or skip a specific offset?

This is the setup of the display:
  set( TOD_SET_DISPLAY_CLOCK_DIV_RATIO  , 0x80 );
  set( TOD_SET_MULTIPLEX_RATIO          , height-1 );
  set( TOD_SET_DISPLAY_OFFSET           , 0x0  );

  set( TOD_SET_START_LINE | 0x0 );

  set( TOD_CHARGE_PUMP                  , 0x14 );
  set( TOD_MEMORY_ADDR_MODE             , 0x00 );

  set( TOD_SET_SEGMENT_REMAP | 0x1 );
  set( TOD_COM_SCAN_DIR_DEC );

  set( TOD_SET_COM_PINS                 , ( height > 32 )?0x12:0x02 );
  set( TOD_SET_CONTRAST_CONTROL         , 0xCF );

  set( TOD_SET_PRECHARGE_PERIOD         , 0xF1 );

  set( TOD_SET_VCOM_DETECT              , 0x40 );

  set( TOD_DISPLAY_ALL_ON_RESUME );
  set( TOD_NORMAL_DISPLAY );

  set( TOD_DEACTIVATE_SCROLL );

  show();

Edit 21 okt 2017
See my posted answer.


texts: i wonder about scott connection [phase shift]

texts:
something like wye-delta and delta-wye connection.

we can originally know wye-delta connection is step-down transformer and second side voltage phase is being to -30 degree. And also delta-wye connection is step-up transformer and second side voltage phase is being to +30 degree.

But the other side, we also can make wye-delta connection is step-up transformer if it get turn ratio like 1:2. So in this case maybe will be become +30 degree in second side voltage.

apply this principle in scott connection, how can work it?

case1) turn ration 1:2 - step up
second side voltage's angle +90 degree?

case2) turn ration 2:1 - step down
second side voltage's angle -90 degree?

if you have any information or homepage link, can you leave it for me?

thank you so much.


texts: Clock Domain Crossing: Is it possible to design an architecture from faster to slower domain and slower to faster domain simultaneously?

texts:
If I have a design which has read clock and write clock, and I want to make it work for the following scenarios:

faster read clock and slower write clock
slower read clock and faster write clock

Is this possible without changing the architecture from one scenario to other?

For example: I have a single pulse passing from one clock domain to another. I want it to be detected in either of the scenarios.

PS: Never worked on CDC before. Just started looking into it.


texts:
I have an RC helicopter with a dead 250 mAh lipoly battery with a voltage of 3.7 V.
Could I use 3 button cells at 4.5 V and a diode with 0.7 voltage drop
to power the circuit, which is somewhat complex?
It has a couple of Atmel uc's and some very small BGA parts.
Or do you think it will tolerate 0.8 V difference?


texts: Circuit for overdrive on vibrotactile motors

texts:
I have a school project where I have to create a haptic feedback wearable with vibrotactile motors. I have gotten the prototype ready which includes motors connected directly to the Raspberry Pi GPIO pins. It all works fine (I am aware of the risks of operating DC motors, without any diodes, on the GPIO pins) but the motors feel kind of weak.

I think this is caused as the motors need to start moving, and at the same time the GPIO voltage/amperage might be not enough. I was searching for a solution and I saw something called Overdrive. The voltage through the motor can be shown in the following image:

The feeling will be quite different then, as the motor will go full force instantly because of the overdrive, and builds off to 3.3V. The motor circuit I have right now is a motor being fed by the GPIO pin itself (digitalWrite HIGH) running through ground.

The circuit I need to build needs to realize the overdrive to make the motors going full force from the start, to make haptic patterns easier to recognize. What has to be done to achieve this?

I found this circuit on another page of this stackexchange, which looked like this:

I understood the use of the capacitor, the diodes and the transistor. But this circuit is designed for PWM. I want to use mine with a GPIO pin whereas I can write HIGH or LOW through the circuit. Is it actually possible to generate overdrive so the motors will kick in quickly? What should I consider in the circuit?

Thanks in advance!


texts: How to get 50 Hz sine wave from inverter bridge driving PWM pins of MCU

texts:
I am using this circuit to see the sine wave coming from a DsPIC Pins to check the shape of sine wave created from my sine table. PWM frequency is 18 kHz

But the sine wave does not seem to be not filtered properly. Also it seems to pick up some other noise or making its own oscillations when connecting the debugger to PC.

How should be the calculations or value for this filter or is there any other better options to see the sine-wave from my PWM output pins?

Image added. Below is the ground referenced Waveform on Pins


texts: I am beginner to Simulink and had a few experience in Matlab before. My question is the following. Is every Simulink model such as battery,resistor has a special code dedicated to them. For example if i had 2 batteries, do they have different codes such as nominal_voltage1 and nominal_voltage2 that i can change while making simulation if a certain voltage level exceeds?


texts: I have a 3-phase wound rotor motor on a cable reel for a bulk material ship-loader. Looking through the prints I see the rotor winding configuration is swapped from wye to delta via a relay at a transition point on the pier. Would this cause the motor to reverse direction as I have not found anything in the line to swap the phases. Please advise and thank you.


texts: Minimum distance between inductor beads and an RF transceiver?

texts:
I there a minimum distance needed between the beads and the RF transceiver?

Like below ... the connections do not really matter, just if there are requirements regarding the distance between the bead and a nRF24L01 transceiver?

Through the bead MIDI data is send/received (31250 bps). I draw only 1 bead, there will be 18.

simulate this circuit – Schematic created using CircuitLab


texts:
Let's say the model is the Ebers-Moll model, but this obviously extends to other models:

$$
 I_{\mathrm{b}}  = \frac{I_{\mathrm{s}}}{\beta_{\mathrm{f}}}\left(\mathrm{e}^{\frac{V_{\mathrm{be}}}{NV_{\mathrm{t}}}} - 1\right) + \frac{I_{\mathrm{s}}}{\beta_{\mathrm{r}}}\left(\mathrm{e}^{\frac{V_\mathrm{bc}}{NV_{\mathrm{t}}}} - 1\right)\label{eq:bjt-base}
$$
$$
 I_{\mathrm{c}} = I_{\mathrm{s}}\left(\mathrm{e}^{\frac{V_{\mathrm{be}}}{NV_{\mathrm{t}}}} - 1\right) - I_{\mathrm{s}}\frac{\beta_{\mathrm{r}} + 1}{\beta_{\mathrm{r}}}\left(\mathrm{e}^{\frac{V_\mathrm{bc}}{NV_{\mathrm{t}}}} - 1\right)\label{eq:bjt-collector}
$$

Most parameters of the model have obvious units e.g. \$I_\mathrm{s}\$ is the saturation current. There are several which catch me out though, the units of:

\$N\$  - Ideality factor/emissivity coefficient;
\$\beta\$ - current gain.

As the current gain is a gain, is it given in the same way a voltage gain is given, i.e. instead of (V/V), (A/A)? I've never seen this notation.

Is it possible that the emissivity coefficient is unitless?


texts:
What is the easiest way to communicate with a device that the bus voltage is 1V, and the clock frequency is 30 Mhz?  The data in the bus is bi-direction.
Since this is only part of my work, I want to find a easy way to realize this part, I need to spend more effort on other part.
Thank you for your suggestions.


texts: Should I buy Duracell or a much cheaper battery?

texts:
So, here are two different batteries. Both are AAA and 1.5 Volt Alkaline batteries.
(The currency is Turkish lira and prices apply to Turkey. You can think of them as dollars or euros if that makes it easier :D)

Duracell: 1400 mAh, 1.5V (3₺ per battery)
Inflame: 1300 mAh, 1.5V (0.66₺ per battery)

In a capacity-price ratio (capacity per 1₺), Inflame battery wins by a lot. And I know that popular brands usually have a high profit margin - like Apple. I'm wondering if it's the same case here. Is it only the capacity in mAh that matters? Or are there other things to be considered?
I'm asking this for my wireless mouse. The Inflame battery usually lasts around 2-3 months. And Duracell claims to have 10 times more durability against cheaper batteries... Should I believe it? If I get Duracell, will I get like 20-30 months of durability in my mouse?

(Mouse: inca - it says it consumes 1.5v 30mA)


texts:
I have bought four of the very same led light bulbs two weeks ago. Their lightning characteristics appeared to be the same (brightness, angle, color). Two days ago I have realized that one of the bulbs became approx. 40% less bright than the others.

Does this decrease in lumen also demand less power? If the bulb is expecting 10 watts initially, is it just demanding 6 watts now? Does the answer for led also apply to traditional bulbs, halogen and other technologies?


texts: Temperature sensor reads higher inside enclosure

texts:
I have an HIH6130 temperature and humidity sensor inside a plastic enclosure with a Particle Photon.

When it takes reading while inside the enclosure, the readings are ~ 2 degrees too high, vs outside the enclosure.

Outside of putting a fan or a heat sink on it, any other ideas on how to reduce the heat buildup?


texts: What makes E-bomb or Electromagnetic pulse (EMP) destructive?

texts:
wikipedia says that Electromagnetic pulse As with any electromagnetic signal, EMP energy may be transferred in any of four forms:

Electric field
Magnetic field
Electromagnetic radiation
Electrical conduction

https://en.wikipedia.org/wiki/Electromagnetic_pulse

I know that the four forms of energy are around us and we use them in our daily life, For example: Electrical conduction are used in transformers and we use Electromagnetic radiation to listen to our radio stations and TV shows. They are not destructive for electronic devices. So:

  What makes an E-bomb destructive?

I believe it may affect signals for a short time and then all electronic devices will work properly again.

As for my second question:

  How can it achieve a very wide range (big radios) of damaged
  electronic devices? How can it damage all the devices of a town or big
  area?

Note: I ask this question because I'm curious and just to learn, I don't want to destroy and thing :)


texts:
The question I need to solve is: how do the h parameters (hybrid) vary as a function of frequency?

In particular, I need to estimate the Y parameters (admitance parameters) for a 2N3904 transistor, but I only have the h parameters, as a function of the collector current, measured with a 1kHz signal.

I need the Y parameters to model a circuit with this transistor, which operates at 10 Mhz. Is it possible to estimate the Y parameters @ 10 Mhz, from the h parameters @ 1 kHz?

I know that it is possible to convert from h parameters to Y parameters, but I don't know how the frequency variation affects.

An alternative is to find a datasheet where the admittance parameters are specified for a range of frequencies, but I have searched with negative result.


texts: Bandpass filter obtained by complementary transformation of lowpass Sallen & Key: what went wrong?

texts:
I am considering the following lowpass Sallen & Key filter:

My components are the following

\$R_1=10 k\Omega\$
\$R_2=10 k\Omega\$
\$C_1=150 nF\$
\$C_2=1.65 nF\$

Now I have performed a complementary transformation to obtain a Bandpass filter. Here is the schematic on LTSpice

Now, when I simulate this circuit I get a very odd response:

It doesn't look at all like a bandpass filter. It looks like a low pass one, but I know that is because of the OPAMP own frequency response.
What went wrong with my simulation, why is this happening?


texts: How solder paste is different from tin when soldering?

texts: I recently bought this solder paste, thinking solder paste should do the trick when not using tin wire. Did I buy the wrong solder paste or does solder paste have another function since looking at it it doesn't seem to produce a connection with tin?


texts: Signal overshoot and undershoot on RS-485 bus

texts:
I'm testing an RS-485 comms network that is having occasional problems.  Looking at the waveforms on the scope it looks like fairly bad overshoot and undershoot of the voltage levels at signal edges.  Is this bad enough to be causing a problem?  I have never had a problem with RS-485 before, so have never actually looked at the analog signals before, so don't know what normal is.

Thanks,
Fred


texts:
I have a DMX controller using a 3 pin connector (gnd, data+ and data-). I need to connect it to some cheap chinese DMX lights. The problem is that the lights are powered over the same 3 lines using a 24 VDC power supply. When I did, it burned out my controller. DMX is a differential signal, so it might work, but 24V is just to much (and clearly out of specs of DMX standard, which allow for at most 7 volt). These are the lights so there would be no problem with other DMX lights.
The 24 DC power is connected to gnd (pin 1) and data+ (pin 3) of the DMX ights and is needed to power the lights.

As extra info, my DMX controller is running on the power of a usb port. When using a multimeter in AC mode (with the lights and 24V disconnected) It measures 2.5-3V on the data channel, while it is sending out some data.

How to prevent my new (expensive) controller to burn out as well? (it shouldn't see the 24V)

simulate this circuit – Schematic created using CircuitLab


texts: Trace both control and power cables in a factory

texts:
I am a fresh graduate engineer and tasked with tracing power lines and control cables of equipment in a site to draw its one-line diagram from scratch.

I thought of using a circuit/wire tracer device, like Suretrace for example, but all of those have a maximum energized line voltage rating of 600V, and as I'm being told some power lines could be as high as 1kV.

Any idea what the correct approach might be in this case?


texts: Eagle Schematic - adding net does not reflect changes in PCB

texts: I have unfinished schematic with PCB. When I add net in schematic, the route is not visible in PCB and I cannot connect pins. Why? I am adding two screenshots for better understanding of problem, first screenshot is a schematic and a second one is pcb of same schematic!


texts: How to identify if noise is coming from circuit or scope?

texts:
Occasionally, I'll be probing a circuit and would expect to see something specific and sometimes I see either crap or the signal im expecting with crap.

This video from EEVBLOG is a good example of some of the things I've seen.
EEVblog #225 - Lab Power Supply Design Part 4 - PWM Control I've jumped to the time that's relevant for my question.

He mentions that those spikes are probably due to his probing.

My question is when you probe an arbitrary circuit, and you see something that you weren't expecting, how can you determine if its coming from the scope/probing or from the circuit itself?

In another video EEVblog #577 - Precision 1A Current Source Part 2 he changed a wire to an alligator clip, and it changed the waveform completely and he gives a reason saying that its inductance. What characteristics should someone be looking for that would identify a signal is being distorted to the probing method or how the circuit is wired up (whether its a long pcb trace or an alligator clip) ?

And are there are tips/tricks, website or book recommendations that would improve my measurement techniques ?


texts:
I am looking for a way to detect a short in a piece of wire. I want for an LED to light up when the wire is shorted. i started off by using an op-amp comparator but this didnt work.

the specs of the task
"

*The requirement is to design a circuit, to drive an electromagnet solenoid, over a length of connecting cable. The cable could be damaged (short-circuit or open-circuit), so the circuit must detect these conditions.

If the solenoid is open-circuit, a red LED must be illuminated indicating open-circuit. If it is short-circuit, then another red LED must be illuminated. If neither, then it’s assumed OK, and a third (green) LED must be illuminated.

The circuit needs a push-button to turn the solenoid ‘on’ (but only if it is OK) and another button to turn it ‘off’ again. When the solenoid is energised, a fourth (power on) LED must be lit.

If the solenoid goes open or short circuit while powered (such as by someone wiggling the cable), the drive to the solenoid must be cut off and the appropriate LED illuminated. And if it then comes good again (such as an intermittent cable), the ‘on’ button must be pressed again to re-apply power.

The solenoid characteristics are: 28V DC operating voltage (operating range 18 – 32V), coil resistance is 76-84Ω. The solenoid will not operate below 5V, definitely operates above 18V, ie somewhere between 5 and 18V it pulls in. When once pulled in, it drops out between 12V and 2V (so if the drive circuit supplies less than 2V the electromagnet will definitely let go).

Assume that a power supply 28V or thereabouts is available to operate the circuit, and that it’s quite permissible to put low-level power to the solenoid to detect if it is OK or not.
The task is to sketch out a circuit which will do this (with approximate component values, and type numbers of any diodes, transistors, IC’s etc used), with a brief explanation of how it works."*

I have attached my first attempt as a sketch.

Any help is appreciated.


texts: Tool for measuring Real and Reactive Power

texts:
I am currently doing a project where I need the Real power (P) and Reactive power(Q) measurement for a Refrigerator.
I understand that if I can measure AC Voltage(V) and AC Current(A) for the Refrigerator, then I can calculate the Power Factor. From that then I can calculate both P and Q.

I want the data to be captured at a frequency of 1 sample/sec.
So, let say if I capture the data for an entire day, then it will be 86400 data points.

Now,
Q1. I was wondering if there is any device/tool/measurement unit that can measure AC voltage and current, or even directly the power and then log that data on some storage device, either USB or WiFi.

Q2. I checked there are multimeters that can be connected to USB and then transfer data to PC, but then how can I measure and log data for both simultaneously using a multimeter?

Q3. Another way is using an oscilloscope. But they are very costly and I am looking for a cheap alternative. Do you know any?


texts: Utilization of MOSFETs as switches, design methodology

texts:
Let's say I want to use an nMos FET in a low side switching circuit as follows:

simulate this circuit – Schematic created using CircuitLab

Datasheet for IRF530 here.

Now, during my education in EE, I have learnt some operation regions for MOSFETs and formulas for drain current related to these regions. And one parameter Kn which was the key parameter shows up in everywhere.

But now, I am having hard time in my calculations, because, there is not a Kn value in the datasheets of such MOSFETs. If it were present, what I would do is:

(For Vgs = high case, SW1 is closed)

Assume an operation region for the nMOS, I start with SAT generally
Use Idsat formula for the SAT region. Idsat = Kn/2*(Vgs-Vtn)^2
Find the drain voltage using Vd = Vdd - Rload * Idsat
Check if Vds >= Vgs - Vtn or not, if so, assumption for SAT is validated, if not, then MOSFET is in linear region, since it cannot be in cut-off

This was working great while doing it on paper, however, now in reality, I am stuck how to approach this kind of a design using the information present in datasheets.

I'm not able to make any comments on the operation region of the MOSFET because I cannot guess drain voltage without any information about drain current flowing through the circuit.

So, what I am asking is something like the followings:

In which operation region a MOSFET should be operated for switching applications?
For ON(mosfet conducts) part of the operation, what should I replace MOSFET with? Rds(on)? Or a voltage difference between source and drain? How should I decide whether I can directly replace the MOSFET with a resistance of Rds(on) or not. What criterias do I have to satisyf for it to act as an almost short circuit when it is ON.

And as an extra, if anyone knows, an answer to the following would be nice:

Why Kn is not present in these datasheets while it is heavily used in theoretical calculations, at least in my college education?


texts: Common mode voltage elimination at differential pair receiver

texts:
Can you please explain to me how is common mode voltage of differential pairs is eliminated at receiver side?
For example, if on RS422/485 bus there is more different transceivers (drivers and receivers), and they all have different common mode voltages. When the buss is idle, there should be common voltage of the driver that is ready to send applied on the bus, am I right?
When driver sends data, than receivers with different common mode voltage rejections receive a same differential signals with drivers common voltage and current is flowing through termination resistor, still correct?
At input circuit of those receivers there are two transistors, and there is current source, now I don't understand how the output signal is regulated, regarding to common voltage. Can you please try to explain this?
Other additional question is, how come some receivers have common mode voltage rejection +-7V and power supply is 5V?

I hope question is not to extensive and unclear, please give me any feedback.

EDIT:

How this circuit suppresses different common mode voltage levels? Is this because of current source?


texts: Photoetching: Developed photoresist coating sticks to the PCB

texts:
I've been practicing making PCBs using the photoetching process and I've come across a problem which I I haven't seen mentioned much on the Internet.

When I put the exposed board in the developer, some of the negative photoresist coating immediately starts dissolving in the developer and creates a brown cloud in the developer.

For developing, I'm using \$ 10 \mbox{ } g \mbox{ } NaOH\$ in \$1 \mbox{ } kg \mbox{ } H_2O.\$

My problem is that if any parts of that cloud come into contact with the PCB again, they will stick to it and the covered pieces will etch with great difficulty. They start etching just before the parts which were supposed not to be etched.

So any ideas how to prevent that?


texts: Why does the Collector-Emitter voltage need to be ≥ 0.3 V?

texts:
I have been going over transistors in class lately and one of the "rules" is that the transistor needs minimum voltage drop between C and E ie, VCE ≥ 0.3 V.

However, no derivation or much explanation was provided to understand why this is true. I have searched in some sites for this as well but haven't found an explanation. Is there something I am not seeing?


texts:
Does anyone know a good way to convert -5/0 volt logic to 0/5 volt? I'm using a chip as seen in the diagram below, but I'm not sure what to do about the inverted logic levels. Basically, I need to add 5 volts to both logic levels to fix it (-5 volt goes to 0, 0 volts goes to 5). I know I can do the level shifting with some MOSFETs, but I'm space limited on the board so it would be really helpful if anyone could recommend an IC to do the conversion. If there is no such IC, what would be the best discrete circuit to do the conversion?

Thanks.


texts: How to switch off from headphone jack insertion

texts:
I am trying to control a boost converter - I want it on when headphone jack inserted and off otherwise.  It is on when it's EN pin is >1V and off when EN pin<0.2V.

I would also like to be able to override the jack and turn the boost converter off when 5V is applied elsewhere in circuit.

I've been running into some issues with the understanding of this and would appreciate some thoughts/if there is a massively more elegant/better version of what I've thought up, or if it has a flaw.

I've attached a schematic of my circuit below.  The 1.2V source is constant.  The headphone jack I've represented with a switch.  The switch is NC and unfortunately for me is connected between pins 5 and 6.  If it was NC but connected to ground pin this would be a lot easier, however it's not.  What I have done is connected a 1Mohm pullup to pin 6 and on pin5 attached a 10k pulldown resistor.  My thinking with the 10k pulldown is that without it, when there is no headphone inserted, the EN pin would be pulled up so I'm using it as a much stronger pulldown.  When there is headphones inserted it will be cut off from the EN pin by the open switch, and will be in parallel with the headphone speakers, however, I don't anticipate this will cause any audio issues.

I need to be able to disable the boost converter if 5V applied on the circuit - however, this is not constantly on.  Even if the headphone jack is inserted it needs to turn off if 5V applied.  So have put a N channel enhancement MOSFET there to allow this.  Have used a 1k resistor on mosfet gate to prevent it from floating.

Thanks for your help/thoughts.


texts: sam3x8e gpio interrupt not working as expeced

texts:
I working on sam3x8e processor with atmel studio 6.2.

I have configured two gpios for interrupt on falling edge as follows:

pio_handler_set(PIOB, ID_PIOB, PIO_PB3, (PIO_IT_FALL_EDGE ), keyPressHandler);
NVIC_EnableIRQ((IRQn_Type) ID_PIOB);
pio_enable_interrupt(PIOB, PIO_PB3);

pio_handler_set(PIOB, ID_PIOB, PIO_PA4, (PIO_IT_FALL_EDGE ), keyPressHandler);
NVIC_EnableIRQ((IRQn_Type) ID_PIOB);
pio_enable_interrupt(PIOB, PIO_PA4);

one gpio belongs to PIOA i.e PA4 and the other belongs to PIOB i.e PB3.

If I press key connected to PB3 pin I get single keypress event.

If I press key connected to PA4 pin I get multiple keypress events.

I have used all the TC channels.  In attached datasheet there is some multiplexing
dependency for PA4 and TCLK1.
Can anyone tell me what initialization is to be done for PA4 and TC section so that PA4 work as expected.  I have also used timers as below:

Timer0_100msTickTimer.tc = TC0;
Timer0_100msTickTimer.channel = 0;
Timer0_100msTickTimer.irq = TC0_IRQn;

Timer1_KeyboardTimer.tc = TC0;
Timer1_KeyboardTimer.channel = 1;
Timer1_KeyboardTimer.irq = TC1_IRQn;

Timer2_DisplayTimer.tc = TC0;
Timer2_DisplayTimer.channel = 2;
Timer2_DisplayTimer.irq = TC2_IRQn;

Please tell me if you can figure out for any wrong configuration.

Thanks and Regards,
Mj


texts: Any transfer function has the same denominator 1+T

texts:
Sometime ago, I came across some theory saying that in a control loop any transfer functions such as input/output impedance, voltage gain can be derived from loop gain. Maybe something like any transfer function related to loop gain will have the denominator in the form (1+T) with T is loop gain. However, I couldn't find it now.
Hope anyone here can help with some material or name of the theory.


texts: Changing Bootloader settings using HEX file in atmega328P

texts:
I am using atmega328P IC in my project.
Currently my process to upload a code is to burn the bootloader according to my requirements and then upload using programmer USBasp .
Now from what I read is when you upload using ICSP you will overwrite the bootloader.
I have a .hex file with and without bootloader I generated by compiling in arduino-cli.
Can I change the fuse settings and upload the code both from one .hex file directly ? Even if the fuse settings are different (different clock)?


texts: For SR timing diagrams, does a bubble on the output of Q' indicate that it is the same as Q?

texts: I understand that with flip flops when there is a bubble on the clock it means the clock cycle is in terms of the falling edge, but when there is a bubble on the output Q' isn't this inverting Q twice, bringing it back to just Q? As in, "not Q' = Q"? I don't understand why this would be beneficial because now won't both output timing diagrams be the exact same?


texts:
I am learning about Diode and its use (Just get interested in electrical stuff after reading a DIY project), I have been reading information around and want to get more understand on diode especially the datasheet.

Can someone explain the use of the each characteristic in the datasheet??

Peak Repetitive Reverse Voltage: 50V
- mean that the current will pass the diode in reverse if the voltage is over 50?

Average Rectified Output Current
- mean maximun current the diode can output? what is T(A)?


texts:
I need some explanations about the electrical model of a Quartz. Everywhere I search the definition of quartz I find that it is a crystal that starts oscillating mechanically if it receives a sinusoidal electrical input, and vice versa starts generating a sinusoidal electrical signal if it receives some mechanical oscillations.

But I read also that it is an electrical component which works as a resonant RLC circuit, and sometimes it is used to implement inductors and capacitors with very high quality factor.

I do not understand the link between these two definitions, how they are related phisically. Moreover, what does it happen if a quartz receives a step pulse voltage?


texts: Motor speed control with Integral only loop

texts:
If you have a motor with a constant load and and travelling at a set speed, could you control the speed using only itegral action, as in theory the output would  stabalise when the error is equal to zero.

Obviously, it might take some to to reach the correct speed, but it should reach it nonetheless.

It seems that Proportional and Derivative are only useful when you need more immediate feedback (such as when the setpoint changes frequently, a non constant load, etc)


texts: Calculate temperature for low side switches?

texts:
I would like to know how to calculate the temperature (to see if I am still in a working range) for a low side switch. Hope you can help me there.
I need to control 10 valves(12/24V - 500mA max. ea.) - First we used a bunch of MOSFETs and controlled them directly over the IO Ports of an ESP. That worked fairly good, but to free up some pins someone told me I could use low side switches. After looking at some datasheets I think I found some that could work but I am kinda worried that I may get super high heat because the voltage is fairly high with decent amount of current.
As an example I looked at a BD8LA700EFV-C  or TLE8110ED as they have decent amount of outputs and allow high voltage with high current. But would they work for my task or should I keep my MOSFETS and just controll them over a driver/expander ?
Thanks !


texts:
I plan to do a Full-Bridge phase shift converter with ZVS. Output 340V @ 2A.
I would like to use the UCC28951 controller but the Texas development tool limits the output to 50V. I think it's because of the two output mosfets, in the figure below.

I would like to know if it is possible to use the controller in the topology of the Figure below: Only with the 4 input mosfets. With output of 340V 2A.


texts:
I'm having a hard time understanding if I will need both swd and st link or just one of them

My understanding is that the level shifter is there for the inputs given by the user which is the STLINK, and then you also have the SWD connectors and it should be similar as in the data it gives.

But I want someone to clear this for me and how they operate.


texts: I have 100' of 2x7 (14) individually insulated 18 ga. solid conductors( I think it is communication cable) I would like to use in  lieu of 16 ga. stranded wire for a gate opener. Is it doable?


texts: Modifying a thermostatic radiator valve for micro control

texts:
The photo below shows a electrical thermostat controller. The upper part is the motor with a gear. The motor has two wires attached. A red and a black one for the current.

What this component does is regulation a heater. There is a little pin which will be brought in different positions by the motor and the gear. From the side it looks like this.
The pin is inside the case the the heater is at max.
|

Here the heater is at half temperature:
|---

and here the heater is at zero:
|------

You can see this pin in the following image.

This function seems to me similar to a servo. The position of the pin has a defined minimum and a defined maximum.
Edit: I do not want to damage the gear. When I use an Arduino or RaspberyPi I can use a GPIO to control it but I have no idea how I know the min, max and current position.
Edit: I got an answer from the manufacturer.

Detection is effected by means of a light barrier and reflectors which
are mounted on the gears of the transmission.

Me: Meaning that that will automatically stop the engine and turn on the gearbox would not be possible, even if you are current in one direction continuously to the engine?

No, that would not be the case. The information of the light barrier
be integrated into the engine control. A durable power of the engine
would not be permitted.

Also I get:

The driving of the motor is realized by a so-called H-bridge.
Depending on the direction in which the motor is to just turn, are
either the transistors T1 and T4 are turned on or dieTransistoren T2
and T3. The base resistors R2, R3, R4 and R5 are at the transistors so
dimensioned that a sufficiently large collector-emitter current can
flow, but the power loss across the base-emitter path is kept low, in
order here also To save power. The diodes D1 and D2 is protection
diodes hervorgeru- an unacceptably high back-emf to the switching
transistors, fen by the motor, avoid. To determine the position of the
valve actuating section If on a gear using the Reflex Opto coupler
RFK20 off the revolution pulses asks. The activation of the reflex
coupler is performed using the transistor T6, which is connected
across the base resistor R16 of port P2.1. As soon as the transit
transistor is turned on, the transmitter diode of the reflex coupler
via the emitter-collector path and R15 powered. The polled gear Berad
contains three reflective markers .Once a emerges these marks before
the reflection coupler, the transistor of the reflex coupler switched
through and the Port P0.1 is pulled to ground, which in turn is
considered a pulse.

(Motorsteuerung means motor control)

Here are my assumptions:

the room temperature is given from a sensor
there is a target temperature given too
I do not want to use the given electronics, I just want to use the gear and the motor and control the motor myself.

How can I control the motor with a GPIO or PWM pin for example to set to different positions?


texts: Why I'm seeing a 90 degree phase shift with a current transformer

texts:
I'm seeing a 90 degree phase shift with a current transformer, I don't get it. The setup is pretty simple.

simulate this circuit – Schematic created using CircuitLab

The lamp is 100 watts. The current transformer is a junk drawer toroid, was used as a line filter, with ten turns. The lamp is one turn.

But here is what is confusing.

You can see the turn on at the start, switched on with a zero crossing triac. yellow is (1)120AC and red is (2)CT_OUTPUT

Because it is a purely resistive load I would expect to see the output of the current transformer to follow the voltage. But it is as close to 90 degrees out of phase as it gets.

What am I missing?

UPDATE:

On one of those line filter toroids with some 50 turns and a .33 ohm burden resistor, this is what it looks like. And good enough for what I'm up to. Thanks all for keeping me looking in the right places.


texts: Level shifter circuit for bipolar battery

texts: I am using a 9 volt bipolar battery and I want to have an output of 1.6V for the ADC. What would a level shifter circuit look like for that? Do you have a better suggestion I can look into?


texts: What are those weird wires in the audio cables?

texts:
Trying to repair a headset cable, I discovered that it doesn't look at all like the “ordinary” cables I used to repair. I was expecting to see, inside the cable jacket, four wires, each one in a wire insulation. Instead, there is:

A wire with a white wire insulation.
A sort of an orange/gold thread.
Something which looks like semi-transparent, very narrow optical fiber, with red, green, or blue thread around it.

I would imagine that the semi-transparent fibers conduct electricity, but I don't get any conductance with a multimeter, including when I try to scratch the surface of those fibers. What are they? And what is the magic which happens inside the audio cables?


texts: Does ST have a separate Cortex M4F series or are its M4 parts essentially M4Fs?

texts: ST's website does not use the term M4F. Also there is no filter for Hardware Floating Point Unit in parametric search so I guess ST includes floating point unit in all M4 parts.


texts: minimum-working example for schematic diagram of a compressor

texts:
CONTEXT

My son recently noticed that the lights dimmed when the refrigerator turns on.  This question has been posed elsewhere [1]. The responses in [1] do not meet my needs.

In my humble opinion, to satisfactorily answer explain how come the lights dim, I must first know what is the simplest schematic diagram of a compressor. It appears that there is a circuit diagram in [2]...

QUESTION

In your opinion, what is a minimum-working example for the schematic diagram of a compressor? Please explain why you think your minimum-working example is the sensible choice.

BIBLIOGRAPHY

[1] https://diy.stackexchange.com/questions/98459/why-is-my-fridge-causing-my-lights-to-dim

[2] Refrigeration compressor circuit, help trying to reverse engineer it


texts: 109 bit tree comparator with generate and for loop

texts:
I am trying to write Verilog code for a 109-bit tree comparator, but I am still new to the generate loop.

I have written some code so far but I am not sure if this will work or if I can use 2-d arrays for g and l signals?

parameter NUM_OF_BITS = 220;
parameter NUM_OF_LEVELS = 7;
genvar i,x;

wire [NUM_OF_LEVELS:0][NUM_OF_BITS:0] g, l;

assign g[0] = in0;
assign l[0] = in1;

generate for (x=1; x<NUM_OF_LEVELS; x=x+1) begin: Ls
    for (i=0; i<NUM_OF_BITS/(2**x); i=i+1) begin: MCs
        mag_comp2_1 mc (g[x-1][2*i+1:2*i],l[x-1][2*i+1:2*i],g[x][i],l[x][i]);
    end
end
endgenerate

assign gt = g[7][0];
assign lt = l[7][0];


texts: Can I develop with the Arduino using an IDE with more features?

texts: The simplicity of the open source Arduino IDE is great, but a bit limiting sometimes - I like to use Netbeans for instance for other work that I do. Do any plugins exist for more fully featured IDEs that would allow me to develop for the Arduino (and directly upload / run code on it?) So far my searches haven't brought much up.


texts: Why are sum-of-products implementations more popular than product-of-sums implementations?

texts:
In my book about circuit design (Fundamentals of Digital Logic with VHDL from Stephen Brown and Zvonko Vranesic), the writers always prefer a sum-of-product for representing and implementing simple circuits.

In Boolean Algebra, this preference is used as well, but I think mostly because writing sum-of-products is just easier and shorter. And maybe easier to understand for readers.

But when implementing using logic gates I would suppose other considerations than these are made as well. Like costs and delays of the gates.

So, is there a specific reason why preferably sum-of-products implementations are made? F.e. are AND-gates cheaper than OR-gates? I read about the transistor realisation of these gates, but I can't recall such a statement.


texts: Power Factor - What is it a characteristic of?

texts:
I always thought it was a characteristic of a powered device, rather than the power source.

A generator (whether it's a station or a small petrol powered one) does not have a power factor. I've been told that the power source has a PF.

Is this correct? Does the PF change depending on the load (type of device)?


texts: What is the difference between stepper motors and servomotors?

texts:
I am not sure I understand what the difference between a stepper motor and a servomotor is. Could someone explain this to me?

Also how do these motors behave when they are paused or turned off, do they have enough resistance force to hold something in position (say 1kg) or do I need to do anything special for that?

Which of these two do you think would be a better choice for an application in which I would like to have slow movement in small steps (i.e. I will need a very small step followed by a pause in that position and then another small step and so on, and I would prefer each steps to change by exactly the same degrees).

Context for this question: I want to create a timelapse rig that will pan and tilt a DSLR camera over a period of time.


texts:
Connecting 2 terminals (like Arduino's) via jumper wires does not secure the wires properly. What do you use to ensure the wires do not come loose?

Connecting Arduino to the pins at the bottom right of:


texts: Beginner Question, Red Wire 12 Volt Output, unsure if it's the correct wire.

texts:
thank you for taking the time to read my question.

I Have 2-Pin 12 Volt Small Fans (4 of them) that I would like to use for a little project of mine. I was going to use this item  to hook up all the fans into one input connector, but I quickly got stumped on something very small.

I wanted to connect the top female molex connector to a male molex connector as you can see here:

I looked up and saw that on the second picture, the yellow wire is the 12 Volt wire while the red wire is the 5V wire. On the contrary, in the 4 way splitter, the red wire is unknown (12 Volt or 5 VOLT?) and the yellow wire is the fan speed control wire.

Since I wanted to hook up the female molex connector (the isolated connector on the 4 way splitter) to the molex cable in the second picture, I have no clue which wire goes where. Does the yellow wire on the second picture molex cable connect to the red wire on the 4 way splitter, and can the 4 way splitter even carry 12 volts? I assume so since it is made for CPU fans, which are all mostly 12 Volt.

This is my question:
Which wires do I need to align together when I connect the two molex cables (EX: yellow with red, black with black), and could re-assure me by telling me "yes that red wire on the 4 way splitter carries 12 volts.


texts: Why is the socket voltage in Mexico 127V?

texts: As per the title, this is a very specific figure. Is there a reason it's 127 instead of 120V or 130V?


texts:
My objective is to generate an interrupt on an Atmega328P processor every second or so, using substantially less average current consumption than the inbuilt watchdog timer.

You can see from the datasheet that with the watchdog timer enabled the current consumption at 5V and 25 °C is around 6.5 µA:

With it disabled we are down to around 100 nA:

Something in-between, say 1 µA, could result in substantially longer running from a battery, but still allow the processor to wake up and check for things like the current light level, temperature, that sort of thing.

I've been experimenting with this:

The idea is that the capacitor will be charged quickly (50 µs) through the resistor which limits current to around 22 mA (assuming 5V operation for the moment). The output then goes to high-impedance, and we wait for a falling interrupt to wake the processor and deal with it.

Test code:

const byte capacitor = 2;
const byte LED = 13;

volatile byte fired = true;

void myISR ()
  {
  digitalWrite (LED, HIGH);
  fired = true;
  }

void setup()
  {
  pinMode (LED, OUTPUT);
  attachInterrupt (0, myISR, FALLING);
  }

void loop()
{
  if (fired)
    {
    delay (1000);
    digitalWrite (LED, LOW);
    digitalWrite (capacitor, HIGH);
    pinMode (capacitor, OUTPUT);
    delayMicroseconds (50);
    EIFR = bit (INTF0);  // clear flag for interrupt 0
    pinMode (capacitor, INPUT);  // high impedance
    digitalWrite (capacitor, LOW);
    fired = false;
    }  // end of if fired
}

This code does not have the sleep code in it, it isn't really relevant to the question.

Testing indicates that this gives a delay of about 970 ms from when I start charging the capacitor, to when the interrupt fires, which is about what I want.

The questions

Is this the best way (or at least a reasonable way) of generating a timed wake-up signal with minimal power consumption?
I calculate that the average consumption would be:

22 mA / (1 / 50 µs) = 1.1 µA

Does that look correct? Or is it even less as the capacitor would take less current as it charges? Like, approximately half that?


texts:
I'm new to FPGA and VHDL. I'm working on lab practical and for the practical we were already given file that has an I2C codec and the basics for the codec registers were already done but I found the given files were too complicated and I couldn't understand it; they were things like slave and masters. So I decided to follow an online tutorial.

I am using a DE0-Nano board. I want to make three different waves (sound) so I followed an online tutorial to make sine wave, but when I tested it on my board nothing happened, and I didn't get any sound. Is there something missing on my code or did I assign to the wrong pins?
Here is the documentation for the board just in case you need it.

I would also appreciate if you can also tell me about any source that will help me understand I2C and the slave/master.

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
entity sinewave is
port (
      clk :in  std_logic; -- I tried connecting it to PIN_B14 & PIN_R8
      dataout : out integer range -128 to 127 -- connect to PIN_A9
      );
end sinewave;

architecture Audio of sinewave is
  signal i : integer range 0 to 30:=0;
  type memory_type is array (0 to 29) of integer range -128 to 127;
  signal sine : memory_type := (0,16,31,45,58,67,74,77,77,74,67,58,45,31,16,0,
-16,-31,-45,-58,-67,-74,-77,-77,-74,-67,-58,-45,-31,-16);

begin

process(clk)
begin
  if(rising_edge(clk)) then
    dataout <= sine(i);
    i <= i+ 1;
    if(i = 29) then
      i <= 0;
    end if;
  end if;
end process;

end Audio;


texts: Why is the Bode plot of 1/s a straight line?

texts:
The magnitude of the impedance of a capacitor is \$(\omega C)^{-1}\$. Plotting the impedance vs frequency should be a curve with slope \$-1/(\omega ^2C)\$. Why is it plotted as a straight line with a slope of -20dB/dec?

Thanks


texts: How can this 2xmolex -> pci 8pin be so terrible?

texts:
Today I discovered one of my 2xMOLEX -> PCIE 8pin adapters had melted quite significantly, I was terribly lucky that the yellow and black wires were separated like they were and melted into each other instead of mixing and shorting out.

I checked the same adapter in my other systems while still running and they were hot! They showed signs of degradation too, some had slight melting going on, some were slightly charred near the connector pins.

What baffles me though is why this is happening. The adapters are of good design (connecting the +12v wires to spread the load evenly) and seemingly of good quality (with each of the wires being AWG 16 both by the writing on the wire and by measuring myself after the melting took place).

By all indication, these adapters should easily be able to handle the load. Especially considering that I was feeding these adapters with 2 AWG 18 molex cables which should have far less amp capacity and those still look as good as new and were cool to the touch.

As for the numbers side of things - the standard defines that the PCIE 8pin should handle a maximum of 12.5 amps. The cards I'm using them for however only draw around 7 amps while fully loaded.

That divided by the 3 12v wires in the cable means that each of the AWG 16 wires couldn't even handle 2.33A, ridiculous.

I'm guessing this has to be something to do with the core material, it looks like plain old copper but...? Not sure what else it could be.


texts:
I have a question about the CAN-bus protocol J1939.
What is ECU and ACU?
Assume that we have three motors that can be controller via J1939. Each motor have it's source address 0x80, 0x81 and 0x83 and destination address 0x22, 0x23 and 0x24.
So what is ECU and ACU here?
Is the ACU = motors and ECU = computer?


texts: Read/write Artix RTL registers at runtime from UART interface

texts:
I have an RTL design on an Arty board that is composed of clock managers and counters. The counters have individual enables and wraparound values (all hardcoded).
I want to enhance it to write commands at the UART interface to enable/disable the counters and change when the counter resets.
I envision c code for the user interface and then memory mapping of registers for the counter control.
How is this done in Vivado and SDK? Most of the tutorials are either RTL-only or Microblaze-only designs. I want Microblaze for runtime user control only while most of the functionality will be RTL.


texts: What shape do the electrodes of a touchscreen have?

texts: I know that capacitive touchscreens need two layers of electrodes, but have not found much on the precise shape of those electrodes. Are they just plain straight ribbons, or are there more elaborate shapes around? If yes, what would be the advantage of those shapes?


texts:
A full wave rectifier has a 12V ac transformer (center transformer) and a 12kohm load resistor. Determine the dc load voltage and current values for the circuit?

I'm really confused. What does  12V ac transformer mean? Is it the voltage at secondary windings or primary windings? or is  it the Vrms?
Please explain Vrms as well.


texts: Find the voltage at the open circuit end of the transmisson line?

texts:
In this question,i know quarter wave length line is a Impedance inverter line so beacause of the left sided short circuited line i will get open circuit at the mid generator,and because of the open circuited line at the left i will get short circuit at at the mid generator.
Now i am confused whether i have to consider a open circuit at the generator or a short circuit.if i take take it open circuit and calculate i will get \$0V\$ at the open circuit end,and if i take short circuit at the generator and calculate i will get \$800\angle-90 ^{\circ} V\$.

What should be the correct and Why ? Can anyone help please?
I am still confused because two high reputed users giving two different opinions.


texts: Is this a 4R9 resistor or somthing else?

texts:
After a power-peak due to a broken main electricity cable, me and my neigbours got some broken devices.

At our house only my motor cycle trickle chargers were connected. And all 3 got broken :(. Since they are rather new and not insured, I would see of I can repair them.

It looks like a resistor(like) component is broken. This component is twice as big as a normal resistor (and smaller than a e.g. a 5W power resistor) and has a color coding I am not sure of. I see Yellow, Grey (or Black, not well to see) Brown/Gold(?? - there is a glitter in it), Gold.

Is this a 4,9 Ohms resitor? Or something else? It is in the beginning of the circuit, just after the 230V AC. The first component is covered with the black wrap and seems to be good (at least, if it should be 0 ohms). Than this resistor(?) comes.

The unit:

The resistor:

The back side of the board where the resistor was soldered:

I was not able to place the sharp detail images here, uploaded them at:

original images

Many thanks for the help!


texts:
I have an issue with 12 volt DC LEDs installed on a 5 volt DC circuit. Switching must be performed as close to instantaneous as possible.

So I searched around but nothing would do what I need. I found npn transistor and MOSFET switches for 12 v using a 5 v base\gate but these solutions modified the ground from the LED instead of the +12 circuit. My problem is I do not have access to the ground side. I must modify the 12 vdc circuit in order to achieve my goal. Am I limited to Solid State Relays or can this be achieved another way?

Hopefully this makes enough sense for someone to help me.


texts: Where does an ATmega328p go on the STK500?

texts: My STK500 manual doesn't tell me, where does an ATmega328p go on the STK500?


texts:
I wanted to move the summing operation (+10) that I perform before the integrator block as shown below: (MODEL-1)

I check in this wikibook page - https://en.wikibooks.org/wiki/Control_Systems/Block_Diagrams and from the transformation "Moving a Summing Junction in front of a Block", it says to add a 1/P block, which in this case would be a differentiator. I tried adding a differentiator block like below, but the outputs (taken @ every 100th clock cycle) of the blocks does not match. (MODEL-2)

The output from MODEL-1 is:

The output from MODEL-2 is:

This is one part of this question.

However the major part is, when using this filter practically, the input to this filter contains high-frequency noise(now - just for example, it contains a pure sinusoid). By adding a differentiator in the front for the purpose of transformation dissolve the whole purpose of filtering?


texts: Help With Simulating Common Collector Amplifier In PSPICE

texts:
I have included as much information as possible, so it should just be a matter of pointing out something simple (hopefully).

I am trying to model a biasing circuit for a Common Collector BJT Amplifier.  I am running a Transient Analysis on the circuit and am receiving the following simulation results (attached images), which I am having trouble interpreting. I have also listed my minimum specs for the circuit and my theoretically computed values. As far as I can tell, I am doing everything correctly, although I am not seeing how to choose the Collector Resistance since it does not appear in any of my equations.  I am also not seeing the voltage gain nor the Q-point as computed by PSPICE in the simulation Output File.

MINIMUM SPECS:

Input Resistance >= \$5\$k\$\Omega\$
Output Resistance = \$50\Omega\$
Voltage Gain \$\geq 0.95\$ with \$5\$k\$\Omega\$ load
Output Voltage Swing of at least \$2\$Vpp across \$5\$k\$\Omega\$ load
\$V_{cc} \leq 20\$V

FORMULAS USED:

Input Resistance: \$R_1 || R_2 || (\beta+1)R_E\$
Output Resistance: \$R_E || r_{\pi}/(\beta+1)\$
Voltage Gain: $$\frac{R_E(\beta+1)}{r_{\pi} + R_E(\beta+1)}$$
\$G_m\$: \$I_c/0.026\$
\$r_{\pi}\$: \$\beta/G_m\$

COMPUTED VALUES:

\$R_1\$: \$36k\Omega\$
\$R_2\$: \$50k\Omega\$
\$R_e\$: \$10k\Omega\$
\$R_c\$: ?
\$r_{\pi}\$: \$5075\$
\$g_m\$: \$0.0197\$
\$I_c\$: \$5.122 \times 10^{-4}\$
Voltage Gain: \$0.995\$
Vb: \$5.772\$V
Input Resistance >= \$20.5\$k
Output Resistance = \$50\$
Output Voltage Swing of at least \$2\$Vpp across \$5\$k load
\$Vcc \leq 10\$V

As you can see, I do not have a value for \$R_c\$, as I do not see how it affects any of my equations.

Circuit Image:

Simulation Waveform Image:

Simulation Waveform Cursor Values Image (Corresponds To Previous Waveform Image):

Simulation Output File:

Where is the Q-POINT?


texts: PCB routing of parrallel capacitors with different values (Based on STM Nucleo64 dev board)

texts:
I have been recently trying to understand how the STM32 ICs should be routed on PCB, in particular parallel capacitors of different values for power design. I have come across various suggestion about that it is legacy design, and that these capacitors should be replaced by only one because of anti-resonance problem.
So checking out the native design of STM dev board should provide insight of the right approach. Luckily everything is provided on STM website. PCB files are from Altium Designer.
Looking at design one interesting thing appeared evident when different capacitor values should be side by side. On schematics the 1uF is used in parallel with 100nF:

The way how it is routed can be seen on the picture bellow.

Whats interesting is the separation of ground connection between C21 and C23, which is only connected through bottom plane, but could be easily connected on the Top plane aswell. This seems to be consistent when it comes to other capacitors, at least by trying to introduce some larger path in between.

Why thats the case?


texts:
I am somewhat familiar with latchup (parasitic transistors in the body of a CMOS device that are activated by over- or under-voltage conditions).  However, I have seen some devices that advertise "Latch-Up Performance Exceeds 250 mA Per JESD 17", while others say "Latch-Up Performance Exceeds 100 mA Per JESD 78, Class II"

What exactly does this mean?  Specifically, what is the mA value in reference to?

Which one of these is better?  I think the JESD 78 standard is newer, so is it also "better" despite having a lower mA rating?


texts: What is the difference between high and low density anti-static foam in terms of protection against ESD?

texts:
As far as anti-static foam is concerned, does it matter if it's high or low density? Or is it just another way to upsell me?

On Amazon I see low density foam, and high density.


texts: I have a digital speedometer which outputs the signal obtained from the hall sensor of a motor with 23 activations per revolutions. This is a bit too much for my MCU to deal with it using interrupts. Is there a simple way to convert a digital signal with a 50% duty cycle but varying frequency to an analog signal?


texts: Weird ULN2003 to 7-segment behaviour in Proteus

texts: I'm trying to drive a 7-segment common anode, in the following connection, however there is no output the comes from the ULN2003 at all, its like when it gets a 0 in the input, it gives a tri state output.


texts: What's wrong with this schematic for powering up Cyclone IV FPGA?

texts: I have followed all the guide lines for powering up the Cyclone IV. However, the 3.3v Regulator is heating too much and also the Cyclone IV FPGA. What's wrong with my schematic? Is there a problem in connecting the heatsink located below the Cyclone IV chip into 1.2v? By mistake I connected it into 1.2v line.


texts: Can I use a USB-FTDI TTL converter cable as a USB-TTL converter cable?

texts:
I have the need of a USB-TTL converter cable, but all I have is a USB-FTDI converter cable, that means I have two additional pins (RTS/CTS). If I do not connect RST/CTS pair, will the converter cable act as a USB-TTL converter or won't it work at all ?

USB-TTL cable : https://www.adafruit.com/product/954

USB-FTDI cable : https://www.adafruit.com/products/70


texts: Clean DC power design for very high precision circuit

texts:
We have been designing a very high precision control circuit for quite a while. And we are thinking to make it much easier to use, which is to get rid of the Lab DC Sources and use AC to DC switching power (get power from 220V/110V directly).

Our circuit runs at +-12V currently with around 200mA current. It consists of a photodiode, which 1pA precision could be measured, many OpAmps, one 16-bit ADC and one 18 bit DAC. As from the description, it can be observed that our circuit is running at very high precision.

One lab DC source costs thousands of dollars and the DC ripples are basically zero. At most on the level of 0.001mV peak to peak. If a cheap AC to DC source is to be used, however, I am afraid that the DC can be far less clean. For example this one (which has 50mV pp ripples).

I need suggestions from you:

Is this kind of AC-DC switching power a good choice (http://www.switchingpowersupply.cc/pdf/D-30W.pdf)? Or maybe the ones used in laptops are better?
How to reject the noises in power supply in the most thorough way? Any material will be appreciated.
Is it possible to make clean DC source from 220V AC, which has similar performance as the lab DC sources?
If large caps and inductance are used to filter the ripples, could they cause stability issues for the AC-DC converters?
How would the DC noises influence the behavior of OpAmp, ADC, DAC? For ADC and DAC, I think the voltage references will not be influenced.


texts: Difference between increasing microphone sensitivity and amplifying output signal in software

texts: I am a bit of a newbie to the audio world, so please bear with me. What would be the difference between getting a high sensitivity microphone and using a low/medium sensitivity microphone and using some software like audacity to increase the gain of the output signal?


texts:
Sometimes after long time working correctly and turning on and off inductive load, Darlington NPN transistor (ONSEMI BD679) which should follow signal (IN4), fails to work and turns on inductive load continuously.
It's part of my schematic:

It usually works correctly and this problem maybe happen after a while.
What issues can do this?


texts: Are charge and voltage in a capacitor always directly proportional, regardless of structure?

texts:
Capacitance is said to be a constant, and is defined as \$C := \frac{q}{V}\$. I have been unable, however, to find an implementation-independent way to show that charge and voltage are directly proportional to confirm this.

Are charge and voltage in a capacitor always directly proportional? If so, how can we show this without assuming the capacitor's structure (e.g. parallel plate)?


texts:
There are a lot of dc-dc boost modules that step 12V to 24V but are limited to low current. Is there a reason why stepping up voltage, while keeping the current high is not available?

In my case, I have a solenoid that works at 24V. I have a 12V 24Ah battery and the solenoid requires 24V, ~25A. Is there a solution to boost my supply?


texts: 2 momentary switches, controlling 4 outputs in sequence using latching type relays

texts:
I am interested in building a solenoid controller using latching type relays(containing 2 coils and DPDT). The relays are controlled using two momentary switches.
The action I am looking to get is by pressing switch (SW1) I can have #1/4 solenoids activate, and by pressing SW1 again #2/4 solenoids activate while #1/4 deactivates. Pressing SW1 will activate each solenoid individually 1-4 in sequence till #4 is reached. SW2 will reverse the sequence direction from #4 to #1. Each press of either switch will control only one action respective to its purpose.  Is this possible?


texts: Verilog : Using previous generate iteration's wire in current iteration

texts:
For background, I am trying to implement something like this:

My idea was to use a couple of nested generate statements to first create each of the 4 stages, then the second to create each mux in that stage. I can create the muxes just fine, but when trying to generate each stage I am running into problems. Specifically when defining the wires between stages.

Is there any way to generate unique wires in each generate iteration and have them be accessed by the next iteration? How would you specify the beginning and endpoints differently?

I imagine trying to make a shift register or adder using a generate statement would have the same problem.

One solution I thought of was to create a multidimensional wire array, but since each index needs to be a different size, is that possible? I could just define them all as the maximum size and only use the bits I need (and let the rest be hopefully optimized away), but this seems inefficient.

Edit: Here is the code as I have it so far, I am actually doing 6 stages (but theres no picture for that one), implementing my inefficient solution above:

wire [64:1]data [6:0];

generate
genvar s;
// Creates six mux stages for each input
for(s=6; s>0; s--) begin
  genvar i;
  // Creates muxes to reduce input lines
  for (i=0; i<((2**s)/2); i++) begin
    assign data[s-1][32-i] = inputIn[s] ? data[s][64-((i*2)+1)] : data[s][64-(i*2)];
  end
end
endgenerate

assign outputOut = data[0][64];

But I would like to not have to create 7 64 bit wires and actually have the wires sized to their need. This could be done using the genvar to constrain the ranges, but the problem lies in hooking them up in the for loop correctly.


texts: Can a variable frequency drive be connected to a motor driving a hammer mill to save energy?

texts: Inductive motors are largely used to drive pumps, hammer mills etc. When used with pumps are there benefits of connecting a Variable Frequency Drive(VFD) to a motor. Does tha same hold true of driving a hammer mill, especially in respect of saving energy is concerned, without compromising milling efficiency?


texts:
The Circuit below shows the opto-isolator circuit I implemented for my RS485 application.

RS485 Transceiver: ISL83483

Optoisolator: SFH615A

Calculated resistor Values are:
R1,R4,R6 = 4.7K.
R2,R3,R5 = 130 Ohms. ( (3.3VDC - 1.35Vf) / 15mA)

Vnode and Vbus are 3.3VDC from different Transformer Secondary Winding. Vnode also supplies power to the MCU controlling the communication flow.

For now, I am yet to connect the RS485 transceiver to the circuit, as i decided to test from the MCU to the PC using FT232 UART cable which supplies 5VDC regulated to 3.3VDC as Vbus.

Now the Issue

The MCU transmits (data to bus) and I am able to view on the PC. However, if I send a response from PC, the MCU never seems to get anything (data from bus).

To be sure, I repeated the above, but without the opto-isolator, by connecting Rx-Tx, Tx-Rx, GND-GND of MCU and PC together. And it was transmitting and receiving on both sides.

I swapped both opto-isolators, and same thing happens.

Where is the cause of this problem? Why can't the MCU get a serial message from PC via the opto-isolator.

Thanks.

Edit

Picture below shows the waveform obtained at PC Transmit (Cathode of R2 Diode), which seems constant each time I send it.

However, this shows waveform at MCU receive (data from bus). Why is there so much distortion?

EDIT2

I observed some communication but at different voltage levels.

Vnode is always 3.3V as the MCU supply voltage.

My FTDI USB/232 cable is 5.0V.

Using a 3.3V regulator I made Vbus as 3.3V, then PC receives from MCU, but MCU does not receive from PC.

If Vbus is 5.0 (not regulator), PC does not received from MCU, however a message from PC get to MCU.

Could there be a Voltage level issues? Can't the optoisolator work at different voltage levels at both ends? and how can I fix this?


texts: What is wrong with my Simulink model of a first order Delta Sigma Modulator?

texts:
I'm trying to design a Delta-Sigma Modulator for frequency synthesizer applications and am (just right now) figuring out how to properly configure a first order DSM in Simulink. I've made a few small variations that I've seen (with the unit delay in the integrator in different paths and one configuration without a delay in the feedback path) but have arrived at a similar conundrum. The 20dB/decade rolloff expected of a 1st order DSM isn't present, and I see very pronounced harmonic tones in the PSD. Specifically, for when I sample at 1MHz (which for a DC input, I'm not entirely sure is needed, but I digress), I see spurs at 100, 200, 300, and 400KHz.
The pictures below are of the Simulink model, followed by the PSD of the three configurations in the model.


texts:
I am trying to recreate this project. I have the circuit constructed on a breadboard. I am using an SP232 instead of a MAX232, a TIP42CG PNP instead of a BC557 PNP, and an Arduino Uno instead of an Arduino Nano. I am not getting any signal when I measure the T+ terminal on the transmitter with an oscilloscope. I have triple-checked all connections and the code so I am not sure what's wrong. Sorry, the schematic is not the most straightforward. I am new to electrical design and I was wondering if there were any obvious design issues with this schematic?
Link to project: http://electronoobs.com/eng_arduino_tut36.php
Schematic


texts: Why does measuring the voltage drop across a thing not simply measure the battery voltage?

texts:
Imagine a trivial circuit with battery and one resistor. To measure the "voltage drop" across the resistor, we stick a voltmeter in parallel with it. However, this means the voltmeter is also directly electrically connected to the terminals of the battery. Therefore, why doesn't it simply measure the battery voltage, regardless of the resistor?

I hypothesized that the answer is because some of the available voltage/pressure/force/power/energy/magic/whatever-it-is from the battery is being drained through the resistor, it will not be passing through the voltmeter and will therefore not be measured by it, but this still doesn't fit, because that means the voltmeter is not measuring the voltage drop; it's measuring the voltage that wasn't dropped. If the battery supplies 5 V and voltmeter reads 4 V, how is 4 V possibly the voltage drop of the resistor, when the available voltage has actually dropped by 1 V and I still seem to have a non-dropped 4 V to play with?

I guess I really do not understand what the voltage drop is supposed to mean. I don't know why the resistor is dropping voltage at all, when it is supposed to resist current. I'm so lost.


texts: why coaxial cable not used in oscilloscope?

texts:
we usually do not use coaxial cables inside oscilloscope, so what is the reason?
what are the conditions which are not feasible for using coaxial cables here?


texts:
I used this  circuit and formula as a reference for 5V to 3.3V

It's from the LM1117 datasheet but output gives 4.2V.  Here  is my circuit:

I changed resistors with different values but output give same 4.2V. What can be the problem or how can I find my fault.


texts: Charging a 12V car battery from a stream

texts:
EDIT: Thanks to everybody for replies and comments, which have been most useful. It seems that the hydro side of the equation would be challenging to implement, given the issues with sufficient head, protection of the generating apparatus and so on. I will look again at the possibility of solar and take it from there.

=====

I am trying to assess the feasibility of using a micro-hydro setup to charge a car battery.

The application is that of a simple time-lapse camera that would monitor a shallow water crossing on a stream.

The problem is that there's no mains electricity anywhere nearby the water crossing where the camera would be situated so it would need a standalone power supply of some kind. The location is in dense woodland and I envisage the camera sitting there all year, so powering it with solar power under leaf cover and in this latitude (the UK) would presumably be tricky.

However, there is the stream, right there. Although small, this runs strongly and reliably all year round. I am wondering if I can hook up a 12V car battery to a small micro-hydro generator like this to trickle-charge the battery and use the battery to run the camera platform. It would probably require something like 5volt and 1.5 amps.

I know something about electronics in the abstract (I know what capacitors are, where roughly they are used, why you'd use an MLCC in preference to an Al etc). On the other hand I have no real technical knowledge, or circuit design know-how, so this would be quite a challenge and probably take me a long time. I'd be more than ready to give it a shot, provided I had some certainty that it is feasible.

Can this be done without wizard-levels of electronics ability? Any opinions or pointers welcome.


texts: Reading the VESA 1.2 spec it seems that the AUX channel may not be essential to the correct functioning of the video channel, i.e. if we already know the EDID data and don't need to do any calibration, i.e. in an embedded device. So, is it feasible to use the DisplayPort without using the AUX channel at all?


texts: ripple carry adder vs carry look ahead DELAY?

texts:
I have implemented 3 combinational circuits of adders (RCA, CLA and IP CORE, adder v.12) in a method to measure the power consumption in the FPGA, but the results in the delays are incoherent.
A ripple carry should be slower than a lookahead however in my results it is not appreciated. I have checked it for different size for the entries.
I leave an image, so you can give me your conclusions.
Thanks for your help.

P.S. The delay I have taken from a circuit that implements a frequency of 25MHz, and I have taken calculations from the term WNS. (Implementation -> Report Timming)

25MHz = 40ns  -> DELAY= 40ns - WNS.

Vivado 2017.1


texts: Q: How to analyze Precision rectifier op amp configuration

texts:
I been scratching my head for the past couple of hours, and might be going mad. If someone can shine some light on this I would be extremely happy. This is probably root elementary to some but I am struggling extremely hard right now.

simulate this circuit – Schematic created using CircuitLab

All starts with this circuit,

I had a gentlemen earlier tell me that on the positive cycle of the input (Vin) since the V- > V+ the op-amp will drive the output to GND and thus cause current to flow from Vin to Vo, putting the diode in reverse bias, in conjunction making the NFB (Negative feedback network) "Turn off". This all make sense.

Isn't the op-amp seeing 0V at both the V- and V+ why is it driving anything to any the rails? In terms of having V- > V+ driving it to GND and having V+ > V- driving it to VCC.

Isn't this a Inverting amplifier, why is it acting like a comparator?

The way I would approach this is by doing an analysis on the 0V node and analyze it from there.

KCL Analysis at 0V Node

Assuming all current is leaving the node making the diode in reverse bias

\$Node 1: \frac{0-V_{IN}}{R1}+\frac{0-V_{OUT}}{R2} = 0\$

\$Node 1: \frac{0-1}{1k}+\frac{0-V_{OUT}}{1k} = 0\$

\$Node 1: V_{OUT} = -V_{IN}*\frac{R2}{R1}\$

\$Node 1: V_{OUT} = -1*\frac{1k}{1k} = -1\$

I know this is wrong, but why?

I understand since I made the diode reverse bias that should indicate my method is wrong as the op-amp isn't driving any current thus can't assume ideal op-amp laws, however how would one approach this then? I assumed current is leaving and etc what if I assume current is going in would result in the samething.

What I am trying to say what is the proper way to see the actual operation of this configuration of op amp. To me this is very confusing as I think its a inverting amplifier however the gentlemen above got the correct operation by seeing it as a comparator.

And here is the actual right model of the op amp when Vin is at the positive cycle.

simulate this circuit

I believe I figured out the analysis

Analysis of Positive Cycle

Assumption: V+ = V-, Current travels High voltage potential to low voltage potential.

Using KCL - Schematic so it saves space finding Vo endings up being = -1V this doesn't make sense as current is trying to go into the diode which is reversed bias, thus meaning our assumption is wrong by using the ideal op-amp laws. Thus meaning the diode has to be in reverse bias

thus meaning our V+ = V- assumption was wrong and needs to be re-checked, this time however 0V being an unknown node this time, and re-solving it will get you Vin = Vo which now make sense as the feedback is not operative

simulate this circuit


texts: Voltage Regulation to Brushless DC Motor

texts:
I am using a 12V brushless DC motor (peak current 4.6A) and I would like to have speed control over it.

Link to pump I am using: https://daviescraig.com.au/product/ebp40-electric-booster-pump-12v-9040/ebp40-electric-booster-pump-kit-12v-9040

After contacting the manufacturer, they informed me that I could accomplish speed control to some degree by reducing the pump input voltage as far down as 6V.

Currently, I am planning on using this high side switch: https://www.nxp.com/docs/en/data-sheet/MC33981.pdf

The switch allows for PWM output, which I have seen can be filtered to an analog output voltage - however I have not seen this done on high current inductive loads. Is this a feasible solution?

Another idea I had was regulating the output voltage of the high side switch using a switching regulator of some sort - not sure if this is a good solution either.

I'm looking for some guidance on which direction I go and if there are any other possibilities in achieving this goal.


texts:
I have, for example, this code snippet:

p1 : process (clk)
begin

if (a = '1') then
    a <= 0;
end if;

if (b = '1') then
    b <= 0;
end if;

end process p1;

Which if-sentece is executed first? a or b? I know that process is a concurrent statement but I don't know if within a process the execution is secuential or concurrent.

Thanks!


texts: Why can't we divide the electromagnetic spectrum into arbitrarily many radio frequency bands?

texts: I understand there is concern over the limited amount of wireless spectrum available for allocation but am somewhat confused as to why. Couldn't we just divide the electromagnetic spectrum into as many radio frequency bands as we need by making the communication frequency more precise, i.e. broadcasting over 101.713 MHz instead of 101.7 MHz in order to make more room. What are the limiting factors preventing us from doing this?


texts: How to prevent microphone from picking up movement?

texts:
I have a MEMS microphone mounted to a PCB in an enclosure. The purpose of the microphone is to detect sound, like someone talking. When I just barely touch the enclosure or move it around, the microphone detects it.

How can you de-couple the microphone from the circuit board and enclosure so it doesn't detect physical movement of the enclosure? How do other devices like smartphones deal with this?


texts:
I want to generate -5 Volts from connecting AAA batteries in series, in order to temporarily replace a charge pump suspected of contributing noise to my embedded system. (See this answer (and its comments) in my previous question.)

Is this possible?
I want to be sure the voltage is negative.


texts: How much more does it cost to fab a 4 layer board compared to a 2 layer board and is it worth it?

texts:
I'm wondering at the moment with my Super OSD project whether to go to a 4 layer board.

At the moment, it consists of two micros and some additional circuitry such as a discrete audio amp and switch logic, and a serial EEPROM plus a temperature sensor. There are probably around 40 resistors, 10-15 caps and a few other components (all surface mount 0805 or 0603.) It might get tricky to route it.

Is it worth paying the extra bucks to get 4 layer boards for a relatively simple project?

I'm on the fence, I like 2 layer because it's cheap and if you've got the right equipment you can even do it at home, 4 layer is more expensive, but allows me to squash more stuff into each square millimeter. I've seen a couple of open source projects (Super OSD is open source) using 4 layers but many more using 2 layer.

So, opinions?


texts: How to 'fix' this in an enclosure without glueing?

texts:
I have an enclosure, and want to fix/put a STM32 inside, a relay and probably later a small circuit board.

However, the STM (STM32F103C8T6) and the relay do not have holes to fix them... and I do not want to glue them because maybe later I want to change/add components.

What is the best way to do this?

Note the USB cable will be get a separate hole to attach (or maybe even a separate connector in the enclosure. The enclosure itself will be attached to a box that will be moved regularly (even during working conditions).

Also, I wonder if holes would be needed to prevent too much heating. The STM32 will run on a very low frequency initially, but later maybe on 72 MHz.

(I know putting this is not entirely an electronics question, however, I think it's better appropriate here because more people doing electronics have experience how to handle my problems. It's the first time I use an enclosure).


texts:
I am facing an annoying problem while using Eagle in Linux.
It is not possible to set the desired position of a component while ALT key is pressed. I hit the ALT key to active the alternate grid and then specify more precisely the correct position.
I also tried to move the component while ALT is pressed, then release the key and left-click to set the position, but then the component moves to the main grid automatically.

I know there is other ways to solve this tricky bug during component placement, but it would be easier using this shortcut. Does someone have already faced this bug?

Thanks,
(I am using Linux Mint with Cinnamon.)