texts:
Here is the circuit (Arduino Due, 1kΩ resistor, LED):

Note how I bring the ground from the Arduino board to the breadboard, and also connect the ADC pin to the gnd rail on the breadboard.

Here is the code:

void setup() {
  Serial.begin(9600);
  #define ADC_FREQ_MAX 250000
  Serial.println(ADC_FREQ_MAX);
    }

void loop() {
  analogReadResolution(12);
  Serial.print(analogRead(0));
  Serial.print('\n');
}

Here is what I do:

600cs: I unplug the LED.
4000cs: I plug in the LED.
6500cs: I unplug
the LED.
7750cs: I plug in the LED.

Here is the result:

I plug this same setup into an Uno, and I get no issue:

Why is ground voltage non-zero, and why does it increase when I plug in an LED? What issue with the Due could cause this?


texts: Can I use the embedded ST-LINK/V2-1 USB of an STM32 Nucleo board to create a USB mass storage application?

texts:
I want to create an application that can act as a USB mass storage device in order to provide its output to other devices. Mostly results from A/D conversion of signals.
I have an STM32L412 Nucleo-32 board lying around that I'd like to use (both for development and running the application)
It has a USB Micro-B plug for programming.
ST-LINK/V2-1 supports

Mass storage interface on USB

As far as I understand, that allows flashing the chip via USB mass storage, which is quite nice.
I wonder if I could also use the USB plug from my application on the chip to make it act like a USB mass storage device when my application is running? That would save me from wiring up another USB plug to the board.


texts: How to protect a signal from output short circuit?

texts:
I have made a signal generator based on DDS and amplified its output to 0-20 V pk-pk. Now I want to prepare the output side. My main concern is short circuit protection to prevent damage to my device. I was thinking about isolating the signal on the device side from the output side.

First choice was a transformer. But it is not applicable because finding a good transformer for such wide frequency and amplitude is not easy. Other option was winding the transformer myself, but I have no experience on transformer winding.

Second choice was a coupling capacitor. Using a coupling capacitor may isolate the signal to "some extent" , but does not seem enough ( AC current passes through it , and also it needs to be of a very large capacitance in lower frequencies that leads to problems as current leakage,... ).

Can anyone give me a suggestion please?


texts:
I'm building a small electromobile. I was planning on using a car alternator as the motor, however I'm now looking into buying a 48V 500W BLDC motor.

The problem is I'm not really sure how to manage the difference in voltage between what the motor requires and the rest of my circuitry.

I have a bunch of components that run at 12V as well as another bunch at 5V. In the scenario where I have a 12V battery I just use a buck converter to step-down the voltage for my 5V circuit and it all seems fine since it didn't draw anywhere near the 3A maximum rating of the converter.

Now my 12V circuit draws ~10A at full load. If I have a 48V battery I think I'll have trouble using a buck converter for that purpose. I was thinking I could tap into a point between the battery cells where the voltage will be 12V but that is probably dangerous, I'm pretty sure difference in voltage in the cells will upset the battery.

What would be the "proper" way to power my 48V motor and 12V as well as 5V circuit?


texts: SystemVerilog: selecting bits without storing calculation in variable

texts:
Is there really no way to select bits straight from a calculation without giving them a name and then selecting the bits from the name in SystemVerilog?

module testbench;
  logic signed [7:0] x = 8'b11100000;
  logic signed [7:0] y = 8'b00010100;
  logic [15:0] z;
  initial begin
    z = x*y;
    $display("%b", z[14:7]); // :)
    //$display("%b", (15'(x*y))[14:7]); // :(
    //$display("%b", 15'(x*y)[14:7]); // :(
    //$display("%b", {15'(x*y)}[14:7]); // :(
    //none of the above 3 works
  end
endmodule

Context: I want to non-blockingly assign the 14:7 bits of the product of two signed 8 bit numbers to another 8 bit number without waiting for the next clock cycle:

z <= 15'(x*y)[14:7];


texts:
Using this OctoWS2811 as an example, when to use a transceiver vs buffer?

It uses an 74HCT245 (bus transceiver) with the direction tied high.
Why not use a line driver like 74HCT541 (buffer)? Specs look very similar other then a few nanoseconds here and there.


texts: LM2940 LDO Regulator Instability, high frequency fluctuations

texts:
I'm encountering some instabilities in my regulated voltage supply. In short, the system is comprised of a High Power AC device and an MCU sub-system used for automation. The transformer is producing the expected output and this is full-wave rectified & smoothed (etc etc...) as per many of my previous designs. However, I have found that higher-frequency fluctuations in voltage are not properly regulated by the LM2940, causing intermittent brown-out of the MCU.

A scope reading shows that these fluctuations are around ±0.7V either side of the desired 5V, and at a frequency of around 18MHz:

Does anyone have any ideas how I might stabilize this output? Or offer an alternative regulator that is more linear at high frequency (As suggested in this answer)?

For reference, this is the LM2940 datasheet.

Any advice or pointers will be much appreciated!

EDIT:
Schematic of the regulation circuit. The 3.3V reg can be ignored as I've tested the 5V output with & without the 3.3V reg... with the same resulting output.

EDIT: Output capacitor C3 is a 100uF Vishay SMD Tantalum, part num TR3C107K010C0100, with max ESR of 0.1Ω


texts: Where to find details of dimensions and doping of a typical bjt

texts: I have been searching for dimensions and doping levels of base, emitter and collector for a typical bipolar junction transistor presently in use. I have tried searching on internet and seen datasheets for bc547 however they contain only voltage limits and transister characteristic graphs.Kindly provide the required data source.


texts: I feel like a fool. As seen in the image below, the nRF module is right next to the VIN terminal. When I powered this up, I was able to communicate with the nrf module via SPI but it wouldn't receive or transmit data. I then powered the board via a seperate 3.3V supply and then the RF module worked. This led me to believe that the RF module was swamped with noise from the VIN cable. It never struck me that this wouldn't work since an earlier version of the board worked fine in the same layout. Since this is now a made board, not many modifications are possible. How do I shield the RF module from the noise or how do shield the VIN terminal so that it does not affect the RF module?


texts: How to convert accelerometer data into G with the ADXL345 digital accelerometer

texts:
Am totally new to electronics and the datasheet is very confusing to me, so can anyone please guide me through the specification of the accelerometer? So that i can have a better understanding on the accelerometer and to be able to convert the accelerometer data into G.

This is the datasheet for the ADXL345 digital accelerometer [1]: https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL345.pdf

import smbus
import time

# Get I2C bus
bus = smbus.SMBus(1)

# ADXL345 address, 0x53(83)
# Select bandwidth rate register, 0x2C(44)
#       0x0A(10)    Normal mode, Output data rate = 100 Hz
bus.write_byte_data(0x53, 0x2C, 0x0A)
# ADXL345 address, 0x53(83)
# Select power control register, 0x2D(45)
#       0x08(08)    Auto Sleep disable
bus.write_byte_data(0x53, 0x2D, 0x08)
# ADXL345 address, 0x53(83)
# Select data format register, 0x31(49)
#       0x08(08)    Self test disabled, 4-wire interface
#                   Full resolution, Range = +/-2g
bus.write_byte_data(0x53, 0x31, 0x08)

time.sleep(0.5)

# ADXL345 address, 0x53(83)
# Read data back from 0x32(50), 2 bytes
# X-Axis LSB, X-Axis MSB
data0 = bus.read_byte_data(0x53, 0x32)
data1 = bus.read_byte_data(0x53, 0x33)

# Convert the data to 10-bits
xAccl = ((data1 & 0x03) * 256) + data0
if xAccl > 511 :
    xAccl -= 1024

# ADXL345 address, 0x53(83)
# Read data back from 0x34(52), 2 bytes
# Y-Axis LSB, Y-Axis MSB
data0 = bus.read_byte_data(0x53, 0x34)
data1 = bus.read_byte_data(0x53, 0x35)

# Convert the data to 10-bits
yAccl = ((data1 & 0x03) * 256) + data0
if yAccl > 511 :
    yAccl -= 1024

# ADXL345 address, 0x53(83)
# Read data back from 0x36(54), 2 bytes
# Z-Axis LSB, Z-Axis MSB
data0 = bus.read_byte_data(0x53, 0x36)
data1 = bus.read_byte_data(0x53, 0x37)

# Convert the data to 10-bits
zAccl = ((data1 & 0x03) * 256) + data0
if zAccl > 511 :
    zAccl -= 1024

# Output data to screen
print ("Acceleration in X-Axis : %d" %xAccl)
print ("Acceleration in Y-Axis : %d" %yAccl)
print ("Acceleration in Z-Axis : %d" %zAccl)

These are the code.


texts:
I implemented an R-2R DAC on a breadboard. Obviously, the output voltage from the DAC is negative. I would like to compare in the operational amplifier comparator a positive voltage so I need to transform the output voltage from the DAC.
How can I do this?
Thank you so much.


texts:
Why don't decoupling/bypass capacitors need resistors to perform their function, like regular filters?

Is it because the stray resistance of copper traces is enough to filter, along with the capacitor, the frequencies targetted by decoupling caps?


texts: op amp with single supply - non inverting circuit gain not being produced

texts:
I'm trying to boost a 12V signal to around 100-120V using an opamp from a single 12V 5A supply voltage (gain of about 10). I can't seem to get it to work though. Right now I'm just trying to make a piezo element louder (with the final hopes of making a pump out of it).

I've tried 3 different opamps, but for the sake of simplicity, I'll just talk about one of them, the LM324 (For a pump, I assume I will need one that has a higher slew rate)

I'm trying to follow the non-inverting gain schematic from this PDF (section 2.1 on page 6).

Here's a list of everything in my circuit (a Fritzing image is below)

Arduino uno
12V 5A power supply
Opamp (LM324)
Piezo element
Ceramic capacitor (100nF)
R1 =  1K ohm resistor
R2 = 10K ohm resistor
R3 = 10K ohm resistor
R4 = 10K ohm resistor

If the arduino pin just sends a high signal, when I measure the voltage coming out of the opamp, I get 11.01V from Vout. With R2 changed to 2K ohms, I get 10.9V.

If I change the adruino code to a modified blink example with the "delayMicroseconds" command in place of the "delay" one....

  void setup() {
  pinMode(3, OUTPUT); }

  void loop() {
  digitalWrite(3, HIGH);
  delayMicroseconds(800);

  digitalWrite(3, LOW);
  delayMicroseconds(800);}

... with a 10K resistor I measure 5.7V, and with a 2K one I get 10.8V.

Have I wired something up wrong, is the value of the capacitor not high enough, or am I demanding too much from this opamp?


texts:
In CMOS mix-signal circuitry, would it make a difference if I set Vdd to 24V and Vss to 0, instead of having +/- 12V supply rails?

I know voltage is just a reference, but do the absolute numbers matter?


texts: Transistor simulation not working properly in Proteus

texts:
I'm recently working with Proteus. So I created a simple schematic for a transistor to work as a switch. But when I simulate it, it doesn't work as it should. In the picture below you can see that the resistor is not receiving current at the base, however the led is lighted up as if it were. I've even tried to remove everything from the base of the transistor and even then somehow the led still lights up. So I suppose it's a problem with the software. But maybe there's a setting missconfigured that I don't know of. Have anyone had this problem or any idea on what could be a solution? Thanks.
PD. I've already tried to reinstall the software and it didn't work.


texts:
I've started learning about Buck Converters, and I made a miniature one on an Arduino prototype shield. But when I turn the thing on, the voltage is stuck at 5v (the voltage input). I tried disconnecting the PWM line, no effect; and grounding the gate on the transistor (a 4800 n channel MOSFET I salvaged from a laptop) only causes a tiny drop (0.5v) on the output. Here is my circuit:

simulate this circuit – Schematic created using CircuitLab

I don't think it's a bad transistor, it took 10 seconds to desolder, and then 15 more to resolder it on a different board. Can anybody show me what I'm doing wrong?

UPDATE: So, I fixed the transistor problem, and made the gate driver an optocoupler. I also added a boost capacitor and flyback diode. Now the problem is that the circuit can't handle any sort of load at all without going unstable. I have updated my schematic.
Strangely, the schematic editor doesn't have any opto-isolators, so sorry if that part is a bit messy. For control, I have an Arduino Nano adjust the PWM to a set voltage (3.3 for testing). The regulator is very accurate, only off by 0.01 volts, until I apply a load. Then the voltage drops anywhere to 1.8v for an LED, to 0.2v for a small fan. The transistor also gets very hot when I connect the fan, which shouldn't be the case because it was designed to handle up to 700v and 1.5A. I really don't know what I'm doing wrong here. Also, the flyback diode only had 3107 for the markings. Another note, the voltage takes a really long time to stabilize, even at 100% duty cycle.


texts: Pull up resistor on P-MOSFET gate. Not working

texts:
I am building a battery-powered datalogger that will communicate using cellular signal, based on the ATSAMD21 microcontroller and the SIM5320 cellular modem. To save power, an outside timer periodically switches the microcontroller on/off (not shown) and the microcontroller should be able to switch power to the modem. When the microcontroller is off, the modem should also be off.

I implemented this as shown in the schematic below, using a microcontroller output to switch power to the modem through a P-MOSFET. This part works perfectly.

I also added a 100k pullup resistor to the gate, which I hoped would keep the P_MOSFET off when the microcontroller is off. This part does NOT work--when the microcontroller is off, the gate voltage drops to ~0.8V and power runs to the modem. I tried using different pullup resistors, but even at 100 ohm the gate voltage increases to ~3V and the P-MOSFET is still on.

Questions:

It looks to me like 'something' is driving the gate voltage toward GND, but what is it? Where did I go wrong?
If the gate voltage is above ~2V, the microcontroller actually powers on. Is it actually drawing power through an analog input/output pin?
It may be simpler to use an N-MOSFET instead, but I am unsure as to how it would work with the SIM5320 IC being connected to a 'GND' that is a few mV above real ground due to the mosfet resistance. Could an N-MOSFET work here? What are better ways to design this circuit?

simulate this circuit – Schematic created using CircuitLab


texts: What is the conductance of this LC tank?

texts:
So, I start with total conductance:

$$
G_{TK} = \frac{1}{\frac{1}{j\omega C}+ 2R_C} + \frac{1}{j\omega L + R_L}
$$

Then, when I take only the real part of this expression in order to know the conductance at the resonance frequency, I end up with the following expression:

$$
G_{TK} = \frac{2R_C}{\frac{1}{C^2\omega_0^2}+ 4R_C^2} + \frac{R_L}{L^2\omega_0^2 + R_L^2}
$$

It's clear that the \$4R_C^2\$ and \$R_L^2\$ were discarded in order to arrive at the expression in the image. However, what is the full argument behind?
I'm guessing it's something along the lines of:
$$
\frac{1}{C^2\omega^2} \gg 4R_C^2
$$

and the same for the other expression.

The question is: WHY? The problem is that I'm not familiar at all with the practicalities and typical values for LC tanks. If I were not shown the final expression, I wouldn't have known that one term dominates.
So, could anyone maybe point me to the right source in order to read more about this LC tank practicalities?

Thank you all!


texts:
I'm building a PIPO register to implement on a fpga. I have written the code below, but there is something wrong with my register module I believe.
The value of Q won't save. My intention was that Q would save the value of D until enable is changed. But Q is constantly changing itself to match the value of D.
I've posted a link to what the project should look like. Thanks for the help.
https://www.youtube.com/watch?list=PLGwEmhvkv6WYhkw0QkGyyJKj_dFdhe3Jk&v=vzGEKGQRNio&feature=emb_title&ab_channel=RealDigital.org
`timescale 1ns / 1ps

module register (
input clk,
input en,
input  [7:0] D,
output reg  [7:0] Q
);
//always @ (posedge(clk),posedge(en))
always @ (en)
begin
   if (en == 1)
     Q <= 8'b00000000;

   else
     Q <= D;

   end
   endmodule

module mux (
input Sel,
input  [7:0] I0,
input  [7:0] I1,
output reg  [7:0] led
);

always @ (Sel,I0,I1)
begin
    if (Sel ==  1)
     led <= I1;

    else
      led <= I0;
end
endmodule

module pipo(
//input clk,
input en,
input  [7:0] sw,
input Sel,
input  [7:0] I0,
output  [7:0] led

);

wire [7:0] sData;
register piporeg(

//.clk(clk),
.en(en),
.D(sw),
.Q(sData)
);

mux pipomux(
.Sel(Sel),
.I0(sw),
.I1(sData),
.led(led)
);

endmodule
```


texts: Audio power amplifier features identification

texts:
There is the power amplifier circuit here:

How 18k/1k/.0012uF filter works in the input circuit?
It's clear for me that Q1/Q2 is a transconductance stage: voltage in - current out. But where is that "current" (that has been amplified and moving through Q9-Q8-Q7) are transformed back to voltage (to form a transimpedance stage)? How that transimpedance stage can be identified in that amplifier where there is no resistor in collector of voltage amplifier stage because of current source is used instead of that resistor?
Why 100 pF capacitor used at cascode? Is it not enough to use cascode to compensate Miller effect?
What is the purpose of 100 Ohm resistors at Q11/Q12 bases?
Why two different voltage sources are used for pre- and out- stages? And what is disatvantage if I will use one?


texts: Power a guitar pedal (usually takes 9V power) with a single AA battery

texts:
This is not necessarily for real life application, but more for the challenge: would it be possible to power an existing guitar pedal (let's say a Roland / Boss saturation, fuzz, reverb, delay, etc.) with just a single AA battery?

I've recently tried different cheap step up converters from ebay, and they work with as little as 2V input to 9V-12V-or even 27V output.

But I haven't found any which works with 1.3 V as input.

Question: are there some chips able to do this, in a micro-size like these step up converters?

Or is there an electronic reason for which there is a threshold near 1.5V / 2V (below: doesn't work, above: working)?

PS: such pedals usually work with a 500mAh 9V battery (4.5 Wh), so I think it would also work with a 2500mAh 1.5V AA battery (3.75 Wh).


texts: Differential Impedance vs length matching vs IC manufacturer requirements

texts:
I'm working on a PCB with a USB 3.0 controller (TUSB7320, Texas Instruments) with SuperSpeed signals and High Speed Signals. There are some specific requirements about impedance and length matching. Until here all ok, but I have requested a budget for the PCB control impedance manufacturing, and a "problem" appears. The manufacturer tells to me that I have to minimize the places where the impedance traces are not controlled: vias and accordions. How can i minimize the impedance on that places?

I have other problem: the 3W rule by Texas Instruments. They recommend 3 times the trace width between trace center and trace center, until here all ok. But, to reach the impedance profiles (100 or 90 ohm) I have to make bigger the width of the traces, reaching 0.22 mm or 0.2 mm. Have i to introduce 0.6 mm or 0.66 mm between this traces and nearby traces? Which rules are stronger?

EDIT: I add images about my design.


texts:
I made a stompbox which is basically a small wooden box with a piezo element inside that when stomped on produces a sound similar to a bass drum except that the thing is much more portable.

The circuit works but I have two problems with it that I don't know how to solve:

It's extremely loud. I hooked it up to two different soundboards and even with the gain at 1 this was super loud.
The circuit produces a really loud and constant "crackly" hiss. The hiss remains at the same apparent loudness regardless of what the gain pot on the soundboard is.

The circuit in question is this:

(I replaced the MPF102 with a J113 because I didn't have one in hand)


texts:
I'm working on an FPGA implementation of a retro '80s computer (see http://fpgabee.toptensoftware.com) and am trying to setup some 8-bit audio support.  I'm using a sigma-delta DAC and a R/C low-pass filter.

What I currently have is a 3.3 V pin from the FPGA driving a circuit.

If I connect a pair of iPhone headphones I can hear the audio, it's sounds quite good although the volume is a little low.

What I'd like to do however is connect this to my PC for recording or to pass-through to my speakers.  I tried connecting the above circuit directly to both line-in and microphone sockets on my sound card but the results were terrible.  Nothing audible on the line-in, and very low volume and lots of noise on the microphone socket.

So I'm looking for is a simple circuit (I presume a amp of sorts) that will let me get a clean signal into the PC.  I'm not talking about hi-fi quality stuff here - this is 8-bit audio driving a very simple dac.


texts:
I have a 640x200 monochrome display from a HP 200LX palmtop computer. On its PCB I can see two types of ICs: HD66204TFL and HD66205TFL from Hitachi.

Here is its schematic (it has 200 px not 240 as in schematic) from datasheet:

Here is the protocol (from datasheet):

I figured it out that CL2 is the highest frequency clock. At every falling edge of this clock 4 pixels in a column are selected and they output according to D0-4. So it has 160 cycles for a full row.

CL1 falling edge selects a row so it must have 200 cycles  for filling the display, one cycle (falling edge) at the end of every 160 cycles of CL2.

I can't figure out what FLM and M do. As far I understood they both mark a new frame. And it needs both signals ?

So my display needs a 4 bit data port and 4 clocks and DISPOFF connected to GND.

So far all I could find on the internet (similar displays but not this one):

I read somewhere (don't know where) that this protocol is called LCD Timing Controller.
http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=49684
http://mikestirling.co.uk/2009/02/mono-stn-display-on-an-avr32-ap7000/
http://www.mikrocontroller.net/topic/92704#new

And could this display be controlled by Arduino? I don't have one (yet) so for my experimets I will use PC parallel port (the 8 bit DATA port) on Ubuntu (I've successfully used it before for I2C with Claudio Lanconelli's EasyI2C and software implementation written by me in Qt C++ for reading an I2C EEPROM and controlling a RF Modulator).

Any help is appreciated!


texts: Should I cut away the ground pour above a diffpair on the first inner layer, which are Z-matched to the ground layer (L2)?

texts:
I'm routing diffpairs on the 1st inner layer of a 4-layer pcb which are Z-matched to the 2nd inner layer which is entirely a ground pour.
The top layer has traces and routing AND also a ground pour around the components/routing.
Should I cut away the ground pour above the differential pairs ?
This is my stackup:


texts: Does MOSFET let current flow through source to drain as it allows it from drain to source?

texts:
Does a MOSFET allow current flow in reverse direction (i.e.; from source to drain)?

I made a Google search, but couldn't find a clear statement about this matter. I have found this similar question, but it is about detecting current direction from the schematic symbol of a MOSFET. And under the same question, there is this answer which states that MOSFETs have no intrinsic polarity, thus they can conduct in both directions. However, that answer has no up/down votes or comments, so I can't make sure of it.

I need a clear answer on this. Does a MOSFET conduct in both directions?


texts: Boolean function minimization for more than 100 variables

texts:
I need to minimize boolean functions with more than 100 variables.
Additionally, each row has some don't care conditions.

For example,

  | A | B | C | D ........................| Y |
  _____________________________________________
  | 1 | 1 | 0 | 1 ........................| 1 |
  | 1 | 1 | 0 | X.........................| 1 |
  | 0 | 0 | 1 | 0.........................| 0 |

In the previous example if the first 3 bits are "110" then we don't need to consider other bits.
Though the number of variables is 100, the number of row entries are very small, around 3000.
I know about K-map and Quine-McCluskey algorithm which works very well for a small number of variables. There are some programs which can minimize such expressions with less than 16 variables. But I have heard there exist faster and better algorithms to minimize such circuits which electronic engineers use for circuit minimization. Unfortunately, I was not able to find such program which will take my inputs and their respective outputs and provide a minimized boolean expression. Or in short I need a boolean expression in the end.
I will appreciate your help.


texts:
Recently I purchased a lab power supply, with banana jack output. Are there any specialized products that snap onto the breadboard on which you can connect banana jacks to deliver power to the board?

Any suggestions to products or DIY solutions are appreciated.

I have looked at the MB102 breadboard power supplies, but they use a USB or 2.1mm jack connection to power the board. I am specifically looking to power it from a lab power supply.

Thank you!

Edit: I must add that I have a simple 830 pins breadboard without any binding posts, so I am looking for something like a MB102 module but for banana plugs.


texts:
I made this circuit, with the intention of it lighting and then fading out the led after very briefly closing the switch:

This is intended for a CR2032 coin cell battery power source and the led is a normal 20ma through hole red LED, probably Vf =~ 2v.

Ignoring the one resistor in series with the power supply, what function describes how the transistor and the values of capacitor and resistor determine the led brightness and how long it takes to fade out? Like if I wanted to make it fade out 50% more quickly or more slowly, how would I change the resistor and/or capacitor?

Does the characteristics of the transistor matter?


texts: I need some means to increase the Hi-pot rating of an Ethernet port to 3000V to meet regulatory approval. The Ethernet controller module is housed in a large metal enclosure and an 18" patch cord connects the controller to a back panel RJ45 connector. The controller module uses a standard mag jack which has a hi-pot rating of 1500V. Redesigning the controller card is not an option at this point. I was planning on making a small PCB at the back panel with two RJ45 connectors and a LAN transformer in between. This would provide an additional 1500V to 4000V of isolation depending on the transformer chosen. Does anyone see any potential (no pun intended) problems with this approach? Is any biasing required and should the center taps be left floating?


texts: PMOS, NMOS length width concept for low power circuit

texts: Why for low power consumption width of NMOS taken same as length of feature and Width of PMOS taken as 2.5 times width of NMOS ? e.g for feature size 180n width of NMOS 180n and width of PMOS 450n. Is there is any mathematical equations that support this concept?


texts: What dc-dc topology to use for a 300W step-up converter?

texts:
I am asked to design a dc-dc converter with the following specifications:
Vin=24V(2 lead-acid batteries in series), Vout=300V and Iout=1A.
My initial choice of topology was the boost converter. Problem is the gate drive duty cycle can go up as high as 1 - 24/300 = 92%, and that's assuming perfect efficiency.
A tapped-inductor boost would solve the duty cycle issue, but at the cost of added complexity.
I am also not sure if the boost family is the way to go at the 300W level.
What dc-dc topology would you recommend for my application?
EDIT(to clarify):
Okay so my main problem is that the duty cycle at the specified load reaches well above 90%. Research tells me that it's not a good idea to push the duty limits of dc-dc IC controllers. Such a very high duty also means high current stresses on the switches. At 92% (ideally), the average switch current goes around 1A / (1-0.92) = 12.5A. That's a lot of current to handle. Same trend goes for the rest of the components.
One idea to fix this is to use a tapped-inductor boost topology such as this one

(source: edn.com)
!
This way, the needed duty cycle goes down thanks to the added voltage boost from the transformer, and so component stresses are relaxed. However, the transformer adds to the complexity.
I have not explored, and am not knowledgeable, with other dc-dc topologies that can step-up the voltage such as the buck-boost, and forward converter topology. Maybe other such topologies can step-up the power more efficiently compared to the boost and tapped-boost based ideas I gave - I am not sure. My only other concern is the complexity of implementation, as this only an undergraduate project :)
Should I push through with the boost-based idea? If not, what topology would you recommend?


texts:
I'm using XTR305 for Analog output.
Below is the circuit for the same. After successful output from DAC which is input to XTR305, I'm not getting the output voltage. Can someone help me with that?


texts: Asynchronous FIFO in clock domain crossing

texts:
Clock domain crossing issue can be solved by using asynchronus FIFO with input frequency f1 is of the source domain and f2 is of the destination frequency.

If the data is sent in bursts, depth can be calculated by

But what if the data is continuously sending ??


texts: Need 1-4 pins controlling 16pins logic level

texts:
I have max four outputs coming from a PIC. I need these four outputs (or one serially) to simultaneously control 16 pins with a logic level. This is for a clock application.

A BCD could accomplish this but I don't believe it is the correct way and no one stocks them.

A set of latches could do this, but that would require me to individually latch each bit and reset when I need to switch the output.

A demux could accomplish this, if one existed that would allow multiple output pins to be high at the same time. Serial to parallel demuxers looked perfect, but all I have found only permit one pin being high at a time.

I'm looking for some type of IC.


texts:
I know this has been asked a few times already, but if we disregard the body diode, or say we tie the body to a low enough voltage that it wouldn't forward bias those diodes, then are modern FETs actually symmetric?

I ask this because the FETs I've used will often have, out of 6 pins, 4 will be dedicated to the drain, 1 to the source, and 1 to the gate. Even if we could control the body and bias it to a voltage of our own choosing, it seems like the FET has an asymmetry built in. I've primarily seen this on higher power FETs.

EDIT: My question is mainly about integrated output power FETs or discrete component FETs.


texts: How do I calculate to get the correct timing for SPI

texts:
I am having an issue with sending the correct HEX registers over SPI to a slave device. I am finally able to see my issue by decoding the SPI using a scope. What I see is random HEX during my test. About every 3rd or 4th test, the correct HEX is decoded. I am convinced that this is a clocking issue but I am unsure how to look at the scope to identify what baud to set the SPI clock. This is my first scope and I am learning how to use it. Is there something I can look at on the scope to resolve my issue?

void SPI_Init(void)
{
  SS_Slave1_High();
  SS_Slave2_HIGH();
  SS_Slave3_HIGH();

  GPIO_PinDirection(SCK_PIN,OUTPUT);
  GPIO_PinDirection(MOSI_PIN,OUTPUT);
  GPIO_PinDirection(MISO_PIN,INPUT);

  GPIO_PinDirection(SS_Slave1,OUTPUT);
  GPIO_PinDirection(SS_Slave2,OUTPUT);
  GPIO_PinDirection(SS_Slave3,OUTPUT);

  SPCR = (1<<SPE)|(1<<MSTR)|(0<<SPR1)|(0<<SPR0);
  SPSR = (0<<SPI2X);
}

///Main Routine
SS_Slave2_LOW();

SPI_Write(0xC0);  /// This is the HEX I should see on MOSI Decode

SS_Slave2_HIGH();
DELAY_ms(10);

The decoding seems to have a pattern but not sure. I get C1, C0, 80, C1, 80, C0. It's never consistent when I execute the test.

My slave is a MCP2515 CAN controller but I think that is irrelevant because this is on the MOSI. Correct me if I am wrong.

Yellow: SCK
Blue: MOSI
Purple: SS


texts: Generation of triangle wave at 15KHz frequency

texts: I want to generate a triangle wave with peak value 5V. I am using a 555 timer to generate square wave pulse of frequency 15KHz. Then I passes this square wave through a active integrator ( A opamp with RC circuit). But for various RC values I used i was just getting a flat line. So please help with the circuit for integrator I will be really grateful.


texts:
I am new to this forum. I am building a prototype board which uses a 48 pin LQFP 0.5mm pitch IC including other components. Included on the board I have 1206 SMT components and SOIC components.

All components reflow well however the 48 pin LQFP keeps shorting during the reflow.

My board is professionally made but it does not include silkscreen and solder mask (bare proto board). I am also using a stencil. I have read that this type of board could cause shorting of pins with fine pitch components during reflow.

I am using a DIY home-made toaster oven following the general temperature curve for solder reflow.

I have tried applying various amounts of solder paste with no luck.

Any suggestions how to successfully solder such a component to the board?


texts: How do I calculate the resistor value for this circuit

texts:
I am playing with a power supply that went bad, to expand my knowledge and just see if I can repair the circuit level board.
Here is my problem. I have a resistor that burned up. I have no idea of it's value as it is a char-coaled crispy critter and it is open so I cannot measure any resistance. I have already replaced the following parts 2 caps-1000MFD 16v, the fuse, a 22pf 1kv ceramic cap, 1 pnp S9015 trans, and 1 npn 9014 trans. Output voltage is 12v-1.5A and 5v-1.5A. I have tried to use the forumla I learned along time ago to calculate the resistance required but it doesn't seem right. V/A=R. I have even looked it up on line and they tell me that if I have a 12-volt circuit requiring 0.015 amperes of current, I will need a resistor with 333 ohms (12V / 0.015A = 0.333). That doesn't seem correct so I did the math and got a completely different answer. Can you help me calculate what I need and show me where I am screwing up please? I can send you pics of the board and where I have replaced the parts so far. The resistor is physically located between the 9014 trans. and the ceramic cap. board By the way I didn't make the mess with all the solder, this is the way it looked when I cracked the case.


texts: Connecting a Volt Ammeter to the input and output of a power supply

texts:
I'm working on a mini adjustable power supply that can give me a steady max of 12 volts, 3A and be able to boost to 24V when needed. Therefore, to do so I'm using a MT3608 2A DC-DC Step Up Power Supply Board Booster Module and 3A DC adjustable Current Voltage Step down converter Battery Charger LED 18650. I know Step-Up Step-Down modules do exist but it is very hard and expensive to obtain those from where I'm from. As for AC-DC power supply I'm using an old 100W computer power supply, hence using the 12V supply rail to power this. I also want to connect a Voltmeter and Ammeter to the input and output of the Buck Converter and with a flip of a switch I'm able to check either the input or the output.

This is the picture of the wiring of the Volt Ammeter that I'm using. Since I'm only limited to 2 links I will try to post the pictures of the modules in the commends.

My plan is to use one high current DPDT switch, one low current 4PDT switch and 2 relays. The DPDT switch will be use to turn on and off the boost converter and the 4PDT switch will be used to switch between measuring the input and output current and voltage. As I'm quite new to electronics I'm not entirely sure this schematic will work, and that's why I'm asking for help.

My main concerns first of all is will this work as I came up with the design myself? The reason why I'm putting a switch to toggle the boost is the boost converter can only supply 2A and my buck converter support up to 3A so in the case that I need 3A the boost converter will bottleneck it. My other concerns are about the relay. Do I need to connect a diode in parallel to the coil of the relay to prevent current back flow? And since the the relay will be switched at a short delay after the toggle switch is flipped, during this small time delay the Ammeter will be short circuited, so can this damage the Ammeter?


texts: Full time vacuum pump/powered by solar array and battery

texts: I am putting together a vapor extraction system consisting of a small 12 volt (500 mA to 1 A) 6-10 Watt, rotary vane vacuum pump, powered by a solar array with controllers and battery. My goal would be to have the pump run 24/7 (and I could install 2 or three pumps on timers to allow cool down). Any suggestions would be great!


texts:
I've got a problem I haven't been able to sort out experimentally and am looking for help from someone who knows more than me.  I'm making a handheld prop with audio and lighting effects.  In the past I've used a commercial handheld amp (Aker VoiceBooster) as a base, tapping switched battery power from its circuitboard. That tapped power will run the controls, audio generator, LEDs, etc., and I'll use the amplifier on the Aker for the audio output. But this time I have a problem with an LED circuit generating noise on the power feed that is messing up the audio on the Aker. The problem seems to be that I'm using an ATTiny85 and pulse width modulation to drive a number of LEDs (with an N-Channel MOSFET because they need more power than the ATTiny can source). Simple circuit show in pic, LEDs on the right, noise apparently running back to the Aker's battery on the left.
How can I fix this? I think the answer should be bypass capacitors, but breadboarding a number of different sizes across the 5V lines near the LEDs doesn't seem to change anything. (Tried 0.1microF - 10microF MLCC.)
I don't have a scope to put on this, so I don't really know the nature of the noise (beyond its audible effects).  I may well be missing something basic, this is just a hobby thing and I'm a software guy.  Can anyone clue me in?

EDIT:
The PWM frequency is the default for ATTiny85, which seems to be 500 or 1000 Hz.  I was trying to avoid having to figure out how to change it, but that might be the best approach.
There are actually 6 LEDs (I only drew 3), pulling 20mA each.  The resistors are 100 Ohm.
I've tried caps across the battery, and across Q1 source to the hot side of the LEDs, without much luck.  But I'm not certain of the PWM frequency, or exactly what values/types of cap is likely to be effective.


texts: How would I test if my low pass filter works on a remote FPGA?

texts:
I am making an example low pass FIR filter design to go on an Intel FPGA. I have an idea about how I'll test it via simulation (by having the input be a sum of sine waves, and the cutoff frequency be between those frequencies or alternatively, by having an audio file), however I am unsure how the system block diagram should look such that I would be able to verify the filter example works on the board without any peripherals.
My goal is to design a low pass filter system on the FPGA such that the person who gets the example design would be able to verify that the filter works without needing a signal generator (to input sign waves. for example) or a certain type of cable (to feed the audio file into the FPGA as an input via GPIO, for instance) and etc.
In order to do this, I need to figure out what is "driving" the filter, and where the output is going -- this is where I need help with the overall system visualization. Simply put, I need help filling out the first and third high-level system blocks in the image below. Any insight would be appreciated - thank you!


texts:
I would like to change relay functionality in electronic switch. As per the concept, relay pole and NC position is short even there is no power applied to it. I need complete exact relay functionality even in power loss condition. Is it possible to implement using JFETs?
Also, in a relay the signal can travel from pole to NC/NO or NC/NO to pole. That means I am bypassing the NC or NO condition as per coil voltage. Is it possible to implement using JFET?
I need more of SPDT switch (pole, NC and NO) configuration even in power loss condition.  Can you please help me with circuit?


texts: Confusion in modelling of total loop inductance of a rectangular loop

texts:
I was reading an article about partial and total loop inductances from this site  and in a section where for calculation of total inductance of a rectangular loop is given as:

In each portion of the loop we assign a partial inductance value as well as partial mutual inductance between all parts of the loop. (In this case, we only show the partial mutual inductance of the parallel sections, since perfectly perpendicular conductors will not have significant mutual inductance.)

I don't understand:

Why mutual inductance is taken into consideration for this model (for total inductance calculation) or why mutual inductance is even important when circuit is not isolated electrically?
Why perfectly perpendicular conductors will not have significant mutual inductance as mentioned by the author?


texts: Are there any standardized steps in validating a circuit design?

texts: I made a sensor front-end circuit for my thesis. The circuit works well as intended, but I think the design should be validated by standard methods.


texts:
I have an appliance (electric skillet) that draws 1500W when plugged into a regular (120V) household circuit.

If I want to be able to use it on an inverter that can supply max 1000W@120V, can I build a device with a transformer to limit the current drawn from the appliance to 1000W?


texts: EAGLE - Doesn't load custom eagle-ltspice.lbr

texts:
Recently I've changed HDD and tried to port all my EAGLE 6.5.0 libs. My custom and new libs works perfectly after I copied all EAGLE backup files from my old HDD to the new, inside "Programms/EAGLE-6.5.0/" path. Same for DRC. But "eagle-ltspice.lbr", that is a default library inside EAGLE, doesn't want to be loaded from EAGLE. My "eagle-ltspice.lbr" is an edited version with some custom packages, and most of my projects use this lib. I've copied it like all library inside "lib" folder, but seems eagle want to load default version and not my edited version. Also I can't find where is this default version to overwrite it. I've tried to delete it from "lib", but eagle recreate this.

Any tips how to make "eagle-ltspice.lbr" accepted and loaded from EAGLE?


texts: Fastest possible memory copy between 2 12ns SRAM DIP chips

texts:
Electronics newbie here...

I'm trying to build a retrocomputer, and learn digital electronics along the way. I decided to begin with the video generation part, with a fast memory copier, independent of the main processor. I don't really want to use an FPGA, I'm trying to do it the "old" way, like this guy did.

I would like to create a breadboard circuit that copies addresses "SA".."SB" of SRAM chip 1 to addresses "DA"+ of SRAM chip 2, as fast as possible. A sort of hardware fast memcopy machine.

The SRAM chips are 12ns 32Kx8 Renesas IDT71256SA (datasheet).

SA and DA would be stored inside synchronous 4bit binary counters (4 SN74F163AN chips each, datasheet), SB would reside in a buffer (SN74F541N), and I would use an identity comparator (2 SN74F521N) between SA and SB to eventually stop the counters, and thus the copy operation.

The counters would be connected like this (I understand this is the fastest way to cascade them):

I would like to use a 32 MHz clock (I know, that's a lot for a breadboard, but I hope to handle it by using uniform short wire lengths and some .01uF decoupling capacitors on the power rails and the SRAM's Vcc and GND pins), but I don't know if that's too fast for the chips.

During the copy operation, pin CS and OE of chip 1 would be low, as well as pin WE of chip 2. I would control chip 2 writing with the CS pin.

I'm having trouble understanding the timings in the datasheets. Can anybody help me figuring out:

The maximum update delay of the 4 cascading counters i.e. how many ns does each counter add to the total.
How many ns pass (at most) from the clock transition low to high and a stable data (valid) coming out of chip 1.
If the above is less than 30ns (the clock cycle), maybe I could latch it in a fast latch so that chip 2 can use it as its data-in. That way while chip 1 reads a byte, chip 2 writes the previous one, effectively copying at 32MB/sec speed.
If that is possible, how do I make chip 2 skip only the first clock cycle?
If that's not possible, what would you change to make it work at such speeds?


texts:
My question is the following:
We have two 220V 20A generators connected in parallel to total power 8.8 kw 220 v 40 A load  is 5.5 ohms I'm interested how each generator sees this load since every generator gives half the power. I put this question because one generator can not see this load like 5.5 ohms because it gives half power to not the full power I would like to have somebody explain it a little bit better because it makes me confused .

simplified question

my question is that since every generator in the parallel circuit gives half power in the ideal case it would mean that the generator 1 that gives 220v 20A that is half the power can not "see" the resistance of 5.5 ohms because if "seen" this resistance he had to give complete current in that case we have two problem generator 1 burned because it is not made for such a current problem two if generator 2 gives the same current then the law on energy conservation is not worth what is absolutely not possible
thanks

The last attempt to explain what I asked is very simple

we have two 220v 20A generators and a load of 5.5 ohms if we connect this resistance to just one generator it exceeds its power because it is 220v and 20 A 4.4 kw
and the current at that resistor is 40A which would mean that it exceeds the maximum power of one generator ok if we add another generator then together have enough power to supply load it if we know that every generator gives half power ie 220v and 20A  it is impossible to "see "a resistance of 5.5 ohms


texts: Block Diagrams with offset in control theory

texts:
I have an equation in the form $$y = mx+b$$.  In block diagram form, I could draw this with a proportional gain block and a summer.  I was wondering if there are some clever tricks where I can make this equation with just a proportional block, as it is often times much simpler to deal with a bunch of series connected blocks rather than including summing junctions and what not.  For the sake of argument, let's say for example the equation I have is $$y = 5x+2$$.

All comments are appreciated.


texts: What is a typical industry figure for the minimum spacing between silkscreen and pads? When I look at a manufacturer's general list of capabilities, sometimes this number isn't even listed. I haven't chosen a fab house yet so I'm looking for a general value.


texts: Assign result of comparison to std_logic

texts:
I'm trying to design an eight bit subtractor. The operands are declared as \$\mathtt{std\_logic\_vector}\$ and the borrow out is \$\mathtt{std\_logic}\$ type. Is there a way to directly assign the comparison of operands to the borrow out, like so?

borrowOut <= unsigned(r1) < unsigned(r2);

When I analyze the file the following error occurs:

eightBitSubtractor.vhd:24:29: no function declarations for operator "<"


texts: Skin effect and mag field distribution inside an electric conductor

texts:
Magnetic field inside a current carrying conductor
Suppose I took a circular current strip in a current carrying wire. At the centre I have marked the directions of magnetic field due to four points 1,2,3,4 in the strip, and as the direction are opposite they cancel each other. Then how can flux linkage be maximum at the centre if instead they are cancelling each other.?


texts: Reversing USB power polarity, but no black wire

texts:
My goal is to create a USB-to-USB cable with reversed polarity in order to charge an old Gameboy Advanced SP. I could just go on Amazon and buy a charging cable, but I do enjoy a fun little project now and then, and I like learning about the workings of electronics. According to the tutorial I watched, I just need to attach the black end of one cable to the red of the other and vice versa. Unfortunately, one of the cables I want to use has some non-standard wiring. I could just find another cable with normal wires, and if this doesn't work out I might, but hooray learning and such.

Here is the cable and what I know about it (sorry the image is a bit crap, I hope it's good enough):

Red, green, and white. I know what those are. Or at least what they should be.
Thin wires which were braided around the foil shield. One forum post answer I read said that was ground, but the video I watched had a black wire in addition to a bunch of small wires outside the shield, so I'm not entirely sure.
Three identical looking thin wires which I'm thinking may be shielding-ground wires.
A bundle of very thin, threadlike wires. I'm assuming they're wires, but they are very very thin and might just be structural support or something. Other than that, I don't know.

At the moment my best guess is that I would connect the red wire from the other cable to the bundle of wires that are wrapped around the shield (2 in the picture), and then the black from the other cable to the red on this cable. Unfortunately I don't have equipment to test out this theory, so I'm not sure. Any clarity would be most appreciated. Thanks!


texts: Performing FFT at low frequencies but high resolution?

texts:
To put this in context, I'm looking to achieve both high speed and high accuracy for measuring biosignals through the FFT. I'll describe a quick example to see if I understand this properly as well as to illustrate my question. So, if I have this correctly, if I wanted to take a low-frequency FFT, say frequencies 0-64 Hz for example, to mmeet the Nyquist criterion my sampling frequency would have to be at least twice that, thus 128 Hz. Then, if I wanted a frequency resolution of 1 Hz to one bin, I would need 64 bins, which would put me at 128 samples because there are both real and imaginary parts. Therefore, to achieve that 1 Hz resolution, I would be presented with having a sampling rate of only 128 Hz while needing to take 128 samples, which would put me in the position of having only 1 full performance of the FFT for every second of time that elapses.

Ultimately, this leads me to my real question: at low frequencies, is it possible to take a high resolution FFT (say 1 or 2 Hz per bin) while still maintaining some semblance of speed? Or is this simply impossible due to the limitations of the transform? If so, is there some alternative method or some sort of compromise to be made between resolution and speed? As an aside, I read an article a while ago about oversampling and throwing out samples at certain integer multiples past a certain point (or something like that, sorry it was a little while ago) in order to speed up the sampling process. Maybe somebody knows what that is (or maybe I'm jut rambling at this point). Either way, thanks for any help you can provide in advance.


texts: How to measure, with timestamps, changes in the received luminance?

texts:
I'm working on a project that is in need of some testings to validate it. I need to make some readings of luminance from a light source and store this reading with a timestamp (milliseconds precision).

I've thought of using a common camera, but it seemed too slow for my application (<= 30fps) and it would need some firmware hacking to be able to integrate it with a computer so I can get my timestamps.

I've thought about photometers also, but I couldn't find one that will allow me to read the data from it through, lets say, an USB interface.

Does anyone have a suggestion about this issue? What could I do to read luminance with milliseconds precision timestamps?

EDIT

I'm sorry, but my question wasn't very clear. I don't need to worry about absolute values of those readings. What I need is a kind of photometric trigger generator for an oscilloscpe or such with a not-so-precise threshold. The idea of using a microcontroller with a photometric sensor seems to be a good solution, but I'll leave the question open a little longer to see if other ideas might pop up. Thanks for all the answers.


texts: How can I create feedback measurement with an operational amplifier? 0-20mA measurement

texts:
I want to build something like this.
This circuit controls 0-20mA but the circuit have one big problem. If the circuit load e.g 100 Ohm changes to e.g 200 Ohm, then less current is going to flow. To solve that issue, I need to tune in the feedback for the operational amplifier by turning on the potentiometern

So I have an idea! What if I measure the current flow over a small resistor e.g 25 Ohm. I then send the voltage difference back as a feedback signal. If I get +3.3v as the reference value, then I should have 20mA as current flow in the circuit.
Like this. But even if I tune in current flow to 20mA when I have +3.3v as reference, the current flow in the circuit WILL change if I change the circuit load.

Question:
How should I build up this feedback circuit so when I have +3.3V as reference input signal, then 20mA will flow through the 25 ohm resistor, no matter what arbitrary load we have?


texts:
I saw some circuits that uses a emitter follower as a buffer for output. The emitter resistance is 470\$\Omega\$. The author says that, since the ac emitter resistance is very small, he put a 50\$\Omega\$ resistor in series with the output terminal, so that the circuit would look like 50\$\Omega\$ from the output.

But what I don't understand is, if you now connect the output to a 50\$\Omega\$ load, the emitter resistance then becomes (470\$\Omega\$ || 50+50\$\Omega\$) = 82\$\Omega\$! This could affect a lot of things, for example the collector current would suddenly change 5-fold, the signal source would see a 80% reduction of load, everything could go wrong. What am I missing here?


texts: I have a simple oscillator, as shown below. As far as I understand, a negative bais is induced on the base of either c1 or c2 which in turn pulls the base of the other transistor below 0 shutting it off. However, I am wondering how a difference in size of the capacitor affects the circuit. It appears that the current can flow to charge the capacitor as well as charge the base of the transistor so how does this work?


texts: How is this PMOS FET working as ESD protection?

texts: Can somebody please explain the circuit functionality? I'm thinking of PMOS (\$V_{sg}=0\$) as a current-limiting diode. Am I right?


texts: Split a Signal Based on Frequency for High-Power Applications

texts:
Normally when one wants to do analysis on a signal based on certain frequency ranges the obvious choice is to filter for those individual ranges and then conduct the analysis based on the result.

Instead of filtering out certain frequencies, I would like to shunt the power in a given frequency range to a different circuit for processing (possibly to be summed up with other processed frequency ranges later).

I expect the solution is to present high impedance to the given frequency range in one leg of the circuit so that it gets shunted to another branch.

I doubt this is a new idea but my google searches haven't born any fruit.  Any ideas how to do this?


texts:
I am checking what I can and cannot do in aggregating and concatenating in VHDL.

while I can combine two vectors by concatenating them, I keep getting error if I use aggregate.

I saw one answer here shows it is possible.

Can someone explain why they are giving errors, or maybe it is the language which does not allow this?

I appreciate any suggestion.

here is my code. I marked the correct and the wrong lines.I use ModelSim.
I comment/uncomment when checking to avoid multiple drivers.

architecture RTL of example_array is
--signal Z_BUS                                  : std_logic_vector(7 downto 0);
--signal R_BUS                                  : std_logic_vector(3 downto 0);
--signal A_BIT, B_BIT, C_BIT, D_BIT     : std_logic;

signal T_BUS                                    :  std_logic_vector(7 downto 0);
signal Y_BUS                                    :  std_logic_vector(7 downto 0);
signal U_BUS                                    :  std_logic_vector(3 downto 0);
signal P_BUS                                    :   std_logic_vector(3 downto 0);
signal E_BIT, F_BIT, G_BIT, H_BIT       :  std_logic;

BEGIN
Z_BUS <= A_BIT & R_BUS & B_BIT & C_BIT & D_BIT;                 -- correct
--Z_BUS <= W_BUS & R_BUS;                                       -- correct

P_BUS <= (E_BIT, F_BIT, G_BIT, H_BIT);                          -- correct
U_BUS <= (E_BIT, F_BIT, G_BIT, H_BIT);                          -- correct

(E_BIT, F_BIT, G_BIT, H_BIT)    <= std_logic_vector'("1011");       -- correct
(E_BIT, F_BIT, G_BIT, H_BIT)    <= P_BUS(3 downto 0);               -- correct
(E_BIT, F_BIT, G_BIT, H_BIT)    <= P_BUS;                           -- correct
Y_BUS <= (2 => '1', 3 => F_BIT, 1 downto 0 => '0', others => '0');  -- correct

--T_BUS(7 downto 0) <= (U_BUS(3 downto 0), P_BUS(3 downto 0));  -- WRONG!!
--T_BUS <= (U_BUS, P_BUS);                                      -- WRONG!!
--(U_BUS(3 downto 0), P_BUS(3 downto 0)) <= T_BUS(7 downto 0);  -- WRONG!!

END architecture RTL;


texts: Providing high voltage tolerance and ESD protection to MCU

texts:
I am working on a design for an automotive application.  Because its for testing and prototyping I expect the inputs to accidentally, or perhaps intentionally, be attached directly to the battery/alternator on occasion.  I want the board to function properly during this time.

What I'm shooting for and my assumptions:

I want all pins to operate normally with up to 18VDC applied
High channel count, trying to minimize components and board space
All inputs MCU/ADC/MUX inputs are high impedance
Signals are low frequency (<1kHz, most below 100Hz) and are a mix of digital an analog where some of the analog is buffered at the sender and some are not (switches, serial, thermocouples, resistance sensors, 0-5v pressure senders. etc)
Some components have built-in ESD and OVP protection, but not all.  I want to assume these features aren't present so that I can have a common solution for all channels.
Most devices have an abs max pin input voltage of VCC+0.3V
For devices that have OVP I want to avoid activating the intrinsic pin diodes for fears of undesirably, or poorly defined, behaviors.

I have made the example diagram below that shows 20V zener diodes near the inputs for ESD protection, current limiting resistors/lpf, and schotkey diode clamps.  Because I haven't determined what regulator I am using yet I am going to assume that it doesn't have good current sinking ability, and have put another zener on the 3v3 line to help sink clamp diode current to ground.

What I like about the approach is:

Relatively low component count
The use of clamp diodes, as opposed to zeners, means I can use the same part for each input even if the voltage is 5v0 as opposed to 3v3.

What I don't like:

The behavior feels ill defined.  I'm not confident that I know the clamp diodes will activate before the intrinsic diodes.  For the diagram below I went out of my way to make the intrinsic diodes have a higher Vf than the BAT54S, but there's no way to know this for sure.
My choice of 3v3 zener is poor (D6, near the regulator), it dumps too much current to ground all the time.  I'm concerned that using something with a higher cutoff would result in coupling input signals into the regulated power lines.
I'd prefer smaller packages for the zeners and clamps than SOD-123 and SOT23, respectively, given the high channel count.
I'm concerned that this might not be a good approach if the input was differential (and biased to mid rail) rather than single ended.

My questions:

Are my concerns well founded?
Is this a good approach, if not what would be better?
Given that this is an automotive application, can you suggest additional or better approaches for both input power and signal protection that I haven't considered?

Notes on schematic: V1 and R2 are an unknown voltage source and source impedance.  I'm making the assumption that the user connect the input directly to a large battery being charged by an alternator.


texts: Which is better for solar inverters - High volts low amps solar arrays vs low volts high amps solar arrays?

texts: I want to know how the two ways of making the solar arrays affect the AC power load that the inverter can supply.


texts: Controls: Getting the feedback transfer function of a Plant and Controller

texts:
I'm designing a function in Python similar to MATLAB's 'feedback(T)' command. I know modules already exist, but it's something I want to do for myself for fun. However, I am running into issues. Let's say I have the transfer function of some arbitrary plant
$$T(s) = {s + 5\over s^2 + 4s + 7}$$
Let's also say I have some arbitrary PID/PI/PD controller (Not to imply this controller is actually good, this is more to demonstrate the concept, so keep that in mind!)

$$C(s) ={2.3802s + 7.7309 \over s}$$

We know that the Closed Loop Feedback Transfer Function has the form of
$$CLTF ={T(s)C(s) \over 1 + T(s)C(s)}$$

When CLTF computed above in Matlab, we get ...
$$CLTF = {2.38 s^5 + 29.15 s^4 + 133.8 s^3 + 292 s^2 + 270.6 s\over s^6 + 10.38 s^5 + 59.15 s^4 + 189.8 s^3 + 341 s^2 + 270.6 s}$$

However, using MATLAB and feedback(T*C,1), we get the result of ...
$$2.38 s^2 + 19.63 s + 38.65 \over s^3 + 6.38 s^2 + 26.63 s + 38.65$$

I already realize I can take my CLTF in MATLAB, put it in pole/zero (zpk) and things will cancel to get the same result as MATLAB's feedback command. However, no symbolic program seems to be able to factor these polynomials. MATLAB is clearly doing something I don't know about then. Does anyone have a clue how matlab's algorithm works? Or how I could code this same function?


texts:
I am trying to understand how the circuit shown below works. More specifically,  I am trying to understand how the comparator outputs only 0 or 12V. (the circuit is from this paper.

Without the 2.2K resistor connecting +12V to the output, I think you have, for the output, +12V if VB>VREF and -12V if VB>VREF.

I am not sure what's going to happen with the resistor in place.

Naively, I am thinking there is no current from the +12V source to go. So the voltage after the 2.2K resistor should just remain at +12V ?


texts: STM32L0 series current consumption oscillation

texts:
I'm working on a low power project that my micro-controller can only have 1 mA in 2.7 V.
My micro-controller is STM32L051C8 and its works nice with its peripherals (ADC and Timer) and its current consumption is about 0.65 mA.
But After working for A few minutes the current consumption Suddenly jumps to higher numbers(about 2 to 8 mA !!) and coming back to 0.65 mA after seconds and again it works nice for A few minutes and  this chain continues irregularly .
I'm working with STM32L031 before and have the same problem. you guys think what is the reason ?


texts: If I have a bipolar stepper motor driver (currently based on a L293, but I may be switching to a A4983) and I would like to control two 4 wire bipolar steppers from it (but not at the same time and the speed of the switching is irrelevant), can I just use a DPDT switch or relay to switch 1 wire of each pair between two motors on the output of the driver ?  Apart from just using another driver per motor, are there better options here?


texts: Calculating resistance when ohm law has no response

texts:
I have a 3v DC source and a 3v light emitted diode, i want power this led with just 5 mA .

There is a formula :
R = V/I

But in my case V is 0

V[source] - V[LED] = 0

So R is 0 always!!!

How can i pick a true resistor?


texts:
I have been trying to test an 8Ω speaker, but I am having some difficulties. I have tried to test the circuit using multisim using the circuit below:

I used the 8Ω resistor in the place of the 8Ω speaker in the circuit. When simulating, I get about 106mA, which should be enough to power the speaker. However, when I built the circuit on a breadboard, I did not hear anything from the speaker. Should I be using an AC voltage source instead of a DC to power the circuit? Am I doing something else wrong? Can somebody help me troubleshoot this circuit please?


texts: Difference between cutoff frequency and break frequency

texts:
what is the difference between cutoff frequency and break frequency?
Maybe the first refers to the attenuation of the frequency response module of a \$\frac{1}{\sqrt2}\$ factor compared to the maximum value of the frequency response module? Whereas the break frequency refers to each point of the frequency response module in which there is a discontinuity?

Thank you for your help.


texts: Is it feasible to use both MCU UARTs if it only has two?

texts:
I love STM32 nucleo boards and they have tons of UARTs. Now want to use two UARTS for protocol conversion (rx at 115200baud, tx at 38400) on a stm32g0316 discovery board that has only two UARTs.
How would I be able to connect the debugger (ST Link) that is using UART as well?


texts: What decides the position of Hall Sensor in BLDC motor

texts:
I know that there will be there hall sensors in a BLDC hub motor. They are placed in such a way that they could detect the poles of the rotor magnets, and two of these sensors always read one pole while the other contradicts. But how is it engineered to place these hall sensors. What is the mathematical calculation behind it?

Or

Is it just trial and error?


texts: Probing With Multimeter Breaks LED - Happened Twice

texts:
Qucik background info:
I am using a 117 Fluke, brand new bought in 2020 from Amazon.

What happened/happens:
This is a very simple circuit, but for some reason the resistor keeps heating when I try to use red LED's which are rated at 0.007 Amperes, so I tried to check the current going through the resistor, which caused the problem.
The LED simply goes out, and it won't turn on again. I tested this with a white LED also, same problem.
I can test the LEDs fine, and they show 0.0087 amps, which is fine, but the second I touch the resistor it burns up.
Does anyone have an idea, why this happens?


texts: Is it Possible to Control Vehicle Key Fob/Remote Start with arduino board?

texts:
Curious if there are any projects out there in which someone controlled a remote vehicle starter with an arduino board.

Specifially, I am considering a method to start my car at a preset time every morning.

I am thinking it would be easy to wire up an arduino to the Remote Fob itself and send the signal to start at a set time (I am an arduino noob and have not done anything but basic tutorials with a small Teensy board).

My specific system is two-way and sends back a success or fail signal after you attempt to start, would be nice to program the system to try to start X number of times after a failure.

Has anything like this been done? Anything similar?

UPDATE:

There seems to be some confusion...

My vehicle already has a viper 2-way remote start system installed.

I would like to wire one of the existing key fob remotes to an arduino board to control the remote itsself(which sends the signal to start the car).

I do not wish to wire anything additional into the car. Basically just emulate the press of the remote button via the microcontroller.

Pics of the FOB pcb:


texts: Why does the measured current differ from the calculated current in this circuit?

texts:
I have the following schematic:

Now I want to know the (more or less) exact current flow in my circuit. For this I did the following calculations:

I = V / R

I = 5V / 330 Ohm

I = 0.015A = 15mA

So with what I now know I expect approximately 15mA to flow across all the wires. However, when I try to measure the current flow by placing my multimeter (in series) between the LED and the resistor I measure I = 9.4mA.

This difference of 5.6mA between the calculated 15mA and the measured 9.4mA seems too large to be due to manufactering deficiencies of the parts of the circuit. Therefore I assume I am making some error in my assumptions/logic, but I cannot figure out what. Can someone help me with this?

Thanks in advance.

edit

As per comments/answers I measured the voltage over the LED and the resistor:
-  Resistor: 3.18V
-  LED: 1.94V
Also the resistor's actual resistance:
-  325 ohm

Now the calculation indeed does make sense:
3.18V/325 Ohm = 9.8mA
Which is close enough to the measured 9.4mA.

Thanks everyone for helping out!


texts: replacement or equivalent material for toroid core inductor

texts:
hi is there any way i can replace toroid core from the circuit?.

there is this circuit which requires a toroid core inductor to function. a toroid core AL=25 with 6 turns of wire. for i know i can get the inductance value required to it from this formula, n=1000[sqrt(L/AL)] . and make an air coil inductor out of that inductance value. but i am not sure if it would really work as toroid cores do since the author of the circuit says the circuit wont work without toroid core.

and also, if an air core will be use with a very thin magnetic wire (AWG 30), can i use stick glue around the coil to support the coil?.

toroids here in our local electronic stores are not available thats why i cant provide it in my circuit.. any help with this would be much appreciated. thanks.


texts: What's the tradeoff of amplifing the output of an inverting op-amp in software vs using a higher feedback resistor?

texts:
Suppose I have an inverting op-amp (part of a trans-impedance amplifier circuit) that gives me a slightly-positive-but-small signal, and the output goes into a ADC. I have two choices:

Increase the Rf (feedback resistor) value which should amplify the output.

After recording from the ADC, use software to scale the value to "look" like I amplified by Rf.

Is there any difference between these two scenarios?


texts: Liquid throughput hall sensor giving odd number of pulses plus only works in horizontal level

texts:
I'm an IT guy, but have lately started working more and more "on the edge" as we say, so close to the real world and with low level sensors. I'm currently building a liquid throughput sensor and reading it with a raspberry pi to send it to a server.

These are the specificiations for the sensor:

2500Imp/L at 20°C
0,05 - 3L/min
using a Hall sensor principle

The link to the product would be this FCH-m-POM-LC

I can read the pulses using a pull up resistor at the signal with 3.3V and 2kOhm. But there are two problems:

when I squeeze 60ml through a syringe into the sensor I get about 300pulses == to 120mL with a deviation of about 10ml (tried 10 times) did I calculate something wrong? I'm listening for "falling edges" so I count every time the voltage drops to 0V
It often doesn't work and if it works, it does so best when in a horizontal axis, so reading pins up, liquid in/out on one level. Is this normal for these flow sensors?

as you might be able to tell I'm used to software, not hardware so treat me like a first year engineering student if you want.

I'd greatly appreciate your help!
Greetings from Germany

P.S. its for a cow milking battle where we want to have several participants milk a fake cow and see who's the fastest. We want to measure on a 1/10sec precision and visualise the data throughput/second for 120seconds

I created an image of my setup. however I used 5x 10k Ohm resistors in parallel since I don't have 2.2kOhm Resistors.


texts: Using a Non-Inverting Buffer for Level Shifting

texts:
I've got a project that involves a 5V Arduino and a Raspberry Pi Zero (3.3V) that need to communicate through a serial interface. The easy solution here would be to connect them through USB, but I'll be using an Arduino pro mini type board, which does not have a USB to serial adapter and thus does not have USB. So I'll be connecting them directly, but I've heard the Raspberry Pi does not like getting 5V through its serial pins, which means I've got to have a level shifter (at least on the Arduino tx to Pi rx line).
I have a few hex non-inverting buffers (the CD4050BCN), and from what I understand, if I have VDD set to the Pi's logic voltage (3.3V), it will only output a maximum of 3.3V. Then I can connect the Arduino's tx pin to VIN of the non-inverting buffers to ensure the output will be 3.3V at most.
Am I not understanding part of this? I just want to make sure--I don't have much knowledge of electronics past basic microcontroller wiring.


texts: I need to design a Bias-T circuit for a diode laser - help choosing component values

texts:
I need to modulate a diode laser with a RF source. I've found parts on Minicircuits that can do this, but I'd like to have the Bias-T and amp on my own PCB. So, I need to design a bias-T circuit that will mix my constant current source with the RF source to drive the laser.

I'm having a hard time choosing the capacitor and inductor values for the Bias-T, since I don't know the load impedance of the diode laser. How can I find this out? Would it just be better to put a 50 ohm resistor in parallel with the diode and then design the Bias-T for a 50 ohm load?

Update: After some thought, it seems reasonable to use the I/V characteristics of the diode, after turn-on, to approximate the resistance. This yields a very low value - 5-10 ohms. This, however, doesn't approximate the load while the diode is off - I assume this would be very high. But, the purpose of the Bias-T would be to bias the diode so it's always on, so I presume just the on characteristics would be sufficient. Sound reasonable?

Update 2:  My design needs to supply ~200 mA to the diode. It's a 405 nm diode, so the operating voltage is ~4-5.5 v. I have a wide bandwidth, so anywhere from a Fc of 5 Mhz to 50 MHz will probably work. My transmit bandwidth is about 2 MHz.


texts: a basic question regarding power electronics

texts:
I understand electronics deals with mainly low voltages, while electrical engineering generally deals with high voltage. Now if we take this as the main difference between the two , where do we put power electronics? Is it a branch of electronics or electrical ?

Also I have seen in many universities power electronics is not taught in electronics engineering courses but definitely in electrical engineering which means it is electrical engineering.

So is there a definite/near definite answer to my question? If yes what is that?


texts: I've seen many lighting circuits protected by 100mA ELCB instead of 30mA, why is that? isn't 30mA safer?

texts: I've seen many lighting circuits protected by 100mA ELCB instead of 30mA, why is that? isn't 30mA safer than 100mA?


texts: Set of Gerber layer files (*.GBO, *.GBP, ...) and how to merge them into a single file in Ubuntu

texts:
I'm new to electronics and PCB projects, but I would like to be able to print a board for the following (so-called) power board:

Here's the project: https://github.com/mlab-upenn/f1tenthpublic/tree/master/power-board-v2.0

My understanding is that, for example, this site: https://jlcpcb.com/ needs a single Gerber file (a "quote"?), but I haven't found any instructions on how to create this file in Ubuntu.

I would really appreciate your suggestions.


texts:
I wanted to check something I was working on, and it's an assignment so I don't want the answer, I just want to know if I am approaching it right.

I have an esaki diode. I have a curve (the s-curve that shows Voltage in vs. current. I am trying to figure out how to get 2 stable operating points, with a simple voltage source connected in series with a 250 ohm resistor. I know to calculate a load line, but for some reason I am not getting answers that make sense (I can't seem to get a lad line that intersects the curve that gets me two stable points unless my Vin is zero).

Any pointers? I am using the relation Vin = IdR + Vd, but I am not sure if that even applies here. I just want to see how to figure out how much voltage i need to bias the diode.

simulate this circuit – Schematic created using CircuitLab

edited to add schematic


texts: How to make linear actuators go in both directions? (Using arduino/microcontroller)

texts:
I'm stuck here,

I want to make the lineal actuators to go up and down,  both of the actuators move to the same direction at the same time.

The arduino receives a signal as input and then the ouptut of the arduino activate the lineal actuators through the mosfet.

For the moment I think my circuit works but only for go in one direction.

Could you help me with some ideas of how to make the motors go in both directions?

I was thinking in add a second ouput in the arduino , one for up and another for down, but I need to go deep to know what is next..


texts: Meaning of current in voltage regulator of power supply

texts:
I have a 5V power supply, I also have a chip that its VCC input is 3.3V, the chip datasheet doesn't specify any information about the current needed in the VCC pin, I want to use a voltage regulator so I can use my power supply to power up this chip, The voltage regulator specifies current limit, I'm not sure what it means because I only need voltage to power up the chip (or do I?), Does current mean anything in this situation? In what situation the current of a voltage regulator will mean something?

Thanks.


texts: Issues in schematic of Microchip LAN8720 & waveshare LAN8720?

texts:
For a project I need to integrate Ethernet with PIC32MX795F512L. For this I had two choices. I thought of purchasing this Waveshare LAN8720 module and directly using its pins to the pins of MCU or using the LAN8720 IC provided by Microchip and design the circuit.
I looked at the Schematic of wavshare board and the schematic of LAN8720 IC provided by Microchip and found a many difference in the schematics of both so thought of raising the question.

If we look at the schematic of waveshare, PIN 14 which is nINT/REFCLK is not pulled up to 3.3v whereas in Microchip schematic it is pulled up to 3.3v.  Also the RXD1,RXD0 are not pulled up to 3.3v whereas in Microchip schematic it is pulled to 3.3v. Resistors R11 R12 R14 have different value if we compare it to Microchips schematic.

I am planning to purchase the waveshare module and use it in the project. Will it work properly given the conditions above.?

Need help. Thanks.!


texts: Aircraft Airbus 320 has two 110/220v 400 hz 90 kva generators, run by two engines. There is an electronic display in the aircraft that also shows the parameters of the electrical system. One of the parameters is 'load'. Shown in percentage for both the generators separately. It's value is about 26% most of the time.  Can anyone please explain to me what this load is?   Thanks in advance


texts:
What happens when Vce=0V and when Vce=-1V?
In the Ic-Vcb characteristic graph, most of them shows around Vcb=-0.4V.
So if Vce=0V(i.e. Vcb=-0.7V) and Vce=-1V(i.e. Vcb=-1.7V) what happens?


texts:
The electric strength test OR dielectric withstand test OR HIPOT test voltage level as specified in EN 60730 standard works out to be 2860VAC for a class II radio product I am developing. The PCB has an isolated switched mode power supply with a 2n2F Y-cap bridging the primary and secondary for radiated emissions control reasons. The PCB also has an SMA connector that sticks out of the plastic enclosure making things difficult.

The product fails HIPOT testing above 1600VAC! Remove the Y-cap and it passes at 2860VAC. I narrowed the failure down to the reactance of the Y-cap and through iterative trials, got a pass at 2860VAC with a Y-cap value of 100pF. However, this caused the product to fail radiated emissions. Following this, I did some research and found several articles advising that you can either remove the Y-cap for HIPOT testing or use DC-equivalent voltage which in this case will be 4044VDC (2860 * 1.414). I tested at 4044VDC and got a pass with the original Y-cap of 2n2F.

I went back to the 60730 standard and found in 'notes' that in fact you can remove electronic components that may render the test impractical and also that a DC potential equivalent to 1.414 times the test voltage may be applied.

I am not convinced because in a real-life scenario in the field where an overvoltage of 2860VAC appears on the power supply, a person who is touching the RF connector could potentially get a shock rendering the product unsafe. So, what is the rationale behind product approvals standards advising removal of Y-cap before HIPOT testing or using DC voltage to get a pass when in fact in practice, a high potential AC overvoltage could appear on power lines and pose the risk of electrocution? Am I missing any key principles?

Many thanks in anticipation of your help in understanding the issue.


texts: Voltage regulator - unexpected voltage drop, is this normal?

texts:
I am using this voltage regulator.

Following this example:

For input power source, I am using old SATA convertor power adapter, which produces 12V 1.5A max (I tried various power supplies, all similar result).

With no load, everything works as expected, instead of R2 I have potentiometer 0 - 5k OHM. I can easily configure any voltage range from 1 to 10V using the potentiometer.

The problem happens when I connect any load. My understanding of voltage regulators is, that you can configure them to provide certain voltage, and they will hold it as long as you don't exceed the maximum current they can provide (3A in this case). But that isn't happening in my case.

I connected Vout to a simple (strong) LED light, that draws 0.2A at 4.5V just to test it out, and while the LED is working, the Vout immediatelly dropped down to 3.3V (Vin also dropped from 12V to 11.5V, but VR should provide same Vout no matter of Vin according to manual, as long as Vin is at least 1V higher than required output). Measured Il was max 0.2A, never more than that.

Is this a normal behaviour? Why is VR not capable to provide stable voltage on output? I would like to use it to power some USB device, which expects stable 5V output, this doesn't seem very stable to me. My expectation is that it will provide stable Vout as long as I don't exceed 3A Il.


texts:
I would like to turn on a 100W LED using a switch. However, while the LED turns on the switch has no effect. What's wrong with my simple circuit?

My 12V and 30V grounds are connected to each other to be a common ground. I'm using an IRF4905 P-type MOSFET.

Does it have something to do with the Vgs?

Thank you!


texts: I use a STM32F407ZET6 microcontroller. I make the connection and data transmission from the microcontroller to the computer through a USB network. I am currently facing some disconnection issues. Sometimes the USB connects and then disconnects. The circuit I use is below. Reading in some places I realized that if I took out the resistors R345 and R346 could perform better. By removing the resistors the connection has improved, but with some cables the continuous error (seems to be with the line impedance). I already tested on USB 2.0 and 3.0 ports and the error happens in both cases. The firmware I use for USB connection is provided by ST itself so I think it is correct. Could anyone tell me if the circuit below is correct or what could I do to stop disconnecting the USB?


texts: has anyone ever attempted to measure servo torque using current? Basically if you have a robot you want to detect stall state and approximate force being applied.


texts: Drive H-Bridge using analog signal instead of pwm?

texts:
Is it possible to drive an H-Bridge like the L298n using actual analog signals rather than digital PWM signals?

If not, what would be the equivalent to an H-Bridge that allows for this?


texts: Electronic schematic of 7408 and 7432 logic IC

texts: How are these schematics different from the traditional BJT logic gates that we learn in high school?  Schematics:AND GATE and OR GATE.


texts: How to delete a file from memory using FATFS library

texts:
I want to use elm-chen FATFS library to delete a file from memory. this link. But I do not see any functions to delete a file. Is there a way to delete a file from FATFS using this library?
Thanks

Edit. I found the remove file in the full version library. The limited version does not contain the remove feature.


texts: Power and current contradictions in transformer secondary

texts:
Two contradictions that I couldn't find a solution for regarding a transformer:
For an ideal transformer, from conservation of energy we can say that:
V1 * I1 = V2 * I2
Where V1, I1 are the primary voltage and current, and the same for V2, I2.
Now, let's assume that we connect an AC voltage source, V, in the primary, and the winding ratio is N. The secondary is connected to a resistor.

The power dissipation on the load is (N * V)^2/R.
So, it appears that I can change however I want the output power by changing N and R.
(a) How come? Will increasing N will increase the power? But the power in the primary side stays the same, no?
(b) Furthermore, V is given by the voltage source. the secondary sees N * V. Therefore from Ohm's law the current in the secondary is I2 = N * V/R.
But from energy conservation we also know that I2 = V1 * I1 / V2
Is changing the resistor in the secondary changes the current in the primary?
The second contradiction is what happens when the secondary is open circuit.
We know that the power on the primary is V1 * I1.
But the secondary is V2 * 0 = 0.
How does the energy conversation holds true? V1 * I1 = V2 * 0 = 0?


texts: I have been taught right from highschool that a conductor can charge through conduction, induction and friction. Yet a lot of physicists challenge me that a conductor cannot store charge? Who's right and who's wrong?


texts: 20 Amp automotive thermatic fan PWM controller

texts:
I have an older car which tends to over heat in the summer, so a 20 Amp electric fan was added in front of the radiator. Currently its driven by a on / off relay.

I want to build an Arduino PWM controller but I am not confident switching that much current especially in an automotive environment.

Been testing the VNP35n07 MOSFET but I dont think I am doing it correctly. When tested in the on state there is a noticeable difference in fan speed (noticed via noise) and the draw is about 1 amp less. Understand there will be lose from the MOSFET, but should it be that high?

The wiring for the test is as follows:

VNP35n07
Pin 1: +5.5V
Pin 2: Fan's ground wire
Pin 3: Ground

My intention is to connect the Arduino PWM signal directly to pin 1.

Any feedback / comments welcome.


texts: Is a line to ground fault always 3 times the zero sequence current?

texts: I'm a little confused, I was provided the 3IO current and I was under the impression that is the bolted 3 phase current but now I am suspecting that it is 3 times Io which is the zero sequence current. My question here is, can I always assume that the single line to ground fault current 3 times the zero sequence current?


texts:
Assume you have a DC voltage V, ideal switch (no switching losses) operating at some frequency f and duty cycle D (in [0,1]), and a purely resistive load R.

If you double V and halve D, does the average power dissipation double?  I.e., does the average power dissipation always equal the integration of the instantaneous power dissipations, as follows?  $$ P_{avg}
= \int_{0}^{D} \frac{V^2}{R} dt = \frac{V^2}{R}D$$
Or is there some "practical" frequency (e.g. 100Hz, 10kHz) at which the heating due to current averages out enough such that the following holds? $$ P_{avg} = \frac{V_{R\_avg}^2}{R} = I^2_{R\_avg} R $$
I saw the following post, which mentioned that at "high enough" frequencies (e.g. 20kHz), the "thermal time constant" of a resistor filters out the instantaneous heat dissipation: https://www.edaboard.com/threads/resistor-power-dissipation.176648/post-742416
If this applies for resistors, does it also apply to the ESR of inductors and capacitors?
Thanks

Edit: So my understanding after getting responses is that P_avg (power drawn from the supply) always corresponds to the first equation.  However, the thermal effects on the resistor (or any device passing current) may not be as non-linear (i.e. more in line with the second equation), presumably due to the fact that higher instantaneous "heat surges" in the device will more quickly equilibrate than a constant heat due to some non-linear conduction phenomena.
So one should always use the RMS (not the average) voltage or current, not the average for calculating power dissipation, as also shown here: https://masteringelectronicsdesign.com/how-to-derive-the-rms-value-of-pulse-and-square-waveforms/


texts:
Gain in feedback system is defined by:
\${V_{out} } /{V_{in}} = A / (1+Af) \$

We have a pole when \$|Af|=1\$ and \$\angle Af =-180\$

Any complex number can be expressed as \$z=r(cos \theta +j\sin \theta)\$

But when \$\theta=180 or -180 , cos \theta=-1\$ in both cases and sine is zero.

So why in the definition, it says the phase is \$-180\$ deg not positive \$180\$, to me both yield the same result.


texts: Question About Computer History in Germany

texts:
I asked this question on the German Stack Exchange, but was told that the EE site might provide better feedback. So, I have a question about a statement on a device produced in West Germany in 1965. I have the original German translation below, along with my own translation.

What is meant by "simulation" here? How could a simulation of a Siemens machine be achieved? Was it a remote simulation? Time-sharing wasn't used very often then.

  Gruppenschulungsgerät für verzweigende Programme bestehend aus einer zentralen Steuereinheit (bzw. deren Simulation durch den Prozeßrechner
  Siemens 303 P)

  Group-training device for branching programs consisting of its central
  control unit or its simulation by a Siemens 303


texts: how to vary the threshold voltage of a MOSFET for simulation in LTSPICE

texts: I have a MOSFET circuit with multi-threshold voltages. I am using TSMC MOSFET with 180nm technology. How to specify these voltages in LTSPICE for simulation. Please help.


texts: How do they integrate logic into a DRAM process while manufacturing SDRAM?

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When SDRAM is manufactured, how do they integrate logic into the IC while they are using a DRAM process for fabrication?
Because SDRAM requires logic to decode its inputs, do the burst ordering, etc.
(DRAM too - though it has less logic)


texts:
simulate this circuit – Schematic created using CircuitLab

This is for Full Bridge MOSFET driver. Switching Frequency is 400KHz.
Hardware is running as expected. Only thing i cannot understand the role of R1 & C1.


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I have a PC that controls some equipment, such as, cameras, solenoids, and DACs. There is also a 45KW nitrogen laser.  The laser has its own service installed, but, when it turns on, there is a voltage spike that disrupts the USB devices on the PC. The PC is on a surge protector, but the spike still affects the PC in this way.

When this happens, shutters open, and the general operation is disrupted.
One option is to avoid the issue, and shut down the PC, power on the laser, and then turn the PC back on. This works well, but is tedious.

I have talked with the building manager, and he will not take any measures to improve the quality of the electrical services available (such as hire an electrician to install a Whole-House Suppressor).

I am looking into putting ferrite beads on the existing USB cables, but those have not arrived yet. Are there other options for noise suppression of this nature?


texts: VHDL 2008 fixed and floating point type synthesis support?

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Which VHDL synthesis tools support the VHDL 2008 fixed and floating
point types as described at vhdl.org/fphdl? The
VHDL.org site states "all these packages are designed to be synthesizable in
VHDL-93".  Which tools have yield successful results synthesizing the
VHDL-2008 fixed-point and floating-point types?

Second question, what is the status of VHDL-2008.  Has it been ratified?


texts: Determining correct requirements of Instrumentation Amp in measuring large current shunt

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I'm trying to plan out a project of measuring large currents from my car battery through a shunt, and specifically I need help with the INA.

I bought this Deltec 250 amp shunt from eBay, that looks to be rated for 250A in short pulses, and 165ish continuously.

My plan is to hook it in series somehow with the car battery and use an INA to measure the voltage across, which peaks at 50mV for 250A

I've read a good deal about instrumentation amps, but I'm still confused on what specifications I should pay the closest attention to.

CMRR? Do I need to somehow detect if there is a common mode voltage near the car battery from a noise source?

Voltage input offset?
Voltage error drift?

Also, there are so many specifications/choices that I'm totally unsure about what would be deemed effective for this project.

I'm also in the process of extensively reading through Analog Device's Designer's Guide to Instrumentation Amplifiers, here, which is fantastic, but I would certainly appreciate any help or input on how to do high current measuring, specifically of a car battery, still in the car.

For example, here is a page from the aforementioned AD guide.

The selection is huge.  How do I know what CMRR is good enough? 70dB? 80? 90? Or the input offset? 1mV? 500uV? 50uV? This is a major confusion of mine and hints at my lack of experience with practical design.


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I have been always using bridges with vias. I gues that doesnt hurt but recently I though is it really necessary?

I know that they're purpose is for the soldering process to be easier, otherwise it would be very hard to heat up the ground plane. But with vias, nothing is being soldered to them, they only connect layers.
My question is, should one use bridges for GND vias?
I would appreciate all help.


texts: 12v on/off switch to toggle state of two circuits

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I have an existing latching button switch that controls a low power LED (no more than 1W) from a 12V power supply.  I'd like to add an extra circuit to the same power source that is controlled by the same switch, the other circuit will consume more power (up to 80W).

I'd like the on/off applications of the switch to cycle the on/off state of the two circuits as follows:

Switch mode             Circuit 1         Circuit 2
Off                     Off               Off
On                      ON                Off
Off                     Off               Off
On                      Off               ON
Off                     Off               Off
On                      ON                ON
(and repeat the cycle)

I'm not clear what I am looking for to achieve this desired effect, is there something off the shelf that can be used to achieve this and wire to my existing switch?  If not, what should I be searching for to breadboard up a suitable prototype? As an aside, I'm not 100% sure the switch can handle 80w throughput, which may be one consideration.


texts: How should i charge 3 lithium ion batteries?

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I'm new to battery charging and I was wondering. What is the best way to charge and manage 3 18650 cell batteries? The load is about an amp and I have a 3.7 amp power supply to charge them. I'd like to be able to charge the batteries and also power my device.

I plan on using the batteries in series, i'm aware that i need to use a 3S balance board, and a constant current converter to charge them, but is it safe to draw power from the batteries while charging? and where do i connect the load to?

Thanks for your response!


texts: Designing a breakout for crenellated (castellated?) pads

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I am brand new to PCB design, so far all i've made a simply 555 timer circuit with an led, a few resistors, a capacitor and a 555 timer and got it printed by OSHpark.

That was my first experience getting a board printed and with pcb design and i used it as warm up.

I am trying to design a PCB breakout board for this, the xs3868 mega-cheap chinese knock off bluetooth module. Here is the footprint, in case its not clear i only want to design footprints for the tiny squares on the upper and lower sides, the center area is just other junk on the board.

I was wondering if there was any advice for creating this. Can i use one of the footprint wizards or would these types of pads not really work for that?

Thanks for the advice!

P.S.  I am pretty sure these are called crenellated pads but i have heard others call them castellated pads, so i just put both in the title.


texts: How can I prove that the NPN BJT is in the active region?

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I created the following circuit using a npn transistor.

simulate this circuit – Schematic created using CircuitLab

After measuring all the voltages, I got: \$ V_{BE}\approx 0.6V, V_{CB}>0 \$. Are those measurements sufficient to say that the transistor is operating in the active region? How can I prove it theoretically?

Also, I'm looking for books/websites/documentation containing different transistor circuits and the explanation of their function. If someone could help me, I'd gladly appreciate it.