texts: Passive Convention for current flow direction

texts:
I understand that passive convention in circuit analysis is when current flows in through the positive terminal of a resistor, thus indicating that the element is absorbing energy as shown in the diagram below. The value of the current is also positive in this direction.

However, if the direction of the current in the above diagram is reversed, it is no longer obeying passive convention and the value of the current would be negative. Does this now mean that it is supplying power to the voltage supply? If so, doesn't it still have to absorb power while the current is entering from the negative terminal of the resistor?


texts:
I recently took apart an HP LaserJet 1320 laser printer to salvage parts from it. Along with 3 solenoids, a fan, lots of gears, 83 springs, and 71 feet of wire, I got a large brushless DC motor with an integrated driver board with the part number RK2-0419 made by Nidec rated for 24V at 1.3A. Since I could not find anything useful by looking up the part number, I decided to look up the driver chip on the board (BD6761FS) and I found a datasheet. The connector on the motor has 5 wires: Vcc, FG, /DEC, /ACC, and GND. Going off of this EE Stack Exchange question about a similar motor salvaged from an HP printer, I decided to connect 24V from a switched-mode power supply capable of supplying 1.75A to the Vcc and GND pins of the motor. The motor immediately started drawing 28 milliamps from the power supply and the driver chip got slightly warm. I did notice that the motor shaft was very hard to turn by hand when power was connected. Following the datasheet and the previous Stack Exchange question, I connected the /ACC pin on the motor to the ground on my power supply. The motor did not move and still only drew 28mA. Nothing happened when the /DEC pin was grounded, along with grounding both the /ACC and /DEC pins.

How should I get the motor to work?


texts: Error: HDL Compiler : 1660 : Procedural assignment to a non-register big_mant is not permitted, left-hand side should be reg/integer/time/genvar

texts:
In the lines wherever I try to do the assignment of value, the above error pops up. Please tell me what's the mistake and guide me with the corrected code snippet.

`timescale 1ns / 1ps

module big_small (

input [3:0] mant_A,
input [3:0] mant_B,
input [3:0] exp_diff,
input exp_diffsig,
input mant_diffsig,
output [3:0] big_mant,
output [3:0] small_mant
);

always@(*)

if (exp_diff == 4'b0000)
begin
big_mant <= (mant_diffsig)? mant_B: mant_A;
small_mant <= (mant_diffsig)? mant_A: mant_B;
end

else
begin
big_mant <= (exp_diffsig)? mant_B: mant_A;
small_mant <= (exp_diffsig)? mant_A: mant_B;
end

endmodule


texts: How does this logic level converter on the Adafruit HUZZAH work

texts:
I am busy with a project where I am connecting a 5V(Amtel ATMega328) MCU to an 3V(ESP8266) via the serial port. Obviously I need some logic levels converted. I looked at the schematics of several open-source ones on the market to gain a understanding of how other people tackled this problem. On a side note I did build a voltage divider circuit just to start on something basic(just want to be sure I get the concept).

So I reviewed the FreeTronics logic level converter that uses a BSS138LT3G for logic level conversion. This makes some sense as it appears that this design is using a transistor with a low drop out to convert between voltage levels. You can find the schematic for  freetronics logic level converter here.

I then looked at the Adafruit HUZZAH schematic board expecting to find one of the following components a voltage regulator or a MOSFET transistor or voltage divider of some sorts. Well I found the voltage regulator SPX3819 on the board but then I realized the serials pins where not using this at all...

When I studied the schematic I found that a 1N4148 diode was connected to the FTDI RX(receive) pin. I never realized you could use a diode this way(I am learning). So since this is a high speed diode it obviously causes a voltage drop from 5V to around 3V by the high speed switching almost like a PWM function would(Educated guess could be wrong). It seemed simple and elegant but then I noticed that they did not do the same on the FTDI TX(transmit) pin.

So at this point I am confused why would you convert a 5V input to the RX pin to 3.3V and then not convert it on the outgoing pin. Surely a serial port cant accommodate both voltages unless it is specified to handle it. Send 5V and receiving 3V just felt wrong.

Now I am speculating at this point but from my understanding, serial data transmissions are essentially bits being transmitted. A 5V being on and 0V being off. However I don't think that is realistic. How can I always have a 5V and 0V with components heating up, resistance variance and all the other factors in electronics? I suspect this designs works because 3V is above the 2.5V mark and the AMTEL MCU reacts to this voltage level like it was ON/1/YES bit being transmitted.

Now if my theory holds are there any risks with doing serial communications between an AMTEL chip and ESP chip via serial this way?

Or maybe I am just mad and missing something very obvious.


texts: How can I confirm that the transformer is broken?

texts:
My Pioneer amplifier (>15 years old) cannot power-on anymore. When pressing the On-Button, you always hear a relay toggling in an endless loop.
So, I got the datasheet (containing the schematics) and started to search and measure:

The voltage from the both green points to GND at the left side is nearly 0
Also the relay (blue circle) is the one that makes the toggling sound (on-off-on-off-....)
Since there is something wrong with the power supply, but the voltages at the points are nearly 0, I assume it is the transformer (red circle) that is broken.

What do you think? Is there any way to confirm 100% that it is the transformer?
Reason, why I want to avoid trial and error is that the transformer is really expensive (80 $). So if I order a new one, I just want to be sure.
Any help appreciated!


texts:
i am still new to electronic and i probably have a stupid question..

i am trying to build a buffer for a piezo microphone following the project on this site:
http://www.scotthelmke.com/Mint-box-buffer.html

but now i am wondering how to make the input of this circuit balanced, to connect two piezo mic in a coupled structure like this http://www.instructables.com/id/Balanced-piezo-contact-microphones/

is it possible to modify this circuit ? or do i need something new ??
thanks ! :)


texts: Chosing a package is according to different matric?

texts:
I need some part with package 0402 .
Looking at Mouser.com, the only packages I get for this part are "0402 (1005 metric)".

I then check the size of it and its not 4x2mm but  1x0.5mm.

For example this inductor that I need in 0402 .

How do you make sure its 0402 ? why there is no 0402 for inductors ?


texts: How to programm AVR ATmega48 in TQFP32 soldered onboard?

texts:
I have a board (actually - many of them) with ATmega48PA (TQFP32) soldered in and no ISP connector. Some of the ISP lines are even not routed.

I used Hobbyking programmer to connect to the processor in the past:

I have had two of them. And I felt my self comfortable with it. However I broke one today and find out that it is not possible to order this connector again.

Now I desperately need any solution which could help me. Processors are already soldered on the boards and it will be a nightmare if I will need to unsolder and flash it separately.

Is there any ideas?


texts: Peltier thermal electric generator power output

texts: I am new to the Peltier thermal electric generator scene and I am wondering if you could recover some of the electrical energy needed for the cooling of a refrigeration system by using another Tec as part of the heat dissipation by connecting the second Tec to a battery charger?


texts: Length of high voltage power transmission in different countries?

texts: Are there any databases containing some statistics of power transmission networks of different countries? e.g. length of transmission network for 380kV in Germany is 5000km. thanks


texts: What is the function and possible applications of a center-tap primary coil transformer?


texts: Is it possible to run a small circut off the power that is output from a unpowered headphone/speaker?

texts:
So I'm currently dreaming up my first PCB project! I would like to make a 1/4 audio switcher for my current audio setup (two outputs 1 input)
I'm fairly new to electrical engineering I'm about 3 years in but have a grasp on the basics from a variety of projects. However, I'm am unsure of the viability of this one and I don't know where to look for the correct resources on this.
My Idea is to power some kind of capacitor/battery that can then be stepped up to a voltage that can run a small chip like an ESP32 to handle the interactions. I then want to use Mosfets to switch the signal from one side of the output to the other. I was wondering if it was possible to siphon the initial power from the output of the headphone jack to charge some persistence circuit that will maintain this power; and or trickle charge an onboard battery without interrupting the audio stream after a while.
My main concern is that there wouldn't be enough throughput to start to process but I have no idea.
From my initial googles, it says the standard output of a headphone jack is about 100mW!
I'm looking to see if anyone can point me in the right direction for this project!
The ESP32 has a deep sleep mode the minimizes power consumption and Im under the impression that this might be possible just due to the fact that driving headphones must take some power. Worst case ill just add a USB connection but I'd rather not go that route.
If anyone can help it would be super appreciated I feel like this would be a great way to expand my knowledge of electrical engineering!


texts: How can picked up FM noise be demodulated?

texts:
I have a set of cheap computer speakers, which happens to use a TDA2822M. Its circuit is almost identical to the example circuit from TDA2822M's datasheet. It's USB powered and has no shielding.

I noticed a very faint audio coming from it, so I turned off the main breaker to reduce capacitively coupled mains hum (it's an apartment complex so this can't be fully eliminated) and plugged it to a portable USB battery. Then, walking around with the speakers, not touching the P2 connector to avoid more capacitively coupled noise, I could hear a faint, albeit very clear FM radio at regularly spaced spots, a few feet apart. I recognize the radio, it has the strongest signal in my town and operates at 105 MHz.

Outside, the radio couldn't be heard anymore. So my guess is a neighbor's radio feeding noise into mains and the speakers' wires acting like antennas.

What I can't understand is how could the speakers demodulate the FM signal so that it could be heard, since it obviously has no FM demodulation circuitry.

This answer mentions that "an FM signal will amplitude-modulate a tuned circuit", but it seems unlikely that the parasitic inductance and capacitance of the wires would resonate at that specific frequency. What am I getting wrong about that?


texts: "Logic Design" vs. "Digital Circuit Design"

texts: I'm aware that different companies have different definitions for job titles, but in general, is "logic design" the same thing as "digital circuit design"?


texts:
I am trying to make one H bridge for four identical motors. I do not want to make more than one H bridge by any means. I got a way to do that but I need your recommendation. I am going to make all the motors in parallel to each other so that the current, that comes from one branch in the H bridge, splits apart to all the four motors.

Specifications:

Each one of those four motors has the following features:

"Voltage:DC 6V
Current:120MA
Reduction rate:48:1
RPM (With tire):240

Motor Weight (g):50
Motor Size:70mm*22mm*18mm"

Purpose of use: Building a small robot that moves with 4 wheels.
Each wheel is with one motor.
Sounds a good idea? Tell me.


texts: Is it important that power supplies for LED strips have limited current?

texts:
I got some strip style LEDs [ link for the curious ], and would like to know if anyone can forsee complications hooking it up to a [very] high-amperage power source, namely a computer power supply. The computer power supply is supposed to maintain the stated 12V with good accuracy.

I'm planning to go ahead and try it, once it arrives, unless someone is reasonably sure I'll short circuit it.


texts: Should I immediately return MOSFETS shipped in non-ESD protective packaging?

texts:
Recently I ordered 100x IRLZ44N power MOSFETs through an eBay vendor based in the US. Today I received the package, and they were simply wrapped in bubble wrap and taped shut. This is obviously not proper packaging for ESD-sensitive parts like MOSFETs.

Should I immediately return the parts? Or should I try some and see if they work?

Thanks for advice. Below is an image of what the shipment looked like. On the left are the packages in question, and on the right is what I would expect for ESD-sensitive device shipping.


texts: Hall effect sensors for BLDC CW and CW positioning

texts: Hi I have just designed a BLDC controller and I have it running in both CW and CCW directions. I have noticed that when operating in CCW the motor is less noisy and more smoother than when operating in CW. I was wondering if the hall sensors need to be repositioned for CW operation or perhaps is there a requirement to use 2 sets of sensors, 1 set for CCW and 1 set for CW to make the operation more smoother?


texts: Recommended isolation paper for hobby circuitry

texts:
I'm having a hard time finding out what type of insulation is enough for my projects.

I will be building this: STM32 OLED Soldering Station Case Temperature Controller T12 KR BL ILS BC2 Handle Electronic Soldering Iron Tips 220v 70W

I'm wondering what type of insulation paper is needed for the metallic body, to protect the internal transformer and other bits.

This video shows what I'm going to be doing: https://youtu.be/25rww-pXqr0?t=5m39s

He states any insulating material is enough (0.3mm?). i'm wondering what is best bang for the buck so to speak. Looking at Aliexpress/Alibaba that is. I'm also planning to use the paper in a few other projects!


texts: To find the maximum power that can be delivered to resistor that is specified

texts:
I have to find out the maximum power delivered to a load which is already specified.

It would not have been a problem if the load was not specified. In that case, I could have used Thevenin‘s theorem and Rth would have been the load resistance for maximum power transfer.

But here internal losses is to be adjusted in order to deliver maximum power to the 3K ohm resistor. So, how can I solve the problem?


texts: Printing the temperature of a device in ngspice?

texts:
I had a simple netlist down here:

Example netlist
v1 1 0 dc 15
r1 1 0 5k
.end

Yes, I could just calculate the power lost in here which yield about 45 mW. But the thing is, is there a command for ngspice to print the temperature of certain a device?

I'm using ngspice-31.


texts:
Im building the following circuit:

Where the analog in is the non inverting input that with a potenciometer I can vary from 0 to -12V

The inverting input (with would vary from 0 to -16) is obtained from an amplifier (UN741) that should change depending on the output of the LM311, the "comp".

The problem is that no matter how I change the voltages values from my inputs I always get a output on HIGH or 5V and never on 0V even when the non inverting input is greater that the inverting input.


texts: If there was a "law/legal" stack exchange site I'd post it there, but it's in its infant stages in Area 51. I'm a musician and an electrical engineering student. I've designed a modification to the pickup system of my acoustic/electric guitar that I know some people within a certain circle would be pretty interested in. I've read a lot of complaints about the stock pickup system on electronics forums, and it doesn't seem that anyone has figured out a solution, so I thought I'd make a detailed video on the work I've done. To be honest there's not too much to it, but if I post some partial schematics of the part of the original preamp I've managed to reverse engineer, can that get me into legal trouble at all? I don't plan on marketing this modification at all; I just want to share what I've done.


texts: How do I interface a microcontroller with PC USB so that I can imitate the keystrokes and movement of keyboard and mouse. I've heard of software fixes, but is there any IC which can mimic the keystrokes after getting input from the microcontroller?


texts: How to choose optimum length for op-amp design?

texts:
I've heard that minimum length is discouraged in analog design due to matching problem but what's the drawback of using very long transistors apart from the size and resistance?

Based on the following design, where should device length be small and large? I think lengths at the input need to be small because high resistance is required in stage 1, but what about the current mirror? What about cascodes?


texts: Earth continuity of slot together aluminium enclosure

texts:
If I were to use a slot together aluminum enclosure for a mains powered device, and I earthed one panel of the enclosure by fitting a stud, how could I ensure continuity of the earth to the whole enclosure, in spite of the oxide layer?

From http://www.schaeffer-ag.de/en/products/housings/

Naturally I'd want to avoid using six earth studs, which would create ground loops in any case.


texts:
I'm using 2 x 1.8-Degree Nema 14, 35 BYGHW Stepper Motors with a DRV8825 Stepper Motor.

I have tried all 24 combinations of wiring the damn 4 wires but it won't work. I am using a 9v battery as the motor power source, which is fine.

It sometimes turns when I have 3 wires connected??

I can guarantee the wiring is correct, and this is the sketch.

Here is the code, which I am almost certain is correct too, I just started this project and I can't even get a damn motor to work!

/* stepper motor control code for DRV8825
 *
*/

// define pin used
const int stepPin = 9;
const int dirPin = 8;

void setup() {
  // set the two pins as outputs
  pinMode(stepPin,OUTPUT);
  pinMode(dirPin,OUTPUT);

}

void loop() {
  digitalWrite(dirPin,HIGH); //Enables the motor to move in a perticular direction
  // for one full rotation required 200 pulses
  for(int x = 0; x < 200; x++){
    digitalWrite(stepPin,HIGH);
    delayMicroseconds(500);
    digitalWrite(stepPin,LOW);
    delayMicroseconds(500);
 }
 delay(1000); // delay for one second

  digitalWrite(dirPin,HIGH); //Enables the motor to move in a opposite direction
  // for three full rotation required 600 pulses
  for(int x = 0; x < 600; x++){
    digitalWrite(stepPin,HIGH);
    delayMicroseconds(500);
    digitalWrite(stepPin,LOW);
    delayMicroseconds(500);
  }
  delay(1000); // delay for one second
}


texts: PIC32 having multiple PORTB's "high" at the same time

texts:
I am trying to set a couple of PORTBbits to "high" (1) at the same time
for that I am using the following code:
I am using thePIC32MX695F512H

#define MOV1A_IO TRISBbits.TRISB0
#define MOV1A PORTBbits.RB0
#define MOV1B_IO TRISBbits.TRISB1
#define MOV1B PORTBbits.RB1

#define MOV2A_IO TRISBbits.TRISB2
#define MOV2A PORTBbits.RB2
#define MOV2B_IO TRISBbits.TRISB3
#define MOV2B PORTBbits.RB3

#define MOV3A_IO TRISBbits.TRISB10
#define MOV3A PORTBbits.RB10
#define MOV3B_IO TRISBbits.TRISB11
#define MOV3B PORTBbits.RB11

int main(void)
{
    MOV1A_IO = 0x00; //output
    MOV1B_IO = 0x00; //output
    MOV2A_IO = 0x00; //output
    MOV2B_IO = 0x00; //output

    //while(1){
    MOV2B = 0xFF;
    MOV2A = 0xFF;
    MOV1B = 0xFF;
    MOV1A = 0xFF;
    //}
    return 0;
}

But what I get is this:

I would expect all 3 to be "high". Anyone knows what is wrong with the code


texts: Why does the intensity of light in LEDs not increase with current after a particular value?

texts:
I read in books that light intensity from an LED does not increase beyond a certain value of current.

The amount of light emitted depends on the combination of holes and electrons. If so, then as the electron flow increases in the circuit, the effective combination must also increase resulting in higher intensity.

But generally why doesn't this happen in a LED beyond a particular value?


texts: Writing a (signal level) micro-controller simulator

texts:
Last year, I created a circuit simulator in C# based on Quics. I split the project into front-end (written in C# WPF) visual editor to create and edit the circuit elements, and back-end (written in C++) to do the matrix computations of the Modified nodal analysis. The connection is data driven through netlist file.

Now I'm considering adding AVR microcontroller simulation support that can interact
with the rest of the elements in the circuit.

My problem is that I don't know how to do this in the current matrix formulation?

Note: What I want to achieve might be similar to this emulating 6502 of NES console. But the problem is I don't know how to emulate the IO's to work with the rest of the circuit.


texts: When scoping the CLK and DATA lines of a PS/2 keyboard it looks... rather odd

texts:
Normally if I look at a digital signal I see a nice, relatively sharp pulse train on the screen, but when scoping the outputs of a PS/2 keyboard things get a little weird and I'm not sure what it means (though I suspect it means I've got something to learn here!)

If I don't hook the PS/2 outputs to anything other than the scope I get a rather normal looking pulse train on keypresses... it's a little odd in that it seems to slope at a small angle, but it's recognizable. However, when feeding an input line to a microcontroller (or using a 2K2 or so pull-up resistor to 5V) what you see below is what I get... (this is in AC mode for ease of display. DC mode looks similar except these oddly miniscule pulses are from 5V, though the pulses themselves are still <1 V peak-to-trough).

(Red = DATA, Yellow = CLK)

No matter what I do, the signal is surprisingly weak. Just for grins I started a normal pulse train out of the microcontroller and as expected it looked perfectly normal. I understand that PS/2 devices use an open-collector design, if that helps. So: what am I seeing here? And how do I get a relatively normal logic-level pulse train out of this signal?

Note: I tried another PS/2 device - same results.

Edit: updated pictures! All the outputs I got, normal-ish or not, are around 600mV peak-to-trough.

Edit 2: This all started because what should've been an extremely simple project (hook-up of a PS/2 keyboard to a microcontroller - with software applied to it and monitoring/driving the correct pins) didn't work... I was surprised at that first and foremost, and then started snooping at the signals (which I planned to do anyway AFTER it was supposed to be up and running, to learn more.) I keep thinking maybe it's the keyboard but I get the same effect from an old mouse as well (though it requires more handshaking to initialize it does at least send a clock burst on startup, and that burst is virtually the same in all characteristics as what I saw with the keyboard. The wiring seems sound and there really isn't much at all between the microcontroller and the DATA/CLK lines... it's virtually a straight shot to power and I/O.

And yet these patterns look vaguely familiar to me from a long time ago (different projects) and I suspect it'll be something simple.

Edit 3: I asked someone I know who is more analog-oriented and they think it looks an awful lot like a signal being clamped by a diode or such (the fact it's in a 0.6V range rather than a 5V range makes more sense in that case... now I know why it looked familiar). More later when I've tested things... might be that the cable I'm using to plug into isn't so passive after all (I thought it was... but *facepalm* I'll bet it's got a diode in it for some reason. Note it's salvaged from an old CueCat FWIW, and I am wondering if it's the splitter that's not in use that's the ultimate cause... and yes, I tested the connections and they seemed normal but I could've gotten lucky and forward-biased a hidden diode without knowing it).

Scope output (with pull-ups, AC mode probes, each centered at 0V):

Scope output (with pull-ups, DC mode probes, each centered at 5V):

Scope output (direct read (no pull-ups), DC mode probes, each centered at 0V):

Scope output (direct read (no pull-ups), DC mode probes, each centered at 0V) (overlay view of the signal above):


texts: Calculating voltage at the output of a circuit

texts:
I have \$U_E\$ as sawtooth signal as shown in the figure, I don't know how to calculate the voltage at the output \$U_A\$.

I have made $$I = U_A - U_E/R_1$$ and $$U_E = U_q + IR_1 - U_D + IR_2$$

but still I'm missing the calculation of the unknown \$I\$.


texts: How to use timers in STM32 board and HAL library in order to measure speed of motor?

texts:
I need to measure the speed of a rotating motor fitted to an encoder disc with 20 slots. The LM393 based sensor is kept at the right place, so that encoder disc rotates in between the sensing part.

I think, I would need three timers provided by STM32 board: one to provide PWM(TIM4), second(TIM1) to measure the time of (1000msec~1sec) and third timer(TIM2) to measure the number of pulses received from encoder disc in 1 sec.

TIM1's counter period(Auto-reload register) is fixed to 1000 and frequency to 1000Hz.
TIM2'S frequency is same as PWM frequency-10kHz.
Sensor output is connected to PC15 and PWM to PD12.

The code below uses HAL library. I have doubt about how to use these two timers/counters inside the while loop, which HAL library functions to use here and how to use.
Also should the code for PWM control and speed calculation be put in same loop.

int main(void)
{
        volatile GPIO_PinState level; // stores input state from PC15, sensor output is connected to PC15
        uint16_t dutycycle=70;
        int speed=0;                  //speed variable
        int constant=(2*3*1)/20;      //roughly circumference/20 slots

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();
  /* Configure the system clock */
  SystemClock_Config();
  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_TIM1_Init();       //for measuring 1 second
  MX_TIM4_Init();       //for PWM
  MX_TIM2_Init();      //for counting output pulses from PC15 pin

  HAL_TIM_PWM_Start(&htim4,TIM_CHANNEL_1);    //Start PWM signal
  level=HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_15); //HAL function is called to read pin status

  while (1)
  {
              counter1=__HAL_TIM_GetCounter(&tim2);
              speed=(counter1)*(constant);          //speed variable, counter 1 related to TIM2

            htim4.Instance->CCR1=dutycycle;   //setting the duty cycle of PWM signal
            HAL_Delay(1000);dutycycle+=10;    //1 sec delay and then increases dutycyle by 10%
            if(dutycycle==90)dutycycle=50;    //resets to 50% duty cycle
  }

Development board is STM32F407, CubeMX is the source code generator and IDE is Eclipse. OS is Linux(Ubuntu 15.04).
Kindly suggest.


texts:
How to find output voltage of microphone when sensitivity given is -38dBV . I want to compare volatges for various Sound pressure level.
Link of datasheet is :  https://store.invensense.com/datasheets/invensense/INMP404.pdf


texts: Is this a true corollary about Ideal Operational Amplifiers?

texts:
I don't see how the 2nd theorem is true for an ideal operational amplifier.

This was from the Engineering Circuit Analysis 8th Edition textbook by Hayt.

If this is correct can you somebody help me understand why?
I'm looking at this model they gave me and still can see why the voltage across is zero.

Ri approaches infinity and Ro is zero.


texts: Power Amplifiers operating in Saturation and VSWR issues

texts: Are power amplifiers operating in saturation more immune to VSWR effects than their counterparts operating in more linear mode and if yes why?


texts: Why does moving the imaginary (\$i\$/\$j\$) component in the capacitor element of a transfer function to the numerator flip the coefficient's sign?

texts:
I'm relearning things I lost since college. I remember you have to flip the sign in \$1/(j\omega C)\$ if you want to turn it to \$j/(\omega C)\$, but I do not remember why.

Is there an empirical method for understanding this, so I don't just "do"?

Is there a comprehensive review source for everything DSP, filters, etc that I can consult besides my class notes in the box in the storage? Right now it's Wikipedia...


texts:
I encountered the following problem: inside an equipment, an added PCB needs 32 V DC and in that enclosure, only 24 V AC is accessible. In order to get 32 V DC from that 24 V AC, someone put a bride rectifier and a 6800 uf (68 V) electrolytic capacitor in parallel to the load. Doing this, 32 V DC were obtained.

Now, my questions are:

How did he calculate the value of the capacitor in order to boost the voltage to 32 V DC from 24 V DC (after rectification)?
I don't have an oscilloscope to see the waveform after rectification and filtration but, is there a better way to obtain 32 DC from 24 AC regarding the output waveform?

If you know good tutorials in order to understand these principles better, please let me know.

Your responses will be much appreciated. Thank you in advance!


texts: 317-325Hz signal with probes detached on JYE Tech DSO Shell

texts: The picture shows DSO Shell JYEtech (in a custom battery powered enclosure - for convenience) with probes shortened (same occurs if probes are not attached at all) with a what appears as a stable sawtooth-like signal of around 317-326Hz. Gain control on the device don't affect apparent amplitude of the signal. Please help to diagnose the cause of this.


texts: High side power consumption measure reversible circuit

texts:
I am tinkering with the problem of making a circuit which uses INA219 for measuring power consumption on high side. The circuit has only one power input and only one power output as pictured below (very simplified only to convey the idea). The power for INA219 and its controller in that schematic is drawn before current sense resistor so to avoid INA219 detecting power drawn by those parts and to only measure power drawn on output end of the circuit.

The problem starts when I am thinking of how to make input/output reversible. With the diagram below it still will work in reverse (that is when VOUT/GNDOUT become input and VIN/GNDOUT are connected to the load). Using circuit below with IN/OUT reversed the INA219 will still function, but now the data it outputs will include power drawn by its controller (and any other peripherals connected to it).

So the question is -- how do I modify this circuit to allow this being reversible, but at the same time avoid INA219 detecting power drawn by controller?

simulate this circuit – Schematic created using CircuitLab

I could in theory insert diode right after VIN, then branch near VOUT and have 2nd current sensing resistor and 2nd INA219 on that branch just like below (diode placement are not exact there, again this is just to convey the idea). But this would mean rather complex circuit and also significantly increases cost of this circuit. Are there any better alternatives to that?

simulate this circuit


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I understand P Channel MOSFET operation and was reading this question which shows this circuit:

but I wasn't sure whether this can be used to load share with an MCU such as Arduino or ESP32 which have a System Load of 5V/3.3V respectively. With a solar panel outputting 6V, the MOSFET will never be on as Vgs will always be positive (Vg - Vs = 1V or 2.7V).
Is the PMOS only used for higher power system loads, e.g. above the 6V output of a solar panel? If so, how best to load share an MCU. e.g. power the MCU (and independently charge the battery) from the solar panel when the sun is out otherwise power the MCU from the battery?
I assume there will be a voltage regulator at the system end to drop Vbat/Vin to the required MCU voltage.
EDIT
after thinking about it, as Vin tends to 0V, i.e the sun goes in, Vgs tends towards Vgs(th) (-tve) and eventually switches the MOSFET on, which allows Vbat to power the MCU via MOSFET D/S. As Vin rises, the MOSFET will turn off, removing Vbat from the MCU and powering it from whatever Vin is when Vgs(th) is no longer met. That suggests the MCU will be receiving power from Vbat and Vin at the same time until Vgs(th) turns the MOSFET off.
EDIT
after reading this question, using a logic level MOSFET (NDP6020P) with Vgs(th) = -0.2V, that would mean at some point Vbat(3.7V) + Vin(3.1V) = 6.8V max going to an ESP32 (until Vin turns MOSFET off). The ESP32 requires 3.3V so an LDO voltage regulator would be required on the MOSFET Source side but when the MOSFET turns off (and Vbat goes away), Vin is < 3.3V so the ESP32 will turn off until Vin rises to 3.3V.


texts: Designing a electronic dice with Arduino, 74HC163 and a 74HC4511 decoder to a 7segment display

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So im designing a electronic dice with a 74HC163 and the 74HC4511.
My problem is that the counter counts 0-7 everytime (using only the 3 flip flop outputs, Q0-Q2)
I would want the counter to count only from 1-6 and go back to 1. I know this can be done by "Presetting" the 74HC163 somehow but i dont know how. Anyone have ideas on how the cables should be connected on them to count from 1 to 6 and return to 1 after the 6? Thanks.
And the arduino is only giving a +5v and a blinking high- low singnal using the basic program "Blink"


texts: Drift current and reverse saturation current

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I have a few questions whose answers I couldn't find. All questions are in respect to a pn junction diode.

1) Does diffusion flow of current (even minimal/negligible) occur at reverse bias?

2) If the answer to (1) is "NO" then does that imply that reverse saturation current is exactly the same as drift current?

3) What is the formula for diffusion current in a pn junction (not total current)?


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I have ran into a problem where some USB supplies drop below 4.6 volts. Is there a circuit that would block the voltage below 4.7 volts and pass the voltage when it is above 4.7 volts.

I have tried a brown out circuit in the below image. It is controlled by the zener breakdown voltage which is set at 4.7 volts.

This circuit works really well when the input actually reach 5 volts. It blocks everthing up until 4.7 + a little volts. The blue line is the output, the green line is the input from V1 and the red line is a voltage of 4.7 volts.

Where this circuit faults is when the input is between 4.7 and 5 volts. The below input only rises to 4.8 volts and the circuit then passes a dropped 4.5 volts.

Maybe this isn't the direction to go. I have looked into a voltage supervisor, but those seem to want to give output pulses only. Anyways, is there a circuit that can block voltages below a threshold and pass everything above that?


texts: Adjusting 300Mhz FM transmitter values for max legal power/range in canada

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I read a law for canada and it states:

  Industry Canada permits transmitters that have an output lower than 100 µV/m at 30 meters (approximately 1 microwatt output).

Now what fools me are these transmitter designs and why I can't produce much output with them when transmitting at 300Mhz.

This circuit was featured under "An Improved Design" half-way down the page at this URL: http://www.talkingelectronics.com/projects/Spy%20Circuits/SpyCircuits-1.html

I looked at it for ideas after building mine. I used the same concept but I changed some component values in an effort to increase transmitting distance.

But talkingelectronics.com claims I should use 330+ohms for the emitter resistor, but I think there's some math with the parts I circled in red in my circuit. I read on another section of this site that to find out the power a transistor was using, do this:

1. find voltage at base via voltage divider attached to base.
2. subtract voltage drop at base-emitter junction (700mV).
3. divide the result by emitter resistor.

The problem is I don't have a real voltage divider as far as DC is concerned, but AC wise, when I used an online calculator, the 470pF capacitor ended up having a 1 ohm resistance at 300Mhz and the base resistor is some sort of multiple of the emitter resistor?. or did I get this part wrong?

So my question is, to maximize the transmitting power possible without increasing the chances of blowing up any part, what values of the circled parts should I use?

For now I'm transmitting audio from the computer but later I'll make it a data transmitter.

I wanted to add that 5VDC is regulated and cannot be changed as this circuit is attached to another unrelated circuit.


texts: USB-C / USB 3.0 alternate mode as low speed serial port

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I want to make a device which can be connected either to a PC with an USB 2.0 connection or to another identical device and have a serial connection. This should be detected acutomatically and I want it to have a single connector. It seems that the USB-C is a good candidate. I can use the USB 2.0 signals when connected to a PC and the SuperSpeed signals when connected to the device.

Is this a proper way to use the USB 3.0 alternate modes? I have seen examples of using it as displayport or PCIe but never as a low speed serial port. This mode would never be used when connected with the computer but of course shouldn't damage or cause problems with the PC.

As these signals are differential, even if I'm working at the typical 115.2kbps I suppose I would need a transceiver to convert them to LVDS and use the TX+/TX- and RX+/RX- pairs, right?
Or could I get away with using the signals SBU1 and SBU2 with no transceiver? I haven't seen any usage example of these two signals.

Using the LVDS transceiver seems to be the right thing to do, but maybe overkill, the distance between devices is short and the speed slow. It's for a low quantity prototype so cost is not an issue, but seems the circuit gets quite complicated with the transceivers, switches and ESD protection.

If I go with the LVDS transceiver, I have seen that the TX pair should have AC coupling capacitors, whould this also be necessary for low speed?

The device doesn't have USB-host capabilities, this is why I want to communicate by UART between devices, it's already implemented and the firmware won't need mayor changes.

Thanks!


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I have the following problem

We want to find the graphical current-voltage relationship for both the mosfets on the left. The only difference I can actually spot is the doping of the body of the MOSFET. There's a slight increase in acceptor dopants in the MOSFET below. I'm not too sure how this would affect the graph... Any suggestions?
For the first MOSFET(with p-), I think we'll get a rough sketch of:


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When I move my EMF radiation meter near a charger it shows me that there is radiation from the charger, and even the device itself radiates when the charger is connected to it.
The chargers emit radiation even if the device is not connected to them.

I understood that the radiation is caused because of the way the modern chargers are working. They are working in a way that they switch on and off very quickly. It is done by a DC/DC converter.
It results in a very high frequency noise (radiation) that travels on the charger's wires and even on the connected device.

But I noticed that when I connect the ground of the output of the power supply to the ground of the wall socket, there is no radiation!

So I have some questions:

Why it eliminates the radiation?
Is it safe to do that? (I know that the two sides of a transformer need to be isolated from each other, but it is just in principal).
Will it damage the device, the charger or the socket?
If it's ok, why the chargers are not designed in the way they will not radiate? (The chargers have only 2 connectors to the wall socket so why they don't have the third connector to the socket's ground?)

Thank you!


texts: Single value capacitor or two different in parallel for filtering the power supply for microcontroller

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I am trying to design power supply for the STM32F446 for my PCB.
I wonder if I should stick to the Datasheet of STM32F446 Page 71  and use two capacitors or be careful about it and maybe just use one 100nF. The picture from Datasheet with suggested values:

I started getting these concerns after checking some other designs, where they just used one 100nF capacitor for this micro-controller. As-well after reading this answer on StackExchange about the effect of 'anti-resonance' when using two different values capacitors. He also referenced to this question where it was elaborated in more details. In these slides they mention that 'anti-resonance' effect can be reduced by reducing ESL.
I am a bit confused by all these inputs. I think the most trusted source is definitely manufacturer Datasheet, but maybe they assume I would be using some special capacitors (for example ceramic X7R), or something else I am not taking into account. And why other designs don't follow this suggestion. It would be great if you can clarify this.


texts: Opamp relaxation oscillator (single supply)

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I simulated and built current circuit.

What I got was a rectangular wave generator with a duty cycle significantly lower than 50%.

Than I made R3 = R4 and got 50% duty cycle.

I managed to think that RC constant is defined only by C1 and R1.
It appears I was wrong.

How can I define RC constant for this circuit?
Can anybody shed some light on the problem?


texts: Switching regulator: How to determine maximum inductor current?

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I am trying to design a buck/boost converter with  the LTC3780 chip from Linear. My specifications are:

Vin = 6 to 32V
Vout = 24V at 100mV ripple
Ioutmax = 2A
Frequency = 300kHz

The datasheet uses the terms "inductor current ripple" and "maximum inductor current at boost mode."
What are these terms and how can I calculate them?


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I've built a simple PIC programmer which works OK on a PIC16F628 but fails on a PIC16F88:

I've checked the VPP voltage and it's within spec (although I had to substitute a 1.8K for the 1.6K to get it to 12.75 - the input is not exactly 5.0v) and I've added a lengthy delay to allow it to settle, but the 16F88 just won't play ball. Sadly I don't have access to an oscilloscope, but my logic analyser shows the right traffic on the logic lines at least, although the data coming back is always all zeroes. I've scrutinized the datasheets side by side but can't find anything which would explain the difference.

Does anyone have experience of these two MCUs? Is the 16F88 'more picky' in some way? Is my schematic, in fact, completely bogus? It works on a breadboard (with the 628).

The MCU is connected only to the ICSP lines, there's no other lines or circuit involved.

I suspected insufficent current, but the datasheet says that the current draw on VPP is very low (it's supplying about 50mA I think, I only have a cheap multimeter and I'm not sure I trust it).

Link to the software: Bitbucket

[Edit] Updated schematic to try and make it more clear.

[Edit] DC-DC step up is based on this tool: http://www.nomad.ee/micros/mc34063a/ with Vin=5, Vout = 13, Iout=35, Vripple=50, Fmin=125

[Edit] Schematic should be clearer now

[Edit] Added MCU to schematic. The capacitor C1 is actually just a ceramic capacitor, not tantalum or anything, but I can't get the right symbol to show in the schematic (so please ignore the little + sign).


texts: Is there something such as an infinite potentiometer?

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I am trying to find a component, that, similar to a potentiometer, delivers an analog output, but which can be turned indefinitely in a single direction.
I have tried searching for something like this, but I never quite found anything that does what I want, while being relatively cheap.
Please note, that I am not searching for a rotary encoder, since they either are clicky, do not have the resolution I require, do not support absolute positioning and are usually too expensive if they do support any of these.
I imagine something like a normal potentiometer with multiple wiper contacts might work in this case.

It would provide a smooth precise output even when turned in a single direction for multiple turns.
Does a cheap part exist that behaves like this and if so what is it called?
Edit: thanks /u/quetzalcoatl for providing the output potential diagram.


texts: Changing the location of components in a circuit

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As you can see in the figure, the author claims that the right circuit and the left circuit are equivalent.

However, in the left circuit, the 6-ohm resistor is connected to the 1-ohm resistor, and in the right circuit it isn't. In the left circuit it is connected in the two yellow markers, but in the right one, in the two right yellow markers.

In what conditions such replacement is allowed?


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I'm building a project where I would have both a bluetooth receiver and an aux in line connected to the same speaker. One way could be to detect the presence of jack inserted in the aux in connector and to switch off the bluetooth module. I read this question How does an audio jack detect when a speaker is plugged in? and it seems that there is not an automatic electronic circuit to achieve this, but only manual or patented solutions. Do you have any suggestion?

P.S.
I need something like this with an automatic switch that switches off the bluetooth module when an input jack is detected.


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If a question simply asked "What is the gain bandwidth product of this amplifier?"

And when I am trying to utilize the equation :

GBW = (Av)(BW)

I am unsure if I should utilize the voltage gain from the signal source to the output (Avs = Vo/Vs), that is, its including the voltage drop accounting for the source resistance, or if its simply asking for the Av = Vo/Vi.

Is there a absolute right/wrong, a normal convention, or is either method arguably correct since the question didn't specify?


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I tried to write VHDL code for a sync JK FF. I have the following error:

  line 18 syntax error near if statement.

Could anyone explain to me what is wrong with the if statement?

Also, is this code okay? I tried looking on the internet, but haven't found code for a sync JK FF anywhere. By sync I understand that the reset should be synchronous with the clk?

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity JK_FF is
Port ( J : in  STD_LOGIC;
       K : in  STD_LOGIC;
       R : in  STD_LOGIC;
       clk: in  STD_LOGIC;
       Q : out  STD_LOGIC;
       QB : out  STD_LOGIC );
end JK_FF;

architecture Behavioral of JK_FF is
   signal M: STD_LOGIC;
begin

process (M, J, K, R, clk)
begin
   if (clk'event and  clk = '1') then
      if (R = '1') then
         M <= '0';
      end if;
   else
      if (J = '0') then
         if (K = '0') then
            null;
         else
            M <= '0';
         end if;
      else
         if (K = '0') then
            M <= '1';
         else
            M <= not(M);
         end if;
      end if;
   end if;
   Q <= M;
end process;

end architecture;
end Behavioral;


texts: Reading values from Force Sensitive Resistor - Arduino

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I am trying to read the values from a Force Sensitive Resistor with Arduino. Actually, I am already reading them, but it only works if I use a 10 Ohm or lower resistor and it really heats up. (See attached schematic). If I try to use a higher resistor, Arduino continuously reads 1023, as if there was no FSResistor. How can I read the values of the FSR without having to use a 10Ohm resistor that heats up?

Note that the FSR, without applying any force has 50 Ohms resistance, and when applying pressure, it goes down to 5-10 Ohms.


texts: Difference between bottom and top dynamo/motor in a dot matrix printer

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What is the difference between bottom and top dynamo/motor in Canon or other dot matrix printer (I'm only aware of one whose job is moving carriage left-right back and forth) ?
Which one should be designed with greater torque but less RPM, and which one vice-versa of that ?


texts: Understanding current sourcing and sinking in TL2426 rail splitter

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I have a 40dB active bandpass filter being powered off a single rail power supply with the TL2426 providing a virtual ground so I can get a dual power supply configuration. Currently, I'm having issues understanding the concept of current sink and current source in this configuration.

When connected to a dual rail power supply, the active bandpass filter draws 60mA. Now according to the datasheet, the TL2426 can source 20mA. Does this mean this is the maximum output current that the TL2426 can provide to the circuit

In the configuration shown above, the whole circuit draws ~71mA and the amplifying circuit still works as expected which I found suprsing, I've not probed the rails to check how balanced they are but unless I've misunderstood the concept of sourcing and sinking, if the circuit requests 60mA and the TL2426 can only give 20mA, shouldn't the circuit not just work?

EDIT: Added Image of the circuit


texts: Need to identify this chip on camera lens mainboard

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I need to identify this chip in order to replace on an expensive camera lens. The code TF1 and TF2 are printed on the board to signify the issue is with the focus motor control. The core is 1mm thick by 3.5mm length.

(Image source)

(Image source)

(Image source)

Thanks in advance.


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I am trying to wind some coils for a RF transmitter, so to get the values right, I though of using a LCR meter, but there is a problem with the measurements.

If I use air core inductors the measured values don't differ that much when switching from different frequencies of operation. But if I want to measure an inductor with a iron core (from a nail) I get the following results:

100Hz:  16uH
120Hz:  16uH
1kHz:   11.1uH
10kHz:  4.59uH
100kHz: 1.708uH

I've read somewhere that inductors below 2mH should be measured with 1kHz, so the 100Hz and 120Hz are off, that I can understand. But 10kHz and 100kHz measurement frequencies shouldn't be that much off from 1kHz, shouldn't they? What am I doing wrong?


texts: What is this most efficient way to power a high powered 6 V and a low powered 12 V device from a battery?

texts: I'm looking to power two devices (two amplifiers, an Akai - EIE Pro and a Behringer - MICROAMP HA400) from a battery source (a big 12 or 6 V sealed lead-acid battery). Unfortunately they require different (regulated, but don't know how tight) voltages. One device requires 6 V, 3 A and the other 12 V, 150 mA. Should I use a boost converter to create the 12 V? I'm looking for an efficient solution (at a reasonable cost) and I'm considering using two batteries if it gets too complicated/costly.


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I'm trying to understand simple things about electricity reading allaboutcircuits.com web. This chapter includes image which´s principle I don't understand. Here it is:

When supplying constant voltage to circuit where resistance and current change, how is it possible that change of resistance affects voltage on resistor?

Please help.


texts: How does installing battery backwards damage a torch?

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Recently, I bought a high performance torch which uses a CR123 lithium battery. The manual warns against installing the battery backward and says it "will damage electronic components".

I recall doing simple circuitry at primary school, and installing a battery backwards never caused any problems.

So what makes a torch vulnerable to a battery installed backwards?


texts:
I am interested in making a DIY PCB soil sensor based on 555 timer IC. The circuit works well but I have problems with regard to manufacturing a durable PCB. As I keep the PCB based soil sensor immersed in soil for longer than a month, the PCB starts to discolor and rust. This does not happen for the commercial sensor shown below. Note: even if there is a laminated layer around the copper to protect it, the sensor detects soil moisture fine. However, this lamination is not durable.

This sensor is still in the prototype phase. I would appreciate advice on how I can ensure the durability of the PCB.

I heard that a process called "Conformal coating" can be done. But I do not know what type of manufactures I should refer to have such a PCB manufactured. The generic PCB manufactures seems not to do Conformal coating.


texts: What is the purpose of the Motor Run Capacitor?

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Looking at a control box for a marine Air Conditioner and it has a HUGE capacitor in it.  The schematics label it a "Motor Run Capacitor", but I always thought it was just used to start the motor.

What function does a huge cap like this have in running the motor?

The Air Conditioner is being run off AC power from a generator, no DC involved.


texts: Arduino-like Platform With Wireless and Video?

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Is there a Arduino-like hardware platform that allows for wireless connectivity (think remote control) and for connection of a webcam (with streaming that wireless video over the wireless connection)?

I really like the idea of a prebuilt hardware platform and would be interested in getting into robotics. Since I am already a proficient programmer, it would be great to take this into the physical world as well.


texts: Is this a universal motor? How does it work?

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I want to know what type of motor this is. It has brushes, 2 coils, 1 electromagnet, and 1 commutator of copper in the middle. I have a lot of doubts because I'm learning.

Is this a universal motor or an AC motor with brushes?
I have concluded that the brushes have 2 different polarities, which will create a magnetic field on the electromagnet, but how does it move? Does the magnetic field of the electromagnet collide with another magnet there?
Does it have a fixed magnet?
What is that yellow thing? Is it a capacitor?
If the same system, with the same coils, would experience a current of 220 volts instead of 110 volts, would it create more power? I mean, does more intensity of current creates a more intense magnetic field, and so, more power?


texts: Intel FPGA equivalents of Xilinx IBUFDS Primitives?

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Im trying to migrate an Design from using Xilinx primitives to Intel Altera FPGA.
The original design uses the IBUFDS for the clock signals.

IBUFDS #(.DIFF_TERM("FALSE"), .IOSTANDARD("DEFAULT"), .DQS_BIAS("FALSE"), .CAPACITANCE("DONT_CARE"), .IFD_DELAY_VALUE("AUTO"), .IBUF_LOW_PWR("TRUE"), .IBUF_DELAY_VALUE(0)) sys_clock_ibufds (
    .IB(sys_clock_n),
    .I(sys_clock_p),
    .O(sys_clock)
);

According to the "AN307 Intel FPGA Design flow for Xilinx Users" Document, Table 38, The Intel equivalents is just simply using wire/signal and IO Assignment. Can anyone give me the example how to do it?

However, I also found this link : https://www.intel.com/content/www/us/en/programmable/support/support-resources/knowledge-base/solutions/rd01062009_916.html
which suggest using the I/O Buffer (ALTIOBUF) IP Core.
Which option should i go for the best?

Thanks in advance.


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i already posted a similar question before and i still don't know exactly how to wire up things. I will try to explain better. I have a pc power supply and a pc fan that works between 5v and 12v. All i want is with a mosfet and a teensy 3.1 change between the 5v and the 12v output of that pc supply.

I have a N Channel mosfet, but i don't know exactly how to wire it up, and i already burned myself because of the overheating of that mosfet.

The mosfet is a RFP30N06L that operates on logic level. If anyone could explain me how to wire it up.

L.E. Here is a screenshot of my wiring, but i get a constant 12V when the pin is not connected and something lower when the pin is connected.(i don't have voltage tester, but the fan goes slower, but not as slow as 5V)


texts: Why does so much current flow into circuit?

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The load is merely 2k yet voltage source provides ~3 amps to the circuit. I hope this isn't the case in reality because I want to build this. Simulations done in ltspice. Why so much current flowing into the circuit? If this is accurate how do I reduce current into circuit to reflect only what load needs?

Greatly appriciated.


texts: AIC1863: How to use this MC to detect the presense of IR transmission?

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I have build simple prototype on STM32 ARM Cortex microcontroller trying to understand the usage of AIC1863 IR Preamplifier for Remote Control System (see the handmade PCB on the breadboard).

MCU generates 36kHz PWM to LED. I have no oscilloscope on this time, so I use multimeter to check voltage on PCB. If I put something between LED and IR Receiver I see the voltage change on AIC1863's output pin. But I don't understand what it has to return me. It seems output should change its value if I open/close the area between LED and IR Receiver. Am I right?

P.S. I have checked the PWM. It's ok, its frequency is 36 kHz with 1 second period and 0.3 duty cycle.


texts:
I am using LED as a light sensor, the range of output is from 0-700mV DC, I want to amplify/scale this signal to 0-3.3V DC.

My question is, what is the best way to scale the output signal to the desired range using only BJTs?

The constraint of using only BJTs is because of lock-down due to Corona Virus pandemic, I cannot go and buy something like an opamp.


texts: How to measure a signal generator with an oscilloscope probe?

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I have a signal generator and an oscilloscope.

When I connect a plain BNC cable between them, and I generate a square wave, I see the square wave on the oscilloscope with the correct voltage.

However, I want to connect the signal generator to a breadboard, and use an oscilloscope probe to measure the voltage. If I connect the signal generator directly towards the oscilloscope (using an oscilloscope probe with banana plugs -> jumper wire -> resistor -> oscilloscope probe) and connecting grounds together, I get a much lower voltage on the oscilloscope.

I guess the problem is that I use an oscilloscope probe to 'output' the signal generator's signal.

Should I cut a BNC connector apart and directly connect banana plugs or whatever onto it?


texts: T.I H-Bridge design with No protection diodes?

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I am still on my struggle trying to design my own Brushed DC H-bridge with all N-MOS, still in the research stage and burning mosfets left and right.

I have come across this T.I design ,relatively recent.
The full document about their design is here.

On page 12 and pictured below is the schematic of the H-bridge portion.

My question is as follows:
I see no schottky diodes protecting it from the proverbial inductive spike. How come?

I do see the zener and resistor network but the paper says:

  a Resistor-Zener network is provided on the switch nodes of the
  driver to protect it from overshoots and undershoots

I assume this "overshoot" refers to overshoot due to the bootstrap circuit and not inductive spiking?

Could it be that if you drive an H bridge in a complimentary manner, where the top and bottom mosfets are driven opposite of each other this gives the inductive spike a route to ground on off times.

For examplel: If you turn Q2 and Q3 ON the motor spins one way and when you turn them OFF there will be inductive spike so if you then turn Q1 and Q4 ON the spike has a route to ground and to Vbus.

that is the only explanation i can think of why they dont have protection diodes...

and yes  I understand there has to be deadtime to protect from shoot through and all of that but my question is why there are no diodes?

One more question is what is the purpose of the resistor and capactors highlighted inside the bridge?? are these what they call snubber circuits?


texts: Defining parameters for the bottom level in an intermediate level in LTspice

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Should parameters defined within a subcircuit pass to a lower level subcircuit in LTspice? If I define the parameters of the bottom level in the top level (or directly in the bottom level) everything works fine, but if I define those parameters in the intermediate level they do not pass to the lower.
Below a simple(!) example. Simple1 and simple2 are subcircuits; simple is the main schematic. If I define .param a=2 in simple or in simple 2 everything works fine. If I define it in simple1 I get the error: Can't resolve .param r=2*a


texts: LED dimmer/controller: preserve state after loss of power?

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Summary:

Are there LED Dimmers that are "always on" and whose settings survive loss of power?

Details:

I am considering a more or less standard led-strip set (consisting of power transformer/driver, dimmer/controller and led strip) for installation behind a mirror in the toilet. I need the dimmer only to set the desired brightness once. After initial setting, it will be sitting behind the mirror, and dimming should be constant. No remote control is needed.

The LED set will be mounted where there used to be a standard 220V light bulb. The 220V driver of the LED set would be turned on/off using the existing 220V light switch on the opposite wall.

This leads to my issue: the dimmer/controller should automatically come back on after loss of power. Also it should preserve its dimming setting.

Does this exist? All controllers I've found have an on/off switch or come with a remote control, which makes me fear they will be off after loss of power.
Does this depend on the brand or type of controller? I couldn't find any documentation on this. Is there a specific term I should be looking for?
Can you name a few brands/types that provide this behavior?
Is this "good practice"? I don't see direct alternatives due to existing cabling in the wall.

Thanks for any insights.

** edit **
this is for 12V or 24V, white led strip (about 1.5 meter)


texts: What does the 902-927Mhz in UHF RFID means?

texts:
I have an ALN9662 uhf sticker with operating frequency of 840-960Mhz while my integrated reader is 902-927Mhz. I'm just wondering if uhf tag sends its data in a fixed frequency in air? or are there instances that it might change while on air?
I configure the reader to 902Mhz single frequency. But it still read the ALN9662 sticker. How is it possible?


texts:
I'd appreciate some help identifying the component in the pictures below. The actual PCB is part of a shift interlock solenoid from an Audi A6 that went bad. I'm trying to salvage the part as it is really hard to come by.

Looks like a fuse, but if you look closely those two pins are overlapping by quite a bit and there is no sign of damage to say that it burned out. The overall circuit is quite simple, there's only a 471 ohm resistor and those two components that I'm unsure of.

Thanks in advance!


texts: Can I reduce the start current of a fridge compressor?

texts:
Not a duplicate question: this question is about reducing start current, not about identifying the motor type.

I have a refrigerator that has a permanent split capacitor (PSC) motor, which I am powering from solar panels/battery/inverter.

My inverter is rated at 1000w (2000w peak), but unfortunately, the motor occationally trips the overload protection of the inverter, with the risk of spoiling the contents of the fridge if it goes unnoticed.

I am considering replacing the motor with a DC compressor (Danfoss BD35F), but it's quite expensive (about $350).

Before I do that, I want to experiment first, to see if I can get it to work with a consistently lower start current.

I realize it might break the motor, that it might not start consistently, but it's worth a try.

I've read about the following options:

a) use a start capacitor, 150uF, for the first 1000ms
b) use an NTC
thermistor
c) power resistors, for the first 1000ms (similar effect
as NTC)
d) voltage transformation to a lower voltage, e.g. from 230V
to 200V

but:

a) I'm having a hard time finding a start capacitor to try with, and random experimentation could be expensive, since they seem to cost about $10-15 a piece and can break if powered for more than a few seconds.
b) I've tried a 10ohm NTC, but that made no difference at all.
c) I'm going to try with various resistors at 50, 70, 100 ohms (rated at 50w).
d) I'm not sure which type, which voltage to try etc..

ALSO:

I tested the motor with the following results:

Disconnected  for 24h, ~850w
Connected for 20min, disconnected for 5min, ~600w
Connected for 45min which included a self-restart, ~1100w
Disconnected, then reconnected after 15min, ~800w

I'm puzzled by these results, because it seems that the motor draws more if left connected. But the thermostat disconnects the circuit.
The only way this makes sense to me, is if the thermostat somehow causes an arc that draws an additional 300w when reconnecting.
But I tested it by disconnecting for 15min, turning the thermostat to 0, reconnecting, then turning the thermostat to 3. The max power draw was only 782w.

Very strange... Any ideas?


texts:
I want to use 12 volts DC and step it up to 400 volts AC or higher at 100khz. I am buiding a signal generator that outputs a sine wave or square wave with an adjustable frequency of up to 100 kHz. I need an isolation step up transformer using a car battery as the power supply.
Does any one know a way to achieve this? I am unable to find a transformer suitable for my needs.


texts:
I am trying to understand the DRAM working paradigm. I just read this article about interleaved memory. It says:

  Interleaved memory results in contiguous reads (which are common both
  in multimedia and execution of programs) and contiguous writes (which
  are used frequently when filling storage or communication buffers)
  actually using each memory bank in turn, instead of using the same one
  repeatedly. This results in significantly higher memory throughput as
  each bank has a minimum waiting time between reads and writes.

And...

  That way, contiguous memory reads and writes use each memory bank in
  turn, resulting in higher memory throughput due to reduced waiting for
  memory banks to become ready for the operations.

My questions are:

What prevents a DRAM bank from being ready? Refresh?
Why is the throughput significantly higher with interleaving?

My current understanding is:

DRAM needs periodic refresh to keep the stored data, which is the the D stands for. For continuous read/write against a single bank, I can think of that such r/w operations will sooner or later collide with the bank's refresh operation. When that happens, the r/w will have to wait until the refresh is done. If we interleave multiple banks, it is less likely that the collision will happen. So there will be less wait and higher throughout.

But it seems my understanding is not quite relevant to the "waiting time between reads and writes" in the first quote.

Any other reasons?

Thanks.


texts: What exactly do electronic engineers do?

texts:
I often wonder what such skills, whether hobbyists or paid, or both, based on titles and descriptions, really do.

Do electronic engineers only work on electrical wiring, such as what a CPU developer would do, or maybe a printed circuit board maker?

Or would they just stick to eletronics primarily, such as transistor-related knowledge on charges, volts, maths, etc.?

I really am curious to know what kind of specifics they do, or what kind of things they know/learn how to do and can apply to stuff.

Also, can't an electrical engineer be the same as an electrician in some tangible sense?

They both know electricty, atoms, electrons, charge, conducting, wiring, etc.

PS: Me, personally, I am interested in this field a little, but suck at math, and find it difficult, and lack resources for learning this in a straightforward way.


texts:
I traced this circuit from Induction Motor soft starter.  My questions are:

What is the function of Q5 & Q6?
How the integrator opamp pin 5,6,7 works, which transistor is used to reset the cap?

It appears to me that custom design was implemented here compare to basic op amp ramp generator like in the question Ramp Generator using op amp.


texts: Why does volume above 80% break my speaker (PAM8403, 3w 4ohm, 18650)?

texts:
I am new to working with electronics and I am building a simple speaker.
The Problem
The speaker I built so far (poor sound quality aside) stops working if the volume is above ~80%. By stop working I mean, emitting a stuttering buzz as if only a fraction of the sound is making it through in between noise.
As per the suggestion in the comment, I have measured the voltage out of the booster and it is 5(.02)V both while playing and while "stuttering".
This is an example of the problem (audio).
The Speaker

battery: 18650 (3.7V) with TP4056 for charging
power: MT3608 boost
converter to from 3.7V to 5V
speakers:2x 3W 4ohm
amplifier: PAM8403
audio-input: 3.5mm jack to amplifier


texts: My keil5 doesn't make RTE_Device.h(Startup) in new projects

texts:
When I create a new project, I choose my micro controller(stm32f407VG) and check "CMSIS" and "Startup" in Manage Runtime Time Environment, but it doesn't build "RTE_Device.h(Startup)" under Device in project menu!

How can I fix that?


texts: LM317 output voltage is rising unexpectedly

texts:
I am using LM317 to get 5.5V out of 12V input

In my circuit R1 is 220R, R2 is 741R
Expected current is ~700mA.
link to the data sheet

This of course will produce a lot of heat, so I choose quite a large heat sink.
when working, The heat sink is getting very hot, I will probably have to replace it.

The strange thing however is that after about 2 minutes the output voltage rise to 8 to 9 volts.

This is very strange as I expected the overheat protection to protect this from happening.

Removing the heat sink altogether is followed by a drop of the regulated voltage as expected.

So, I am suspecting that the heat sink keeps the LM317 working, but something else is causing the voltage to drift upwards.

I will appreciate any explanation for this phenomena.


texts: Same address for different registers in LPC2418 UART

texts:
I have a very basic question regarding LPC2418 UART. The UART has got different registers with the same addresses. So while loading the data from the test bench, will it not load into all the registers?

1)  For example,RBR(receiver buffer register) and THR(transmit holding register) have the address 32'hE000C000.And I know that you can only read from RBR and only write into THR. So if(addr = 32'hE000C000) data = 32'h10100010; wont the above code write into both THR and RBR?

2)Same case applies even for IIR(interrupt id reg) and FCR(FIFO control register) as they share the same address E000C008 and there is no signal to distinguish between the two registers like we could have used a sel signal of a mux to select either IIR or FCR,but there isnt one.


texts:
Are there differences between residential circuit breaker and industrial circuit breaker? When I browse through various online catalogs on circuit breaker, ABB and Schneider Electrics are often labeled as "residential", but when I look up Eaton, they claim their circuit breaker to be "industrial". When I compare their specs, I cannot tell the difference.

I am planning to use a few MCB on a control panel, but not sure whether I should go with residential or industrial MCB...


texts: Why are there no BGA chips with triangular tessellation of circular pads (a "hexagonal grid")?

texts:
Ball grid arrays are advantageous integrated circuit packages when a high interconnect density and/or low parasitic inductance is paramount. However, they all use a rectangular grid.

A triangular tiling would allow π⁄√12 or 90.69% of the footprint to be reserved for the solder balls and the surrounding clearance, while the ubiquitous square tiling only allows π/4 or 78.54% of the footprint to be used.

Triangular tiling would theoretically allow either reducing the chip footprint by 13.4% or increasing the ball size and/or clearance while maintaining the same footprint.

The choice seems obvious, yet I have never seen such a package. What are the reasons for this? Would signal routing become too difficult, would manufacturability of the board somehow suffer, would this make adhesive underfill impractical or is the concept patented by someone?


texts: Modelling the equivalent series resistance's voltage in a circuit

texts:
Say a 2H inductor has an equivalent series resistance of 2000 ohm at a particular frequency.  Logically to me, that inductor would be modeled as an inductor in series with a resistor.  However, that doesn't quite work in my mind.  For example, that would imply that the resistor has its own voltage across it, when (I believe) it is the same as the voltage across the inductor itself.  If that's true, then it would be a parallel resistance, not a series resistance.

I obviously misunderstand something.  How do you model it?


texts: What switch do I use so as to be open when pressed, and closed otherwise?

texts:
I need a switch that turns the circuit off when pressed on, but turns on when lifted off. this is to go under a lid I am making to turn on the lights when lifted. What is this switch called? it is the the only missing piece of the puzzle...

Update: I need a switch for one circuit. low voltage @4.5v. What is the switch called, or is the more than one switch needed.


texts: PIC24 Open-Drain Config for 5V PWM Operation

texts: I'm running a PIC24HJ series processor with a supply voltage of 3.3V. I need my PWM signal to be 0-5V, not 0-3.3V. Can I simply connect the PWM line to a 5V supply with a pull-up resistor? Or do I need to configure the pin for open-drain control with a pull-up resistor to 5V?


texts: Memory interfacing with 8086: IP/CS pointers in EPROM while RAM addresses start at F0000H

texts:
Design an interface between 8086 CPU and two chips of 16K x 8 EPROM and
  two chips of 32K x 8 RAM. Select the starting address of EPROM suitably.
  The RAM address must start at F0000H.

I have a doubt how RAM address starts at F0000H as the IP and CS pointer will be present in EPROM as it is initialized at FFFF0H.


texts: Should I optimize ground plane for AC or DC return currents?

texts:
I am doing  a 2 layer PCB. Based on my resaerch I have solid ground plane on the bottom and try to route as much as possible on top with unavoidable crossings on the bottom. (see here and here). But you can have at least 2 ways implement such crossing (horizontal and vertical) and the question is about the best way to roganize them.
I explain further based on my example:
I have digital connector on top (designed to be plugged directly to a part of I/O of Raspberry Pi). Therefore I preferred vertical crossings, because they present smaller obstacle for the DC currents flowing toward ground pin on the top connector (yellow line).But then I remembered that AC currents (light blue) try  to follow the corresponding trace on top, and got doubts if got it right. The question in other words, should I keep current implemention or scrap it and try to minimize the paths of AC return currents?
The  AC in this case is represented by SPI interface, which despite being nominally relatively low frequency, would still produce high frequencies on level transitions (edges)
EDIT: while giving it a thought I  decided to move the IC on the top right to the left and here is the result:

I beleive, this improved the layout (i. e. eliminated the cluster of crossings) to the point making the question irrelevant for this example. But since this sis perhaps not my last  engineereing task, I still would like to get the anwser.


texts:
I want to read the state of a switch sensor (magnetic contact). I'm thinking to connect the switch between an interrupt pin of my micro and ground, listening for CHANGE status.
In this way I have debounce problems, so I wonder what's the best way to deal with this problem:

1 - Disable the interrupt listening when it fires and enable it after the program has read the value (0 ->ground->switch closed OR 1->floating->switch opened)
I don't think a floating state could be good, but if I set the interrupt input pin as INPUT_PULLUP it's no more floating and could be good, am I right?

2 - Connect the switch to an interrupt pin and also to a digital input pin through a transistor as a switch.
In this way, when the interrupt is triggered I read the value of the digital input pin. On the other hand, in this way I complicate the circuit

3 - To use an hardware debounce circuit

Are these three solutions valid? Are there any more better than these?

MORE CONTEXT:
I'm using these switches as limit switch for a garage door.
In my code I'm using a timer to raise the garage door for ten seconds OR until the limit switch interrupt is triggered

EDIT:
with a change in my code I solved the problem using interrupts. However you suggest to use polling since it's not a real-time application, so I wonder: isn't better the same to use interrupts so that I can use a power safe mode for my micro and wake-up it only when an hardware interrupt is triggered? If i use a polling solution the system would not be suitable for battery power supply; isn't it?


texts: Strategies to come up with chip design (Full Adder in this case)

texts:
(I'm not asking for a solution to the Full Adder chip design, just strategies for how to come up with a solution myself)
For a course I'm following (Nand2Tetris), I'm trying to design a Full Adder using previously designed chips and logic gates (starting with Nand gates).
Designing the Half Adder was extremely easy and obvious, but I'm really struggling to come up with a design for a Full Adder. Even knowing that I should be able to use 2 Half Adders and some other basic gate(s), I still can't figure it out.
I can tell I'm not smart enough to crunch it in working memory, the brain power is just not there. I keep staring at the truth table (['a', 'b', 'c', 'sum', 'carry']) and my Half Adder diagram and rebooting over and over, not getting anywhere.
I also derived the canonical form for sum and carry, where for example: $$sum = (\lnot a \land \lnot b \land c) \lor (\lnot a \land b \land \lnot c) \lor (a \land \lnot b \land \lnot c) \lor ( a \land  b \land c)$$
but it doesn't seem like the right way to go about it.
I also tried staring at a binary addition example and working through it in my mind, but again the brain power just isn't there to translate the operations directly into chip design.
Question: Is there a strategy I can use to overcome the lack of brain power? How can I figure out the design of the chip in a systematic way? Draw more? Look at the truth table in several steps or break it down in smaller tables?


texts: Why is there a large "well-shaped" distortion when the input voltage exceeds the power rails of an op-amp?

texts: The specific model in question is the LM258 op-amp. After looking at its datasheet I understand why the output swing at both the positive and negative voltages, however I don't understand the physical scientific reason as to why the waveform distorts when the input pk-pk voltage is increased significantly beyond the power rails (+-6V) . In the shown diagram, the input peak-to-peak voltage is only 14 V and there is significant well formation.


texts: How do I measure the reactive power of a single phase system?

texts:
In books and various websites, I have seen that the reactive power is measured using two wattmeter method. This method is applicable to a balanced three-phase system.
But at home, just a single phase is supplied. And we use different types of load. For example water pumps, electric fans, LED, etc. Is there any way to find the value of the imaginary power? The load impedance is also unknown. (As it varies time to time)


texts: Variability in color temperature of white LEDs

texts:
I am trying to understand what causes variability in the color temperature of white LEDs.
I recently got some white LED strip lighting and it was sold to me as having a color temperature of 3000K. I also have some overhead LED downlights that were of the recessed bulb type and they also are supposed to be 3000K.
I used a high-quality spectrometer to measure the color temperature of all the lights. I found that the down lights varied from 3000 by about +/- 50K. Also, if I measured the same light multiple times I got a variation of +/- 5k, which I guess is the limit of precision for the instrument. The down lights where never less than 2975K or more than 3080K.
The LED strip, however, was a completely different story. Depending on where I measured on the strip it varied anywhere from 3200K to over 3400K. If I measured in the same spot, I got the same +/- 5k, just like the overhead lights. Why would the strip be so much more variable? Also, how do they control the color temperature of the manufactured LED in the first place?


texts:
I found this circuit that will auto switch between power between USB (5V) or a LiPo Battery (3.0V - 4.2V range).

The schottky diode, D4, can have a voltage drop of about 0.4V which is too high for me. I need the voltage to be 5V with 0.2V tolerance at the maximum. I'm thinking of using an IC similar to U2 in the schematic. But rather than a 3.3V output step-down IC, I'll need a 5V boost output one and at least a 600mA output.
Is there an IC that can do that even with a 4.6V input?


texts: Providing external voltage to a motor connected to arduino

texts:
I am a noob in electronics . I am just learning it bit by bit. The below is my connection.

As you can see pin 13 is connected to one terminal of the motor and the other terminal of the motor is connected to the 5V source of the arduino. My motor is a 9v motor and hence I would like to operate it at 9v so how can I do this? Help is appreciated .


texts:
I have built a breadboard prototype of the following dummy load schematic:

however, neither the current stays stable nor the potentiometer adjustment to vary the current is working as was expected. I have done three modifications to the original circuit by:

using 9v dc from a wall AC-DC adapter instead of supplying 12V DC and a voltage regulator

removing the 1N4004 diode and the capacitors

I wonder is my circuit unstable due to above changes and/or the breadboard is also contributing to the problem.
Replacing the 1.5 ohm with a 1 ohm resistor didn't make a difference. I have also tried using a 2 x 100nf and a 10uf cap on the power rails but it still doesn't work. After triple checking the connections and building the circuit again from scratch I am unable to solve the issue on my own.
So could you please help me figure out the problem?
EDIT
Here is my actual circuit

I rebuilt my circuit again and now I am reading around 0.6 A flowing in the circuit that is very slowly going down (like 0.001 A per second). Some other measurements that I have done are as follows:
Power supply voltage : 9.19 V
Mosfet V+ : 9.19 V
Mosfet Out1 : 0 V
Mosfet Out2 : 5.65 V
Vgs = 5.65 V
Vds = 0.012 V
Now adjusting the variable resistors isn't having any effect on the current value. Getting more and more weird :(


texts:
The same circuit as in Explain “Audio Loopback Dongle"; I wanted to know how it worked. Anything I couldn't figure out I found out via CircuitLab's time analysis:

simulate this circuit – Schematic created using CircuitLab

This is how I plan to use it. I want to know ahead of time if there are any problems. Will it smoke the phones?

simulate this circuit

One thing I can't decide. Should the ground lines be connected?

simulate this circuit

Edit v1: Changed the 0.1 uF capacitor to 1 uF because the 200 Hz signal was too filtered. Compensated by reducing the 100 Ohm resistors to 50 Ohm to keep the microphone signal between the standard 5-50 mV. Hope this makes sense.

Edit v2: Well it works. Only the grounded version above. I have no idea. Why? Answer this and I'll accept. I hope it doesn't switch the jack from CTIA to OMTP and bypass the entire circuit. Also the ground and mic lines on the left have to be shorted for a headphone to be detected.


texts: I have a problem to understand how electromagnetic waves works. Why do transistors create EM waves when they're switching? And difference between antenna and transformer with secondary coil. When I have a antenna, the EM field is changing and electrons go forward and backward and the circuit with antenna isn't closed, so we can turn on a light bulb with two wires. Transformer uses also AC, so why does the circuit need to be closed to flow current?


texts: Oscilloscope: when to use coaxial instead of probes?

texts:
I understand the difference between passive and active probes, and between x1, x10, x100, ...

I also understand that at high frequencies the capacitance of the oscilloscope has to be considered, so a 1 MOhm probe in x1 or x10 cannot be used at, for example, 300 MHz, because a capacitance of 9 pF means a 59 ohm impedance, and a 50 Ohm input oscilloscope would be much better.

But I also saw that sometimes a coaxial cable is connected between the DUT (device under test) and the oscilloscope. When is better to use a coaxial? Why would I use a coaxial instead of a probe?


texts: Is it possible to enable wireless switching between two EV charging circuits using a relay and an ESP32 controller?

texts: I am working on a project where the end goal is to enable bidirectional charging in an electric vehicle. The vehicle is equipped with a unidirectional OBC that connects to the 230V AC mains via a Shuko-CEE 16A-6h cable. My company will be replacing the current standard Shuko socket with bidirectional charging poles. The next step is to enable the vehicle to feed power into the pole. My idea is to construct a secondary circuit, meant only for discharging power from the battery to the pole. The plan so far is to hook up a DC/DC boost converter to the high positive side of the 48V battery, boosting the voltage to match the desired mains voltage and discharging into the grid. For switching, I am thinking of using a relay between the OBC and the discharging circuit, controlled by a WiPy 3 micro-controller for remote switching. Could anyone please let me know if this can be achieved?


texts: MOSFET Gate Current Draw and Understanding Gate Driver IC Datasheets

texts:
I am building an ESC for a three phase BLDC motor based on the ST demo board STEVAL-ESC001V1.
For the given motor I have currently decided on using a Nexperia PSMNR90-40SSH MOSFET.
Based on the Vishay document AN608A, Toshiba document "MOSFET Gate Drive Circuit", and TI document SLUA618A, I have been able to calculate the on and off times of this MOSFET using a 36 Ohm (external) gate resistor; ton working out to be approximately 269ns and toff being about 391ns.
Based on RC circuit theory, the peak gate current will be about 278mA (10V/36 Ohms @ t = 0s).  Based on the total gate charge (~110nC) the current required to charge the gate is 11nC/269ns = 408mA (based on my reading in the Toshiba document this would result in a 24 Ohm gate resistor).  Which value for gate current and resistance is correct to use?  Is my approach to calculating estimated switching times using the Vishay document correct?  Why do the numbers not line up?
Next I am reviewing the datasheet for the L6398 gate driver IC from ST which is used on the demo board.  The datasheet states that this IC can source 290mA and sink 430mA (typical), and the minimum it can source/sink is 200mA/250mA.  How does ST derive these values, what do they mean, and how do I apply these values to the design I am working on?  How can this be a minimum value if these are short circuit currents?
It is rather overwhelming how much information is out there.  Could someone with experience designing such a circuit provide me with some guidance?


texts: Side of length matching within a differential signal

texts:
When we are matching the length of positive and negative tracks of a differential signal in a PCB, is the position of matching important? Does it matter we match the length immediately after the transmitter or the receiver? If yes, which side is preferable and why?
It seems there is no discussion about it in the Internet!

I have drown an image to clarify the question:

Edit:
The length difference is mainly due to the connection of tracks and pads as shown  in this picture:


texts: How to interchange between two cores (inside a coil) in a simple brushed motor

texts:
I am going to build a very simple brushed DC motor. The rotor will not be enclosed in a stator (the rotor will be built on a bench with free space around it), and I will using permanent magnets to make the external magnetic field.
I plan to compare the torque generated on the rotor with a non-iron core, with the torque generated on the rotor with an iron core (the two cores will have the same dimensions). I will do this at stall torque, and I think this will help me find the permeability of the iron core (assuming the non-iron core has a known permeability). The permeability isn’t constant in a ferromagnetic material such as a material made up of iron but knowing the permeability at stall torque should be enough for this assignment.
The best way to compare the two different torque values would probably be to just build a single rotor with a single coil and have the ability to just interchange the cores since this hopefully will eliminate some error when comparing the torque. This would mean that the coil can't be permanently attached to the first core, although the coil also has to be attached strong enough so that it doesn't fall off when the rotor spins. I got this suggestion from an electrical engineer, but I can't get in touch with him anymore. I could also build two different motors and try to make them as similar as possible to eliminate error, but the first option I think is better if it's possible to accomplish.
The dimensions of the cores will be 30x28x90mm (it's a rectangular shape, I couldn't find a cylinder), and I have the ability to cut and drill the iron core that I’ve bought, although I can only cut and drill across the short end. I plan to put the axis of rotation across the short end, but I don’t know if I should make the axis by drilling a hole (and inserting a small steel rod), or by cutting the core into two pieces and attaching each piece to a bigger prebuilt axis. This decision could influence my main issue, namely how I can switch the cores.
Any help is greatly appreciated, and please let me know if the question is unclear or badly formulated, and I will explain more about my assignment.


texts:
I recently bought a 10-30 kV DC, 8-10 mA power supply that I am looking to test before its incorporation. However, the retailer advised me that I should place a load on this power supply - as one usually should - before testing.

When looking at methods of doing this, I have come to the conclusion that using a string of 1 Meg resistors should act as the load and then finish the circuit at a grounding rod. The only major issue with this set up is that I am not aware of the actual load's resistance that I am planning to use the power source for once testing is complete. In order to maximize voltage output by the source, I was wondering if my voltage drop due to the resistor's load should be greater than the 10-30 kV range that I am working in or if I should exceed it. And if it should be exceeded, by how much? Thank you.


texts:
Context
The project is using the SPI output of an Espruino Pico to send messages to an LED strip controller. The issue is that occasionally the Pin is damaged. Using an oscilloscope has shown that there is some noise on the comms lines. The thinking is that occasionally there may be voltage spikes that have traveled along the comms line and blown the pin (although this has been seen on the scope). I am looking for a way to electrically protect the SPI pins. I set up a transistor in line so that the SPI signal would switch the transistor, but the voltage drop was too great and the signal is inverted, making this not an option. I have also tried an optoisolator, but with no luck.
Question
Is there a chip/IC that can achieve electrical isolation for an SPI line?
Thanks in advance for any help you can give.


texts: BJT Differential Amplifier deliberately saturated?

texts:
Happy New Year!  I've recently completed a metal detector project (see my recent questions) and I've been going back over some of the parts I didn't fully understand first time around.

This question relates to the differential peak detector section and my simplified spice model equivalent.  I was trying to compute the small signal gain according to some standard equations (i.e., Rc/2Re) and comparing them to the spice output, but was confused by what I saw.  I was expecting a very large gain (>600 according to the standard formula), but instead spice was reporting a rather disappointing Ad of < 90.

It took me a while to figure out that Q1 (see spice image) is saturated and I'm guessing the typical formulas don't apply.  Unless I've made a stupid error, I think I know "why" Q1 is saturated:  the output impedance of the DC reference is (by my calculation) around 260k; this high impedance coupled with a high value collector resistor is starving the transistor of current and forcing it into saturation.  The transistor wants to draw 700uA/2, but it can't.

So, assuming my analysis about the arrangement is correct, why would the author deliberately saturate Q1?  Is this a common pattern and what are the advantages of doing this?  Also, given that the standard formulas no longer work it seems, is there any "pencil and paper" way to calculate the AC gain at the output? (by this I mean, what heuristics might the author have had in his head when putting the arrangement together) Many thanks!


texts:
If a battery of 60v with internal resistnace 4kohm (in series) is connected to a zener diode of v_z=10v in parallel and a load resistance of 2kohm in parallel too, what will be the currents in different circuits. since zener diode will breakdown at 10 v the load voltage will be max 10 v so as 60 v is > 10 v the currrent in load must be 5ma and the remaining 50 v will be across internal resis. so the current in that branch will be 12.5 ma and using kirchoff's rule the remaining current must be 7.5. but this is wrong. I don't understand why. this is surely due to conceptual mistake.

simulate this circuit – Schematic created using CircuitLab


texts: Is it safe to define a memory section over multiple physical memories?

texts:
I am working on the memory mapping on my MCU.
Let's say I have this mapping for physical for memories:

 0x1000
     RAM 0
 0x2000
     RAM 1
 0x3000

Then I have memory allocation. In this part the RAM 1 is not used as a whole:

RAM0 : origin = 0x1000, length = 0x1000
RAM1 : origin = 0x2000, length = 0x400  // <= Only 1Ko used

Then I have sections:

.stack : > RAM0
.ebss  : > RAM1

This is just as an example, since it is not the reality of my project.

To avoid wasting memory in RAM 1, I'd like to create a memory allocation over both memories:

RAM0_M1PART1 : origin = 0x1000, length = 0x1C00  // <= Added 3Ko here
RAM1_PART2   : origin = 0x2C00, length = 0x400   // Moved at the end of the range (2C00 -> 3000)

The question is quite simple: is it safe?

Thank you!


texts: Need Help With OpAmp Circuit for Cell Phone Recording

texts:
I'm trying to make a simple circuit that will allow for the combining and recording of both sides of the conversation by tapping into the connection between a cell phone and a headset.

For convenience sake, I want to also use a spare cell phone as the recording device due to portability,etc.  I am using iPhones for the cell phones in this application, although that shouldn't matter.

NOTE: The iPhones provide approximately 1.8V to the microphone to power it, thus my decoupling capacitors on both the input and output.  The 4.7K on the output is to trigger the recording iPhone to switch over to external mic mode, otherwise it will only record the internal mic and ignore the input signal.

I've tried designing this to the best of my knowledge and understanding, however I am not getting anything on the outputs.  I've checked the input with an oscilloscope and I'm getting a good signal at the opamp input pins, but nothing on the other side.  I've tried changing out the IC and still nothing, which I'm guessing there's a flaw in my design since I don't fully understand each component's role/effect in the circuit beyond basic theory.  Any help would be awesome and much appreciated.


texts: Does the equation V1 X I1 = V2 X I2 hold for a transformer when coefficient of coupling is less than unity? Or does the coefficient have no relevance?


texts: Does this circuit, used to subtract capacitive responce, have a specific name (picture in body)?

texts:
What I'm doing:

I'm applying voltage pulses to thin films and measuring the resulting current transient, then using these transients to extract the hole mobility.

The problem:

When the films are very thin, the transient cannot be observed as a result of a capacitive response. The paper I am reading from describes a circuit used to "clean up" up the transient by removing this capacitive response:

  In order to overcome this problem, we used a simple bridge circuit ... where a differential ampliﬁer is used to subtract the capacitive
  response of the circuit recovering the ‘‘pure’’ SCLC transient

The problem, as my background is in physics, is I have no idea how I'd even start to use this circuit (connecting with the oscilloscope, what values for the components etc).

What I'm asking:

Does this type of bridge circuit have a specific name so I'm able to learn about it and find out how I'd be able to use it? I'm basically just asking for a starting point that will allow me to read into how this circuit would work.

What I've tried:

General googling on bridge circuits, but it turns out it's a massive topic and I wasn't able to find anything specific to subtracting capacitive responses.
In the paper I linked, it says the circuit is "described by Scott et al [21]". I have found this paper, however it is locked behind a paywall.


texts: Current draw of through hole LEDs and LED strips

texts:
I'm confused about led current draw, my understanding of through hole LEDs was that whatever current is going through one, is going through the others. By that I mean if I had 3 1.5v 20mA LEDs I would only require a 4.5v supply with 20mA output.

So the reason I'm confused is that I read my led strip requires .4A per meter... What does that even mean, do I need a whole amp for 2 meters now?

My application is in actuality driving 1 meter strip of rgb LEDs. So what current output would I need per channel on an led driver chip? 400mA I suppose...?