texts: Integral in mathematical expression of capacitor/resistor LTSpice

texts:
I know how to simulate a variable resistor in LTSpice. For example for a heating resistance the equation can be made by considering heating equation and can be expressed like R=(Ri-Ao*EXP(-time/To)) and further simulated,

But how to write a more complex mathematical expression like below-


texts: Does the orientation of transmit antenna affect the path-loss of a signal transmitted by an omni-directional antenna? If so, how are antennas optimally oriented? I am specifically interested in knowing how eNode antennas in LTE are oriented in the downlink transmissions to ensure propagation loss is minimized?


texts:
I'm using DC/DC converter LTC3112 to supply GSM module. Battery source is about 12V and DC/DC output is 3.7V. Microcontroller logic is 3.3V powered from other DC/DC converter. The application is working fine but I want to limit the in-rush current in new PCB which charges the GSM capacitators using resistor and MOSFET-P as a bypass. The schematic and components values are just a draft. I would like to limit the DC/DC output current to 300mA when MOSFET-P is off and turn it on through microcontroller GPIO to bypass the resistor. The peak current flown through DC/DC and MOSFET is 2A.

I would like to use IRLML6401 as a MOSFET-P but Im not really sure if it will work properly. I'v got IRFML8244 (MOSFET-N) in stock  as well.

1) What is the best way to make such bypass circuit using MOSFETs?

2) Is it possible to make such a design to drive MOSFET from single voltage rail, let's assume I don't have 12V and only 3.7V?

simulate this circuit – Schematic created using CircuitLab


texts: Is it possible to eliminate output ripple of SMPS's by using two parallel SMPS's to produce outphase outputs to each other?

texts:
simulate this circuit – Schematic created using CircuitLab

Obviously it can not be that way. But why? Imagine one converter with a phase detector of its switching frequency, outputs a flag when the phase is 180° and other one synchronises its own oscillator to output an outphase ripple to other. Then it will be like below:

Green one is the output sum of two AC ripples and the common DC. What are the reasons why this can not be done?


texts: The task is to calculate i here, and the answer is 0.5A (specifically -0.5 due to its direction) but I have no idea how to get that. I've tried separate calculations of the circuit with only 1 voltage source and adding them up but I seem to be getting 1A. Any hints or tips?


texts: I am referring to the symbol with +4V next to it. Seems like a voltage source to me. I just haven't seen this anywhere before.


texts: Choice of heating element (power resistor)

texts:
Basically I need heating element which can heat up small volume of air (lets say shoes box size) up to about 60 C degrees. I am going to use 25 V source supply with 2 A current.

What I thought about doing is:

Cp= 1.00 J/gK (air specific heat)
q=1275g/m^3 (density of air)
V=0.05m^3 (volume of air I need to heat up)
T=333.15K - 293.15K = 40 K
Lets assume room temperature is 20 C = 293.15 K

How much energy does it need to heat the 0.05m^3 volume of air:

U = cp * m * T = 1*1275*0.05*40 = 2550 J

If I want it to heat that kind of volume in 2 minutes how much watt do I need?

P=U/t = 2550/120 = 21.25 W

So I know how much watts should heating element produce, but what about ohms? Should I calculate Resistance needed by:

P=I^2 * R   where I=2A, P=21.25W
R=21.25/4 = 5.3125 Ohms

So my resistor should be 5.3125 ohms and handle AT LEAST 21.25 W (probably much more for safety?)

I am just asking if my calculations is correct as I don't know if i am going into the right direction and doesn't have anyone to ask about it.

Thanks for any help :)


texts:
I am trying to connect an ESP8266 module to an Arduino. Giving the fact that ESP8266 runs at 3.3V and the Arduino at 5V i need a logic level converter from 5V to 3V3.

Is there a way i can build one using discrete components? I searched the web and found recommendations for TXS0104E / 74LVC245 / BSS138, unfortunately none of the local shops sell them.

Although the 3.3V TX pin from the ESP8266 does not require a logic converter since Arduino will read the 3V3 signal as HIGH, i would like to add some protection for the wifi module. Is a 3.3V zenner diode a wise choice for this?


texts: Where does an ARM based system find its OS?

texts: I'm not sure if this question is device specific. After some reading I found that you need a bootloader to load the OS. Is there some specific memory address where the code of the OS begins, else how can the bootloader find it? And about the bootloader: is the ARM bootloader really just the code at the reset vector that gets executed when you power on the device?


texts: USB ground on MSP430 Launchpad interfering with Comparator_A input voltage

texts:
I'm trying to read an audio signal from an Android phone as a serial input to an MSP430G2553, adapting this design to use the MSP430's onboard comparator module instead of an LM324. The Android code to make a square wave out of the audio jack is available here. The output is not pretty, but that's for another question.

In my case, the comparator's positive input is the internal precision voltage reference (0.5*VCC) instead of an external pot. I have applied a DC bias to the audio signal in order to center it around the 0.5*VCC mark before going to the comparator's negative input on P1.5 (CA5) like so (the AUDIO net is CA5):

Here's where things get weird. Now, if I plug in USB to the Launchpad to debug, the DC bias on the CA5 input cuts in half from 1.6V to about 800mV. What could possibly be causing this?

I've tried:

Confirmed that ground between the MSP430 Launchpad board and my perfboard are nicely connected together like they should be.
Set up all of my MSP430 peripheral config in the Grace GUI tools so there's no chance of a careless mistake in setting up a register.
Disconnecting the jumper that powers the MSP430 over USB and powering up the 3.3V regulator on my perfboard (there's a DIP socket on the perfboard waiting for the MSP430 once I'm done debugging code). Neither source solves the problem, and the measured VCC-GND voltage is exactly 3.3V in both cases.
If I run the MSP430 off external power with the USB cable disconnected (no debugging!), I get my 1.6V bias like normal.
Took my laptop out and verified that it wasn't something weird with my work computer, connecting USB to the laptop causes the same behavior.
The bad 800mV bias will temporarily go up to the desired 1.6V if I hold the MSP430 in reset with the pushbutton on the Launchpad. Releasing it from reset immediately restores 800mV.
Swapped in another MSP430G2553.


texts: How do I plot the response to a step disturbace of a control system in the time domain?

texts:
I would like to plot the time response of a step disturbance of a control system, but I am not sure what I have to plot.

I have tried to plot the step response of the Sensitivity function, but I am not sure it is the correct thing to do. So, what I have done is something like:

s = tf('s')
S = 1/(1+C*P);

step(S)

I my case, by doing so I get:

where in my case I have plotted the step response of different sensitivity functions.

Is this the response to a step disturbance? And if yes, how do I interpret this?


texts: With Altium 17, what is the result of placing and SMD Pad inside Solid Region?

texts: When an SMD pad resides in a solid region, created with default settings, is the result the same as if the pad were inside a polygon pour with the exception that there is no thermal relief?


texts: How to filter noise of different frequency based on motor power

texts:
I am taking torque readings from strain gauges on an actuator and trying to filter the signal to look usable. I have already put in place a median filter that reduces sporadic spikes.

When I have the actuator locked, I can set its power (through PWM duty cycle) to different values and see the torque readings accordingly.  In such a situation, I have 0.1Nm of noise. This is acceptable.

However, when I leave the motor unconstrained, and set it to turn at different speeds (again, set it to different powers through PWM duty cycle), I get high noise on the torque sensor readings that seems to have a direct relation with the speed of the motor.

In this image, you can see the readings while the motor goes from fast to slow in 4 quite obvious steps:

(Obviously, since the motor is free running, the torque readings are (should be) a constant 0.)

My question is, how can I filter this data during the operation of the motor? Offline processing is out of the question, and I imagine the filter window can't be too large (as it produces a large latency in reading the current torque value), but perhaps that's inevitable?

I thought about a low pass filter, naturally, which would work great for high speeds of the motor, where the noise frequency is quite high, but as the motor slows down, I would essentially have to look at seconds of history to be able to filter out that low frequency noise, which is just too high to be useful for feedback control.


texts: Antistatic wrist strap without earth - ESD protection when using an inverter

texts:
I would like to be able to work off the grid on electronic circuits and I have at my disposal a large 12V battery and inverter (used for lighting in the remote location) which give me the problem of no mains earth being present.
Would using an antistatic wrist strap (wired to 3 pin mains plug via 1M ohm resistor) with an inverter still provide effective ESD protection when handling components and circuits?

I also have a wireless antistatic wrist strap but have read online (and seen the debunk on EEVblog) that they are ineffective.


texts:
I am trying to build an audio amplifier circuit based on this design using an LM386 opamp. On the output side (pin5) an Arduino is connected constantly reading out the pin

#include <Arduino.h>

const int analogPin = A0;

void setup() {
  Serial.begin(9600);
  pinMode(analogPin, INPUT);
  Serial.println("Setup");
}

int i=0;

void loop() {
  int val = analogRead(analogPin);
  Serial.print(val); Serial.print(" :"); Serial.println(i++);
  delay(1);
}

The result is constantly reads ~30 (out of 1023 range of the analog pin). I have redrawn the circuit looking only on the breadboard  (soldered PCB) and added the measured voltages across key points (using oscilloscope, time scale 5ns to recognize fast changes).

After inducing sound (knocking, clapping,...) no change on the output side of the opamp is detected.

A similar article states

  Pin 5 is the output. It is biased to 1/2 of the supply voltage Vs

The opamp is supplied with Vdd (4.64V). For the power supply I used the Arduinos internal 5V and an external power source, connected via the same Vss.

Is the detection too slow? Do I have an error in my schematic?


texts: PI filter (on PSU) and electrolitic capacitors after

texts:
I am designing a small DAC and I want to clean the power supply (its noisy) I used a PI filter.

However after the PI filter , I need an electrolytic capacitor (330uf) to help with some transients. The problem is that the output of PI filter has a capacitor that its in direct correlation with the L...so by adding this electro capacitor I will change that correlation...so any pointers on what to do ?


texts: How to fade in and out light bulb(220V) (Arduino)

texts: I have relay conected with arduino and high voltage bulb, now how can I control voltage to fade in and out bulb? I know that a relay is an on off device so maybe a triac or IGBT would be needed?Would an optpcoupler be good for isolation? Should I use a PWM output on the arduino?


texts: How to prevent Buzzer circuit to drain battery

texts:
This circuit drains my battery way too fast.

What can I change to minimize the power consumption?

The Buzzer is a electromechanical variant with these specs:

Rated Voltage:3V;
Operating Voltage:2VDC~5VDC;
Frequency:400±100Hz;
Rated Current:≤25mA;


texts:
I've been experimenting a bit with time-lapse photography lately. Still basic stuff. Right now I have to change batteries every so often which is a pain because it's hard not to move the camera when changing the batteries. I've used the ACK-E6 power adapter to run my camera from mains, but this is only possible in some situations.

So I'm looking to somehow attach some higher capacity batteries to my camera.
The regular batteries for my camera (LP-E6) deliver 7.2V. The specifications of the ACK-E6 mains adaptor list the output to the camera as 7.6V 3A.

I've read some things about buck/boost regulators (but I'm hardly an electrical engineer) that I can use to regulate the voltage to that desired 7.2V for my camera.

The goal is to attach a 12V car battery, but have other (smaller, lower weight) options if needed.

I was thinking of buying this buck/boost regulator (or one like this):
3A Power Adapter DC 3.8-32V to 1.3-35V Automatic Buck/Boost Voltage Regulator 3A Drive Power Supply #090040
http://www.aliexpress.com/item/5-PCS-LOT-3A-Power-Adapter-DC-3-8-32V-to-1-3-35V-Automatic-Buck/1609180228.html

I guess the numbers add up, and this should work. But I'm not really sure about the possible risks, because I don't want to damage my camera.

I've searched a lot but I can't really seem to find an answer, so that's why I'm asking here.

Is there a possibility that the 12V from the input goes straight to the output? Are there other risks I have to take into account before attempting this?


texts: How to make pulse wave from sine wave - audio frequency

texts: I'm looking for a quick-and-dirty way of converting something close to a sine wave to a narrow pulse wave. Please see the image: a low bass note played through a broken transformer. I'm trying to re-create the effect, preferably using discrete components.


texts: Priority MUX - select one of the options based on previous value

texts:
I have several workers that need to access single bus (memory channel). Several of them can be ready at the same time and I would like them to alternate with writers having priority.

I have some pseudo-code with two writers and two readers to showcase but it's not good solution and I need it to scale with arbitrary number of workers (writers and readers come in pairs). I also care about resource utilization.

if curr_worker = wr0 then
    curr_worker <= wr1 when w_rdy[1] = '1' else
                   wr0 when w_rdy[0] = '1' else
                   rd0 when r_rdy[0] = '1' else
                   rd1 when r_rdy[1] = '1' else
                   dummy;
else if curr_worker = rd0 then
    curr_worker <= wr0 when w_rdy[0] = '1' else
                   wr1 when w_rdy[1] = '1' else
                   rd1 when r_rdy[1] = '1' else
                   rd0 when r_rdy[0] = '1' else
                   dummy;
else
    curr_worker <= wr0 when w_rdy[0] = '1' else
                   wr1 when w_rdy[1] = '1' else
                   rd0 when r_rdy[0] = '1' else
                   rd1 when r_rdy[1] = '1' else
                   dummy;
end if;

And just to be sure, the when-else statement will assign the first option when the condition is true, even if the next condition is also true, correct?


texts: What is the price of increasing the QAM number?

texts: In a QAM modulation scheme, you have a certain number of possible states which have different amplitudes/phases (like 4-QAM, 16-QAM). If you increase the number, for example switch from 16-QAM to 64-QAM, you will get a higher bit rate. But what is the price you pay for this bit rate increase?


texts:
I'm fixing a Denon AVR-788 AV receiver that won't boot but would turn on with the light in front blinking red. Naturally, I looked to the Service Manual (link goes to schematic) and started following the diagnostic procedure. It said to test for 5.6V between a couple pins on the power board. However, when I did that, the receiver no longer turned on.

I'm getting power after the sub transformer and after the bridge rectifier circuit (specifically a little over 11 volts) but no power to the input of the voltage regulator. There's a component that is labeled "ICP-N15" as shown on the schematic below which has power on the side of the diodes but none on the side connected to the regulator. I'm assuming that the N15 is what's preventing the regulator from getting power and is dead. However, I don't understand what this device actually is. Here's the datasheet for the ICP-N15. It's a 50V 600mA "Overcurrent IC protection device". The datasheet is pretty vague about what that means and I can't seem to find more specifics online.

So here are my questions:

What exactly is this and how does it work?
(Somewhat related) Is it a fuse?
If it's not exactly a fuse, can it be reset?
Am I right to assume that this is likely what's preventing the receiver from turning on? If not, what are some other possibilities/what should I check?

Also, this part is obsolete and I'm having a difficult time finding a similar replacement. Could someone point me to one? Thanks in advance!

Schematic for reference:


texts: Short "High" Output In Response to a "High" Input

texts:
I am new to electrical engineering. I would like to make a circuit that will go to low after a short given time (lets say 0.2s) of being High. Using graphics I would like to convert this:

to this:


texts:
Say I have an open circuit with a battery. I have a wire connected to the negative terminal and a wire connected to the positive terminal. The wires aren't connected.

In this scenario, would their be electron flow for a very short amount of time? Would the electrons from the negative terminal flow through the wire connected to it, since the potential would decrease between the electrons?

To clarify what I mean, consider the first diagram in this image:

In the first diagram there a large amount of electrons in the negative terminal. Would the electrons in the negative terminal distribute themselves through the wire to minimize the force between them?


texts: Is it normal for a micro SD card to have higher write speed for the first blocks?

texts:
I'm using a micro SD card of 4Gb from Kingston in an embedded project and I'm accessing it with a low level SPI driver.

Everything is running just fine, except for a weird behavior: after a given block (around 16 Kb of the card), the write speed drops to 1/3 of the first block's speed.

Is this normal? Maybe the first blocks of an SD card are of a higher speed memory, I don't know. Does someone have info about this?


texts:
I have a reasonable amount of experience writing drivers for pre-existing hardware and I am looking to develop my skills and learn some more.

Can anyone recommend good angle, resource or starting point for beginning the development of computer controlled electronics?

I'd like to get to the point where I can control a series of motors using C or C # via usb/serial from my PC using a custom built circuit.

I realise that this question is anlittle vague but without already knowing the terminology, its hard to find a better resource than good ol' stack exchange.


texts: Pole at infinity and zero at finite frequency

texts: Is there any circuit that has a pole at an infinite frequency and zero at some finite frequency? A first-order RC Low pass filter has a finite pole and zero at infinity and it makes sense, I am just curious if another way around is possible in circuits?


texts: Why would an audio circuit output through two caps like this?

texts:
I'm studying a circuit that is based on a clone of the Apple Mockingboard from way back when.  Being new to EE, the first thing that struck me as odd is why the designer put all three output pins for the audio IC through two capacitors that are arranged back to front.

For example, looking at the image:

...notice how Ch.A, Ch.B, Ch.C all pass through two capacitors where negative ends appear to be tied together ("Left Channel Combo" section).   Am I reading that right or is it just a goofy way the image was drawn?

Does that just mean the negative ends should really be to GND?

Any help in understanding this layout is appreciated.

Oh, the original URL for the image is here:

http://www.downloads.reactivemicro.com/Public/Apple%20II%20Items/Hardware/Mockingboard_A/Technical/Mockingboard%20Schematic.gif


texts: How are you supposed to work with enamelled wire?

texts:
I'm trying to work with Enammelled copper wire such as below, used for winding transformers due to its insulation. How on earth do you work with this type of wire?

When cutting the wire, the internal exposed copper surface is so small it makes a very weak connection. Am I supposed to blast the Enamel with heat and melt it away? Are there any common practices when working with this type of wire?


texts: Do I need to use any external parts with a voltage regulator?

texts:
I have recently bought a voltage regulator (link, specs, and datasheet below) and I am regulating a AC-to-DC 9v power supply into 5v with as little components as possible. In the datasheet, all of the diagrams use capacitors, and I don't have any on hand, nor do I have the desire to use them if I can. I have seen people create phone chargers with Altoids cans with only a voltage regulator, two wire, 9v battery, and 2 resistors (from 5v to to both of the data lines), so I don't know if it is just providing additional circuits for different uses.

Basic Information:

LM7805 L7805 7805 Voltage Regulator IC 5V 1.5A

Manufacturer: STMicroelectronics - SGS THOMSON
Manufacturer Part No: L7805CV
Package / Case: TO-220
RoHS: Yes

Specifications
Product Category: Linear Voltage Regulators - Standard
Polarity: Positive
Number of Outputs: Single
Output Type: Fixed
Output Voltage: 5 V
Output Current: 1.5 A
Line Regulation: 50 mV
Load Regulation: 100 mV
Dropout Voltage (Max): 2.5 V @ 1A
Maximum Operating Temperature: 150 C
Minimum Operating Temperature: 0 C
Mounting Style: Through Hole

From eBay descripiton.

Datasheet

P.S. This is not a duplicate of Proper use of a voltage regulator because that one is not about the schematics, it is talking about if it is needed in the first place.


texts: TEA1733T switching in small bursts and with very brief on time for [external] FET

texts:
I should start, possibly, by saying I am no expert on offline SMPS, but am having a go.

I have built up the schematic below:

I am getting no proper voltage out of the outputs. The transformer outputs are switching to negative voltages.

The image below shows:

Yellow (bottom trace): FET gate (Q1 pin 1)
Green: CTL (U1 pin 7)
Blue: Protect (U1 pin 6)
Purple: Vcc

The be absolutely clear, the bottom trace is a train of 17 pulses. The gate pulses are less than 1us, in the region of 700ns, which strikes me as being way too short.

The optimer pin on U1 doesn't seem to move. Vin_sense is bang in its correct range, I have an output load, but I'm not by any means stretching the transformer.

I have also looked at Isense, and below is the same type of scope traces, but with top trace as Isense, not Vcc.

I've read and re-read datasheets and apps notes, and although I did find three things with the original schematic that I have fixed to reflect what's in the above schematics I can see nothing else obviously wrong.

FWIW I am currently supplying the input voltage from a bench PSU at 142V, not yet directly from mains.

Do the very narrow pulses seem wrong? Can anyone see anything I am doing wrong? If you want some more scope traces or info, please ask.

The data sheet can be found here.


texts:
I'm a volunteer firefighter. We have two kinds of radio traffic. Tones and voice. Tones trigger our pagers, but are also audible when listening to the radio. The trouble is that the tones are much louder than the voice traffic.

What happens is that we turn the radio up loud enough to hear dispatch and other units, then tones are dropped for another call and they are incredibly loud. We scramble to lower the volume (which is not easy on the model of radio we have) and then have to turn it back up quickly as soon as the tones are over.

The radio is connected to a single speaker in the cab.

What can I put in-line between the radio and the speaker that will let me temporarily reduce (ideally not mute) the volume quickly and return it to its original volume?

I'd really like a momentary switch (foot peddle). My initial thought was to use a simple resistor, but now I'm thinking that won't work as expected. I need something simple and robust (firefighters are good at breaking stuff).


texts: To what pins of the relay do I need to connect a device to be able to control that device ? NO or NC? Why?

texts:
I am very bad at electrical things, as I don't understand much of electrical engineering.

I was tasked to design a software that will take some inputs, randomize them and give some outputs to some relays. I did the software and somebody else designed the circuit.
The problem is that now that somebody else is on vacation and I need to explain how to make connection to the relay and I have no idea how.

First of all, I found terms of Normally Closed, Normally Open, Active Low and Active High and I have no idea what they mean. I read about them but I do not understand.

Secondly, this is the relay module:
https://www.tme.eu/ro/details/oky3012/module-pentru-relee/okystar/

https://i.postimg.cc/kg9xyGJ6/prime-presentation-pres-0004.jpg

It doesn't say which is NO, COM, or NC.

Thirdly, I understand that I can use a multi-meter to check for resistances from only-God-knows-where to I-have-no-idea-which point.

The program that I did on an ESP32 sets the relays output pin to HIGH, which means that the relay is off or not activated (for me it's output. basically the pin that will control something):

pinMode(Relay1_1,OUTPUT);
digitalWrite(Relay1_1, HIGH);

And when I want to activate the relay or switch it on (make it click) I send a LOW signal to it.

digitalWrite(Relay1_1, LOW);

To what pins of the relay do I need to connect something to be able to control it?


texts: How sinewave pwm inverter filter output?

texts:
I know about inverters is as follows (correct me if I am wrong)
DC source such as battery fed current into transformer by controlled switches such as mosfet or IGBT. This controlled current fed into primary side of step up transformer. While the control circuit modulate the high frequency carrier wave and referance sine wave. By modulating we get gate signals as follow.

Using fullbridge we converte DC waveform into single sine wave PWM signal. And when fedding it to primary winding of inverter we use LC low pass filter and use filter also on output(I read on research paper but not sure).

Ok my question is:

How to filter this PWM sine wave into sine wave? Does LC filter do the job?

This inverter circuit I explain here is seems much simple than commercial inverter. Am I missing anything?

Does output waveform change if load varies?

Correction and suggestions are welcome for question. Thank you.


texts: Is there a Raspberry Pi B+ GPIO header footprint for kicad?

texts: I attempted to make my own using the ModEdit utility in kicad but I'm still having issues adjusting it to the grid even though I followed the standard 0.1'' pitch.  It still seems to be off.  Is there a footprint available for the 2x20 pinout on this board?


texts: How to properly pull up a single-relay module

texts:
I've previously discussed in this post how to drive the relay with an ESP8266, and eventually came up with this circuit:
Problem is, the particular type of relay module used has an "active low" input: it is OFF at ~vcc in its input pin, and ON on ~GND.
The circuit actually works, but the system boots with the relay ON, so I think a pull up resistor should be added between the transistor and the relay IN. In the mentioned post, a 10k resistor it is suggested, but in practice it didn't work. I think a lower resistor would get the job done, but I really don't know exactly why.
I'd like to know how to tell which is the proper value for the pull up resistor and why a high value like 10k does not work in this circuit.

The relay module is this:

And the schematics:


texts:
I'm creating a grid of 200+ pressure sensors and need a clean way to get their values back to the master controller without a mess of wires.

To me it seems like daisy chaining all the sensors together would be the most straight forward. I was planning to use daisy chained SPI, unless there was a better way.

ADC chips would be the most straight forward, but the only SPI daisy chain-able one I found (AD7685), which is ~$15 a chip.

As a cheaper option, I could use an ATtiny and write a custom serial data chain protocol; however, it seems like a bit of overkill to have a microcontoller per sensor.

What do you think? Is there a better way? Perhaps another chip that I'm not familiar with?


texts:
I need to detect AC voltage with MCU for ensure relay health condition, the cheapest and smallest solution are most welcome.
I have no hard time restrictions or noise canceling\debounce requirements (will processed inside MCU).
Most of cheapest optocouplers (OC) has adequate CTR only with If >= 1mA. But with VAC 230V, the dropping resistor (Rdr) must have decent power dissipation raiting, size and price.
To use SMD or cheapest THT resistors, in worst case Vac == 270V, i must have Prdr < 0.2W. It means, what Rdr must be not less 360k (or 510k for long life safety).
So in another wrost case Vac == 185, i will have If ~= 0.3mA with pretty low CTR.
For example, for TCMT110x what i used in project it would be near 0.2x.
Ok, that looks pretty clear, i just need to use:

Double diode optocoupler (otherwise the OC will breaked by reversed 230VAC voltage).
Amplifting transistor on the output.

simulate this circuit – Schematic created using CircuitLab
Does my thoughts has mistakes?
Does i not consider some effects, what i must consider?


texts: How can increasing the voltage/frequency ratio of an induction motor result in magnetic saturation?

texts:
The information below pertains to an induction motor:

The magnetic capacity of the motor's magnetic (iron) circuit is designed to the relationship: voltage/frequency (V/f).   If the frequency drops the V/Hz goes up.  This means that the motor needs a larger magnetic circuit. Without it, the magnetic circuit can be overloaded.  This is called saturation and it leads to a rapid increase in current draw and a corresponding large increase in temperature, a motor's chief enemy.
If the frequency increases, the V/Hz drops with no issues since the magnetic circuit will remain plenty large enough.

https://www.engineering.com/ElectronicsDesign/ElectronicsDesignArticles/ArticleID/8154/Changing-an-Induction-Motors-Power-Supply-Frequency-Between-50-and-60Hz.aspx
My question is: why does decreasing the frequency result in magnetic saturation when it doesn't cause any variations in the magnetic field of the stator?


texts: What kind of contactor or device do I need to keep a contactor closed until power draw of the primary circuit is complete?

texts:
I have an application where I need to signal a start by sending a 120V signal to the contactor, so it will close a 208V 3 pole circuit. The load on the circuit will run for an unspecified amount of time, until its work is complete.

At that time, I want the contactor to open again, so that the load will not restart until signal is sent again. I can have no feedback from the load to send a second pulse, and the time may range from 20 minutes to several hours.

The load will cease consuming power on its own at the end of its task, but I want to disable power back to it until I send a signal back to the contactor.

Any ideas? I though of a latching contactor, but that does not work for my application as I can not send an "I am done" signal to disengage the latch.


texts:
I am working on robotics project. The drive chassis is powered by a 3-cell 12V 8 Amps battery (I might also go for connecting two batteries to attain speed as my drive motors work at 24V full power). The battery can get charged up to 12.8V.

As I start driving the chassis, the voltage goes on dropping which is obvious! But that's where the problem arises. All my calculations of Arduino are based on a constant value of voltage. So when the voltage drops the calculations go wrong. I tried taking feedback from the voltage and changing the code, but it gets too complicated. I need a stable voltage of at least 11V (or 22V in the future). What can I do?


texts: CMFB - wide devices reduces voltage drop?

texts:
In the above CMFB using triode devices, one of the drawbacks is stated as being a limited output swing due to the drop of the triode devices (acting as resistors) M7 and M8.

It says in the hightlighed section that to reduce the drop due to this, M7 and M8 are usually made wide - my question is, how does making a transistor wide reduce it's drop. I mean the output resistance is dependant on the length so why would voltage drop change?


texts:
I have some doubts about different configurations of differential pair I have seen in many cases:

In these schemes, biasing network for the gate is not shown for simplicity. All of them are excited by an input differential signal, but

In 1) two different opposite signal sources are applied to the transistors. The output is taken between the drain of one MOSFET and GND. It is clear for me.
In 2) the pair receives a differential signal in a different way, by using only 1 voltage source. I have the following doubt: how can that signal be amplified by the MOSFETS, if they are not referred to GND? How can that circuit work?
3) is like 1), but the output signal is taken from both drains and not from 1 drain and GND. This allows to double the gain. But, despite that difference, is there a reason to prefer 3) on 1) or viceversa? I'd say that 3) is better because noise on GND is not transmitted to the output signal. Is it true?
4) is like 2), but the output signal is taken from both drains. I have the same doubts said about 3) and 1).

Other doubts:

I have seen that the current source is often replaced by a simple resistor. In this case, it is important for it to be very high in order not to have common mode gain. But, in general, which is the reason for choosing a current source between Source and GND, or an high resistor between Source and GND?
Sometimes this kind of circuit works with VDD and -VDD, so with dual voltage supply. Which is the reason for choosing it or a single supply?


texts: What is the purpose of using MOSFET instead of free-wheeling diode in Buck topology?

texts:
(Source)

I usually see Buck circuit models in which a MOSFET is used instead of a free-wheeling diode. What I understand from the Buck topology is, when the upper MOSFET is off, it doesn't matter whether the lower one is on or off since the current will be going from ground to the inductor through the body diode.

So, why do they use this second MOSFET? A MOSFET is generally more expensive than a diode, isn't it? Isn't this an overkill? Or does it make the circuit better in some way?


texts: Intuitive and iterative approach to understanding of blinking LED circuit

texts:
I've used following schematics to build blinking LED circuit and it worked.

I tried to understand how it works qualitatively without solving differential equations. By this I mean understanding voltage dynamics across each element (when and why it goes up or down and whether faster or slower in comparison to previous time interval) and same about current.

Using KVL, KCL and basic properties of circuit elements I come up to the following (time interval from the start and until the LED turns off for the first time):

The process starts with maximum current that is split between NPN E-K and PNP E-K branches and therefore source voltage is less then 3V.
The source voltage is increasing and approaching 3V value.
The current through NPN B-E path is decreasing.
Voltage across LED is increasing.

By initial voltage and current values I take those when I replace capacitor with short circuit. Removing capacitor removes dynamics and for me it sounds logical that these values are initial when we put capacitor back.

My question is the following:
Is there an approach to understand how each element voltage and current change qualitatively in time so I could draw approximate plots?

I think this is important because solving complex differential equations just give you magic result - it just doesn't let you "feel" the circuit.
Also I doubt that the one who created this circuit for the very first time draw dozens of circuits, solved dozens of diff equations and finally found the one that makes LED blinking. I think this person could "feel" the circuit the way I want to.


texts: Design of a motor SPDT switch that can be triggered by 5 V or 3.3 V digital output

texts:
Problem:

I am designing the electrical system for a vehicle that has 12 brushed dc motors / linear actuators, they are driven by 6 identical dual-channel motor driver boards, that provide a maximum output current of 10 A. Only six of the 12 motors are in use at any one time.

In order to save cost and weight, I would like to reduce the number of motor driver boards to three. In this configuration, each driver board channel would be connected to a SPDT switch that can be triggered by a high / low (3.3 V or 5 V logic level) electronic signal. This configuration is represented in the figure:

My attempts at a solution:

I have tried using a SPDT relay for this purpose. Due to the current draw of the coil of each relay, all six of the required relays could not be driven from a single output pin of the microprocessor board that is being used. Therefore, a lower power switch was needed to provide current to all of the boards. This resulted in a complicated design that was unreliable. Around 20% of the time, the relay armatures switched back and forth in high frequency oscillations when the coil was energised. This would only stop when the circuit was powered off. In addition, the circuit was heavier than a solid state solution.

I then tried building the same circuit using n-MOSFETs. In this circuit, the output of each motor driver board channel was in series with the source pins of two MOSFETs, whose gate were triggered by a 5 V signal from the microcontroller. In order to switch the output, one mosfet was switched off while the other was switched on (see Figure below).

The MOSFET had a nominal internal drain to source resistance of 0.050 Ω in the ON state. At a current draw of 10 A, the MOSFETs should dissipate ~ 5% of the power supplied to the circuit due to the drain-to-source resistance. However, when the MOSFETs are switched ON, the no-load speed of the motor decreases significantly more than 5%. I am uncertain why this is, though perhaps it is as the motors are a highly inductive load and this changes things. The data sheet for the n-MOSFET can be found here:
https://docs-emea.rs-online.com/webdocs/0025/0900766b80025d5e.pdf

Questions:

Is there an appropriate component or circuit for this application? Also, are my approaches reasonable, and if not, how could they be fixed? I have researched triacs and think that these could be the basis for a solution to my problem, is this the case?


texts: Would it be worthwhile to replace this OpAmp by a discrete amplifier?

texts:
We have a circuit which works correctly with an OpAmp (as shown below) but we are considering replacing it with a discrete amplifier.

The gain we need is about 2200. The input signal comes from a resonant LC antenna (L ≈ 4mH, C ≈ 15nF, Rs ≈ 70 Ohms). The frequency of interest is 20 kHz with a 1kHz BW.
The noise generated is critical given the amplification. We would like the discrete amplifier to be as good or better than the OPA838 in terms of noise, only in the band of interest, because we are doing digital filtering of the signal afterwards. This is why non linearities would not be that critical.
Our goals are the following :

low power consumption (lower than the 1mA of the OPA838 @ 3.0V)
amplification of x2200 at 20 kHz with 1kHz BW
lower cost than OPA838
gain error < +-20%
output impedance < 10kOhm AC coupled
input impedance should be high enough in order not to decrease Q

Given the small BW of the signal, and the low center frequency, do you think it is worthwhile (knowing our goals) to replace the OpAmp? If so, which transistors types and which topology would you use? We have everything at hand to simulate and then test in the real world.


texts: Software control system. Which one is it?

texts:
I wrote a software which replaces a discrete closed loop PI control circuit and now I was wondering what kind of control system is this equivalent to? This code drives the PWM which regulates the R_DS,on of a MOSFET to keep currentflow at a certain level.

pseudo-code:

while(limit < 10000){
    if( valuefrom_ADC < 1234) {
       dutycycle++;
    }
    else dutycycle--;
    TIM1->CCR1 = dutycycle;
    limit--;
}


texts:
How to decide whether to place a microcontroller on the top or bottom side in PCB layout?

What are the advantages on the top side?
What are the advantages on the bottom side?


texts: “Cross simulation” between analog and digital

texts: I was interviewing for an analog/digital design engineering team and the guy said that my first task on the job will be to run cross (or crossing) simulation between analog and digital section, what does it means extactly ?


texts: High-Power H-Bridge - Heating Calculation

texts:
Background

Hi there,

I'm using a H-Bridge to drive a thermoelectric cooler (TEC or Peltier) module. I'm not here to discuss control circuitry/drive voltages/slew rates/switching losses, which I know all are important.

I've accounted for all of these and optimised my circuit to make sure these are all as efficient and effective as possible. The last remaining problem is \$ R_{ds(on)} \$ losses in the P- and N-Channel MOSFETs in the H-Bridge. A H-Bridge is used in order to heat/cool different sides of the Peltier plate, depending on the direction of the current (just an FYI for those who didn't know).

simulate this circuit – Schematic created using CircuitLab

(Note: This circuit is simplified. There are various extra components such as flyback diodes, series current shunt resistor, etc. in the actual circuit)

As you can see, this is a fairly high-power system. With a 24V rail over a 30V peltier, rated for 12A (I've shorted it through a power supply and it never exceeded 10A, however). This means each FET will (excluding switching losses) dissipate power somewhere in the order of \$P = I^2\times R = 100 \times R_{ds(on)} \$ Watts - nothing to laugh at!

I've never calculated a component's heating before, and so I wanted to make sure I am doing it right here. I know this has been done on other threads countless times, but I just wanted some guidance and to make sure I haven't missed anything from following those as guides. For simplicity sake, I will just do the P-FET.

Accurate \$ R_{ds(on)} \$

First step is to find an actual \$ R_{ds(on)} \$ that I'll be most likely operating at. I'm driving the P-FET with MOSFET Drivers, all the way to the rails. So, \$ V_{gs} = -24V \$ (yes, I know the FET is only rated for max 25V, and I know ideally I would use an isolated gate driver with an N-FET or some sort of voltage divider to lessen the drive voltage etc., but for now this is the case for a simplistic prototype). From the datasheet graphs:

Since they only graph to -15V, I'm over-specing and basing my calculations off that. This gives \$ R_{ds(on)} = \frac{1}{10 \div 0.2} = 20m\Omega \$, which you can see from Figure 2 will be even better as the FET gets hotter and hotter, with a constant drive voltage (up to 30A, which I'm going nowhere near). So this is really absolute worst-case.

Power

With this, the power loss in the FET will be:

\$ P = I^2 \times R = 10^2 \times 0.02 = 2W \$

Heat

From this, we can use the thermal resistance given in the datasheet to calculate heat. Now, this is a fairly complicated figure, and obviously depends heavily on PCB design. That is why, fortunately, this datasheet specs a thermal resistance, junction to ambient, for a 1 inch squared pad of 2oz copper - exactly what I have done on my PCB design for the FET.

Again over-specing, I will use a compromise between these two figures of 50 degrees per Watt. So, this gives:

\$ T_J - T_A = \Theta_{JA} \times P = 50 \times 2 = 100 \$ degrees Celsius

\$ \therefore \$

\$ T_J = 100 + 25 = 125 \$ degrees Celsius

Conclusion

There are a lot of assumptions here, which is (I guess) expected without any experimentation beforehand. But, I'd like to think I've over-spec'd what I can, and assumed worst-case here. Since the device can operate up to 175 degrees Celsius, should this design be okay? On top of that, this also assumes this thing is being driven constantly, with absolutely no cooling - which isn't the case. This will be run sporadically, with different duty cycles, and with 3 small fans cooling it.

Thanks for your time.


texts: MOSFET with very low Rds_on for very small current

texts:
I'm building a uCurrent Gold clone (https://www.digikey.ch/reference-designs/de/sensor-solutions/current-sensing/2637) - with a digital interface (measuring the voltage directly with a microcontroller). However, I also want to automatically select the Shunt-Resistor by two solid state relay or two Mosfet's.

However, is this feasible? Is there a Mosfet with a very low Rds_on (<10mOhm), very low Gate and Drain leakage current and very low Drain-cut-off current, such that there are nearly no unwanted effects (similar to a regular switch with on resistance of ~10mOhm)?

This is what my intention looks like (out goes to input of OpAmp, pull-down on MOSFET should be 100k):

EDIT: ADDITIONAL PARAMETERS

Rds_on <10mOhm

Gate & Drain leakage current should be 0nA, since they would sophisticate results very heavily in the nA range.

Drain-cut-off current should be around 0.1uA

-> As there isn't any MOSFET with this characteristics, especially for the Gate leakage current, maybe a Photo-Transistor would help. But the Drain leakage current would still remain.
I would also be satisfied with an electromechanical solution, like a relay or a reed-relay, as long as the mechanical dimensions aren't to big (Footprint of SOIC-8 would be acceptable).


texts: How are terminal blocks depicted in a wiring diagram?

texts:
I have started to document the electrical system in a custom machine that we own. I'm using TinyCad for the schematic and that's working OK. I also want to create wiring diagrams to represent the routing of wires, which DIN rail they equipment they are connected to is on, etc.

I'm new to ALL of this. I'm trying to figure out why DIN rail mounted terminal blocks don't seem to be represented on the diagrams I see when I google. To be clear, I'm referring to terminal blocks like this:

Two questions:

Is there a standard symbol used to represent a terminal block?
Is there a reason why I don't see terminal connections depicted in
wiring diagrams?


texts: Load capacitance estimation for compensation of switching power supplies

texts:
I'm calculating a compensation network for power supplies based on the LM20323MH from TI.

I have slight doubts about correct estimation of output capacitance to use in the calculation. The board is a CPU motherboard (i.mx6q quad core, 1.4 GHz) so there is a lot of distributed capacitance around the board, bigger then the output caps for the switcher itself.

Should I account for all the capacitance across the board or just the capacitors close to and associated to the power supply. I do not have much insight at the moment into how the capacitance separated some distance away plays into the stability of the switchers.

So the question is: Should I account for all capacitance seen by the output of the switchers or just the capacitors close to and associated with the switcher?

Intuition tells me that I should account for the total board capacitance since there will likely be a low impedance connection to the distributed capacitors via power planes, but I'm not 100% sure.


texts:
I'm really quite a beginner, so bear with me. :)

I'm starting to work with RF transmitters, and I only have one Arduino (It's an Uno R3). I have the transmitter and receiver set, but without another Arduino, I can't test it the way they're normally meant to be used.

However, I was wondering if there was something I could make that could be plugged into the USB of my computer, and allow it to write a byte of data to the device, and allow me to output that byte of data to some header pins.

I understand that USB can't be used for serial transmission on its own, but was wondering what I'd need to create in order to allow me to write to the header pins?

TL;DR:
I'd like to be able to have a setup that reports as a Virtual COM Device, and allows serial data to be passed along it.

I apologize if this is a really newbie question, and I appreciate all the help I can get :)


texts:
I am busy with synchronize all my ADCs on data acquisiton systems. My ADCs need to clock signals for their duty. So in my opinion for synchronization, if i send to all my ADCs clock signal which is driven by 1 a GPS with accurate 1PPS output, it can be be synchronous with each other. So i am looking for a knowledge or a component which do that timing job. My ADCs need to 24.576 mHz Clocking signal with accurate GPS PPS signal. How can i do that? Do you have a solution or any idea for that?

Thank you for all your reply. But i want to give you a detailed explanation below;

I have two data acquisiton device which includes ADCs on their own (MAX11040K maxim integrated). And each system has 4 ADCs. There is no connection between those systems (no cable, no wireless connection). They are totally seperate from each other. I want to put one of those systems on somewhere in England, and i start to system for data acquisition. And i want to put other one on somewhere in Germany. And i start to system for data acquisiton too.

Now i want to watch these raw data ( which comes from ADCs) on systems by an software in USA. I want to see raw data on both of these devices at the same time. So i need to know "time knowledge" with raw data. I can do that by putting a GPS Receiver Module on each systems. GPS gives me a Peak Per Second signal which is valid all over the world. Beause it has Real Time Clock signal. All GPS Receiver Modules in the world produce PPS signal at the same time. I want to use that signal for sychronization. I need to trigger a circuit with that PPS signal only at start. By this way, Triggered circuit can produce a 24.576 mHz signal for my ADCs clock signal. So all systems work synchroniza to each other. This is a theory what i want to do.

Sychronization can be done with two way;

The first one;

I put a crystal for every ADCs on two device, and if i push the start buttons of seperated systems at the same time, systems will work sychronizally with each other. And i can watch raw data on USA by a software. But this never can happen because of systems located different countries.

The second way which i need to help for this;

The ADCs, which is in DAQ system, need 24.576 mHz clock signal. if I design a circuit which is triggered by GPS PPS signal, the circuit can produce a 24.576 mHz clock signal for my ADCs. The ADCs works without a crystal. This circuit which i planned provide them for synchronized clock signal. After that i can watch systems on USA.

Now the circuit which i need to has one input (PPS signal) and one output which is accurate GPS PPS signal.

Finally, how can i create this circuit?


texts: Finding impulse response by a non-Laplace-transform method

texts:
The input function is $$x(t)=e^{-t}u(t)$$ and the corresponding output function of a linear system is $$y(t)=10e^{-t}\cos(4t)u(t)$$ where \$u(t)\$ is unit step function.

I understand how to find the impulse response of the system using transfer function of Laplace transform. The other way would be to experimentally try to determine the impulse response.

My question is that if there is any other way other than Laplace transform or other transform to find the impulse response of system. So, by using some time domain tool.
Thank you.

Edit: This is not a homework related problem. Actually I was doing self-study and was motivated by this example problem: http://imageshack.com/a/img923/6360/i1N0U3.jpg


texts: How to Design a State Feedback Controller using an algorithm

texts:
I'm studying for an exam and am having a great amount of difficulty wrapping my head around this as I have minimal electrical engineering background, and my notes are confusing. I have read a few examples from various sites but I'm looking for a step-by-step example to hopefully make things make sense.

The question I'm trying to use as a learning example is:

Design a state feedback controller using the algorithm u=-kx to stabilize the following continuous linear time-invariant system:

A =                       B =
   [-1  .5  0  -.5]          [ 1]
   [0  -.5  0 -1.5]          [ 1]
   [0   .5  2  -.5]          [-1]
   [0 -1.5  0  -.5]          [ 0]

Thanks for any help, I'm really quite confused.


texts: Is FCC-accredited testing required again if circuit board is placed in a different package?

texts:
I am considering enhancing a commercially-available device so that it can be installed outdoors.  The enhancement would be to seal the product inside a resin case to make it weather-resistant.  The result will be something that looks like a brick with wires sticking out for 12v DC power and Ethernet data.  Once inside the sealed case, the product, along with its FCC sticker, would be invisible.  The resin case would have my branding on it and not that of the sealed device.  Can I just remove the FCC sticker on the original device, before encasing it, and apply it to the exterior of the new sealed case, or do I need to go through the FCC conformance testing as if it were a new totally different product?  The sticker would have the branding of the sealed-device manufacturer on it.  The device is an unintentional radiator.

I have the option of either sealing the entire device, as it is sold, or removing it's circuit board from it's original enclosure, only sealing that, and discarding it's original plastic non-shielded enclosure.  Would it make any difference between any of these two scenarios, from the point of view of FCC conformance testing requirements?

Thanks for your attention.


texts:
Does max switching current from a relay mean only at the switch moment or is it the  current which it can handle when it is switched on?

If I switch a relay without a lot of current and afterwards I set a load of 20A.
Do I need to take a relay with 20A switching current?


texts: Best Option for Charging a High Voltage Capacitor?

texts:
I was looking for a good option to charge my 450V 6800uF Electrolytic Capacitors. I initially followed the dc - dc booster path with a voltage divider comparator (op-amp) something similar to

But then realized a still have several MOTs (Microwave Oven Transformers) that will convert my 110v up to around 440v ac. toss in a bridge rectifier and a HV smoothing Capacitor Bank from my old Tesla Coil and a Variac to fine tune the numbers and I feel like I'm pretty close. I think I will end up with the more portable DC - DC booster but I don't need to be portable in my Lab while I setup the initial experiments so the bulky AC - DC route seems simpler.  The end goal is the multi stage coil gun but I want to fine tune the coils and saturations before worrying about shrinking it down.
Some thoughts on a specific design that would allow for a fairly safe (for the capacitors) charge rate and method to stop charging when full or a little under full to extend life.  I have a smaller transformer from a bug zapper but the voltage is higher and the amps are pretty low so I figured MOT would be best. I am trying to keep it simple (ish) because I learned the more feature pack we make things the more opportunities for system failures there are and with HV systems mistakes can be lethal. I'm open to any and all approaches as this part of the project only just started and I haven't committed many resources to any one method.

This is what my second look was and it seemed good. sooo simple... Thoughts?

Thanks


texts:
I'm a complete noob when it comes to electronic so if you feel the need to call me stupid for not figuring this out on my on, I wont be offended.

I have searched Stack Exchange without finding an answer, or not understanding the answer.

I have a small solution to control the radiators in my cabin. It's  ugly as....
I use a Raspberry Pi(old version) to control a key-fob. Since I read, somewhere that the key-fob might use more power than the RPI can deliver it could potentially fry the RPI.
My solution is to use one cellphone charger to power the RPI and one to power the circuit with the key-fob. I have put a relay between the two.

Below is a simplified fritzed version of the current solution.

What I want is to change to use a single cellphone charger.

Below is my version on how to solve this.

The problem for me is that I am to much of a noob to figure out if this will fry my RPI. Any suggestion and/or help on how to solve this is much appreciated.

@Elliot Alderson want's more information. Which I totally understand. As I stated before, this is a VERY ugly solution.

This is an image of my "electronics" box, it's the device that want's 2A. In reality it doesn't at the moment but in the future, when I want to control the world it might use much more than 2A.

The green card is a simple remote to control lights over 433Mhz. It's sold by a Swedish company called Clas Ohlson. This item looks the same as the one I have, but I'm not sure, Remote to control lights. The remote control uses a 3v button battery. I use a voltage regulator to get 3.3v Spec for voltage regulator to replace the battery.

The electronics box is connected to the RPI

I'm not sure which version of pi it is but I know it's first generation.

The RPI communicates with a server in my closet. The server holds and controls state for the radiators. I have written the server software. The hardware of the electronics box is a ugly hack. The server software is worse. The RPI polls info from the server.

The 2 buttons on the electronics box is so I can "manually" turn on and off the radiators in the cabin. The buttons actually sends a state-change to the server and then change state of the radiator.

I use the same charger for both RPI and the electronics box. I bought them from Kjell.com. Linocell usb charger.

According to the sticker on the charger

LINOCELL
Wall charger
Art No: 95717
Input: AC 100-240V 50-60Hz 0.3A
Output: DC5v 2.4A Max

I am aware that the more functionality(components and so on) I add to the electronics box the more power it will need. The Wall charger I use today might not cut it, and I have to upgrade.

The question remains.
To day I use two power sources and a relay between RPI and the remote control(green card) since I don't want to accidentally fry my RPI.

Is it safe to share one power source for both RPI and my remote control circuit, regardless if I add more power hungry crap on the non-RPI side of the relay?

I'm sure that some of you are rofl - happy I can contribute to some happiness. I am a noob that are willing to learn. Any tips,pointers, suggestions and so on are very welcome.

If anyone needs more info, I'll do my best to supply it.


texts:
I studying the Atmel's ATSAME70Q19 Datasheet and i'm a little confused about boot operation mode from HSMCI.

In Page 892, "38.11 HSMCI Boot Operation Mode" there's a reference which says:

  In boot operation mode, the processor can read boot data from the slave (MMC device) by keeping the CMD line
  low after power-on before issuing CMD1. The data can be read from either the boot area or user area, depending
  on register setting.

What is the "boot data"? Binary file? Hex File? or something else?
Where is "boot area" and "user area" on microSD card?

I realize that it need to store a binary file into the microSD card but how?
In formated card (e.g. FAT) or like a raw data?


texts: Can I use a NPN Transistor as a Varactor Diode?

texts:
I am currently building a crystal controlled AM transmitter. The circuit that I'm using call for a NTE – 613 varactor diode (which will come in a few days). I was wondering if there was an alternative to the director diode that I could use for the meantime to test the circuit?  couldn't I use an NPN transistor as a varactor diode? Any help would be appreciated thank you so much! I will attach the schematic link below that I am using below:

http://www.radio-circuits.com/images/ab1.jpg


texts: Oscilloscope measurement: unsure how to connect the scope ground to the target

texts:
I have some control board equipped with a microcontroller.
This control board is supplied by 24V voltage source. I
would like to measure signals on some microcontroller's
output pin with a digital oscilloscope.

I have only two common probes with earthed crocodile jack connector. I am not sure whether the measurement with a probe connected to the output pin and crocodile jack connector connected to minus pole of the voltage source is correct.

Would be better to use both probes with their crocodile jacks connected together and then connect the first probe on the microcontroller's output pin, the second probe to the minus pole of the voltage source and use ChA-ChB function?


texts: Recommended Layout for Parallel Current Sensing Resistors

texts:
I'm working with 12V DC systems and high currents (up to ~40A). In order to meet the wattage and price requirements for my design, I'm using two parallel sense resistors. The IC I'm using for sensing is (PN: PAC1710-1-AIA-TR), though this question should be applicable to just about any sensing solution requiring SMD resistors.

I know that when using a SMD resistor for current sensing, this is the ideal layout:

But what about parallel resistors? Which of these two below is ideal, if either? Is there something more I need to consider when applying parallel resistors in this manner?

(Also, can anyone provide resources for further reading on this particular topic? I'm usually quite proficient in finding answers to my queries, but I haven't found any useful info on laying out parallel resistors in current sensing applications.)


texts: Relation between instant power and electric-magnetic power in a series RLC circuit

texts:
I know that the instant power of a circuit is given by the product of the voltage and the current of a circuit while the expression for the electric and magnetic energies is: $$
W(t)=W_e(t)+W_h(t)=\frac{1}{2}v_{C_1}^2(t)C_1+\frac{1}{2}i_{L_g}^2(t)L_g
$$
My circuit is the following:

The values of the components for my circuit are:
$$C_1=31.66nF$$
$$R_g=5000\Omega$$
$$L_g=320H$$
$$V_g=311\cdot\sin(100\pi t)$$
In this first image, the red graph is the power delivered by the voltage source, the green graph the power disipated by the resistor and the blue graph the difference between both (I was told to represent this specific graphs)

While the electric-magnetic energy is given by this yellow graph (just substituting the values of the components above):

I am trying to find a relationship between both types of energies, but I do not see a correlation between them. Maybe that both tend to a defined value when the transient finishes? However, the magnitudes are very different. Does anyone know a better approach for that question?


texts:
How to make push button switch with auto off after about 5 seconds.
Output circuit is high (active) for max 5 seconds when I keep pressing push button.
Output will be low after this time or  when I release push button.
To reactivate, I have to release push button and press again.
I think that it's using a capacitor charging with some transistors. But how to make it work?


texts: How does this RC circuit in a fan regulator work?

texts:
simulate this circuit – Schematic created using CircuitLab
I came across this circuit in this link,  but I am not able to understand how this RC circuit works.

Could someone explain it to me?
Should I consider this as a parallel RC circuits?
If the input is a 220V 50Hz sine wave, what will the waveform be?
How are the calculations of capacitors done?


texts:
Been solving this for hours please help. My answer is written on ink. The correct answer is given.

I tried Nodal Analysis and got Va = -100 V at node A (beside -100V)
and then

KCL@A: -0.01V1+Va/20k = 0 ; Since Va=-100, V1 = -0.5V <-- from here I know something is wrong

For Isc: (Imagine shorting the terminals)

Mesh Analysis:

@M1 : I1 = 0.01V1 = 0.01(-0.5) = -0.005A

@M2: 20k(I2-I1) = 0 (I assumed 100V is off since I am getting Isc=0 when it is on, I dunno)

20k(I2+0.005) = 0

I2 = -0.005 A = Isc

Rth = -0.5/-0.005 = 100 ohms


texts:
I want to design a computer vision device that will act as a "driving assistant". The device will improve driving safety by acoustically or visually alerting the driver of certain hazardous situations (lane crossing, safe braking distance etc.) but will not be directly connected to any car controls. My question is: how to design my device so that it complies with regulations if I want to sell it as a "car accessory" in aftermarket in the US and EU?

By aftermarket I mean that the device will not be mounted into a vehicle by car manufacturer but by the end user/customer. The mounting should be as simple as placing a camera on the windscreen (out of the driver's field of view), connecting it to the "processing unit" by a cable, placing that unit somewhere (under dashboard, seat etc.) and plugging the unit into the 12V outlet (or rather wiring directly to 12V).

I am a software developer and I have already a prototype running on a x86 platform. The prototype consists of a common mini-ITX board, an USB camera and a picoPSU power source. All these have an "FCC Class B Part 15" certification (I guess this is standard for consumer-grade electronics intended for home/office use). Besides these I will also use an USB 2.0 or 3.0 cable to connect the camera to board and the board will wire to those 12V.

The device will be only an "assistant" and will not carry any life-critical function when driving. I think it may fall in the same category as car GPS navigation devices (Garmin etc.). I know that demands for a mission-critical automotive electronics (things like engine electronics, brake systems etc.) are very high, but as I said my application is not anywhere near this kind of usage.

The best situation for me of course would be no need for re-certification since I only bring/bundle already certified components together (besides the cabling) into a new product without altering any of them. In case the x86 setup could not get car-compliant my second attempt would be finding a powerful automotive-compliant embedded board (nVidia Jetson TK1 or Jetson Pro?) that I could compile my computer vision code on. I would like to avoid doing an FPGA-based design because rewriting my code to hardware is likely to be very costly.


texts: How can I improve my Freq to Voltage circuit?

texts:
I had a term project which was based around Analog-to-Digital convertors.
We used anLM2907 Freq-toVoltage convertor to take a 150mVpp sine wave (0- 1kHz) and convert that to a voltage.  The voltage was sent to a PIC 18F4685 mcu that ran on a Northmicro101 proto board and through some embedded code would take the anaolg voltage and convert it to a 10bit value.  This value was translated back to a frequency value and displayed on the LCD.

It wasn't meant to be a bullet proof set-up, more about learning and implimenting the concepts learned through the term.  However what we found was that the frequency on the LCD would creep upwards 1 or 2 Hz after about 15-20 minutes and would keep on doing a very slow creep the longer we ran the circuit.

My question is what would be the most likely cause for this creep and how would we eliminate it in a future version?

The F2V circuit was tied to the NM101 protoboards +9V power supply and the output of the F2V circuit was set for +5V output max for PIC input pin protection.


texts:
I have an "U" shaped metal profile that is 2 meters long each side is 1.5 cm.
It is sprayed with acrilic color. and i want to use it as indirect light profile/enclosure for a 12v Led strip.

While playng with the capacitve touch libs of the attiny85 i tried to connect
one sensing pin to the above mentioned profile getting really perfect results.

Altough the testing was made without powering the led strip, leaving so a all the working electronic circuitry outside of the "U" profile.

As i attached the ledstrip to the active circuit the touch did not work anymore.

Basically the sensing is disturbed by the ledstrip.

There is no way to get it to work if there is something elecronically active inside the profile.

Then i made another test.

I put two "U" shaped profiles side by side, paralell at 5cm distance.
One of the profile contained the circuit & led strip and the second was connected to the Touch sensing pin with no electronics parts inside. this worked again.

Is there a way i could properly insulate the led strip & the circuit from not interferring with the enclosures capacitive abilities?

The plan is to use the whole enclosure as a big touch sensitive on/off switch.

EDIT AS REQUESTED

Video showing the working capacitive surface.
https://youtu.be/I-JkjfGwqEo
Video showing the same circuit but powering the leds inside the profile. https://youtu.be/Mz7KTxXNz5Q

As you can see in the videos avbove the circuit won't work if the leds are inside the the profile.. i made verious other tests and as soon i add the ledstrip stored inside the metal "U" the EM field is disturbed.

simulate this circuit – Schematic created using CircuitLab

EDIT2

I apologize for the quality of the following diagram. i'm not good at drawing diagrams.I also totally don't know what software i could use to draw a diagram. Here is how it should look like


texts:
I am trying to measure the power consumption of IFC6410 . The below mentioned schematic describes what I have tried.

.

(A) works, (B) does not show me any current reading and the board does not boot up, the power LED keeps on blinking. Multimeter is set at 10A. Let me know if you need any more info.


texts: Why does converter's efficiency degrade with higher V_IN?

texts:
Please consider the following efficiency graphs of the exemplary MP2384 buck sync converter:

What I am trying to understand is why is the efficiency at light loads worse for the cases in which the VIN value is a lot higher than the VOUT. In the end, the efficiency difference is negligible for higher loads. This behavior I have observed for different buck converters in the past as well. I would appreciate all feedback regarding this case.


texts: unwanted stimulus time offset in hyperlynx si

texts:
I am using hyperlynx-si to simulate the eye-diagram of a serial link in my design.

I've took a 0.66 Gbps random pattern as the stimulus, but as can be seen in the picture, there is an unwanted 300ps offset in the signal just at the driver's output pin, which caused the eye-mask not to fit in the center of the bit. How can I avoid this time offset? or it is a normal case?
thanks in advnace.


texts: Powering 10V motor fader in Raspberry Pi 4 project

texts:
I am building a project that uses a motorized slide potentiometer with a Raspberry Pi 4, for the purpose of controlling multiple audio sources (such as system volume, VLC, OBS, and any other I can interface with). I acquired this motor slider and this motor controller, and when looking at the slider's spec sheet (PDF), I read that the motor expects 10V, though in testing with a multi-voltage power adapter, it happily moves fairly snappily at 9V (and less and less snappily at 7.5V, 5V and 4.5V, and doesn't work at 3V). The motor controller is rated at 1.2A constant, which is well within the 800mA the motor is rated at.
In order to move the slider at a good speed, is it possible to make or buy a step-up converter from 5V to 10V and connect it directly to one of the 5V pins on the RPi (which AIUI is connected directly to the power rail from the USB power adapter, in my case a 3A adapter), or would it be better to get higher voltage power from another source such as the power adapter I used for testing?


texts: Verilog: Implementation Using Primitive Modules vs. Bit-wise Operators

texts:
The textbook I'm reading implements 1-bit adders using built-in primitive modules:

module yAdder1(z, cout, a, b, cin);
     output[0:0] z, cout;
     input[0:0] a, b, cin;
     wire[0:0] tmp, outL, outR;

     xor left_xor(tmp, a, b);
     xor right_xor(z, cin, tmp);
     and left_and(outL, a, b);
     and right_and(outR, tmp, cin);
     or my_or(cout, outR, outL);
endmodule

But why not use bit-wise operators? Seems simpler.

module yAdder1(z, cout, a, b, cin);
     output[0:0] z, cout;
     input[0:0] a, b, cin;

     assign z = (a ^ b) ^ cin;
     assign cout = (a & b) | ((a ^ b) & cin);
endmodule

Unless bit-wise operators implicitly use  primitive modules?


texts: I'm just learning about Schmitt triggers with op amps. I have the circuit below, and I tried to go through the calculations to find the high and low thresholds. What I'm understanding from my calculations is that the high voltage threshold and low voltage threshold are the same (-5V). Is this correct, or did I make a mistake?


texts: Voltage divider in combination with pull-down resistor

texts:
I am working on a project using the Attiny13 and a simple push button. Since I power the whole circuit with a 3.7V 18650 battery, I have to use a voltage divider to make it safe for the Attiny whenever the push button is pressed (the Attiny can only handle 3.3V on the input pins, but the battery voltage can go up to 4.2V).
For the divider however, I use a 100kΩ and a 300kΩ resistor to create a voltage of 1.88V (when the battery is nearly empty) and 3.15V (when the battery is full). Here is my schematic:

I am wondering why there is only a voltage of around 0.4V at the Attiny's input pin when I press the button. I guess that the pull-down resistor is too small (at least compared with the two from the voltage divider) and if the button is pressed, all the current (and so the voltage) are going to GND instead of flowing through the Attiny. So, in order to make the circuit work as it should I have to either change the pull-down resistor to a bigger value or change to two resistors from the voltage divider to a much lower value (like 10Ω and 30Ω).
So my questions are:

Is my theory why this circuit behaves "weird" right?
If yes, should I use a pull-down resistor with a higher value OR a voltage divider with lower resistance?
What is the biggest possible pull-down resistor in this scenario?


texts: Reverse engeneering a home automation RF 315Mhz transimtter

texts:
I have this remote control and transmitter and I want to reverse engineer the 2 RF signals sent by the transmitter.
This is the board.
The board says "ak-rk01se".
I can also open up the transmitter and see it has a PT2264 chip.

To my disposal is also a DVB-T hacked ham radio device. so I can see all the data coming out from 315MHz.
Here is an example recording from the big button with AM demodulation

Does anyone know how to tackle this?

Update, this is how it looks when I import it and run a normalize signal in audacity. The same square wave is repeated over and over again.

The question remains: How do I use an RF signal transmitter to imitate this signal? I have a raspberry pi and I can get an RF transmitter.


texts: Inconsistent GPIO values on Beaglebone Black running Debian

texts:
I'm trying to use GPIO on my Beaglebone Black, but I'm running into some behavior I don't understand. I have two pins (gpios 27 and 61) configured to input with active_low set to 0. There is nothing connected to either pin (or any pin on the board for that matter), but one of the pins (gpio 61) is showing a value of 1 while gpio 27 shows a value of 0.

Can anyone explain why this is happening?

Here are the exact steps I took to get this result:

echo 27 > /sys/class/gpio/export
echo 61 > /sys/class/gpio/export
echo in > /sys/class/gpio/gpio27/direction
echo in > /sys/class/gpio/gpio61/direction
cat /sys/class/gpio/gpio27/value
0
cat /sys/class/gpio/gpio27/active_low
0
cat /sys/class/gpio/gpio61/value
1
cat /sys/class/gpio/gpio61/active_low
0


texts: What is the best way to desolder epoxied surface mount components without damaging the pad? I have tried using hot tweezers at 400C, but the epoxy never melts. It is the epoxy under each small component, not over several components.


texts: Capacitor in parallel with resistor on xoscope amplifier schematic

texts:
Short version: Why is C3 necessary in this circuit?

Explanation:

The schematic for the input buffer/amplifier circuit for xoscope is made up of subsections that are mostly broken down in the descriptions on the site:

C1: AC coupling, to remove DC component from signals

In notes, the author suggests moving this to after the impedance stage

R1, C2: Impedance, to avoid impacting the operation of the circuit under test
R2, D1, D2: Clamp to +12.7V, -12V, to keep input within spec limits of amp
R3, D3: -11.3V reference for clamp to avoid dropping below common mode limit of amp
R5, R4, S1: Switchable 1x/10x feedback divider
R6: Output amplitude trim

I haven't found an explanation, however, for C3, the 100pF across R2. The circuit this derives from (The Art of Electronics, figure 4.74) does exactly the same thing, once again with no explanation.

Apparently the utility ought to be obvious, but I'm new to earnest analog electronics. I can only assume that it's stabilizing something, but I don't know how the operation would suffer without it.


texts:
I am trying to decode a WCDMA signal on MATLAB and I am having some trouble trying to grasp the concept of it and was hoping for some feedback.
I have a row vector, 'scrambleCode,' containing 38400 elements, which are either '1' or '-1.' This vector was already defined for me, and to get the spread message, I created a new vector called 'spreadMsg,' where:
if scrambleCode(i) is equal to '1', then spreadMsg(i) = 1. and
if scrambleCode(i) is equal to '-1', then spreadMsg(i) = 0.
I have also been given the transmitted signal, a 1420800 element row vector. This row vector consists of elements valued in the range of -0.92 to 0.92.
I have been informed that this signal has 'n' blocks, each of 38400 chips, and that the chip scrambling code is the real part of the 512 primary downlink scrambling codes.
With regards to the 'spreadMsg' vector that I created, is it correct that this is the signal of a user after the users data has been 'x-ored' with the spreading code?
And as for the transmitted signal, how come the signal does not consist of integers? I am assuming that the transmitted signal is the signal that contains the signal of all the users (ie. the addition of each users corresponding 'scrambleCode'), so how come the elements of the transmitted signal are instead decimal values?
I appreciate any guidance. Thank you :-)


texts: USB to RS232 without host (slave devices)

texts:
I'm trying to get two slave devices (ie no host controller) to communicate.

Slave 1: USB with FT232RQ chip
Slave 2: DB9

Using standard USB to RS232 converter cables, I cannot get the two devices to communicate with each other. I believe this is due to not having a "host controller"?

So to get communication I think I need to introduce a "host" controller between the two slaves:

TTL <-> Host <-> RS232

Am I along the right lines with this idea/solution?


texts: Problem regarding Stephen Hobley's lib for Pixart Sensor

texts:
I wonder whether anyone here would have actively worked with the Stephen Hobley library for Pixart Sensor here. I used the same hardware configuration as mentioned in Stephen's website. However, I run in to this problem:

I read somewhere that the Pixart camera returns a value only when it sees a IR Blob. So, accordingly, the Pixart Library should also return values only when the camera sees any IR blob, right?

But, in my setup, as soon as I power Arduino, my serial port monitor starts displaying:

Blob 1 detected x=0, y=0, size=0
Blob 2 detected x=0, y=0, size=0
Blob 3 detected x=0, y=0, size=0
Blob 4 detected x=0, y=0, size=0
...

I don't show it any IR source, yet I keep getting this. When I give it an IR source, it doesn't track it and still I keep getting the same result!

Please help, I dont seem to be getting to the root of problem.

Thank You


texts:
I have a UM3561.  With the circuit below I could achieve  95dB sound.

I would like to increase sound level to 100dB.

What changes must be made to the UM3561 circuit to meet the sound level requirement?

simulate this circuit – Schematic created using CircuitLab

I have made changes in the circuit. I have limited current here.  If I use a 3.3V regulator I could achieve less dB level.  As I understand the higher the voltage the higher the volume.
Yes it's true if I use a 4ohm speaker I could achieve more sound.


texts:
Basically my question is:

I doubt noise density goes to infinity because we can reach the limit f→0 in any DC circuit in contrast to the limit f→∞ (which is an idealization because all circuit behaves as a low pass for enough f).

If noise density is limited, at which f, and how does it decay?


texts: Different digital signal input voltage than running voltage

texts:
I assume running an IC at one voltage (3.3v), and having the (digital) signal input be at a different voltage (5v) is fine. If both of these voltages are within the operating range of the chip, am I right in my assumptions?

Is this chip-dependent?


texts: Purpose of oval/oblong PCB through hole pads

texts:
What is the actual purpose of using the oval/oblong pads that are commonly used for ICs? Everywhere I read the answer is the possibility to allow a track between the pins, but as long as the pad diameters of a round and oval pad are the same I don't see the difference. I would prefer to avoid those when space is limited, does the elongation of the pad give any real benefit?

Thank you in advance!


texts: Will a 30cm antenna read Pet RFID chips over more than a few cm?

texts:
I'd like to detect my cat at different locations, but I don't want the cat to walk through a tunnel like the sureflap products, which I have both the RFID-reading feeder and door.

If I make a say 30cm or larger coil and put it under a floormat, will it be able to read the cat walking over it?


texts: How are Verilog "always" statements implemented in hardware?

texts:
The Verilog always statement, namely

always @(/* condition */)
    /* block of code */

executes the block of code whenever condition is satisfied. How is such an always block implemented in hardware?


texts: Connecting encoders/SPI devices/LEDs/buttons to a Rasperry Pi

texts:
I'm trying to connect a model B rev 2 Raspberry Pi to a whole bunch of stuff to create a MIDI foot controller:

Adafruit touch screen
20 switches (some foot, some encoder buttons)
8 x SPI LED drivers (TLC5925 chips in 4 groups of 2)
MIDI in / out ports
6 quadrature encoders (Each: 2 IO for rotation, 1 IO for button)

The screen just clicks onto the Pi without hassle.. it's already working but it eats quite a number of pins. The current pin-out of the Pi is as follows:

P1:
    01: +3.3V power
    02: +5V power
    03: SDA i2c1: SCREEN
    04: +5V power
    05: SCL i2c1: SCREEN
    06: GND
    07: --free--
    08: UART transmit: MIDI
    09: GND
    10: UART receive: MIDI
    11: --free--
    12: --free--
    13: --free-- (GPIO 23)
    14: GND
    15: --free-- (GPIO 22)
    16: --free-- (GPIO 23)
    17: +3.3v power
    18: GPIO: SCREEN
    19: SPI MOSI: SCREEN
    20: GND
    21: SPI MISO: SCREEN
    22: GPIO: SCREEN
    23: SPI SCLK: SCREEN
    24: SPI SC0: SCREEN?
    25: GND
    26: SPI SC1: SCREEN?

P5:
    01: +5V
    02: +3.3V
    03: i2c0 SDA: LED ring driver (GPIO 28)
    04: i2c0 SCL: LED ring driver (GPIO 29)
    05: --free-- (GPIO 30)
    06: --free-- (GPIO 31)
    07: GND
    08: GND

I already have a lot of code and experience with all of these components individually. But I'm overwhelmed with the quantity of input and output required to make this work.

There is currently 10 free GPIO pins. 2 of which could be used for hardware I2C.

By my estimate I need these GPIO pins:

Inputs:
    12: Encoders x 6 @ 2 channels each
    6: Encoder buttons
    14: Foot switches

Outputs:
    3: common SPI lines
    4: SPI select lines

Or 32 inputs, 7 outputs.

Anyway. I'm assuming there isn't some nice way of addressing all those SPI devices in hardware and I'll probably have to bit bash them in software. I don't like the idea of chaining them all together into one long SPI device (although it's physically possible) because of the chance for errors to propagate down the chain and also the time taken to update all those bits just to change the state of one LED. I much prefer shorter chains where I can address things quickly. Also if there is a hardware fault in one chain it doesn't effect all the others.

Is there a break out board that I can drive via I2C maybe?

Other ideas?


texts: When using mA on analog devices, does the other wire go to 0V or Earth?

texts:
On the Schneider analog input module (link) we have IC, IV, IS, 0V and Earth terminals for a single channel.
I've seen people connecting the signal wire from a transducer to the IC terminal and the other wire to the earth terminal.
Also,  I've heard that you should actually be connecting the other (reference) wire to 0V instead since the cable screen will be connected to earth too.

When using mA,  where should your reference wire be connected, 0V or Earth and why?
Also, is it wrong to connect the reference wire to earth, because I've seen it many times in the plant?

Any information would be really appreciated


texts: RC step-response and how to go about voltage across capacitor

texts:
I have this task with this circuit:

and the question is:

First I looked what would happen when t = 0:

To begin with, Vc(0) = 0 V, the reason for that is that t = 0 and before that the switch has been open a very long time which leads to the fact that the capacitor have not had the chance to charge and that is why the capacitor is 0 V.

So that gave me:

Vc(t) = Vc(∞) + [Vc(0) - Vc(∞)]e^(-t/τ)

And then I looked what would happen when t = ∞:

If I let the circuit run for a long time that implies that the capacitor will act like an open circuit. That leads to that the voltage over terminal a and b will be the voltage across the capacitor.

Vc(∞) = Vab

Which gave me this circiut:

Edit: I wrongly put 6 A on VA, but of course it should be 6 V.

Now to my question:

I want to calculate the Vab and my main question is if I could use the voltage divider rule and calculate it as:

10000(R2)/(10000(R2)+5000(R3)) * 6 V = 4 V

or do I have to consider the R1 too? Should I think another way around?


texts: Discolored negative lead on electrolytic capacitors

texts:
Would the discoloration around the negative lead of these capacitors be a sign of failure? If so, why would the negative lead darken instead of the positive - or both leads.

They are Maron EFM 35 volt 680 uF electrolytic capacitors.


texts: DC-DC boost converter voltage spike at power on, popping sound

texts:
I'm using a 3.3V DC-DC boost converter (https://www.torexsemi.com/file/xcl101/XCL101.pdf) as the power source for my audio circuit. There is a popping sound (headphone output) that happens when the circuit is turned on. There is no audible noise after power up. I viewed the boost converter's output on my scope at power up, and there's an AC-coupled voltage spike of about 2.5V that quickly decays back to zero:

I'm using 10 uF capacitors at the input and output of the boost converter, as shown in the datasheet:

How can I eliminate this AC-coupled voltage transient that's creating the popping sound?
Edit: I don't have any popping noise issue when using a bench power supply. It's only a problem using the boost converter. This is my audio circuit:

I put the 1k resistor at the output in an attempt to eliminate the popping sound, as a discharge resistor. There is a large decoupling capacitance at the output because I needed a low cut off frequency. The op amps are power op amps that have the required current capability.
I tried using a different 3.3V booster circuit, and did not hear the pop sound. The booster IC is different, and the circuit includes a diode and 68 uF output cap:

Datasheet of 3.3V booster: https://cdn.sparkfun.com/datasheets/BreakoutBoards/NCP1402.pdf


texts: How to avoid interferences (antenna effect) in long traces in PCB?

texts:
I am working on a PCB layout in which I have a 40cm long traces (bus of 4 traces). This traces will support between 50mA to 100mA and 5V. I want to minimize possible antenna effects that may occur due its length.

Could you provide me any tip on how to avoid this effect (width of trace affects?)? Or at least methods of how to protect the circuit?

Thanks.


texts:
It occurred to me that it ought to be possible to make a vacuum tube which, instead of a heater, uses an intense light source, such as a laser, to kick electrons off of the cathode through the photoelectric effect instead of them being excited using a heated filament. I am aware that two terminal evacuated tubes have been made, using the photoelectric effect to sense light and its wavelength too (as in Einstein's experiment). However, this device would have one or more grids, a plate (anode), and a cathode just like a typical amplifying vacuum tube, the only difference being a light source in place of a heater. Would this:

A. Be possible?

B. Be practical? (at least to the extent to which a vacuum tube is practical at all)

And...

C. Has it been done?

I cannot find anything about this using Google, some lab equipment is taking precedence over the results I am looking for, if they exist.

EDIT:

Here is a functional diagram:

Here are the first drawings I made of the device. The scans aren't so great, but it shows my original concept and a proposed Class B amplifier, as an example of an application which almost certainly would never work. Connections points A and B are an incoming audio signal. C is a connection to voltage supply. D is power for the lasers. I suspect that the laser diodes ought not be connected in parallel as is shown, but I didn't think of that while drawing this. Perhaps it is okay.


texts: If I am measuring 2.3 V on a 1.5 V AA battery from Duracell, is my multimeter broken?

texts: I recently measured a brand new Duracell AA battery which is labeled as 1.5 V. The reading was 2.3 V. Is this ever normal for a fully charged battery, or is my multimeter broken?


texts:
I want to know if it is possible to use a 2.4 GHz magnetron as a oscillator for a Tesla coil circuit. The idea is to use a oscillating relay-driven step up transformer (12 V to 10 kV) and then charge a capacitor bank up, just to smooth the DC output. This would then be used to power the Tesla coil circuit. I saw VTTC circuits on the web and was wondering:

What if I use the antenna of the magnetron and the positive and connect those to the primary coil of the TC? I do have a magnetron but I want to know if it's going to be worth the try, since I still need to buy the transformer and the copper coils.


texts: How to correctly connect audio plug to LM386?

texts:
I'm working on my first circuit which includes LM386 chip and some music. Since I don't have a lot of experience with electronics I need a little help with audio plug. It's the same as that:

I know that number 1 on the audio plug is GND. The biggest problem I have is that I don't know how to correctly connect other four pins to my input on LM386. As I read, this audio jack is stereo, but LM386 is mono. I followed this tutorial and I would like to somehow connect this audio jack to 10K potentiometer. Here's schematics of my current circuit:

What should I do now - how to connect this audio jack to my LM386's input?


texts:
I am just trying to to figure out what this is called.

What I am referring to in this picture is the white board with all of the connectors and the led light attached. I am trying to purchase one but I have no idea what they are called.


texts: Dc-dc stepdown converters, NUC, servos and cameras

texts:
I am playing / built a mini robot of sorts - made from a 12v dc NUC slimline PC, 2x  7.5v 500ma servos, 2x 7.5vdc IP cameras , a 3vdc laser pointer and an arduino.  I've got 4 different power supplies powering it (one for the NUC, one for the servos and one each for the IP cameras). The arduino takes it power from the USB port on the NUC.

I am a software developer and not an electrical engineer, hence the question:

Would it be possible (or a good idea) to buy some dc-dc stepdown converters (1x 12v to 7.5 for the servos and cameras, and  1x12v to 3v for the laser) , wire these on parallel to the 12 supply and power lot from the one supply?

I'd need to make sure the 12v supply has enough capacity to power them all/get a bigger one. Although these are cheap (as are the converters) so would be willing to get the kit if it means one power supply for the  lot.

Possible? Or oversimplified or plain dangerous?


texts: Advantage of using an op-amp connected emitter follower for LED driving?

texts:
I came across the following circuit used to set a microcontroller-controlled fixed current in an LED to around 100mA (target current):

As far as I understand, the voltage reference at the IN+ (1.2V) and the negative feedback force the voltage at IN- and consequently across the R1 to be the same 1.2V. R1 is then chosen to limit the current to 100mA. The right-hand side BJT acts as a switch and when a micro outputs a +5V, the transistor is biased into the linear mode and current flows through the LED. If a micro outputs a 0V, the BJT is in cutoff.

This is all very good and I know it works but I don't really see how this topology would be advantageous over a classic emitter follower with a single BJT that would simultaneously act as a current amplifier and a switch. Isn't this an overkill and unnecessary complication? The final device is going to use many multiples of this circuit and having unnecessary components would be very unreasonable.

Unfortunately, I have no chance to ask the designer whether he chose it for some specific reason, so I wonder whether I'm missing some perks of the circuit in question.

Also, I'm not sure how justified the use of C6 is at the emitter of U6.


texts: LaunchPad development board talking to itself using a CAN bus

texts: I have one Texas Instruments Tiva-C Series TM4C123GXL LaunchPad and two MCP2551 transceivers. I am trying to send and receive messages via a controller area network (CAN) bus. Is it possible to do this using only one LaunchPad?


texts: How to hook up a 5x7 LED matrix to Arduino?

texts: What is the best way I can hook this 5x7 LED matrix to an Arduino board?


texts: Data corruption while using RTOS queue services

texts:
I am trying to create a gatekeeper task to display the sensor data over the screen via UART. The attributes are defined in the structure as follows,

typedef struct Peripheral_data
{
    volatile char data[5];
    char Source[15];
    char String[5];
    char Nextline[3];
}PeriData;
/****************************************************************************************************************

 An array of structures can be declared and initilized according to the need.

 ****************************************************************************************************************/
static PeriData Peripheral[2] =
{
        { "", "TMPSEN", "Temp:", "\r\n"},

        { "", "Light_Sensor", "Lumos", "\r\n"}

};

But on sending via the queue the Source[0] of Peripheral[0] is changing to

  \0

from

  T

I am attaching screenshots for reference.

Screenshot 1:
            This picture shows the initilization of the structure at the beginning.

Screenshot 2:
            This picture shows the data present in Source variable for the structure one. Here the data indexed by the 0 in the Source variable is T. But automatically, after sending via the queue, the Source[0] for the first structure becomes zero sir. But sometimes this happens before sending via queue aswell.

Could someone suggest me what could be the problemhere. Moreover I developed this code, around one month back and it ran seamlessly over the same board. The chip am using is lpc 1768.

But when I tried to run the same code now, the above mentioned problem is arising.


texts:
I have the following circuit here, a high-side N-channel MOSFET driver, with gate voltages being generated via the circuit in the middle/NE555 section.
I'm wondering, how does the voltage doubler section actually work? The first 10uF cap charges up with 12v, then is somehow backfed from the 555, effectively doubling the voltage? I'm lost on how the voltage really "adds" up. I've only ever seen voltages increase in series. In my mind, the diode is forcing the 12V through and locking it in, and the charged capacitor is also feeding in "doubling" the circuit. This doesn't really match my understanding as to me, it seems the capacitor and 12V battery are essentially in parallel. Any help is appreciated. Thank you!
The circuit in the image below can be found at this link.


texts: How can I determine the circuitry in this module?

texts:
Previously I asked about the purpose of this module.  Now I'd like to figure out how module accomplishes that by diagramming the circuitry. What is the best way?  The backside of the PCB is obscured by a metal disc.

Is it sufficient to check for continuity between all the exposed terminals using a basic multimeter? What cautions do I need to take to avoid damaging the module?  For example, does the  capacitor need to be discharged before, and if so, how?

Or, is the white layer removable in a non-harmful way with a solvent? and if so, with what solvent? and would this reveal enough information to draw the schematic?