texts:
Electronics theory newbie here (please be gentle):

So I have an old guitar amp that had a crackly volume control. It also had an annoying habit of going from no volume to "too loud" with the slightest twist past 0 (let's assume this was by design and not a fault of the pot for now).

I opened it up and it was a 10kΩ type B pot (linear taper from what I've read).

I went ahead and replaced it with a 5kΩ type B pot, my logic was that I could get finer grain control when twisting past 0, as a given rotation on a 5kΩ pot would change the ohms by a half the amount of a linear 10kΩ pot. The crackle went and I did indeed get finer grain control.

Now I'm puzzled why this worked in the first place? My basic understanding was that originally, whilst the potentiometer was dialed into zero, it would have had a 10kΩ resistance, which kept the volume so low to be inaudible, as the pot swept towards 0Ω, the signal faced less resistance and the volume increased, however this 'theory' cant be correct as the 5kΩ pot when dialed to 0 was also inaudible. If my 'theory' was correct then the (linear) 5kΩ pot should of had the same volume as the (linear) 10kΩ when dialed half way, which was VERY LOUD, it didn't!

I can only really think of of the following as to why this is happening:

The circuit is wired to "sweep backwards" i.e. 0Ω (on the other terminal) would be inaudible, turning the dial to 1 would INCREASE the ohms and this somehow INCREASES the volume. I do see a 4558d IC op-amp in the circuit, perhaps it has the logic to "inverse" the ohm reading passed to it? (if this "theory" was correct, I would now never be able to run the amp at full volume?)

Hope someone can help me understand what should be a basic concept.


texts: Why Op-Amp Saturation voltage drop with increasing frequency?

texts:
i was Implementation of square and triangular wave generator using op-amps LF353.

I observed that when I choose different values of Resistor and Capacitor for different frequencies, with increasing frequency the amplitude of Square wave decreases and amplitude of triangular wave increases. If I extrapolate a trend line in the graph of Amplitude Vs frequency they join a common point where both amplitudes become the same.

Why the saturation voltage(square wave amplitude) is decreasing and triangular amplitude increasing?

Note: There are two points at 45Khz. The lowest amplitude point of square wave are taken when I selected a greater value of capacitor and smaller value of resistor to form the same combination for 45KHz.

Circuit Diagram: R1 and R2 are capt constant: R1=1kΩ & R1=2KΩ


texts: EAGLE detecting error at Copper Trace intersecting Dimension Outline

texts:
The ARDUINO_MEGA part from the Sparkfun Eagle Library is used in my board design. However when performing a DRU check, it seems that there is an error where the top copper traces (red) intersects with the outline (Layer 20, DIMENSION, white) of the ARDUINO_MEGA part, as shown in the screenshot below.

Why is there an error?


texts: What is the current draw of a capacitor in a VOLTAGE BOOSTER

texts:
I'm trying to learn by myself the principles of a voltage boost converter.

**BATTERY IS 1.2v@4300mAh

I noticed that many sources* suggest not putting a resistor in series with the capacitor (as in the picture).

But doesn't it make an infinite current draw by the capacitor? (R=0)

Thank you.

*for example: http://www.electronoobs.com/eng_circuitos_tut10_1.php
http://www.ti.com/lit/an/slva372c/slva372c.pdf


texts: Using KCL/KVL to derive differential equation of a mixed RLC-ciruit

texts:
I have the following LTI sinusoidal circuit, and I am trying to derive its differential equation using KCL and/or KVL. I need this to derive the Power Factor as function of the components, so I can optimize it. Solving the equations is generally no problem.

I already asked a similar question a while ago, but what got me confused this time is that my teacher said that I should end up with two equations, one depending on C and the other depending on L, but that is not what I derived.

simulate this circuit – Schematic created using CircuitLab

If I am correct:

$$i(t) = i_{C1} + i_{L1} + i_R$$
With $$i_R = i_{L2} = i_{C2}$$

$$v(t) = v_{C1} + v_{L1} + v_{R} + v_{L2} + v_{C2}$$

But if I use the i(t), and derive the differential equation, then I find the same equation of a simple parallel RLC-circuit. This does not seem correct, and I do not find the two equations my teacher was talking about.

I am allowed to use the identities:

$$v_b(t) = L_b \frac{d i_b (t)}{dt}, i_b (t) = C_b \frac{d v_b (t)}{dt}, v_b (t) = R_b i_b (t)$$
With $$i(t) = I_m \cos(\omega t + \phi_i), v(t) = V_m \cos(\omega t + \phi_v), \phi = \phi_u - \phi_i, etc.$$

I am a math student btw, so unfortunately my circuit-theory knowledge is limited.


texts: Can you use your computer to make a radio transmitter?

texts: I was wondering, is it possible to oscillate the electronic signal emitted from the audio jack on a computer ? Because I would like to somehow create a simple radio transmitter just using my computer.


texts: Transmission line reflection. I would like a non-mathematical explanation

texts:
I am a licensed radio amateur, and find bewildering the many different explanations, which range from folksy urban myth to Maxwell-Heaviside Equations, of what happens at the termination of a transmission line or feeder. I realise that they all come to the same thing in the end (or should do, pun perfect), but none of them give me a gut feeling for what is going on.

I like diagrams, so an answer in terms of (graphical) phasors for the currents and voltages at the load would suit me best. How, for instance, does a step pulse down the line cause twice the voltage at an open circuit termination? Similarly for current at a short circuit. And how is the reflected step generated by the inductance and capacitance of the line?

Can anyone help, without getting all mathematical, and not telling any "lies to children"?


texts: Can a water drop do a "fake" touch on a capacitive touchscreen?

texts:
If a capacitive touchscreen is hit by water drops, like rain, will it report a touch?

I'm trying to evaluate what is the most appropriate touchscreen solution to use in an outdoor kiosk.


texts: Can I use any digital component to avoid 7805 killing my microcontroller directly when its ground is disconnected (hence 12v goes to uC directly)?

texts:
My idea is to have an intermediate cheap component that will blow-up before my uC if the voltage goes above 5v from 7805 (or even some fuse, but I am not sure if a fuse will blow-up with over-voltage like it blows-up with over-current). I have lost many Atmega328P chips because of 7805 accidentally supplying 12v to them. I have heard of SCR - is it the component I am looking for which blows-up with voltage?

Also, please tell me how to use a zener with 7805.


texts: BOOSTXL-DRV8323RS Set up - trying to spin motor in 3x PWM mode

texts:
I have been following the datasheet for the TI DRV8323 and the BOOSTXL-DRV8323R dev kit. I am trying to spin a BLDC motor by sending 3 SPWM waves (all 120 degrees phase shifted) generated by an arduino to the INHA, INHB, INHC pins on the DRV8323 board. As specified by the datasheet, for 3x PWM mode, I also tied the low inputs for the gate drive (INLA, INLB, INLC) to logic high, and added the 47k resistor to the MODE pin.

I checked all the input signals being sent are correct on the oscilloscope - the Arduino is correctly generating the SPWM signals.
The motor won't spin - my question is if anyone knows if I am missing a connection or if people have experience running a BLDC motor with this board.
Thanks :)


texts: Very high speed counter (around 1.5 GHz to 2 GHz)

texts:
I am thinking of a device that can measure the distance of an object from a sensor using a radio transmitter and receiver pair.

I'm thinking of using a counter at the sensor side, with a fixed-frequency transmitter and receiver on the sensor.

There will also be a transmitter and receiver on the object whose distance with respect to the sensor I want to measure.

When the transmitter on the sensor transmits a pulse at the previously agreed radio frequency, the counter on the sensor will start counting.

When this pulse is detected by the receiver on the object, the transmitter on the object will transmit a pulse to be received by the receiver on the sensor at which moment the counter will stop and the distance will be measured according to the time lag.

The problem is that I can not find a counter and a clock source compatible with each other in the 1.5 GHz to 2 GHz range. Any suggestions as to what I can use?

The measurement error that is calculated is 33 cm/s at 1.4 GHz and 13 cm/s at 2.2 GHz. So basically, the faster the counter is, the less error.

Can anyone tell me what counter to use together with the clock source for the counter?

I looked at MC100EP016A counter IC but can not find a clock source for this IC.

I require a clock signal with the following characteristics:

Input high voltage = 2075 to 2420 mV
Input low voltage = 1355 to 1675 mV


texts: Who can show a schematic for a voltage switch

texts:
In earlier questions I raised a problem about a DC-DC booster that destroyed itself when its load was disconnected by drawing a large current from its input power source. This was specific when using Lead-Acid batteries (probably because a LA can deliver a large burst).

The task was (for me) to find a current-limiter solution on the input. I have tried a simple solution with a resettable (push) fuse, but that is too slow.

I have then found this device, based on a Allegro current sensor ACS712.

With this I can get a corresponding voltage reading from its current flowthrough.

So here we go. How do I use some external discrete components to activate a relay that disconnect the input power to the DC-booster? I know about electronics - but not that much. My simple guess is a zener that controls a transistor that powers the relay. But it must be good (with good I mean quick acting) and reliable.

From the curve, I can see that the wanted breaking point is around 3,2V at 6-7Ampere (It must break from 6A and up).

Below, links to my earlier questions about this problem

Fuses - Are there any voltage conversion for the break-off

How to prevent large inrush current without a reset-fuse

DC-DC booster fails with lead-acid battery source

simulate this circuit – Schematic created using CircuitLab


texts: I have a 2.7V 100F super-capacitor. I am going to be charging it with a 6V 1W solar panel. Now the solar panel only puts out 6V when it is receiving the best sunlight so this means the output from the solar panel can be lower. What is the best way to go about charging the super-cap. I was thinking of just using a voltage divider with resistors but I wanted to get  some other opinions.


texts:
I need a band pass filter that only accepts frequencies from 1000 to 1400 Hz and then toggles the transistor. It has to work from .1 Vpp to 1 Vpp and rejects anything else. I have been testing this circuit in different ways and I keep getting a similar result.

In the circuit my source is .0005 Vpp I have changed it to .05 Vpp and only the dB value changed.


texts: Correct arrangement of current sensing resistors for a BLDC motor?

texts: I am designing the current limiting (fault detection) circuit for a three phase BLDC motor and I wanted to ask, If I have three switches on at any given time (180 degree commutation) than should the sensing resistors be placed as shown in figure 1, or is it fine to have it as shown in figure 2 which is typically used for 120 degree commutation method. Thank you.


texts: Designing Battery Power System For Robotics

texts:
I'm building a mobile robotics project for a class and I'm trying to figure out how to (or even if its necessary) to design a nice battery power system for it. I sort of wanted to learn how to build a nice power system so that I have the knowledge and to experiment a bit, but i'm sort of losing my mind on a part of the project which isn't super necessary. I basically wanted to try to build a few nice features.

1) USB power muxing, power the device off of USB power if its available

2) Battery Charging (Off of USB or some other connection)

3) Regulate 3.7V to 5V and 3.3V

4) Battery Protection, Undervolt, overvolt, short circuit are the main ones

5) Be able to provide enough power at 5V for (At least) 2 small steppers, 1 small DC motor, and 2 small servos. One of the steppers might be close to providing stall torque.

Basically, i've knocked up a few circuits that might work using several purpose built battery management IC's, but these small multi-purpose ic's are only really able to provide 1.5 - 2 A, which I really don't think is enough. Below is my latest idea.

This circuit uses

1) TP4056 for LiOn Charging

2) TPS2115 for automatic power muxing (max current is like 1.5 A)

3) TVL70033 for 3.3V linear regulator

4) TPS63002 for 5V switch mode boost

My friend is placing bets on which part of this circuit is going to catch fire. I'm getting pretty close to just trying to buy some ebay BMS chinese special and an ebay 5V boost converter and forgetting this whole thing because it's been a pain in the keister to get to this point. I've seen some power muxing solutions on here like this one but they're a bit complicated. I could also use a 5V boost manager and sort of build my own boost converter instead of buying an all in one IC to get some more current but i've never done that before and it looks difficult. How are medium power battery systems like this usually designed? Is this all more trouble than it's worth? Thanks for reading, I hope this question is slightly interesting.

Also as a completely unrelated question, how do you put out a lithium battery fire?


texts: How to connect DAC - MCP4725 to the speaker?

texts:
I don't have any experience in hardware.
I am writing a simple program in Raspberry pi to write
audio samples to the DAC MCP4725. Next, I want to connect to
the small speaker. What should be the rating of the speaker?
I need a simple circuit to do so. Like, I checked that I need to
connect the ouput of MCP4725 to a capacitor to get a pure AC signal.
Next, I need to amplfiy this to drive a small speaker. I am planning to
connect this to 3W minimum speaker 4 ohms or 8 ohms. What are the things
I need to check in the datasheet of MCP4725 in order to drive the audio?

Here is the datasheet -

https://docs.rs-online.com/18f7/A700000006619099.pdf


texts: how to make wire bend easier to wrap inductors?

texts:
enter image description here

so obviously, the wire is thick (for a wire) how to make it easier to wrap around a core?


texts: Can connector pins oxidize while mated and lose contact?

texts: Can oxides build up enough to force contacts to disconnect?


texts: Practicality of generating electricity from ambient noise

texts:
My living space has constant supply of a variety of annoying sounds thanks to a lack of proper sound deadening. I was wondering what is the practicality of creating an energy "leech" array using microphones? my current circuit that I am thinking of is using a lav-mic, slapping a full bridge rectifier across the output. That feeds into a small ceramic capacitor for some semblance of smoothing. Five of the previously mentioned would be wired in series and feed into a 5v supercap and then a joule thief will step up the voltage to 5v and will be fed into a li-ion battery management (charge/discharge circuit like the ones found in battery banks). I was thinking if there is such annoying noises might as well put them to use.
TL;DR: Is it feasible to create a low-power generator from microphones to harvest power from annoying noise sources?


texts: What happens if the SINR of a signal is less than 1 in a (wireless) network? Is that practical at all to have a SINR < 1? Using the Shannon capacity formula, it seems that we must be able to have SINR < 1, but we get a rate < 1 bits/sec/Hz.


texts: difference between warning and a fault in Linear Technologies chip

texts: My team is executing a design and using LTM 4677. They asked to write software to read the status of the device. The documentation for it quite comprehensive, but what I can't figure out is the difference between a fault and a warning in this device. Can someone help me out on this? Here is the link to the documentation is you need it.


texts: DSPIC33EP AN1307 application note source code

texts:
I've downloaded source code of an application note from Microchip's web site (AN1307). In order to try it, I created a new project in MPLABX. Then I added all source and header files that I've downloaded to the project. When I built the project it gave an error because header file uart.h was not included. But there was no uart.h file in the source code that I've downloaded from the web site.

What should I do? Where can I find that header file? Should I write it on my own?


texts: How much current does a DM3 connector require?

texts:
I'm trying to have my PIC32MX470F512L communicate with the sd card for some time now without success (using harmony sd card example)

I checked that the pins CMD,CLK,DAT0,DAT3 are receiving a signal.

So now im questioning what is the minimum and maximum of current the micro sd card with SPI when in a DM3 micro SD connector? because i've been testing with ICD3 power, that provides only 100mA for both pic, sd card and other small things.

the model i'm using for sd card connector is DM3CS-SF


texts: I'm in need for some schema validation. I'm about to send the schema for PCB making. Parts that are being used are DW01 (Lipo Cell Protection IC) and FS8205A (Dual Channel Mosfet). Do you see any obvious mistakes? Out + goes out to a boost circuit and from there to a microcontroller.


texts:
My plan is to make RPM counter to my motorcycle. I'm planing to read ignition box signal with arduino. I think that ignition box gives 0-12V (or 14.5V max) square wave signal to coil. I was wondering if I can read that signal with something like this:

I found similar thing called Chippernut from the net.
That device reads signal with PNP transistor. I circled a part where signal comes in. Schematic:

Does my design work at all with NPN transistor? Why? And if it does can I have some advice with that transistor model and resistor sizes. It have been while since last transistor calculations. Also is there any danger with coils recoil?


texts: Ground noise while using multiple switching regulators

texts:
Is there any important points to consider especially about noise when more than one switching regulator is connected into the same ground reference or having a separate ground layer in the pcb is good enough ?

To summarize, is there any extra precautions to take while dealing with multiple switching regulators or designing them one by one as if they were the only one would be fine when it comes to dealing with noise.


texts: How could I make a water-resistant touch/tap sensor (similar to push button) for all-weather outdoor use?

texts:
I am building an Arduino-based device to be used outdoors (on a bicycle), and it is expected to work in all weather conditions. The device will have some buttons to turn lights on and off, honk the horn, etc.

Since regular push-buttons would not be water-resistant, I thought about creating some sort of "touch sensing push button" with bare wire ends (either one or two wires), or exposed metal plates. I have already read about single-node capsense, but I don't know if it would work.

Also, I wonder if piezo crystals found in small buzzers could be hacked to work as touch or tap sensors in this same application, thus enabling the use by people using gloves.


texts: Ripple current in a linear power supply transformer

texts:
I'm a bit confused regarding linear supplies and their input currents (i.e. on the input side of the voltage regulator).

To start with, here's a test circuit:

\$R_{bogus}\$ is just to make LTspice happy (all nodes need a connection to ground).
BTW, I guess I should add another input cap for high frequency noise - though that's hardly relevant to this question (and the schematic is just a very rough test circuit anyhow). The goals are 0 - 12 V at up to 2 amps (1.5 would probably be good enough, though).
The voltage source is 230 \$V_{rms}\$ since that's what it'll run on, and the transformer is set to simulate ~15 V RMS, so about 21 V peak.

The problem is, depending on how you view it, too large current spikes, or too high of a voltage drop due to series resistance. Or both, really.

Here, the red voltage is the input to the voltage regulator, and the green/blue is current through two of the rectifier diodes. Note how the voltage is lowered a lot (from 15 Vrms - 2 diode drops) due to the series resistance combined with the 5.5 A current peaks.
This graph is at maximum output current (12 V / 6 \$\Omega\$ load) = 1.87 - 1.99 A due to the output ripple; the input voltage is too low for it to regulate properly due to the drop on the secondary.
Of course, the smoothing caps have peaks similar to the diodes, but lower magnitude (~1.8 A).

What sort of series resistance would the transformer's secondary have? I'm looking at a 2x 10-15 V multi-tap transformer, with 2.2 A per secondary rating (66 VA in total). The data sheet lists a few details, but not series resistance.

Assuming a 1 \$\Omega\$ series resistance on the secondary (as in the simulation above) and 0.11 \$\Omega\$ ESR on the smoothing electrolytics (some ballpark figures I found when searching), I end up with something like the above. With 0.5 \$\Omega\$ on the secondary, the output is great at 12 V and less (the target), but of course the 5+ amp spikes remain on the input side.

So, finally, the questions:

Am I in the right ballpark with 0.5 \$\Omega\$ on the secondary, or is twice that closer to the truth? I do realize that it differs between transformers, of course, but I can't really find any figures and I have nothing to measure myself... but in this simulation, one works and the other doesn't.
Are the current spikes of ~5-6 A for a 2 A supply normal / to be expected? Same for the smoothing caps (~2.4 A) - I assume that is the "ripple current" spec for capacitors, by the way?
How much does the transformer need to be rated for to handle this? Surely I don't need a 6 amp transformer to get 2 A DC out? The current RMS is below 2.2 A, but is this really okay?

And, though this is pretty much answered by the above:

Should I really expect such a huge voltage drop at load? If the spikes are at 5 A, with 0.5-1 \$\Omega\$ on the secondary, I obviously lose multiple volts even before the bridge rectifier, which causes the whole thing to fail (massive output ripple).


texts: Powering an amplifier with lower voltage?

texts:
This amplifier uses a 24V 700mA power supply (more details here):

Question: The amplifier currently drives an 8Ω speaker, a comment from my other question says that to be able to drive a 4Ω speaker, I should half the voltage (giving it only 12V). Will that work right away?


texts:
Consider the following asm.S

.global main
main:
rjmp main

Compile and dump it with these commands:

avr-gcc -mmcu=atmega32u4 -g -o asm.elf asm.S
avr-objdump -S asm.elf

In initialization code, among other, there is this command:

ae: 1f be           out 0x3f, r1    ; 63

Why there is this command?


texts:
I am making an electrical fridge for a school project. I am using a 12v Peltier cooler and using a 12v 30a power supply. I have all the wiring and everything already set up, and no matter what I cannot afford to have the Peltier burn out or anything even though I had one burn out before using the exact same setup and wiring, though that was a smaller model still 12v, but the Peltier isn't working at the cooling power that its supposed to be. it cools down the fridge to 68° f when it should be cooling to 20°f, and I think it might not be getting the power it needs, but the wires that I'm using are extremely small, like 22 gauge, but I have them doubled up, one concern I have is that the input and output wires for the Peltier warm up a lot, but not enough to melt the wires, even though it melted the wires for the first Peltier that burnt out. The reason I'm going into such detail is that I know basically nothing about electrical things like that and want to know if the context matters and I really need to know what the warm wires are because of, and more importantly if it would be safe to use thicker wire.

Update: I do have a lot of cooling on the hot side, I have a CPU cooler meant for a computer on the hot side, so there isn't a problem with that, but the first time that the Peltier burnt out it didn't have any cooling at all and was extremely hot. Also, I am also wondering if a wire too thick would damage or cause the Peltier to burn out? Like I said before, I can not afford no matter what fo have that Peltier burn out.

Also, my power supply's input is 115 or 230 but I keep it on 115 because I don't want the thing to burn out just in case that matters


texts:
The question:

"At a carrier frequency of 2 GHz, assuming a transmit antenna gain of 3 dBi and a receive antenna gain of 0 dBi, calculate the line-of-sight received power at a distance of 100 m from the basestation (in units of dBm). Assume 100 mW enters the transmit antenna port."

My attempt:
The equation to use
$$P_{r}=\frac{P_{t}G_{t}G_{r}\lambda^2}{(4\pi R)^2}$$

I am not sure what to do next, I think that \$G_r=0\$, hence the \$P_r\$ will be 0 since the numerator is.

EDIT:

Thanks for the help, I iwll try to solve it now:

\$\lambda=\frac{c}{f}\$,
Therefore \$\lambda=0.15\$ m

\$R=100\$ m

\$P_{t}=0.1\$ W

\$G_t=10^{0.3}=1.996\$

\$G_r=10^0=1 \$

Hence
\$P_{r}=2.844*10^{-9}\$ W \$=-55.5\$ dbm

Is this correct now?


texts: Which term is right? "No load" or "infinite load"?

texts: If I have a generator that rotates in open circuit, do I call it "the generator has no load" or " the generator has infinite load"?


texts: RC Circuit Analysis - Finding Capacitance

texts:
I'm lost on how to approach the following problem (apologies as I'm not an EE).

In the following circuit, I'm trying to find the capacitance that will limit the node voltage (where the voltmeter is attached right above resistor R2) to below 4 volts for 15 milliseconds.

Can someone provide some guidance on how to approach this??


texts: Reducing power consumption of RF433 module

texts:
I'm trying to build a remotely-controlled switch using Atmega328p.
For radio communication, I've chosen a generic RF433 transmitter/receiver combo, just like in this tutorial:
https://randomnerdtutorials.com/rf-433mhz-transmitter-receiver-module-with-arduino/
The receiver is battery-operated, so power consumption is really important.
My plan was to power a receiver from a digital pin and give it power every second, see if any data is coming through for 20ms and either read it if there is any data or power it down for the next second.
The transmitter would send the same message in a loop for 2 seconds so the receiver would be able to 'catch' it between sleep cycles.
My problem is that it seems like it takes a while for the receiver to "wake up" and start reading the data.
Her is my code:
#include <Arduino.h>
#include <Servo.h>
// uncomment #define RH_ASK_ARDUINO_USE_TIMER2" in RH_ASK.cpp
#include <RH_ASK.h>
#include <SPI.h>

Servo servo;
RH_ASK rf_driver;

int NEUTRAL_POSITION = 57;
int POWER_PIN = 5; // VCC of RF433 is connected to this pin

void setup() {
  servo.attach(9);
  pinMode(POWER_PIN, OUTPUT);
  digitalWrite(POWER_PIN, LOW);
  rf_driver.init();
  Serial.begin(9600);
}

void on() {
  servo.write(137);
  delay(500);
  servo.write(NEUTRAL_POSITION);
  delay(500);
}

void off() {
  servo.write(10);
  delay(500);
  servo.write(NEUTRAL_POSITION);
  delay(500);
}

uint8_t buf[1];
uint8_t buflen = sizeof(buf);

void loop() {

  digitalWrite(POWER_PIN, HIGH);
  long start = millis();

  bool isAvailable = rf_driver.waitAvailableTimeout(700);
  long waited = millis() - start;

  Serial.print("isAvailable: ");
  Serial.print(isAvailable);
  Serial.print(", waited");
  Serial.println(waited);
  if(rf_driver.recv(buf, &buflen)) {

    int command = atoi((const char*) buf);

    Serial.println(command);
    if (command == 0) {
      off();
      delay(500);
    } else if (command == 1) {
      on();
      delay(500);
    }
  }

  digitalWrite(POWER_PIN, LOW);
  delay(1000);

}

I'm using RadioHead library for RF433 communication.
When the data is being transmitted it takes about 600ms for the receiver to be able to detect that, hence the 700ms timeout:
rf_driver.waitAvailableTimeout(700);

Here is the transmitter code:
#include <Arduino.h>
// uncomment #define RH_ASK_ARDUINO_USE_TIMER2" in RH_ASK.cpp
#include <RH_ASK.h>
#include <SPI.h>

RH_ASK rf_driver;

void setup() {
  Serial.begin(9600);
  Serial.println("starting");
  rf_driver.init();
  pinMode(LED_BUILTIN, OUTPUT);
}

uint8_t on[] = {"1"};
uint8_t off[] = {"0"};

void sendOn() {
  digitalWrite(LED_BUILTIN, HIGH);
  unsigned long end = millis() + 2000;
  while(millis() < end) {
    rf_driver.send(on, sizeof(on));
    rf_driver.waitPacketSent();
    delay(30);
  }

  digitalWrite(LED_BUILTIN, LOW);
}

void sendOff() {
  digitalWrite(LED_BUILTIN, LOW);
  unsigned long end = millis() + 2000;
  while(millis() < end) {
    rf_driver.send(off, sizeof(off));
    rf_driver.waitPacketSent();
    delay(30);
  }
}

void loop() {
  if (Serial.available() > 0) {

    String command = Serial.readStringUntil(';');

    if (command.equals("on")) {
      Serial.println("Sending on");
      sendOn();
    } else if (command.equals("off")) {
      Serial.println("Sending off");
      sendOff();
    } else {
      Serial.print("Unrecognized command: '");
      Serial.print(command);
      Serial.println("'");
    }
  }
}

Obviously this is far from the original idea of sleeping most of the time and just wake up for a quick 20ms check.
Is it the correct approach to build this kind of system?
Should it really take 600ms for RF433 to get up-and-running and detect that there is data being transmitted?
Is there maybe a different RF/BLE module to achieve this kind of sleep/check-for-data pattern?


texts:
I have a questions regardin charging batteries.
I have a Li-ion, 3.6V, 150 mAh battery and I am looking for a suitable charger. Unfortunately I was not able to find a compatible charger. The ones I found had a lower limit on charging current which was around 500mA. This would set my charging current to over 3C. Now this could probably work, but it would be very bad for the battery. Can you please provide me with the charger IC or some idea on how to do it with the given IC that has higher charging current.
Thing that crossed my mind is to do a current divider, but that would lead to unwanted heating that I do not want.


texts:
I have been told in classroom that there are several methods (one-step autotransformer, the star-delta connection and a solid state controler) to start a induction machine above 500 hp, but what I was not told its why the 500 hp limit.

Is this  a rule? Below this level is not necessary these methods? Is this impractical?


texts:
What kind of components are those two at the left? What's their purpose?
The one of the right has been making a "buzzing" noise for the past couple of weeks. Why is that?

￼

Thanks!


texts: RLC Series circuit V(t) = Vss(t) + Vt(t)

texts:
I am having difficulties trying to obtain the voltage expression for the below circuit.

When I simulate the circuit, the values obtained from my v(t) expression do not match the simulated circuit results.

v(t) = Vss(t) + Vt(t)

v(t) = 6 + 0.00176sin(29806)(0.000112) != 9.690 at 112uSeconds

What have I done incorrectly? I am truly clueless on why I am not getting the right answer.  Is I(t) not 0 at t = 0?

Thanks in advance.


texts: QAM demodulation , hard vs soft if there is any

texts:
I am trying to find the answer to , what types of demodulation methods are exists. Each of my searches results with different names, but converging to one metric , which is finding the closest symbol among all the constellation points (square qams).
In one reference it is called slicing , in another it is called "hard-decision", another one is named maximum likelihood...

Are all really the same ? is there any "soft-decision" metric ?


texts: How do I invert the output of this current sensor using the other side of the LM358?

texts:
Referencing a design that uses a more expensive OpAmp, I have put together (in simulation) this current sensing circuit that uses one half of an LM358. I would like to use the other half of the LM358 to invert the output of this circuit. That is, where right now the output is 0V when there is no current through the load increasing linearly to 5V when the maximum current is reached, I would like an output of 5V when there is no current decreasing to 0V when the threshold maximum current is reached.

I have made several attempts at adding an OpAmp inverter circuit (again referencing the basic diagrams found via Google), but I have not been able to hack the two circuits together properly. How can I wire the other side of the LM358 to accomplish this?

Edit: After some more playing around with the simulator I realized that I was misunderstanding the inverting OpAmp concept, among other things. I am still curious to know if there's a relatively simple analog circuit that will accomplish my stated goal, but I (think I) understand now that it's not going to be a matter of just wiring up the second OpAmp with a few resistors.


texts: Astrom-Hagglund Relay PID tuning - relay transfer function?

texts:
I'm implementing a PID temperature controller on a PLC. To cut down on installation time (this design may be reused many times), I want to have the PID parameters tuned automatically rather than manually.

To do this, I'm trying to implement Astrom and Hagglund's relay tuning algorithm. Essentially, the control effort is inverted each time the feedback crosses the setpoint (eg, each time the sign of the error changes).

Now, I'm pretty sure that when I do this, I just change the input to the plant back and forth between a positive and negative amplitude. Most descriptions of the method seem to also indicate this. The trouble I'm having is that right next to that description, I always see a diagram that looks like this:

This diagram seems to contradict this idea by seemingly suggesting that the plant input should be the error multiplied by the setpoint value. That is, the output from the relay is
$$
\text{Plant Input} = \left\{\begin{matrix}
Ae(t);\; e(t) > 0
\\ -Ae(t);\; e(t) < 0
\end{matrix}\right.
$$
rather than just
$$
\text{Plant Input} = \left\{\begin{matrix}
A;\; e(t) > 0
\\ -A;\; e(t) < 0
\end{matrix}\right.
$$

where \$A\$ is the amplitude and \$e(t)\$ is the error signal.

Intuitively, the first one seems wrong as this is essentially just a proportional controller, and when the error becomes negative, the double minus sign means control action is still positive. Still, I want to be absolutely sure about this - which one is right?


texts: Soldering techniques for PCB modules where all pads are on bottom

texts:
I am prototyping a board that uses one of two modules (that is another PCB with components already on it). One module - all pads on that module are underneath (not exposed and not castellated), rather small and tightly packed:

Another module is less problematic as most pads are castellated holes and only a few pads are underneath (bigger and more dispersed compared to first module):

While 1st module is more complex, it is most preferable to be used as it is more reliable one as far as I know. And even with 2nd one I still would need access to those hidden pads. I only have 1 of each module for prototype, so I would highly prefer not to screw this up.

Tools I have access to:

Simple soldering iron with a few different tips
Quite good hot air station
Solder wire with rosin core
Syringe of solder paste (low temp ~130 C) and syringe of flux

I am thinking I should be able to solder it with the hot air using low temperature solder paste. However I will have no way to verify that solder has melted and created reliable joints.

Another concern is that during the pre-heating flux in the paste drops in viscosity and spreads solder balls all around the area where it has been applied. On open joints the surface tension usually brings melted balls together into a nice and clean joint, but with this being sandwiched between two surfaces I am very concerned about making bridges.

I guess my question is what techniques I could use for increased chances of a good quality soldering of those hidden pads?

PS: as a workaround for bridges I was thinking to prime the pads with paste and melt it using hot air, then apply extra flux from syringe, put module atop and reflow this using hot air. Would that work, is there any issues with this approach?


texts:
I had a hair-brained idea the other day and put together the attached circuit.

The problem: the instant I push the switch to place a voltage across the inductor, the power supply shuts down. Clearly this is some sort of emergency power-down because I can start it right back up, but I'm not understanding why such a feature would get triggered? Is it just the voltage drop is sudden enough to flip off such a power supply? I would have thought that the series resistance would be enough to prevent something like this.

simulate this circuit – Schematic created using CircuitLab


texts: If a wire is rated 10A, 120v AC. How many amps could I put through it of 13.8v DC?

texts: I am using a wire that is rated 10Amps at 120v ACwith a car headlight and a SLA battery.  About how many amps could this wire carry before getting warm or melting of DC current at 13.8volts?


texts: Tools to compile pointers to arrays of static size

texts:
Are there any static code analyzing tools for C that convert pointers to arrays of a static size? It is a marginal pain and I just figured I'd check with the community. A quick google search did not turn up anything useful because "to" in the phrase "pointer to array" generally means something completely different from what I'm looking for here... Any suggestions or keywords would be helpful.

P.s. I'm trying to convert some code into synthesizable C for a hardware implementation.

So for instance, this code is not synthesizable:

void sum(float *a, int size, float *out) {
    int i;
    for (i=0;i<size;i++)
        *out += a+1;
}

It is not synthesizable since the size of a is not statically declared at runtime. (Note, that out should be ok since it is not an array - though I'm not 100% sure on that.) It would be lovely if there was a tool to convert use of variable sized arrays to arrays whose sizes were known at compile time.

Furthermore, this code must be transformed (currently manually) to something like this:

// Not 100% sure if float * is still allowed.
void sum(float a[SIZE], float *out) {
    int i;
    for (i=0;i<SIZE;i++)
        *out += a[i]; // Not sure if this is necessary.
}

Right now, I would have to do this manually. I have to resolve all usages of dynamic arrays. This is how HLS works. It is a serious issue. It is hard (or at least time-consuming) to do when you did not write the original code. It must be converted so that you can synthesize the code to hardware.

All array sizes must be resolved - they may not have been explicitly declared initially. Then these array sizes must be propagated to all affected functions/references.

Finally, for those of you confused by "synthesizable", feel free to check out these two links that describe it much better than I can...

http://www.cse.psu.edu/~xydong/files/proceedings/DAC2010/data/1964-2006_papers/PAPERS/1988/DAC88_330.PDF
http://www.xilinx.com/support/documentation/sw_manuals/ug998-vivado-intro-fpga-design-hls.pdf


texts:
What are the tradeoffs and design considerations for capacitor dimensions? Specifically, I need to select 2 electrolytic capacitors (C2 and C3) for a car voltage (noisy 12V) to 5V converter.

Here's the circuit:

How would I pick a capacitor from this datasheet?
http://www.mouser.com/ds/2/420/al-kze-e-140701-514740.pdf


texts:
I have a Verilog module for which I want to check its timing in isolation to the rest of the system. The problem is that the FPGA has a limited number of physical pins, and my module has more inputs bits than there are physical pins, so Quartus II cannot compile (the fitter complains the FPGA does not have enough pins).

As I understand, in order to make Quartus II happy, I need to some input pins of my module as virtual. These are the constraints in my .sdc that I have tried:

set_input_delay -clock clk_i 0 [large_bus]
set_instance_assignment -name VIRTUAL_PIN ON -to large_bus

Even with those constraints, Quartus II is still complaining. How can I make a "dummy synthesis" of my Verilog module to check for timing?


texts: Good NPN configuration vs bad configuration

texts:
Let me try this post to see if I can properly ask the question.

I have the common emitter configuration which works for me, the math (Ie = Ic + Ib) works. The load is in series to the collector. And all it takes is a very very little current through the base to turn on the path from the collector to the emitter:

Now I also have been playing around with the following. After further reading, it appears it is similar to the common base configuration except, that I'm using a NPN transistor not a PNP which means the whole thing is wrong. I actually get current from the base through the emitter, the collector has no part in it. I disconnected the power source to the collector but the LED still lit with no variation.  Based on what I have read, the configuration really just acts like a diode from the base to the emitter. The load is in series with the emitter. Am I getting this 2nd diagram's explanation right?

Follow up info #1 regarding figure #2. If I remove the resistor on the collector leg, the following is what is being measured:

 the Re in the table means after the resistor on the emitter leg
1- now I do not see emitter voltage = input voltage (even if I account for the 0.7v for the register-LED).
2- when I disconnect the collector leg, the LED actually is brighter.
3-when I reduced the collector voltage from 4.98v to 2.2v, I thought the emitter voltage would be reduced too.
So obviously I'm missing something regarding the common collector/emitter follower.


texts:
I've got Sparkfun's FT245RL Usb to Fifo Breakout Board.
I need 5V output from data bit ports(D0-D7). While I'm working with it, I've found out I need to unsolder SJ1 jumper between Vcc and Vccio then connect Vusb to Vccio in order to get 5V output. I did it but unfortunately I cannot get 5V output from that ports. Did I miss something? Did I do it wrong? Or do I need to supply external power?


texts: Why do we need communication protocol and what is the difference between UART and i2c other than clock?


texts: Why are the pins RC3 (SCL) and RC4 (SDA) configured as inputs during I2C initialization in PIC18F?

texts:
I am on the process of interfacing a RTC DS1307 with PIC18F. So, the controller will be the master and I2C the slave, therefore the controller will generate clock and data as outputs, If i am right?. However, I went through a couple of codes and noticed that the RC3 and RC4 pins are configured as inputs during the I2C initialization. My question is, Aren't these pins supposed to be configured as outputs in order to clock out and data out (as it is in Master Mode) to the RTC?.

Below is an example from one of those codes:

void i2c_init()
{
 TRISC3 = 1;
 TRISC4 = 1;
 SSPSTAT |= 0x80; //Slew Rate Disabled
 SSPADD = 49;

 SSPCON=0b00101000; //Master mode
 SSPADD = 49;

 /*SSPEN = 1
 Enables the Serial Port and configures the SDA and SCL
 Pins as the Serial Pins
 SSPM3:SSPM0 --> 1000
 I2C Master Mode
 Clock = Fosc/4*(SSPADD+1)
 */

}

Can someone please explain why are they configuring these pins as inputs ?

Thank you all in advance!

Regards

~VD


texts: Darlington Emitter-follower used as a buffer

texts:
I have a  circuit with a Darlington emitter follower used as a buffer between a common emitter amplifier and a low resistance load (speaker). i wanted to know if this arrangement could alone (with the corect values ofcourse) amplify an input from a microphone and give output at the speaker. could this arrangement be used for applications such as mobile phone speakers?
if i have an overall voltage gain of say, about 170? would this be enough to drive a speaker of less than 1watt power?


texts: DIY EOG (Electrooculography) Circuitry Dangers?

texts:
I wanted to try to build my own EOG filter and amplifier circuit. I've found many online sources that use an instrumentation amplifier, high pass and low pass filters, and additional amplifiers on the end, or a similar combination of those basic things.

However, I've been curious as to the safety aspect of this. I am not too experienced with hooking up hardware to the human body, so I am not sure what I need to look out for, or if it is even dangerous at all, since the probes should only be reading the information, and not delivering electricity to the body.

Others seems to have success with these designs. What could possibly go wrong? What should I look out for? And is it more recommended that I don't do this?


texts: Analog sensor output incorrect when sensor not connected

texts:
I created a simple circuit to measure an analogue photo detector output that has 3 pins (vcc, gnd, output).

I create a PCB by iron method to test it. But the problem is when the sensors are not connected to the board and the supply is connected, I measure the output pins of the sensor on the board with voltmeter (note that there are no sensor connect on board) it shows some voltage instead of zero volts.

The SENSOR1 shows 3.9V and the SENSOR2 shows 0.3V. (I used a 0/1 switch to control the supply and an LED to show the supply and also pull-down the outputs of sensors with 10k resistors.)

Please help me.
Sorry for my bad grammar and description.


texts: identifying overshoots in given state space system with step inputs

texts:
Suppose I have the following state space system:
$$
\dot{x}(t) = Ax(t) + Bu, \quad y(t) = Lx(t), \quad x(0) = x_0\neq 0
$$
where \$A\$, \$B\$ and \$L\$ are real matrices, \$u\$ is a constant real vector (so that the system is subjected to a step input at \$t=0\$, and \$L\$ is just an identity matrix. In addition, it is also known that all eigenvalues of \$A\$ are real and negative.

Given this information, can I know (without solving the system in time) if all states of this system will have a monotonic behaviour (i.e. if a given state is increasing it will keep on increasing and vice versa)? In other words, if any state of the system has "overshoot" like behaviour, is there some sufficient condition to detect it?


texts:
I'm developing a flyback converter with the FT838NB1 IC, and I got some doubts about the Collector-Emitter breakdown voltage of the integrated NPN switching transistor.
IC datasheet link: https://datasheet.lcsc.com/szlcsc/1812230403_Fremont-Micro-Devices-FT838NB1-RT_C190118.pdf
Absolute maximum ratings shows that the Collector to GND voltage can goes to 700V:

By the internal schematic I understand that Collector to GND value can be considered the Collector Emitter breakdown voltage im my circuit, as the emmiter is connectec to GND by a low resistor (and the current doesn't exceed 0,4A).

All right so far, because the circuit is operating well, with full load and in universal input voltage range (85V to 264V).
But in the Electrical Characteristics section of the datasheet I found Minimum Collector-Emitter breakdown voltage of 400V. So for me, reading this information, values larger than 400V would cause troubles to the BJT.

But as you can see below, the ringing voltage on my circuit is reaching 513V, and it's working well (I achieved this value with a good snubber, it was worse).

Can someone explain were my interpretation is wrong please?


texts: On an Apple 12W USB Charger, how are the D+ and D- lines configured?

texts: Looking for the voltages on the V+ and V- lines of an Apple 12W charger that corresponds to the 2.4A output.


texts: Calculating the resistance required to limit current in order to prevent diode burnout - I can't make sense of this textbook problem

texts:
I am reading through Complete Electronics Self-Teaching Guide with Projects, which has turned out to be a fantastic resource for quickly learning electronics basics. But I've come across an example in the section about diode breakdown and burnout that has me completely confused.

When I tried to calculate this before I looked at the answer, I came up with 5K for the resistor (I think the 100V on the right is saying the voltage there should be 100, making the drop across the resistor 100V, so 100V/.02A = 5K).

Obviously, this doesn't match with the answer provided. It looks like I was right about the drop, but why are we suddenly talking about a full ampere? I thought I was supposed to be calculating for 20mA?

Am I completely misunderstanding this example, or is there a problem in the example itself? Thanks in advance for your help.


texts: I'm not too experienced with electronics and made a really noobish mistake. I was holding up the board with a set of helping hands. I was padding the alligator clips with some fabric but I knocked it over and scratched the board with the clips in the process. Is this serious damage? If so, can it be fixed?


texts:
Scenario
I have a LiPo battery connected to a DC > AC inverter and these two adapters (images below) are plugged into the inverter.
Hypothesis
Everything runs fine currently but I know I'm losing juice in the conversion back and forth. Cutting out the DC > AC inverter, AC > DC adapters, and running power straight from the ~12v battery to the 12v devices should work.
Question
The LiPo fluctuates from 12.6v (full charge) to  9v but my shut-off alarm is set to 9.9v. Are there any caveats here? The first adapter from "FSP Group Inc." is for an "Nvidia Jetson TK1" computer so I'd hate to fry that.
Extra
What is the name of the plug on the "FSP Group Inc adapter"? I'd like to buy a separate one instead of cutting that one off the adapter.
LiPo Specs

11.1v
6500 mAh
20C

Edit - Power Consumption
Jetson TK1 Power Consumption link

Booting up: ~3.6W (for ~2 minutes booting)

CLI via SSH: ~1.6W

Heavy Disk Usage: 1.6W - 4.7W

Input Range: 9.5v - 13.5v

Microsoft Kinect Power Consumption link

12 watts

Input Range: 8.5v (~0.42A) - 12v (~0.35A) link

I'm surprised to see that the kinect requires so much more than the computer.


texts: Usb charger not charging only with vcc and gnd

texts:
I want to charge my tablet on the wall. And I have a charger behind the tablet and connected 2 wires to vcc and gnd, the same pins as usb female, it turns out that I can't have more than 10 mA. If I connect with usb cable I get values like 2000mA.
Shouldnt it be the same? Is it because of the shield? Should I short the shield to GND?


texts: Is there a way to put a relay in series with another load?

texts:
To layout my situation, I have a 12V DC pump with a built in float switch that I don't want to try to crack open and possibly compromise the waterproof of.  The pump draws around 6-7 amps.  I would like for an alarm to sound when the pump is running, and was thinking of trying to use a relay to trigger this.  However, from what I can tell most relays have very high resistance coils that likely aren't meant to be run in series with another load and I believe will limit the current to the pump too much.  Is there any kind of low coil resistance relay that is made for a purpose like this?

Alternatively I was looking at trying to use an inline current sensor to trigger activate a relay but don't have any experience w/ those and aren't quite sure they would work correctly.  I was hoping I could find some kind of current sensor / relay combination but haven't have any luck so far.

Otherwise, any other ideas on how I could do this?


texts:
Is is possible to check if an analog voltage is zero (or very close)? If it helps, the input to this circuit will be the output this differential amplifier:

(source: electronicshub.org)


texts: I have this glass PCB I took from a calculator that I'd like to get working with my Arduino as a numpad, but it's a glass PCB. Is there any way I could solder wires to it?


texts: Do you know how to initialise this ov7670 camera?


texts: Using two 14 AWG wires instead of one 12 AWG

texts: I do understand there are many factors when choosing what AWG wire, however by the charts, tools, and info I have found, using two 14 AWG copper wires should be equal to a single 8 AWG wire. 8.025 AWG to be really specific. Am I missing anything important?  If I have several hundred feet of 14/2 with ground and 14/3 with ground, is there any technical problem with running a pair of them to replace the 12/2 or 12/3 that I try to use as a minimum, or should I toss the extra 14 AWG Romex as useless?


texts: Connecting WIFI Module to RJ45 pins output of device

texts:
Extreme noob questions here.  I have a Lantronix XPico 240 wifi module that I need to connect to the rj45 output pins of a device the device pins are clearly marked but I am not sure about which pins to connect to on the WIFI module.

Pictures are below. I'm sthinking it is the RMII pins at the bottom of the module but I want to make sure.  If so, what does RMII stand for?

Bonus question - what type of connector is in the first pic I want to use this type of connector to connect the WIFI.  Like I said...noob questions.

Here is the device:

And here is a diagram of the wifi module:


texts:
Can anyone explain me the meaning of lumped element and lumped circuit abstraction in detail.
What does lumping or discretizing matter mean?


texts: I want to work on a project where you could replace a magstripe with another item which can change the data stored on it via a PIC but still be read by a magstripe reader.  This means that the PIC could 'write' another value to the different tracks on a magstripe to replicate different cards.  So what method could be used to do this?  Would a magstripe be used?


texts: Need help on speed control of single phase ac induction motor

texts:
I'm working on a project "single phase ac induction motor speed controller". The spec of the motor that im going to use is

230v,1/8hp ,8000rpm@no load

I want to know whether it is possible to control the motor for speed upto 5000 and in steps of 100 from 0 without having the problem of overshoot and delay to achieve max speed

my control options are only phase angle control using triac or slip control using IGBT.

which is the best suitable option out of this ?

Any help would be appreciated

Thanks in advance


texts: Line driver circuit with with MC3487 not clear

texts: I am looking at an old Heindenhain LS623 optical slide with with a LM339N comparator and an MC3487p line driver. This slide is about 20 or more old and can not be repaired anymore by Heidenhain. I found out that the that printed resistors on the ceramic substrate are not stable anymore and therefore I intend to recreate new electronics for this slide. It took me a while to understand the working but all of that is clear now with the exception of the small capacitors at the outputs of the line driver channels. What is the purpose of these capacitors? Maybe the are there to reduce incomming noise ? Actually I have no idea? Both channels are in use Y and Z.


texts:
I have a question about an LM741 op amp IC.

I am using the op amp as an comparator (open loop with no feedback), as seen below:

When the op amp output is low, the output voltage is still around 1.2v. Is this normal? Is it because the op amp can't output the full voltage swing in either state (low 0v or high 9v output) due to the op amp's non-ideal properties?

Note, problem remains with load transistor removed from circuit.


texts: What is the meaning of handling error in 1.5 bit ADC?

texts:
In the diagram shown bellow we have 1.5 bit ADC stage. We have Vin which is an analog signal and it could be translated as 00, 01, or 10.
In one bit we have only the option of 0 or 1. I can't see how it fixed an error, it's just dividing the range to more logical sections. I can't see any error fixing in here.
Is there simple practical example I could use to visualize how it happens?


texts: Inverters in parallel. Forcing one to be in phase with other?

texts: I have two cheap 800 watt (continuous) power inverters. Input is 12v AC. Output is 120v 60hz modified sine wave AC. I would like to run these in parellel to achieve 1600 watts. I have one already opened up because I had to change fuses. It seems to be a reletively straight forward circuit. It looks like an H-bridge... with 4 sets of 4 200 watt mosfets (irf640s possibly but I'll have to check). 2 sets are different from the other two, so I imagine they have p channels in there rather than 4 sets of n channel. Instead of going to all the trouble of having a microcontroller sense the zero crossings of the other and time it out and what not, would it be somewhat reasonable to just parallel all the non-IC components together like the mosfets, transformers, and rectifiers(Oh and the transformers are quite small, so I'm guessing the diodes rectify mains first,  then the iCs pulse high frequency dc thru them)? If I understand this all correctly (which I'm not sure I do, hence this posted question), the effective gate-source capacitance will now have doubled,  so the current capability of that which drives them must be considered,  as inadiquate current in that regard might make the transition from OFF to ON too long, causing unnessesary heat. Anyways, am I on the right track? What are the obstacles I will likely face that I am not seeing? I am posting this from phone so I apologize if there are spelling or grammatical errors. Thanks! -kurt


texts: Okay, having decided to pitch myself at the PIC family (including dsPIC), I now have a question about programmers. I've been hearing a lot of bad things about the new PICKit 3, and am wondering if I should get that or the apparently more venerable PICKit 2? If I want to be able to use the newest PICs, I think I might need to buy the latest, but I'm not so sure. Thank you!


texts: Arduino Input/Output Range (Cable Length)

texts:
So I have this crazy idea to illuminate a few Christmas lights on the exterior of my house this weekend. I plan on running 2 Cat5e cables about 11.5 meters (~38 feet) from an Arduino board to sensors and Solid State Relays (all DC and all around 5VDC). I would like to take this "network" next year and setup a little home automation. The current setup would use:

The SSRs can crunch anything from 3-32 VDC.
The sensors are looking for 5 VDC.

Do you believe that Cat5e cable can deliver what the input and output requires? Am I going to loose power running with Cat5e at that distance? (It is twisted pair but not plenum or shielded twist pair)

If not, should I be looking at thicker wire, a power boost at the end, or is this just not feasible?

I plan to test the setup in the morning either way, but I value your input!

Thank you in advance for your reply!


texts:
I am trying to control the speed of a DC motor speed by varying Vds and keeping Vgs constant at 9volts by potentiometer, but I am not getting appropriate and smooth control of the DC motor this way. The speed increases only at the end point of potentiometer when it starts burning.
Why this is happening?


texts: Proper name for "a switch-over time-delay relay"

texts:
I have a joystick wired to a relay that spins a motor either one way or the other way.

The problem is that I need to enforce a small "dead-time" when the user pushes the joystick quickly from one side to the other to avoid stressing the gear to much.

What is the name for the component I am looking for? Its not strictly a time-delay relay since there should not always be a delay when the joystick is pushed, only when it is pushed from one activation state to the other.

Is it a standard component or will I need to design my own?


texts: how to define HFPERCLK using HFRCO in I2C EFR32FG14

texts:
from page 280 of the manual HFRCO goes from 1Mhz to 38Mhz.
In the diagram shown bellow i only saw HFPERCLK usart.
the is no HFPERCLK I2C.
If we go from the starts then using CMU_HFCLKSEL value 1 we select HFRCO.
then using CMU_HFPRESC we define the prescale.and we enable It as I2C using 11.5.27 bitfield 8.
But as you can see in the diagram its our frequency goes threw the prescaling twice.
So is it realy doing twice the prescaling for every prescaling value we put?
Thanks.
https://www.silabs.com/documents/public/reference-manuals/efr32xg14-rm.pdf


texts: Do MOSFET relays for DC output always have a polarity specified?

texts:
I have a DC load (12 V, 72 W) that I sometimes need to give positive polarity, and sometimes negative.  Upstream of the load, I have a 12 VDC power supply and a circuit that lets me swap the polarity given to the load (+12 VDC or -12 VDC.)
I want to use a SPST-NO solid state relay (SSR) on one of the load's wires to PWM control the load.
While specifying the SSR (with DC output) via Digi-Key, it seems a lot of the recommended products use MOSFET relays.  I also observed that MOSFET relays seem to always only work in one polarity.  Notably, all of the relays I saw have an internal diode that enforces the relay only working with one polarity (see examples below.)
Do MOSFET relays always enforce this polarity?
Are there MOSFET SSRs for a DC load, where they act similar to a mechanical relay and just "connect the dots"? (regardless of load polarity?)

Examples

Sensata-Crydom CMXE60D10 datasheet, page 2

TE Connectivity SSRDC-200D12 datasheet, page 2


texts: What is the meaning of the triangle above with "5v" written next to it?  is that a ground symbol or an input voltage symbol?


texts: Building a CNC with external drivers - RAMPS needed?

texts:
Well, I'm upgrading a closed-source CNC machine with Arduino (and GRBL), but I'm confused if I really need the RAMPS board. I want to drive the motors with external drivers. I have a RAMPS 1.4 board here, a Arduino Mega, external stepper drivers and whatnot. Until now, no issue here.

I tried to use the Arduino Mega without RAMPS, plugging the external drivers directly on the Arduino and it worked just like it should. Then I used RAMPS and to no surprise it also worked like it should.

(A RAMPS board)

(External Stepper Driver)

Now there lies my question: Is the RAMPS board just there to provide more "ease-to-use" and/or "plug-n-play-drivers" or does it more? I noticed that there are some capacitors and stuff on the RAMPS board, are they still useful if I use external drivers or won't I need them?

Thanks for any help.


texts:
I'm looking for ways to control the holding torque on an axis for force feedback purposes. I stumbled upon electromagnetic brakes which might be useful for this. But i'm not sure to what extent you are able to control the holding torque of a electromagnetic brake, maybe its just a on/off kind of thing.

So can you control the holding torque of an electromagnetic brake by for instance pwm the voltage on the coil?

i'm looking for the model on page 420: http://sriramalenze.com/download/lenze%20Clutches11.pdf


texts: Output voltage of 3-phase in / 3-phase out inverter

texts:
I am using UK mains (230 V phase, 400 V line) to drive a Japanese motor expecting 115 V phase, 200 V line), presently using 2:1 transformers. I would like to control speed between 30 and 70 Hz, ie +/- 20 Hz away from the current fixed speed of 50 Hz. The motor is running at 3.5 kW from a standard 3 phase mains supply.

I now want to add speed control to this system using a 3-phase in / 3-phase out inverter. I would really like to dispense with the transformers for all sorts of reasons. Is this possible, or is the output phase voltage of an inverter always equal to the input phase voltage.


texts: here's a picture of component that is not a LED but emits light, it's a tiny glass light bulb with a resistor and a red plastic case for mounting it.


texts:
I am considering using Impulse C to write C code that will compile down to HDL for my FPGA. I'm curious as to what experiences people have had with Impulse C, to better understand the advantages and disadvantages, and in what cases it makes the most sense to use Impulse C as opposed to raw Verilog or VHDL.

In the pros I expect:

Faster development time
Cross platform FPGA programming
Possibility for writing very complex algorithms take will run in an FPGA

In the cons I expect:

Added layer of complexity with the Impulse C framework
License fees for using Impulse C
Less control over the behaviour of the FPGA
Longer compilation cycles

Are these assumptions correct?

I also have specific questions:

Does using Impulse C for one part of the project impose using Impulse C for the whole project?
Is using Impulse C more or less bug prone than using an HDL?


texts: What can be a good modelisation for an open wire?

texts:
How to modelise an open wire for a simulation purpose?
I think that it is more complicated than it sounds.


texts: MFB Analog filter with Reference voltage transfer function

texts:
I am looking for the transfer function of the filter below :

This is a multiple feedback second order analog filter, I was already able to calculate the transfer function of the filter without VRef in the positive pin of the op-amp, but I couldn't find it with Vref.

Can anyone give me the transfer function of this filter or maybe a tip on how to calculate it ? Also how does it affect the offset is it added directly to the output?


texts: I want to be able to add code to this MCU by connecting it to my mac by USB connection. How could I do this?


texts: Electrical Switch for LED’s (Providing enough MOSFET gate voltage)

texts:
I am designing a circuit to independently control (ON/OFF) up to 8 LED strips. So 8 independent channels

The LEDs are of a single color (Not RGB). LED’s are also rated 12V.

The controlling signal is from a 5V Microcontroller (maybe 3.3V later on).

The maximum continuous current possible for a single channel is 2A (1A is an option).
A major constraint is the size of the final PCB layout. As such I have chosen to use N channel MOSFETS as the switching device.

Another constraint is that all parts will have to be sourced from ALIEXPRESS, with a low Bill of Materials cost.

NOW TO MY QUESTION:

Most of the low cost mosfets need a gate voltage of about 10V or greater to efficiently turn on the MOSFET (archive low Rds).

I found an Ideal product from Microchip (MIC4468) that fits the application. However, it seems to be on the high side in terms of cost.

Another solution I was looking at was to use level shifter circuits. I found CD40109B which I can design around.
I will like to know if it is good practice to use a generic level shifter IC like the CD40109B to drive MOSFET gates.

Also any recommendations and alternate solutions are welcome.


texts: connecting arduino to industrial motor controller through RS232

texts:
I need to interface with a motor controller through RS232. I am using an arduino for this. The datasheet has a page on RS232 interfacing shown below, could someone please identify what I would need to communicate with this from an arduino?

there are no details on the RS232 voltages, as far as I know following the standard I should be able to communicate with lines from 0 to +3.3v since this lies within the spec of 0v to +3 - +12v however so far I am unable to get a response from the device by connecting Tx, Rx, and GND to a ttl logic USB serial device, nor my arduino.

Using the RS232 cable supplied with the controller I am able to communicate both with the supplied software and through a serial COM port sniffer, so I am sure my data addressing is correct.

I feel like there is a perhaps a voltage level difference issue, or maybe i need to control the other pins however I was under the impression these were optional, could someone please shed some light?

Cheers


texts:
I have a situation where a small DC motor is moving the flap from one side to the other. The flap can be in two positions but without limit switch. Change of position lasts about 3 seconds. The problem occurs when the motor reaches its position, but still has supply. After some time it can easily break gears. So I want to limit the current for the motor in at least one direction.

I have been thinking about this simple current limiter, but is it a problem when it gets reversed supply? Is it ok to solve it with one diode which will conduct most of the current in that situation?


texts: Combine outputs from 1kW and 2 kW Inverters

texts:
I have a 3 year old 1kW PV System and recently bought a 2kW system. Both are off grid. And since the batteries on 1kW system are old, and since I availed subsidies for both systems I cannot change the configurations.

Both inverters are 230V ~50Hz

How can I combine both the inverter outputs to get a 3kW output?
I came across some combiner boxes but most are for grid-tie systems or way too expensive.

Is there any other way? How can I build my own combiner box if it's the best option?

I have a 3-phase electricity connection. Is there a way to make use if it for this?


texts:
The diagram below is for wiring up a 6 cell laptop battery. Visually, there are four batteries in one row, and two batteries in a second row. The cells are the usual 3.7v 18650 cells. I am pretty sure I managed to diagram the connections as they were in the old battery, but I feel like there's something missing.
The battery casing says we should be shooting for  11.1V and 5200mAh (though that depends on the mAh rating of the individual cells, so ignore that). I know some batteries are 14V units, but this one says it should be 11.1V. So bear that in mind.

The lines that are not black are monitoring wires. So if you can take a look at the black lines and tell me whether it all is as it should, that would be appreciated.
UPDATE: this is the diagram as I expect it to be with three sets of parallel two's with the one set awkwardly hugging the other two:


texts: I have a momentary switch that is usually on and I want my circuit to be off when the switch is letting the signal through, how would I do this?


texts: Crystal clock oscillator giving out sine wave, help?

texts:
I am building a 50MHz clock by using ABRACON ACOL-50-EK crystal clock oscillator. I have connected 3.3V supply (with a 0.1uF capacitor to ground) to Vdd (pin 14). GND (pin 7) is grounded and output is from OUT (pin 8). I am getting a sine wave and I do not think that would be a good clock signal.

Unfortunately ABRACON has not given any circuits that I could refer to and I got the capacitance hint from another circuit around a different oscillator manufacturer. [Before I connected the 0.1uF capacitance, I was getting ~25KHz oscillation which made me think, may be I got the wrong part - that went on for a while]

I suspect many of you have done this before, so what am I missing ? How is the 15pF output capacitance figure into the design ? How is the 0.1uF calculated ?


texts: How to save a bit sequence from oscilloscope?

texts:
I'm using two wires to communicate between devices. First wire is a clock, second is a data bit. Logic is simple: master device (AVR ATMega in my case) sets a value on the data pin, then raise "1" on the clock pin. After that, slave device (ATtiny) reads that bit and waits for the next rising edge.

To be sure that I'm sending the correct bits from the master to the slave, I've connected an oscilloscope to the clock and data lines. Please see a snapshot (yellow is a clock, red is a data):

As you can see, there are eight raising edges of the clock. Also pulse width is different, it can't be less than 1ms, but there is no max limit: clock may keep "0" or "1" for seconds, minutes or even hours.

This sequence send "1, 1, 0, 1, 0, 0, 1, 0" or 0xD2. So my question is: How can I configure my oscilloscope to get this bits/byte?

I'm aware that I can capture RAW voltage information, but in my case there only two voltage levels: 0V and +5V. It would be awesome to capture only edge changes info.

P.S. My oscilloscope is Instrustar ISDS205A


texts: does adding Vias through the antenna feed line change impedance?

texts:
I have a GPS through-hole patch antenna, the through hole need to be connected to the bottom layer and then from there the feed-line flows to the GPS receiver. But I want the GPS receiver to be on top to be facing the sky so that means adding vias on the feed line which will change impedance, right?

I also have a question about the antenna ground plane since I'm a beginner in that field. My PCB is 4 layer with gnd plane as 2nd layer, can I use that as ground plane for the antenna or does the gnd plane of antenna has to be on the top layer directly underneath the antenna?


texts:
I am looking for a simple SR Latch. I'm new to electronics though and just doing a hobby project/teaching myself. Are SR Latches sold (I'm hoping to avoid building mine because I actually need at least 5) and if so where can I buy them (Radio Shack?) and what do I ask for? I link to a site with a part number would help too.

Per the comments. I have called Radio Shack and they said they didn't have them. The local big electronics store could only help me if I had a part number. I don't know if they actually can't help me or if I just don't know what to ask for. Is my best option just building them? I was kind of hoping I could just buy a small self contained item that was a SR Latch. If I were to wire them myself they would take up significantly more space.


texts: Frequency response of MEMS sensor in datasheet

texts:
I am looking for a MEMS acceleration sensor and the frequency range of 0 to 20 Hz is required. But after checking a lot of datasheets I am confused. Because in most datasheets I am unable to find any info related to frequency response characteristics. But at the same time acceleration (g) ratings appear in the first place.

Shall it be calculated out of the relation between frequency and acceleration?

KX112-1042-SR


texts: controlling a DIY spot welder with a momentary push button switch?

texts:
I have a 240v to 12v transformer even bigger than a microwave transformer and i want to control how long it is switched on for in the range of 50-300 milliseconds to spot weld things.

I was thinking of a big momentary push button switch same as thet have on factory walls to control robots, that i can hit a bit like swatting a mosquito at different speeds in order to get different contact durations.

Perhaps i could make a switch to control the transformer input, out of wood, copper and some silicone rubber springs? to finely adjust the physics of the spring to change it's rebound depending on how it is wedged?

Is it a feasable DIY experiment? would a switch on the AC side be too imprecise, seeing as the AC phase is 20ms and i need to let through 5-10 periods of AC into the transformer, is it not logical?


texts: I am working on an Arduino project where I would like to use an output pin to control a 12v load with a mosfet.  I think it should be an n-fet, but am not sure.  I have been looking at specs, and don't know how to pic a fet that will do what I want.  Can anyone point me at a part I could use?


texts: Invisible magic components that spoil the Eagle preview

texts:
You know, after the eagle board design is finished, you can see the card on the preview screen.
I'll show you two examples. There is no problem with one. The card is centered on the preview screen.
But in the other, the card is not centered because of the components that are not visible in the upper right sections. I cannot zoom in on the card. As if the eagle is showing me something very big.
I tried these but didn't work:
1- I open all layers from the Layer tab. Nothing is visible.
2 - I am trying to delete that space by selecting it with a mouse. Nothing is caught.
3 - I saved the design as a desing block and included it in the new project. Nothing changed.
Does anyone have an idea?  Btw, the same is true for the manufacturing tab.


texts: Is it OK to connect not used segments of an LCD display to the backplane pin?

texts:
I have a digital voltmeter using the ICL7106 chip and the FE0203 LCD display. It has not been used for many years. It is still working but some useless segments on the LCD display are always visible. Especially the first and second dots and the colon at the center of the display. Since those segments are not used by the voltmeter, they are not connected at all. When I clean between the LCD pins on the glass, those segments get invisible for a short time. They get soon visible again probably because of humidity.

I have searched the web to know where should not used pins of such LCD display be connected to. But no luck. Nothing is said in the datasheet regarding this problem.

My aim is to make those unused segments always invisible. I think there should be a standard way to connect them. When I connect them to the backplane pin of the display, they get totally invisible. Is it a proper way to connect them?

Thanks for your help.


texts: Can Earth be utilized as the whole circuit's common ground?

texts:
I'm currently handling a project that requires a transformer to step down 230VAC to 6VAC; and from there, further scale-down to a voltage that is in the readable range of the microcontroller (as not to damage it due to high voltage input). And the microcontroller will process the read value and display the voltage measured from the AC wall supply; making the whole system to function as a voltmeter.
Thus, I am thinking of a way to convert the AC sine voltage from the transformer's output to pulsating DC and with the help of 7805 voltage regulator and some capacitors, I'll be able to get a constant 5VDC as the supply for the microcontroller.
The question is: Where will be the pin for the microcontroller/components to connect to as voltage reference/GND? I was thinking that the 'Earth' from the AC wall supply could be used as the common GND but after some practical testing via oscilloscope, the readings are not as expected.
I need some clarification on this.


texts: How do I get started with PIC programming?

texts:
So I opened up a big bucket o' worms asking this question. Two of the answers mentioned that instead of using a 555, a PIC10F200 or PIC12F675 may do the trick.

Now, I've been spoiled with Arduino's programming interface...and have looked at this answer, and I want to expand on it a little bit. Mainly, I need someone who knows what they're talking about to confirm ro redirect my assumptions.

Assumption 1: There's some universal language for programming. It's likely assembly or some such.

Assumption 2: There's likely some software for PC that will allow me to write the program, and possibly even debug it.

Assumption 3: There's likely a USB or serial device that takes the completed code from my PC and flashes the chip. If I'm working with DIP-8, DIP-14 and DIP-28 chips at different times, is there some kind of universal IC flasher? or do I need a separate device for each  chip?

What are some of the other questions that I need to be asking or pitfalls of which I need to be aware?


texts: drilling a heatsink for a hot silicon diode?

texts:
I had to adjust a CC/CV charger by 0.5-0.8 volts. The charger is rated at 3.5 Amps 58.8V, and I have some 50-100V diodes rated at 5A ( 6A10 MIC ).

The diode gets to about 100'C which is a bit on the hot side to ensure longevity and reliability. I'm thinking of making a small heatsink from aluminium for it.

If i put two diodes in parallel inside one small heatsink, would it be better than 1 diode in the same sized heatsink, and would it provide redundancy, seeing as it's only for a voltage drop?


texts: Oscilloscope sweeps only once with DC sources and shows nothing on GND setting

texts:
I got an old CRT oscilloscope someone had laying around unused in his garage (an ATAIO AI 751A which seems pretty obscure, not getting any meaningful Google results). Unfortunately the user manual is missing, I couldn't find it online and this is the first CRT oscilloscope I work with, so I'm not sure if I'm operating it properly.

It powers up but there's nothing on the display when the probe is not touching anything, even when it is set to GND. Touching the probe's tip triggers a (very flickery) 50Hz ~10mV peak to peak signal (yes, I'm european) but setting it to GND to center the signal vertically stops showing the signal. At dual display mode both channels are shown when I touch the tip in channel 1 (channel 2 disconnected is shown at ground level), but as soon as I release the finger, both channels are gone too.

Touching a 9V battery gets a single sweep when the tip touches or releases the battery, while I'd expect at least that channel to be shown at a constant value.

Setting a high period for the time division and touching the tip triggers a single sweep, but as soon as it reaches the far right it stops. I can trigger another sweep touching or releasing the tip again.

I pressed a switch labelled "Auto Level" which I think should make the trigger level automatic based on the last samples (which seems plausible since the trigger controls don't do anything when auto is on) but still nothing is shown on the display when touching a 9V battery.

Fiddling with the controls (e.g. pressing the "Auto Level" switch) triggers a single sweep too.

Is the oscilloscope broken or am I doing something wrong? Where should I start troubleshooting?

Images: (don't pay attention to the settings)

Full oscilloscope

Triggering controls close-up


texts:
I have a counter which counts number the of interrupts at pin 3.2 in 8051. I'm not sure about the implementation. So far I could count the number of interrupts but I couldn't send the integer value in UART. It's giving me the ASCII values actually. I know that SBUF = 'A'; will send ASCII value of 'A'. How to send the integers ? This is my code that I've been trying to make it work.

#include<reg51.h>
#include<stdio.h>
#include<stdlib.h>

/* function prototypes */
void delay(unsigned int ms);
void putc1( chr);
void windspeed_read( void);
void initialize(void);
void record_wind(unsigned char counter);
void puts1(char* p);

sbit P3_2 = P3^2;
sbit P3_3 = P3^3;

// global variables declared
unsigned char c = 0;
char *ptr;
int i;

char buf[16];
char *p;

/* delay function to create a delay of 1 sec */
void delay(const unsigned int ms)
{
 unsigned int x;
 unsigned int y;
 for (x = 0; x < ms; x++)
 {
 for (y = 0; y <= 113; y++)
 ;
 }
}

/* to print the character in UART and serial window*/
void putc1( c)
{
   SBUF = c;
   while(TI==0);            /*Wait until the character is completely sent */
   TI=0;                   /*Reset the flag */
}

/* main function */
void main()
{
IE = 0x81;
EX0 = 1;
EA = 1;
while (1)
{
}
}
void initialize()
{
 SCON  = 0x50;   /*SCON: mode 1, 8-bit UART, enable receive      */
 TMOD |= 0x20;   /*TMOD: timer 1, mode 2, 8-bit                  */
 TH1   = 0xFD;   /*TH1:  for 9600 baud                           */
 TR1   = 1;      /*TR1:  timer 1 run                             */
}

void windspeed_read( void ) interrupt 0
{
c++;

sprintf(buf, "%d", c);
p = buf;
while(*p)
{
    P2 = *p;
   putc1(*p++);
}
}


texts: How to detect an unconnected LED with an ADC?

texts:
Let's consider the following simple example :

An MCU controls the lighting of an LED with the wire "CMD_LED" by switching the state of an NMOS transistor.

When CMD_LED = 1, the transistor is closed and the LED is lighted.

When CMD_LED = 0, the transistor is opened an the LED is off.

The red rectangle can be connected or unconnected from the circuit.

I want to detect an unconnected LED. To do so I have to use an ADC input of the MCU to measure a specific voltage. I cannot measure the voltage inside the red rectangle.

Is it possible to detect that the LED is unconnected, based on this method ? If so where should I measure the voltage ?
I don't know how the MCU can distinguish between the unconnected LED and the open transistor...

Thanks for you help. :)


texts: What open source virtual serial port code exist which can run on a Microchip IC?

texts:
Microchip have a free but non-distributable USB stack source code available.

However, what open source virtual serial port code exist? And which one should I invest my time in using?


texts: 9V wallwart powering a fan via Raspberry Pi

texts:
I have a fan rated at 12V, 0.14A, 12/0.14 = 85 Ohms (taken from an old PC case) and a wallwart that outputs 9V, 1A.

I have connected the fan directly to the wallwart and it works fine.

Now I'd like to connect them to the Raspberry Pi so I can turn the fan on and off using a simple script.

The problem is that I've never done something like this (the electronics part), while I know some theory from school I've never applied it.

So I decided that the 2N3053 transistor would be a fit choice for what I need (\$I_c = 0.7\text{A} > 0.14\$A of my fan and \$V_{ce} = 40\text{V} > 9\text{V}\$ of my wallwart) and then I proceeded with calculating the resistance I need to saturate this transistor:

$$I_b = I_c/h_{\text{fe}}$$

$$I_b = 0.14\text{A}/50 = 0.0028\text{A}$$

$$R_b = \frac{3.3\text{V}}{3 \times 0.0028\text{A}} = 39.28\Omega$$

simulate this circuit – Schematic created using CircuitLab

Is this OK? Would this work?
If not, then please explain keeping in mind that I'm a beginner with these things.


texts: Why is the power factor obtained by performing a short circuit test on a transformer higher than the power factor obtained in an open circuit test?


texts: DC motor vs AC motor weight considerations

texts:
For a given power rating, does a permanent magnet DC motor have a weight advantage over either a three phase permanent magnet synchronous machine, or vice versa? Or does it work out that they would be approximately equal?

Mainly interested in the mass of copper and core material, assuming equal torque constants as well. A colleague asserted that the 3phs machine would use significantly less copper, but did not have any evidence to that effect, whereas I believed they would be about equal but that's only an intuition.

For that matter, is it even possible to generalize?


texts: Why computers can be modeled as sample and hold system

texts:
I was reading digital control system from book by Norman S.Nise and in book it is written that
"computers can be modeled as a sample and hold system "
Isn't computer is discrete time system and its output should be discrete  while sample and hold is a analog  system and its output is continuous ?
So how a discrete system (computer )can be replaced by a continuous system (sample +hold) ?
Or I'm missing something?


texts:
I have to give a signal to a inverter. I am trying to do this using two push button.

First pushbutton can turn on and turn off the signal(a relay coil) like a toogle switch.

Second push button can only turn off the signal (previously on by first pushbutton)

Is there any way to do this only using several relays  (relay logic)?
If not suggest a simple method.


texts:
I am trying to determine my battery sizing for the NRF52840 BLE. To do so, I want to estimate the peak power. But I am struggling with this.

Is it safe to go with transmit current as the peak current and then just multiply with the voltage to get estimate peak power?

So in the case of the NRF52840, the peak power I am thinking would be 6.4 mA x 3V = 19.2 mW. The values I got are on page 58, 1Mbs BLE, DC/DC on


texts: Help identifying this RF connector Icom FR4000

texts:
J1 is a coax push-in connector from an Icom FR4000 repeater. The gray wire is a thin piece of coax, unsure of the actual type (RG316?). Not a common connector but I've seen it before. Doesn't click in, just pressure fits in there.

I'm trying to make another pigtail so I don't have to cut the gray coax to add an N male connector on the other end. The manual recommends modifying the cable but I'd rather just make another one and keep the original intact to revert back.


texts: Determine the output voltage of an integrated ciruit

texts:
I'm planning to use an HPA674A (bq25504 EVM) which is based on the bq25504 IC to connect a device (wsn) that works from 2-3.6V which is connected to the Vstor pin and the storage element is connected to Vbat. The input will be a solar panel of 3V (as it increases the efficiency). The device consumes 30mA for 0.6sec every minute and 80uA for the rest of the minute (normally it operates with 2AA alkaline batteries giving 3V).

What I dont get is how the output voltage (Vstor, Vbat) varies with input voltage as a voltage of more than 3.6V would damage the device (wsn) and I dont seem to understand it from the datasheets. Could someone help me with that?


texts: Cannot find some parameters details for this board

texts:
I have this micro controller development board and I want to use one of its pin called +5V pin to power a sensor. But I cannot find or figure out the max current this pin can source.
Here below is the highlighted pin in question:

And also I cannot find the input impedance for the analog inputs.


texts: Charging lead acid (car) batteries with a common ground

texts:
I have three identical lead acid batteries. All three batteries are on a common ground since they power different components on a same circuit. I have three independent "intelligent" chargers whose charging outputs are on isolated grounds.

I wonder if there is a counter-indication of charging all three batteries at the same time when on a common ground (their positive poles are disconnected from the main circuit, of course).  I know this could be charger-specific, but if anyone knows anything about it.

Here is a quick schematic of what it is (would be) like when charging:

simulate this circuit – Schematic created using CircuitLab


texts: Can ESD from a person damage circuitry even though it was not perceivable?

texts: I know that when working with circuits it is important to avoid ESD onto sensitive components.  But I am wondering when I inevitably make the mistake of discharging static onto a PCB will I know?  Like the typical sensation of being shocked. Are there ESDs from humans to circuitry that are too small to perceive by the human, but still damaging to the circuit?


texts: How to drive this 115VDC coil through a 480VAC system

texts: Below there's the electrical specification of a coil I'm using. It says it can be supplied 115VDC. If I were working with a 120V system, that would be OK. However, I'm trying to use this coil in a 480 VAC application. The 480VAC gets rectified for a SMPS which feeds a microcontroller. The idea is to drive this coil from the micro. It would only receive like a ~30 ms pulse under certain conditions. It's no intended to keep it ON all the time. The problem I'm facing is with the voltage. 480VAC rectified gets around 680VDC peak. And that's probably too high, and will require a high voltage FET. Is there a way to drive this coil so it doesn't see the full voltage? It can surely be quickly overdriven, but not from ~700V I think.


texts: Here is a device that is used to switch on/off power supply (240V) via a 24 volt relay. Issue is that R4 (510) and C1 constantly burn up due to overload(?). Can't seem to see what is the issue. Can someone pls help?


texts:
I'm not much of an "electrical engineer" but the required courses in my CS degree have given me enough to [albeit just barely] understand a few things, so don't judge me if what I ask is complete nonsense.

I'm trying to develop a circuit in which a high state is driven to something at a frequency (eg 50Hz). This way, the "on" state of the aforementioned something is when it is getting that signal at the frequency and off is no signal. The tricky thing is that the frequency must change and there are more than one of these "somethings" to be driven, by a limited number of signals.

My thought was to use something like how PWM works, except I would need a component to which you could write a PWM signal that it would then duplicate (upon an enable signal). How can this be achieved? What would be a better approach?


texts: power supply multimeter voltage test differ from the label

texts: I have a router's power supply. 12 Volts is written on the label. When I use a multimeter the voltage is 16.80V. Should I use it to power a small LED strip that requires 12V?


texts: electronic interference generated by blood?

texts: Hi so i made a little electrical signal detector that can detect electrical interference/noise(for example putting it near a light or plug makes it squeal). I was messing around with it and noticed it picked up a signal near the right elbow of almost everyone I know. Is there some sort of field generated by the blood moving? Also no one I tested was left handed, not sure if this has to do with the signal because everyone was right handed. The people I tested did not have cell phones with them at the time and it cannot detect most RF anyway, only things such as magnetic fields, or other such fields that can induce a larger current. Also, I tested this on my cat and it goes off weakly near his chest.


texts: What Happens When You Exceed a Solid State Relay's Max Amps?

texts:
Had a quick question. I am using a Crouzet GA8-6D05 SSR to relay xmas lights for the holidays. I basically hacked an extension cord (120VAC US <1Amp) to do this. I am currently using a spliced extension cord to perform on and off operations via a micro controller.

During the summer, we commonly use this same outlet for a water fountain on our patio (also 120VAC US <1Amp). I was thinking to use the SSR mentioned above to switch the water fountain on and off also. I am thinking that the best way to make this work would be to hack the actual outlet. I already know that you can separate a two plug receptacle by cutting the metal plate which connects positive on one side and negative on the other.

My question is: What will happen to the SSR if the load exceeds more than the max 5 amps it is rated for? Will it blow up, start a fire, or just reject the call for the extra amps? I am concerned about fire hazards, not really concerned about the thing dieing necessarily. I worry about leaving this in the wall if I sell the house as I do not plan to use the outlet for anything more than what is stated above, but the next home owners may not follow directions.

Thanks in advance for your help!


texts: Resources to make 8-bit computer like this one?

texts:
I am 15 years old and love electronics. I made very basic circuits using breadboard and basic components. I want to build 8-bit Computer like this one: https://www.youtube.com/watch?v=qYvr0b8jqbg
which includes Graphics Processor, Central Processing Unit.

What are some resources to make this kind of computer?  or tell me what should I search on google to make this kind of computer as shown in the video.
At this age I have lots  of time and I am ready to do a lot of hard work.

If the question is too broad then please suggest me some websites where I can read about collection of resources like books, videos etc. to make 8-bit computer.


texts:
If I have a piezoelectric crystal and apply pressure to it , it will be deformed and a voltage between its 2 ends will be generated.

Is the voltage generated due to its deformation or due to the pressure?
If I continue to apply the same pressure and it doesn't get anymore deformed will there still be voltage?
If I stop applying pressure, it will return back to its initial position. Will voltage be generated?


texts: Help understanding a 30 year old schematic for a contact aligner

texts:
I got this old contact aligner I want to fix up but it is missing the control box, this is the diagram which is from like 30 years ago. Any suggestions on how to interpret this? J2 and J3 are the main cables which connect to the unit, i see the capacitors, and the BJT, doesn't seem that the rectifier or transformer is labeled? Any help is much appreciated, I am more on the device fabrication side then the EE side.

Manual, Pg 75 starts diagram


texts: How to safely expose one wire of an AC mains circuit?

texts: I need to use a rail to connect one moving piece where a switch is, to a fixed piece where a power tool is. The rail is exposed, so I need this connection to be safe, like 12V or below. I'm guessing I will need some sort of MOSFET module, but each and every search result is about Arduino. Is there such a thing, that will let me use small wires and switches in a "safe" exposed circuit to turn on and off a mains powered device?


texts: How to shift out 16 bits fast on arduino board

texts:
I'm coding a system that need to shift out 16 bits fast from a uint16_t variable to two paired 74HC595 shift registers. I'm running the code on an Arduino (atmega328@16Mhz) and the shiftOut in the Arduino is way too slow. The librarys digitalWrite function is slow as well.

The best idea I came up with is a for loop that loops through all the 16 bits of the variable and writes 1/0 to data pin, set the clock bit high as short as possible and then goes to the next bit of the variable.

Is this the fastest solution and if so, how do I loop through a uint16_t variables bits in c++?


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When loading flyback converter with heavy load, waveforms are as expected. But with light load, waveforms are not as expected. What can be the reason ?
Duty cycle is less than 50% so no slope compensation issue.

(Attached one is waveform of drain to source of MOSFET)