texts: Thevenin equivalent circuit with current and voltage source

texts:
I have the circuit below and I have to calculate complex current i1using thevenin equivalent circuit method:

I tried to follow the rules and open the terminal AB across the resistor:

I want to ask if this is a correct way to convert the circuit to thevenin. Also I am not sure is capacitor's reactance -4iis same as -4j or 4, 90 degree ?

Then The voltage across AB terminal would be equal to voltage across the capacitor? Is it ok to in this case see the voltage source as a short?


texts: Help identifying encoding scheme for RF device

texts:
I have this RF encoder that I am trying to customize with an MCU. The remote control device uses an encoder called HS2260. I believe it is a clone of PT2262 device. I was able to get the waveform but I have trouble understanding what modulation scheme is used. I am planning to write my own code in C for an MCU, I know a bunch of libraries exist for Arduino but couldn't find any C libraries for this.
I new to RF so any help will be much appreciated.

This is what the waveform looks like. The frequency is 2.68 kHz.
This is what the multiple waveforms look like:


texts: Lab power supply with motor startup spikes (inrush?)

texts:
I want to buy a lab power supply. However (30 V, 5 A).

However, when a motor starts (inrush it's called afaik), it uses extra current. But I don't know really how much this typically is. Or  if there s there some capacitor inside a power supply to take care of this small extra current spike.

I would like to know how much I need to take these current spike/inrush into account when buying a power supply.


texts:
I've got an STM32 with a straightforward voltage divider bringing in a battery level line to an ADC. The problem is that I'm getting a value that doesn't make a ton of sense to me. According to my scope, B_LEV (which is the divided line, going to GPIOC pin 1 / ADC1 channel 11) is 2.49V, with a VREF of 3.3V. The value I'm getting is 2148 (12bit adc), which should translate to 2148 / 4096 * 3.3 = 1.78V, which is obviously not true..

Am I screwing up on the math, or my ADC setting?

Here's the initialization and reading code:

void InitADC() {
  ADC_InitTypeDef ADC_InitStructure;

  RCC_ADCCLKConfig(RCC_PCLK2_Div4);
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);

  GPIO_InitTypeDef GPIO_InitStructure;
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
  GPIO_Init(GPIOC, &GPIO_InitStructure);

  ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
  ADC_InitStructure.ADC_ScanConvMode = DISABLE;
  ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
  ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_NbrOfChannel = 1;
  ADC_Init(ADC1, &ADC_InitStructure);

  ADC_RegularChannelConfig(ADC1, ADC_Channel_11, 1, ADC_SampleTime_239Cycles5);
  ADC_Cmd(ADC1, ENABLE);
  ADC_ResetCalibration(ADC1);

  while(ADC_GetResetCalibrationStatus(ADC1));
  ADC_StartCalibration(ADC1);

  while(ADC_GetCalibrationStatus(ADC1));
  ADC_SoftwareStartConvCmd(ADC1, ENABLE);
}

int ReadBatteryValue() {
  // Make sure we have conversion completion
  if(ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET)
    return 500;
  // Reset the flag
  ADC_ClearFlag(ADC1, ADC_FLAG_EOC);
  // Get the conversion value
  return ADC_GetConversionValue(ADC1);
}


texts: Is it possible to design a three-phase delta generator only with two generators?

texts:
I've always seen 3 generators in a three-phase generator, but this question came to my mind. I've tried to add an element instead of the third generator, although with no result.

I hope someone can help me. Thank you for your responses.


texts: What should I use to filter noise from 5V power supply with multiple consumers

texts:
I want to create a PCB board that would have:

input - 5V wall outlet USB charger or for example MeanWell Din power supply
output - 3 usb ports that would be used by RPI-like devices. (5V 2A max each).

Question - since all devices would share same power line and I can expect noise from the consumers - could you please point at extra circuit items that I should use ?

I would imagine that it should contain capacitors from 5V to ground near each output and probably optional input capacitor (not sure if needed with quality power supply's).

And I would also assume that RPI-like devices have already some input filtering in place, so probably it would be overkill.

Also, there would be no data lines included, just the power lines.


texts:
Bought from here

I have tried the magnet trick and it does not stick to either of the two wires of this TC. More so, screwing it inside an oven and turning the temperature up does produce some micro and then mili Volt reading on a DMM. However after turning the oven off the output voltage still rises for 1-2 minutes before it starts dropping.

Is this really a K-type thermocouple and if it is, is it a broken unit ?

edit

I have bought another such K type TC. This one responds well to the magnet on one of its wires. There was a problem with the PCB, not the TC. Fixed it and the non-magnetic TC started working as well. It seems not all K type thermocouples will have their negative wire magnetized enough for a HDD magnet to pick it.


texts:
simulate this circuit – Schematic created using CircuitLab

I'm working on a system that will go into ESD testing, The system is powered by an external regulated DC voltage.

I'm now using an LC filter for High frequency noise reduction, but i'm not sure if this alone will help with ESD.

I have added the supply voltage schematic, the VCC_5V_PIN comes directly from the connector, VCC_5V is connected directly to the ICs in the circuit with decoupling caps connected to each IC.

Other electrical signals comment from the connector are ground and 4 Pins for SPI communication(MOSI,MISO,SCLK and CS) which are protected by TVS diodes.

Should i use a TVS diode to help for ESD protection or just change to a PI filter by adding a capacitor close to the connector ?


texts:
I've noticed that when I pick up my smartphone first thing after waking up, the touch screen is not very accurate in picking up my "clicks" and gestures.  I'm speculating that it's got something to do with the fact that my fingers are colder and dryer than normal when I've just woken up.

Can anyone confirm or debunk my speculation?


texts: Why my M25P16 SPI Flash is not responding to Read ID command

texts:
I have interfaced M25P16 with PIC32MX795F512L. MISO and CS is pulled up to VCC with 10k resistor.
I am sending the 0x9f (MSB first) command for reading device ID and after that 20 dummy bytes are transmitted for generating clock for receiving bytes. But I'm getting unexpected noise pulses on MISO pin as shown in image below.

I have selected clock mode as 1 (i.e. CPOL = 0  and CPHA = 1). I'm sampling input in middle of clock.
One more thing HOLD# and W# are directly connected to VCC(3.3 V). Do I need to make changes in W# and HOLD# states?


texts: What's the difference between the term 'Device' and 'Machine'?

texts: Limiting the question only to the electrical domain. Calling AC machines as ac device mean the same or there is a difference in the terminology.


texts: Is this a capacitor? If nota.. what Is it?

texts:
.

This component was removed from a Nintendo 64 console PSU. I have no idea what it is. I thought it was a ceramic capacitor, but I can't find any information about it.


texts: Building an AM receiver for 10Mhz (NIST WWV)

texts:
I've read a vast amount of information on this topic.

I'm trying to prototype in a circuit simulator and it seems that there is a bug with transistors.  Hit the reset button to mess it up.  Even when I build one from several sources it gives a similar odd signal. -- I'm trying to building a transmitter so I can virtually demodulate it in the simulator. (Tomorrow I'm going to try this with a 555 timer instead of common emitter AC amplifier)

What I'm looking for

A very simple AM (DSB) receiver -- eventually for the NIST WWV station.
Preferably 10Mhz.
Made of simple and irreducible components.

What I'm not looking for

Reducible components such as op-amps and 555 timers kinda scare me.
High fidelity - I'm fairly certain that I can program around noise on my Arduino.

What I know

The signal is received on an antenna and frequency resonated on an LC circuit tuned to 10Mhz.  This "filters" out the unwanted frequencies.  The output from this is a carrier wave.

I've solved the LC equation for both the capacitor and inductor using wolframalpha.

The carrier wave is put through an RC circuit (parallel low pass?) Envelope detector to demodulate it into the output to decode on my Arduino.

440Hz, 500Hz, 600Hz, 1000Hz, and 1500Hz for tone markers
There is a 100Hz "subcarrier" that continuously broadcasts "date" information (Year, month, day, hour, minute, and DST to name a few)

What I do not know -- Links & explanations greatly appreciated!

Do I need any special length for my antenna?
Can any inductor/capacitor combo be used that meets the LC resonance frequency equation? (C=100nF, L=50.3uH, should resonate at 10Mhz)

I'm guessing this is tied to the output voltage or current of the antenna.  How would I calculate this?

Would amplification between any step be useful for final input on my Arduino? (Antenna->LC->Envelope->output->Arduino)
Would I run the output into another LC->RC circuit tuned to get the sub-carrier?
Does an LC->Envelope circuit even work for dual-side-band? (I honestly couldn't find a difference between normal AM signals and AM DSB)

Bonus: Is there any good free simulation software? (I can't seem to get circuitlab to output any useful simulation graphs, unlike Falstad's "View in Scope" or scope-probe)


texts:
so i am an EE undergrad, and i am wondering if and how exactly does a transformer core limit its power capacity. From my understanding, the rated power of a transformer is due to the current carrying capacity of its windings. As far as the core is concerned, the magnetic flux is pretty constant, and maximum (close to saturation) when the transformer is open circuited. Also core loses are more or less constant with respect to the load. Am i correct? So for example will a transformer with superconducting windings have near infinite power capacity?

I got confused, because i remember a while back i ordered a transformer for a power supply and when discussing the power rating with the guy , he said something like(for eg i wanted a 160va transformer) "we have 150va and 200va cores".


texts: Disadvantages of dimming LEDs via current regulation as opposed to via pulse frequency?

texts:
I bought an LED stripe from näve (very similar to this model), but found that it created flicker in video recordings. The flicker got less visible with lower frame rates, but even at 24 fps it was there. I found that the frequency of the flicker was certainly not 50/60 Hz, but I believe the controller varied it to set the brightness (as I tuned it brighter or darker, the number of flicker "bands" caught on video changed) - and as I moved towards the maximum brightness, the flicker got less perceptible in the video recording.

I was able to fix this by connecting the stripe to another controller. As far as I can tell, this controller does not pulse the light, but rather adjusts the current. It causes no flicker at any frame rate (24/25/30/50/60Hz), and no bands at any shutter speed (up to 1/4000 s). If I go over a certain current, the LEDs just stop getting brighter, and the controller emits a faint humming noise - but no part of it seems to overheat.

I am wondering - why would LED bands not use this approach? Is there any detriment to me using it?


texts: I am looking at the datasheet for this 64k EEPROM, and I am having trouble understanding how to use it. I would like to do a lookup from a 16-bit address to an 8-bit data word. The chip only has 13 address pins though. It looks like the memory is divided into 8-8K sections, which makes sense,because the 13 address lines can fully address 8K. I don't see any facility, however for switching pages or for giving a full address. How can I get all of the memory from this chip? Do I need to upgrade to something like this 512K model to get a fully 16-bit addressable parallel eeprom?


texts: Confusion about inductors in series vs. combined

texts: I suddenly was getting confused while reading about inductors.  The formula for inductance I was using was the one like in the answer to this question.  However, I have also read that the inductance of inductors in series is the sum of the inductances (like with resistors in series), but that suggests to me that longer inductors would have larger inductances.  The formula in the link has length on the bottom.  I'm probably missing something simple here but I'm not sure what.


texts: How to wire a button for input on an Attiny85 using Arduino code?

texts:
I am trying to "shrink" my arduino project to an Attiny85. But for some reason I cannot get an input button to work on the Attiny85? To simply the circuit and to make sure I didnt make a mistake somewhere I took everything off except for a button and an LED.
First I tried it on the Arduino and used the example from http://arduino.cc/en/tutorial/button to try a simple example. I changed the ledPin to 10 which I plugged into my breadboard, through a resistor, to the LED and to ground. I plugged the button into pin 2 on the arduino and connected the ground wire of the button to a 10k resistor, then to ground. All of that works.

So then before I upload it to the tiny I changed the ledPin to 0 or 1 (it works on either one - I uploaded a simple blink sketch without the button code to test the LED) and then left the button pin to 2 as is shown by the diagram here http://www.pighixxx.com/pgdev/Temp/attiny.pdf or http://hlt.media.mit.edu/?p=1695 but nothing happens when the button is pressed. If I reverse the logic so the LED is on unless the button is pressed, then the LED is always on.

I cannot figure out what I am doing wrong. The same wiring works with the arduino, but I cannot get the attiny to register the button press. The final goal with the button would be to use the attachInterrupt(0, increment, CHANGE); for the button, but I cannot get even a simple sketch to work.

Any help is much appreciated! Thanks in advance!

Edit1:

// constants won't change. They're used here to
// set pin numbers:
const int buttonPin = 2;     // the number of the pushbutton pin
const int ledPin =  1;      // the number of the LED pin

// variables will change:
int buttonState = 0;         // variable for reading the pushbutton status

void setup() {
  // initialize the LED pin as an output:
  pinMode(ledPin, OUTPUT);
  // initialize the pushbutton pin as an input:
  pinMode(buttonPin, INPUT);
}

void loop(){
  // read the state of the pushbutton value:
  buttonState = digitalRead(buttonPin);

  // check if the pushbutton is pressed.
  // if it is, the buttonState is HIGH:
  if (buttonState == HIGH) {
    // turn LED on:
    digitalWrite(ledPin, HIGH);
  }
  else {
    // turn LED off:
    digitalWrite(ledPin, LOW);
  }
}


texts: Converting Pronto hex codes to raw on/off pulses

texts:
I'm really just getting my feet wet when it comes to IR protocols and IR codes in general, so my knowledge and understanding may be a bit shaky here.

I am a programmer and am trying to create a tool to convert Pronto Hex codes to RAW IR pulses. To do this I'm trying to understand the process manually. I'm testing this with an IR blaster app on a specific device.

What I have so far is the result of lots of searching, playing around with tools and piecing things together.

Considering the following HEX code:

0000 006E 0011 0006 0012 0052 0014 0051 0014
0051 0014 0051 0013 0052 0013 0052 0024 0051
0014 0031 0014 0052 0023 0052 0034 0051 0014
0051 0014 0052 0013 0052 0013 0052 0014 0051
0014 0632 0154 0051 0014 0CE5 0154 0051 0014
0CE5 0154 0051 0014 0CE5

Here is pseudocode of what I have

I know the first set, "0000", indicates it's raw oscillated code.
I believe the second set "006E" indicates the frequency for the code and can be converted to khz via:

freq = 1000000 / (toDecimal("006E") * .241246)

I know that the third and fourth sets of codes have to do with the sequence lengths.

I know the rest of the sets can be converted to pulses in microseconds with the following, using "0012" as an example

microSeconds = 1000000 * toDecimal("0012") / freq

So "0012" would be (rounded) 478.
So, applying the above to the full code and separated with commas  I end up with:

478,2176,531,2150,531,2150,531,2150,504,2176,504,2176,955,2150,531,1300,531,2176,929,2176,1380,2150,531,2150,531,2176,504,2176,504,2176,531,2150,531,42088,9023,2150,531,87599,9023,2150,531,87599,9023,2150,531,87599

When I test this out with an IR blaster I don't see the device I am trying to control respond. However if I prepend the opening pulses for NEC protocol 9000,4500  I get a response from my device.

My questions are - Could someone tell me if I am on the right track here? How would I discern from the HEX code that I needed to use the 9000 on 4500 as the opening pulses? Any input/advice would be really appreciated, as I've said I'm just getting my feet wet here. Thanks much!


texts:
I own several spectrum analyzers and build various RF boards at all kinds of frequencies.

I was looking over a BLE FCC test report for emissions, and I saw this lab uses a RF power meter to measure the output of the system.

Why would you not use a spectrum analyzer for this?

Why does an RF Power meter even exist?  Is it simply because it is cheaper than the spectrum analyzer?

Can anyone weigh on the rationale for an RF power meter?

I'm looking at this very expensive looking RF power meter, and it seems like just a spectrum analyzer that sweeps over frequenicies:

4500C Peak Power Analyzer

I understand the smaller handheld RF power meters probably just take average readings of power without the frequency sweeping?


texts:
I have a circuit and I need to calculate the RC time constant. Here is the circuit and how I simplified some of the resistors:

simulate this circuit – Schematic created using CircuitLab

where

R2//R4 = R2*R4/(R2+R4)
R3//R5 = R3*R5/(R3+R5)

Since we have multiple resistors and only one capacitor my first thought was to calculate Thevenin equivalent across the capacitor C and say τ=RC=RTH*C. First I calculated RTH:

RTH = R2//R4 = R2*R4/(R2+R4)

And then I calculated VTH (using voltage divider):

Vo = (R1/(R1+R2//R4)) * VTH => VTH = (Vo*(R1+R2//R4))/R1

Now I have 2 questions:

Is this the correct way to calculate time constant (RC)?
What would I do when there are more than one capacitors?


texts:
I have close to zero experience with cameras modules. I need a global electronic shutter camera for my application.

While I was browsing I see that the shutter speeds that are 1/1000th of a second.

Is it possible to control these modules for: (in general, I realize each module has its own mechanism)
- Turn on/off the shutter from software at the desired speed? (i.e. turn on the shutter for 1/500th of a second although frame rate is 50fps. I know the image will have a lot less light but that is ok). (The idea is to make sure the camera is no longer integrating the light when the electronic shutter is off)

Start a frame conversation on demand as opposed to a fixed FPS. (i.e. convert two consecutive images only but do that such that the speed is controlled by the uP)


texts: How to connect LED strip to be powered by charger and batteries

texts:
I plan on using it mostly plugged in, batteries are there just for extra mobility and won't be used most of the time. Don't know lot about batteries so in first scheme I added a switch (pos. 1 charging, pos. 2 normal usage when plugged in) which would be on pos. 2 most of the time and I don't know if it is necessary?
Anyway, I'm not sure any of those two schemes is good so please correct me or suggest a better way to do this.
Thanks.

Link to batteries.
Link to charge protection board.


texts: Total power measurement in 3-phase unbalanced delta system

texts:
I have a 3-phase system with an unbalanced delta load, as seen in the figure below.

I want to measure the total apparent and active power consumption and if possible, the respective power consumption for each of the phases, but I am a bit confused.

I am using a 3-phase equipment from National Instruments which shows that Vc = 380V, Vb = 380V and Vc = 0V. I assume that because of the absent neutral, it uses phase A as a reference, thus Vc = Vca, Vb = Vba.

I am also measuring all three line currents.

What is the total apparent power equation? I am aware of Blondel's Theorem, but it is valid only when measuring instant power right?

Also, is it possible to measure the power of each separate phase?


texts: I made an inverter in LTSPICE and it is not working

texts:
I made a symbol and library file, and I think I well matched the subckt with the symbol.
I can run the circuit with the inverter but it shows 0V at output node..
Can anybody help me with this problem?

.SUBCKT inverter_min input output
M2 output input VSS VSS NMOS
M1 output input VDD VDD PMOS
V1 VDD 0 0.5
V2 VSS 0 -0.5
.model PMOS PMOS
.model NMOS NMOS
.ENDS inverter_min

------------------

Version 4
SymbolType BLOCK
LINE Normal 16 0 -16 -16
LINE Normal -16 16 16 0
LINE Normal -16 -16 -16 16
LINE Normal -32 0 -16 0
LINE Normal 24 0 32 0
CIRCLE Normal 24 4 16 -4
SYMATTR Description inverter
SYMATTR ModelFile inverter_min.sub
SYMATTR Prefix X
SYMATTR SpiceModel Inverter_min
PIN -32 0 NONE 8
PINATTR PinName A
PINATTR SpiceOrder 1
PIN 32 0 NONE 8
PINATTR PinName B
PINATTR SpiceOrder 2


texts: Please critique my high-current voltage regulator

texts:
A project I'm working on requires a source of power which need to be both regulated (5.00V) and high current (~4A). An external power source may be any from 6V to 12V but it can be assumed that it can handle required current.

I found out that there are very few high-voltage LDOs and they are very expensive. And none of precision and high-current LDO. I was looking at switching power supplies but they looks too complicated for me (I'm just hobbyist) and I don't understand how they work.

I developed following schematic (don't consider particular values of components, it is just a sketch). It consists of voltage-controller PWM generator which controls high-current driver on MOSFET. The output of driver goes to OP-AMP which evaluated difference between reference LDO and output of the driver.

So my questions are:

will it work in hardware as expected (it works on simulation)?
how stable/reliable this design?
maybe there are better solutions for a problem (like cheap ICs or modules)?
how do engineers usually solve such tasks (i.e. voltage stabilization/regulation under a high-current)?

simulate this circuit – Schematic created using CircuitLab


texts: WS2812 high inrush current in big installation

texts:
I have a "big" installation with WS2813 (WS2812b successor) LEDs. The installation encompasses over 350 LEDs which should consume about 21A if all powered on, which should never happen (it's a simply dimm and sparse art installation). The display objects must be connected by cables at lest 2m long.

When I start up the supply or connect enough LEDs, the PSU goes into OC protection and shuts down. When I connect just a few the PSU keeps up and now LEDs re light in this instance.

I'm now suspecting either the LEDs to draw enough current at startup or the long cables having enough capacitance to trip the OC protection. Unfortunately I don't have access to an oscilloscope to check the short startup current...

I was thinking about reducing the inrush current to the supply lines.I'm only an amateur-level tinkerer. My ideas were resistors, NTCs or inductors, but a resistor would be an obvious bad choice, an NTC wouldn't stay low resistance if not a lot of current is drawn (am I right?).

Now I'm thinking about an inductor, but do recall reading about it being a bad choice for that, but am not really sure.

Do you have experience with supplying large numbers of LEDs and did you ever encounter any issues like that?


texts: PIC16F877A stops working when I remove the PICkit 3

texts:
I've made codes of different sequences of lights but somehow this one does not work when I remove the PICkit 3, as long as the PICkit is on the circuit works.

I am supplying my circuit with a 5V-3A power supply and I am using a PIC16F877A

When I press a button situated in RC0, the following sequence of lights happens:

DEFINE OSC 4

TRISC=%00000001
TRISD=%00000000

START:

PORTC=0
PORTD=0

IF PORTC.0=1 THEN

PORTD=%11111111
PAUSE 4000
PORTD=%00000000
PAUSE 500

PORTD=%11111111
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%11111111
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%11111111
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%11111111
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%00000011
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%00001100
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%00110000
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%11000000
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%01010101
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%01010101
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%00110011
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%00110011
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%00110011
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%11000111
PAUSE 500
PORTD=%00000000
PAUSE 500

PORTD=%01010101
PAUSE 100
PORTD=%00000000
PAUSE 100

PORTD=%01010101
PAUSE 100
PORTD=%00000000
PAUSE 100

PORTD=%01010101
PAUSE 100
PORTD=%00000000
PAUSE 100

PORTD=%01010101
PAUSE 100
PORTD=%00000000
PAUSE 100

PORTD=%01010101
PAUSE 100
PORTD=%00000000
PAUSE 100

PORTD=%01010101
PAUSE 100
PORTD=%00000000
PAUSE 100

PORTD=%01010101
PAUSE 100
PORTD=%00000000
PAUSE 100

PORTD=%01010101
PAUSE 100
PORTD=%00000000
PAUSE 100

ENDIF
GOTO START
END

Here is the schematic of the circuit:

I have already uploaded other sequences into the PIC and they work just fine with the external power supply, I am not really sure why this one does not work without the PICkit 3


texts: How does asynchronous and synchronous reset signal affect the setup and hold time in a Flip Flop?

texts: Does the async. and sync. reset signal follow the setup and hold time conditions of flip flop? If so how would they affect the output?


texts: Any suggestions to solve shielded jumpers between different PCBs?

texts:
I've a problem where I got one PCB and then another and I need to get some small power, ground and signals from the other PCB to the other one.

The power and signals will also need shielding and good insulation.

Do anyone here happen to know any good cost effective, solution for this?
I have looked at flat shielded cables but been unable to find anything I like due to I have a hard time finding the connector housing fitting my needs.

What I'm looking for

I'm looking for a connector and cable with shielding, the connector in one end would must suitable not build height over <3mm or <3.5mm, if that isn't possible the lowest possible is still wanted.

The cable and connector need to withstand vibration over a long period of time >10-15 years, it's fine to glue it or mold it in around the connectors. It may also be okey to change the cable every 5 year if the connector can handle it.

The insulation on the cable to surrounding should be some 100Vdc, the insulation is mostly for functional however the higher the nicer (wished target 500Vdc, with no added insulation on top).

Ideal would be a 24 pin cable or depending on solution (haven't decided yet) a 9 pin cable could be sufficient, cables in parallel would also work if not taking to much place.

1 pair for power and ground return is needed in above, a 100mW carrying capacity at 3-5V should be more than sufficient.


texts: Constant voltage charging phase of Li-ion batteries

texts:
I've read on batteryuniversity.com that the constant voltage (saturation) stage of Li-ion charging adds approximately 10% of SOC compared to charging with only the constant current (CC) charging phase. For example when charging only with CC to 4.1 volt you get approximately 80% SOC, but with full adsorption approximately 90% state of charge can be achieved. Link: https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

I have not yet been able to find a good visual representation of the saturation stage of the charging and how it is different from the constant current stage of charging. What is a good visual representation of this?
There is clearly some current flowing into the battery while in the constant voltage (CV) charging stage, meaning electrons must be flowing. Wouldn't that mean the amount of free electrons trapped in the graphite layer would increase and thus the voltage would (slightly) have to increase? Or is my assumption that during the CV charging stage electrons are moving in the same way as they do during the constant current charging stage - albeit at a much slower speed - incorrect?
If my assumption is incorrect and the amount of electrons trapped in the graphite layer does not increase during CV charging, then what happens inside the battery that causes the SOC to increase during this charging phase?
Another question (regarding C-rates and saturation time):
The same page on batteryuniversity.com mentioned that faster charging (higher C-rate) of Li-ion cells results in reaching a relatively high SOC (for example, 85% SOC) quicker than when charging with lower C-rate, but mentions that, when charging with this higher C-rate, the saturation stage of charging will take longer. What is the reason behind this? Does some of the 'saturation' already occur during the CC stage of charging? And because, when charging with a higher C-rate, there is less time spent in this CC stage of charging for a full charge, so will there be less time for the 'saturation' to happen? Does this (my) theory make any sense? What is the approximate difference in 'saturation time' when charging at different C-rates (for example, when charging at 0.5c vs. at 1c vs. at 2c)?
Even though saturation takes longer with higher C-rates, I would expect the total charge time to be lower since the average power going into the battery is higher (accounting for extra losses due to charging inefficiencies being higher with higher C-rates), unless the saturation stage is very significantly slower for higher C-rates, is this assumption (higher C-rate always equals faster total charge time) correct?
Last question (regarding image from batteryuniversity.com):
The text under the image at the top of my post reads "Adding full saturation at the set voltage boosts the capacity by about 10 percent but adds stress due to high voltage"
I don't understand why this would add extra stress when according to the charging graphs the voltage during the CV charge cycle is the same as the charger cutoff voltage. If for example charging to 4.1 volt (a voltage which is well within the specs for most Li-ion cells) and charging the cell to full saturation, would this prolonged charging at 4.1 volt (until the cell is fully saturated) be harmful to the cell?
Second example: Let's say we're charging to 4.2 volt, would this prolonged charging at 4.2 volt (to reach full saturation) be any more harmful to the cell than the CC charging up to this level (4.2 volt)? If the maximum voltage for CC and CV charging is the same, why would CV charging be more harmful to the cell? Because the average charging voltage is higher? Am I missing something?


texts: Can I power a photomultiplier with a camera flash power supply?

texts:
The RCA IP28 photomultiplier works well with a total voltage of 750-1000V.

Some flash power supplies (especially those for older ring flashes) provide about 400V or more that would still be enough for the PMT tube.

Would it be possible to use one of them, provided the total current through the PMT is kept within specification through a proper series of resistors between the dynodes?

What other easily available options are there to power said PMT, assuming an optimal 1000V target voltage?


texts: Is it possible to connect a reed switch to two separate arduino boards?

texts: I'd like to add a bit of redundancy to a security system. I use reed switches for doors. How can i safely connect the same reed switch to two separate arduino boards? (the boards are not connected between them in any way, they use separate adapters).


texts: What is the purpose of this transistor in this schematic?

texts:
First thing first, I am not native speaker and I am new here.
This schematic is reverse engineered from searchlight PCB traces (which is broken) by me.
D+ and D- terminals connect to the rechargeable battery.  I couldn't read the voltage rating of the battery.
"LED"s are white and all of them parallel and voltage drop is about 2.6V.
There is a switch and a button in the middle of the schematic, nothing special.
I have a guess that these two diodes, one transistor and 520Ohm resistor makes up constant current circuit. But simple constant current circuits generally have zener (or at least 2 diodes at base) to implement.
If my guess is not correct, please tell me how this circuits drives the white LEDs.


texts: What's the function of "reactive power diode" n3 and n4?

texts:
I am trying to understand how the circuit above works. It is an inverter.
P1 and P2 are thyristors, they are fed with alternating pulses. What I have understood so far is that, Capacitor K4 is there to turn thyristors off (otherwise thyristors can't turn themselves off), Inductor K1 is there to smooth out excessive current because in brief moments, P1 and P2 may be conducting at the same time.

What I can not understand is why n3 and n4 is there. The documentation states:

  if the current has been flowing through section 3-1 of the primary winding and through thyristor P1 during the preceding half cycle, section 3-1 of the primary winding and diode n4 will carry the reactive current after commutating. This current is being driven by the inductive component of the load

I am guessing that K1 may at some instances drive point 5 or point 1 to negative voltage (let Vdc- be 0v). But my limited circuit knowledge can not handle this transient-heavy circuit.

If any kind person can simulate the circuit that would be nice, I would really like to see some wave forms around K1, K4 and the primary coils to gain better understanding of the circuit.


texts:
I have a question about the circuit above.
In the first place we can measure the current IR2 in given values, then using the current mirror topologies we can express IC7, IC8, IC3, IC11 and the other currents at the top which is active loaded differential amplifier topology.
But I cannot find a way to evaluate the currents IR3, IC9 and IC12. Anything would be very helpful.


texts: 12V vehicle voltage filtering and protection: R or L in the diagram

texts:
Can I replace the 62 Ohm resistor in this schematic by an inductor ? Would it be any better and how to size it ?

https://electronics.stackexchange.com/a/347348/35737


texts: how much is it safe to common-ground power supplies?

texts:
Some circuits requires more than 1 power source for voltage comparison or whatever reason and the circuit requires that the power sources shared the common ground. Most of the time it works perfectly but are there limitations to this ?

Is the common ground trustworthy ?

Can some mA go from one power source to another ? is it problematic/safe ?


texts:
I like to protect a sensitive circuit of mine with a shield. I don't have a picture but basically, I have put together a 1 mm thick ground rectangle on the top layer, and I will place the shield on top of this such that it will contact to this ground trace.

I have some concerns.

Am I creating a ground loop by doing this?
If I don't use the shield, am I making an antenna that will pick up noise?
What is the recommended practice for this type of shield?

Actually, I like to connect the shield at a single point, but a hardware person who has more experience insists that he like to have a full rectangular ground exposed, so that the shield can touch to the ground at every point.

Update

Here is a very rudimentary representation.

UPDATE 2

Noise is at the output of our amplifier (transimpedance). It is around 3-5 mV for an amplification of 300,000. (I have made mistakes in the first layout and am now doing a better board and the goal is to reduce the first stage noise to less than 1 mV.)

I have two LDOs that take energy from the battery. Both of them are high PSRR. This is a six-layer board with the following stack up, S/G/S/G/P/S. This is a bit unusual stack up, but I hide sensitive signals between these grounds. The board doesn't need to be six-layer, but this later will become part of another crowded board, hence the six layers.

Noise sources are in abundance:

Power supply: We mitigate this with good LDOs, filtering (pi filter), bypass capacitors, etc. So far, worst case I see 1-2 mV ripple on power; this could even be my equipment. (I don't have good equipment, also the amplifiers have 50+dB PSRR, so this should have minimal impact on the output.)
Opamp noise: This is the inherent noise coming from the amplifier. I have a low-noise opamp. \$3\ nV/\sqrt{Hz}\$.
Photodiode: I use a large photodiode, this picks up noise, unavoidable.
Other electromagnetic sources: We have seen the board is very sensitive, the noise goes up in various situations. Also, the reference schematics from some sources recommend shielding the reduce outside noise sources, so we are putting this shield option to test our next board.

UPDATE 3

3-5 mV exists even without the 10K and the C1. Essentially no input to the opamp. This makes me think that my layout is not perfect.

Here is the basic schematics for the amplifier. I can add more if we think it is necessary.

The following rules have been observed:

Complete two ground layers connected via several vias.
The 3.3 V supply (also the supply for the opamps) are filtered via a 2.2 µF tantalum capacitor and the pi network (100 kHz roll over) before the supply to the photodiode (that is, before the 10K resistor). We also have 1/100/10 nF capacitors close to the 10K. (I am not sure it is great idea, but it is better to be safe.)
C1 blocks the DC (AC-coupled architecture), we only amplify AC.
Opamp has 1/100/10 nF at supply and bias pins (bias is provided by the second LDO).
The feedback capacitor and resistor are placed as close as possible to the opamp.
All signal traces between the photodiodes and opamps are minimized; we are talking <2 cm worst case.
All the critical deemed signals are placed between two ground layers.

Also another observation that explains why we think of shielding: I connect a resistor to our function generator and turn on, this is via crocodile cables, (essentially a loop antenna) so we know it radiates at the frequency we choose. I can see the output of opamp picking this up nicely and amplifying. So, it is very clear to me the outside sources come in to play, hence the whole discussion.


texts:
I recently was riding my e-bike (with a bldc hub motor) and decided to cool the motor (it -the stator- was approx 100-150 celcius I think) in the river.
The controller is on the top of the bike and definitely stayed completely dry. The motor has cooling holes drilled in its housing through which the water can flow in.
cooling holes in motor housing:

This method was very effective for cooling but the drive train (motor/throttle/controller/battery started acting up after riding it again after cooling...)
Note: after the motor had dried/warmed up again the issues were gone (not sure what caused the issues so not sure if the water or the sudden change in temperature or something else caused the issues).
Symptoms: -weird wining noises from motor when accelerating (much higher pitched and louder than normal) -when the motor reaches a certain rpm (above this rpm) it appears as if the coil groups are misfiring (motor vibrates/shakes and appears to be braking rather than accelerating). The severity of this braking effect appears to be random, sometimes it's worse but not sure why.. The issue appeared to mostly start occurring when a certain rpm was exceeded but sometimes (less often) the issue also occurred at much lower rpm. -the issue was gone after approx 30 minutes of riding when the motor was approx 60 celcius (motor housing)(stator was probably approx 80 Celcius).
There is no temperature sensor from the motor connected to the bldc motor controller (the controller does not have this feature).
What might cause these issues?

Can the water entering the motor mess up the signals coming from the hall sensors? If so what causes this?
Could the sudden temperature change cause issues similar to this? If so please explain how
Is there another explanation which I did not think of?

video: https://www.youtube.com/watch?v=l2dHn89Dvso&feature=youtu.be
Thank you!


texts: If a device takes in a range of voltages, is there an optimal choice of voltage to supply?

texts:
I bought an LED light for photography, which came with a battery.

I realised later it also has a DC port for a power supply. The range is 6.5v-17v.

I happened to have an adjustable laptop power supply, which can supply 15-24v, and a couple of other adapters that do 9v and 12v.

Is there an optimal choice of voltage to supply when it comes to power consumption / longevity for a device that takes a wide range of voltage inputs?


texts:
Working on a portable boombox powered by four 18650 Panasonic NCR 3400 mAh cells in series. I bought a PCB and I have a small 4s balance charger. The PCB will be secondary if anything fails and cuts voltage at 3 V.

That's to low for me during daily use. I want a primary cut off at 3.5 V (14v in series). I was thinking maybe this can be done with a Zener diode and a relay?

Don't know if it is a good idea? Or is there any other simple way of doing this. I'm not very good at electronics but understand some basics and can solder.


texts: Are some integrated circuits magnetically sensitive?

texts:
In general, are ICs magnetically sensitive? I have a bunch of logic gate ICs, driver ICs and Atmel Chips that I carry with me regularly. In addition I have small magnets that I use to pick up little components like resistors that are hard to get with your fingers. What other types of components might be magnetically sensitive?

Thanks!
Jarrod


texts: Confused about battery rating specifications

texts:
I'm confused about how to understand battery capacity by its ratings.  I though I understood Amp-Hours, as a nominal rating where they usually specified a period of time where that rating was approximately valid.  So below is the rating a particular batter, where nominal capacity for 20 hours rate-Ah is stated as 74 and the 10 rate-Ah . I assumed means that for 20 hours it can sustain the 74 Amp-hour rating, so I would expect that the amp-hour rating for 10 hours would be as high or higher but it's 65.  So i'm not sure it means what I thought it means.
So does it mean that I can operate the battery for 20 hours at 74 Ah /20 h = 3.7 amps, but if I use it for 10 hours, then it can run at 65 Ah /10 h = 6.5 amps for each hour?
Why this reasoning doesn't seem quite right to me is that I thought the Amp-hour rating was high if you specify shorter periods of time.

Below is an example of a battery rating.  And the link to the published chart.

| Volts| PHCA | CCW | HCA | MCA |       Nominal Capacity          | Reserve Cap. |
|      | 5 sec|     |     |     | 20 HR Rate-Ah  | 10 Hr Rate-Ah  | in Minutes   |
----------------------------------------------------------------------------------
| 12   | 1750 | 950 | 1350| 1070|       74       |       65       |        145   |

Extreme Series Battery Specifications


texts: Which is better for full bridge rectifier circuit? MLCC or Electrolytic?

texts: If I place 100uF multilayer ceramic capacitors at the output of a full-bridge rectifier will there be any problem? Or I need to place electrolytic capacitors? What difference do they make (except size)?


texts: Using 2 LiPo 18650 with L7805CV, is 7.2V enough to run the device?

texts:
I am interested in powering a robot using two LiPo 18650 batteries, in addition they need to be fed through a regulator to produce a 5V output for a microcontroller.

The problem is the regulator has a dropout voltage of 2V - am I cutting it too close?

Looking at the discharge cycle of the battery it appears it maintains a greater than 3.6V up until close to complete discharge meaning that at least 7.2V will be fed into the regulator.

Is this enough to keep it running?

I could add another battery but that is going above the ideal voltage range for the motors(though with PWM, I believe I can make them not overwork).


texts: Noise from car amp when grounded to the body

texts:
I am busy installing sound in my car. I have installed an amp and have VCC running to the battery and ground connected to the body of the car. I have noticed that there is noise, seems to be a high frequency noise, that is produced when the amp is on. The pitch of the noise increases when I accelerate (this is quite annoying). This noise did not happen when I didn't have an amp so I'm assuming its the way I have connected the amp. I would like to know if this is a common problem and any suggestions on how to fix it would be appreciated.

Extra: after connecting my amp my radio reception is terrible, I noticed that my aerial is also grounded to the body so I'm wondering if the amp could be affecting the aerial.


texts: Can you help in identifying the connector? It's used for Ethernet signaling.


texts: Is it okay to use a MOSFET in its resistive region with a heat sink?

texts:
Using transistors in with limited gate (or base) voltage will make them limit current, which will introduce a significant voltage drop across the transistor, causing it to dissipate energy. This is considered bad, wasting energy and shortening the life of the component. But if I keep the temperature low, either with a heat sink or by limiting the power, is it okay to use a MOSFET this way? Or is it fundamentally bad for the component to make it dissipate power?

I ask because I get excellent results by controlling a MOSFET with variable voltage to drive an LED strip. With 8-bit PWM, the LED jumps in brightness from zero to "reading a book" levels, while the voltage-driven mosfet allows very smooth turn on, despite also using 8-bits of voltage levels. Linear versus exponential power makes all the difference, and PWM is linear. Our eyes don't perceive light linearly. The voltage-controlled result is too good to not use.

Addendum: I have done extensive experimentation with PWM, including adjusting the prescalers. Changing the PWM duty is not an effective solution, though if someone wants to donate an oscilloscope, I might be able to make it work :)

Addendum: The project is a lighting up alarm clock, like these Philips products, but more carefully tuned. It is imperative that the gradation between the low power levels be miniscule. The brightest acceptable low-power state is around 0.002%, and the next is 0.004%. If it's an x/y problem to ask about the solution rather than problem, then this is an intentional x/y question: I've found my preferred solution after extensive testing, and I want to know if my solution is workable. The device is currently working with a less preferred workaround involving a much dimmer auxiliary light.

Addendum 3: I gather this is what BJT transistors are used for. Since they're current-controlled, the circuit is much harder. I need to look into that when I have time to draw diagrams. I'll post another question if I have trouble.


texts:
I'd like to preface with saying that I'm quite new to this.

Given emf E = 9 V, and that both resistances are equal, R = 1 kΩ, calculate the voltmeter reading if voltmeter's internal resistance is Rv = 10 kΩ.

So far, I have calculated E * R2 / (R1 + R2) which gives me a result of 4.5V.

But, I'm not sure how to apply the internal resistance of 10k ohms. How does it affect the final result?


texts: Measuring voltage output in a voltage divider

texts:
I'm currently working my way through Electronics for Dummies, where I am shown a simple voltage divider circuit consisting of a 9V battery and two resistors, R1 (12,000 ohm) and R2 (15,000 ohm).

Given the voltage divider as shown in the schematic below, and the voltage divider equation to calculate the output voltage (Voltage out) given as:

\$V_\text{out} = \left[ \frac{15000}{12000~+~15000} \right] \cdot 9V\$

simulate this circuit – Schematic created using CircuitLab

Question:

Why is the equation (shown above) using 15,000 as the numerator? Seeing as how the voltage output is after R1 and before R2, shouldn't we be using 12,000 as the numerator in the equation to calculate Vout?

Why then Does the equation above use \$\left[ \frac{15000}{12000~+~15000} \right] \cdot 9V\$?


texts: PIC32 does not get UART RX interrupts in xc32 Compiler

texts:
I'm trying to setup a UART channel on my PIC32 MCU (PIC32MX470F512). But the code does not reach the ISR at all.

I have verified that the PPS (peripheral pin select) is configured properly and the UART reception under polling mode works perfectly fine. Also, the transmission part is working without any issue from day one. But I need to get UART rx to work with interrupts for my application.

At first I tried using the plib (which didn't work either) but then decided to hand code it eliminate any issues caused by the library. Here is the configuration that I have done.

void UART1Inint(unsigned long int baudRate) {
  ANSELDCLR = 0xFFFF;
  CFGCONbits.IOLOCK = 0;      // PPS Unlock
  RPD11Rbits.RPD11R = 3;        // Assign RPD11 as U1TX
  U1RXRbits.U1RXR = 3;      // Assign RPD10 as U1RX
  CFGCONbits.IOLOCK = 1;      // PPS Lock

  // Baud related stuffs.
  U1MODEbits.BRGH = 1;      // Setup High baud rates.
  unsigned long int baudRateDivider = ((GetSystemClock()/(4*baudRate))-1);
  U1BRG = baudRateDivider;  // set BRG

  // UART Configuration
  U1MODEbits.ON = 1;    // UART1 module is Enabled
  U1STAbits.UTXEN = 1;  // TX is enabled
  U1STAbits.URXEN = 1;  // RX is enabled

  // UART Rx interrupt configuration.
  IFS1bits.U1RXIF = 0;  // Clear the interrupt flag
  IFS1bits.U1TXIF = 0;  // Clear the interrupt flag

  INTCONbits.MVEC = 1;  // Multi vector interrupts.

  IEC1bits.U1RXIE = 1;  // Rx interrupt enable
  IEC1bits.U1EIE = 1;
  IPC7bits.U1IP = 7;    // Rx Interrurpt priority level
  IPC7bits.U1IS = 3;    // Rx Interrurpt sub priority level
}

And Here is how my ISR looks,

void __attribute__((vector(_UART_1_VECTOR), interrupt(IPL7SRS), nomips16)) UART1_ISR(void)
{
  PORTAbits.RA4 = 1;    // LED to indicate the ISR.
  char curChar = U1RXREG;
  U1TXREG=curChar;  // Echo back the same character.
  while(!U1STAbits.TRMT);
  IFS1bits.U1RXIF = 0;  // Clear the interrupt flag!
}

I'm doing two kinds of test in the main loop. One will poll for data in rx and then echo it back to the user. The other will monitor the RILDE flag and turn on an LED to show when the rx pin is actually active. It also toggles a bunch of LEDs for the error flags (least significant 3 bits in U1STA register) in UART1 module.

Both the tests are working fine which indicates that the UART module is setup fine. Just the interrupt portion of it is faulty. So I tested this code on Explorer 16 Development Board, Bluetooth Audio Development Board and the Ethernet Started Kit. I did this to eliminate any hardware related issue as all the three boards are microchip certified hardware.

I don't know what I am missing out please help me fix this issue. Any help would be greatly appreciated.


texts: DS18B20 - is current consumption of pullup resistor relevant for battery powered project

texts:
In my project, I'll be using a DS18B20 digital temperature sensor, which requires a pullup resistor of around 4.7k between VCC and the signal.
Please see the datasheet here for reference.
Is there any current flowing over that pullup when my MCU sleeps and no measurement is performed with the DS18B20.
Basically, I have the same general question for I2C sensors, do those regularly draw current or just during operation?


texts: Hall effect current sensor ACS712 for battery application

texts:
I want to measure the current of 12V lead acid battery for charger application. So mostly, I need bidirectional current sensing.The current measurement can be done using shunt resistor or using hall effect sensors. I see the shunt current sensors comes with I2C or SPI analog output.
But the ACS712 can be directly hooked up to the analog pin of MCU.
Do I need to use any op amps here to maintain the current gain.
Or just use ACS712 sensor hooked up directly to the battery terminals and sensor output terminals to the MCU.
Please suggest me.


texts: Are there any chips which manages supercap charging and releasing power?

texts:
I'm not looking for recommendations but simply the existence of such a chip, I know where to look for them but want to make sure they do not just exist in my imagination.

I want to use a supercap as not just back up power, but a main source. I want to use a 5V, 12f one, and the cost at this point is of no concern.

There are a plethora of problems associated with supercaps, with voltage dropping being one. And I want a smooth, constant 3.3v output from the super cap.

So I'm thinking, there has to be a chip somewhere which not just monitors the power left, how long it takes to charge it fully, but also manages its output? I.e make sure the output stays @ 3.3V for a very long time before going under?

I could be wrong. I need confirmation?


texts:
I have the following circuit for a 555 Timer PWM generator:

With 1: GND, 2: TRIGGER, 3: OUTPUT, 4: RESET, 5: CONT, 6: THRESHOLD, 7: DISCHARGE, 8: VCC

I dont quite understand the use of R1. Is it just used to limit the current from VCC trough DISCHARGE to GND when DISCHARGE is set low?


texts: Does a 555 timer actually have a flip flop?

texts:
I'm new to electronics and have been studying the 555 timer. One of the key components within the 555 timer is the "Flip-Flop", at least that's how every resource on the internet refers to it.
Here is a diagram of a 555 timer that is commonly found across the internet.

You can clearly see the component is labeled a "Flip-Flop". If you look at the Wikipedia page for a 555 timer it states it uses a "SR Flip-Flop".
As we know, a "Flip-Flop" uses a Latch as an integral component. So what is the difference between a Latch and a "Flip-Flop"? Every resource I find, describes a "Flip-Flop" as having one of these two defining characteristics:

It is a Gated Latch
It is enabled through a clock signal

So, the problem is, in a 555 timer, every diagram shows the "Flip-Flop" only taking 2 inputs, and has no enable pin, therefore, it is not gated. Thus, it must be a simple Latch.
Again, I'm new to electronics, but my question is:
Does a 555 timer actually have a "Flip-Flop" or is it just an SR Latch?


texts: How do I build a TRRS headphone jack with a jack that is detectable by an iPhone

texts:
I have a circuit and I am trying to integrate it with an iPhone via a TRRS headphone jack's microphone input. I have a generic TRRS cord and am trying to send a signal through it. However, the iPhone does not detect that a mic is even plugged in. However, if I plug it into my Mac via line-in and record, I can record the signal I am sending perfectly.

I have read online that it needs to detect resistance between the ground and mic, which I have. Are there any other things I need to do? It seems like this is an issue that stems from Apple's proprietary technology, as the earbuds are from a Windows Phone before they were spliced.

Thanks so much!


texts: Huge variation of impedance calculators with same parameters?

texts:
There are many free (e.g. AppCad from Agilent) microstrip impedance calculators on the web. I've tested now several, because the first two did show a huge difference in the calculated impedance for a CPW waveguide on silicon, with exactly the same parameters (dieletric constant, geometry etc). One 50 Ohm, while the next 68 Ohm. This will probably generate huge losses.

So how can I be sure, I've chosen the right geometry of my waveguide and get correct impedance match? Should I switch to commercial simulaion software like CST microwave studio or HFSS to get the results nearest to real-world physics in this waveguides?


texts: Why doesn't my pull-up work on S-35770 I2C counter IC?

texts:
I designed the following PCB from the schematic below to make a breakout for an I2C counter IC, datasheet is here.
However my RST pin doesn't go up and the IC stays in reset state. I'm feeding 3.3V to VCC. A multimeter is showing 0.29V on the RST pin. I probed also with the multimeter and the 10k resistance is there from VCC to RST PIN.
I added another normal 10k resistor from my breadboard to the RST pin and the pin went up and it's working after that. Any idea why my board 10k resistor is not working?


texts: can i connect wires in a single transformer to get higher volts?

texts:
I have this transformer, and i want to get 27V output. i don't know what's inside, but i just have the product. it's a 15/12/0/12/15 vac center tapped transformer.

The question might be dumb, but is it able to connect those 12,15v wires in single transformer to get 27 volts?

if it's not possible, will i be able to get 30v by putting one more transformer and connect 15volts in series? it's a 0.7A transformer.


texts: How do I replace this bike light cache battery?

texts:
This Luxos U dynamo powered bike light has a cache battery that provides backup power for the light when the dynamo isn't providing power, and it also provides power to smooth the USB charging that it also supports. The nominal power output of the dynamo hub that feeds it is 6v, 3 watts.
I have not been able to locate a replacement battery given the identification on the existing, 2-cell battery. I'm hoping to figure out how to remedy this since I have some nearing end of life, and I'm considering buying more of them -- but I don't want to do that if I can't refresh them with new batteries when they need them.
The internal battery pack label reads:
802025p LiFePO4
6.4V 150 mAh
0.96Wh 1710
It looks like 2 (3.2 volt) cells wired in serial with another yellow wire coming off -- a thermistor?

The cells measure 8mm thick x 20mm wide x 25mm long, so it's clear that ID number refers to the dimension of an individual cell.
The only cells I can easily dig up with the same dimensions are similar to these (https://www.aliexpress.com/item/33052412361.html) that is, 3.7 volt polymer lithium batteries, which, if I understand correctly, are more energy dense, but at the expense of operating temperature range and service life.
The device itself is very easy to open up, so if a suitable, less long-lived replacement could be created by wiring together a couple of those 3.7 volt, 300 mah cells, that would be a reasonable replacement.
Would I need to worry about the 7.4 volts that would make, versus the original 6.2? I haven't tried to pull apart the original packaging, so I don't know what that yellow wire is attached to. If it's a thermistor, I assume I can just recycle it by attaching to the new penultimate cell and maintain the same performance. If I understand correctly, these little cells often have overcharge protection built into the electronics between the cell and the leads anyway.


texts: BJT reverse base-emitter voltage 1 Volts?

texts:
Using the multimeter diode setting in a powered down circuit, on the TR6 transistor (BC548), the forward B-E and B-C voltages are ~0.7 V, reverse B-C is OL but reverse B-E is 1.08V.
Does this mean the transistor is bad, or can it be a consequence of measuring in circuit and due to the neighboring components?
All other transistors (TR1-TR5) have ~0.7V forward voltages and OL when measured in reverse on both junctions.

PS: this is related to and somewhat the complement of yesterday's question, when I asked if correct measurements in-circuit guarantee a working transistor.


texts: PIC - How to skirt around low maximum ADC input impedance?

texts: Reading a 9V battery on a PIC is nothing new. The most simple and straightforward way is with a voltage divider. I'd like to keep the divider resistances cranked up into the hundreds of kohms so I'm not killing my battery unnecessarily, however I looked at the datasheet for the PIC18F4550 and the max "recommended" analog input impedance is 2.5kohms. This means I can stick 2 5Ks for my divider, but 900uA is a lot to waste on just checking the battery. What can I do to my design (passively) to minimize battery drain? I've considered active solutions such as a software controlled pfet or a buffer, but board space and budget are a bit of a luxury, so I'll only do it if I have to. I'm also wondering if I'm I being concerned over nothing.


texts:
I'm new to using buck converters. In the past I've just used a linear voltage regulator but due to heat issues in my current project I've decided to give a buck converter a try but I'm getting really confused.

I'm trying to convert automotive voltage to 3.3 V. Automotive voltages in our typical applications can vary from around 8 V to 16 V. I'm trying to power a Onion Omega which gets really unhappy at even a small bit under 3.3 V so getting an operating voltage of around 3.35 or even up to 3.6 V would be ideal and must be able to deliver at least 500 mA, preferably 1 A to be more future proof.

I have looked at a few IC's and I started designing around a LTC3621HMS8E-3.3.

I started copying the reference design

then I realized that even though I'm using the 3.3 V version of the IC, that the reference design shows that it's for 2.5 V out. Reading on in the data sheet here: LTC3621

I've come to the conclusion that I'm really confused.

The buck converter explanations found here on SE make sense from a conceptual standpoint but I seem to have a disconnect when it comes to actually making one of these things work.

Maybe I've also simply chose an insufficient IC and something else is a better fit.

I'm not asking someone to build this whole thing for me but maybe someone can help explain these things a bit better and what I should be doing to get the correct passives hooked up to this IC.


texts: Is it possible to play music with a PIC16F628A

texts:
Is it possible to generate and send PCM audio from a PIC16 (or an arduino/atmel)? It does have an analog port, so it should work right?
And if it does, is the PIC fast enough to generate the clockspeed necessary to play an MP3 for example?
Also is there a way to generate or capture raw PCM data to be send out over the analog port?
Has anyone ever done something like this or any hints on how I get my hands on PCM music?
Also since analog voltage can't be amplified using a transistor, what would be a simple way to increase the voltage?


texts:
Is this the same? I would say no.

On the other hand: Frequency dependent components (capacitors, inductors) store energy/information and hence introduce the memory.

Also, smearing out of signals from systems due to its impulse response can be interpreted as memory effects, hence suggesting both being the same.

So if there is a difference, what is it precicely?

If not, does it just depend on the field or application if one says frequency dependency or memory effect?


texts: Can I replace an AT28c17 with a CAT28c65B without changing my software?

texts:
The AT28c17 is a 16k e2prom while the CAT28c65B is 64K bit e2prom and both are in a 32 pin PLLC package. They have 10 adresss lines with the only difference being the AT28c17 has
 A0-A10 adress lines  while the CAT28c65B has A0-A12.

The pin configrations of both are same but the pins 3 and 27 are NC on the AT28c17 while they are A12 (adress 12 pin) and A11 (adress 12 pin) on the CAT28c65B. Only these pins differ.

Can I replace the AT28c17 with a CAT28c65B without changing my software? Will it work?


texts: Improved method of instrumentation amplifier input noise and RFI filtering

texts:
The following circuit diagrams are taken out of Niel Albaugh's The Instrumentation Amplifier Handbook

I understand how the RC (tolerances) mismatches in Figure 4-16 (left circuit) cause the two time constants to not perfectly match and result in differential signal, and the error gets amplified to the output. OK.  Then the author suggested a fix to the circuit by adding C3, and that the circuit on the right (Figure 4-20) is an

(page. 52) ... an improved method of instrumentation amplifier input noise and RFI filtering ... even though the R1C1 and R2C2 mismatch remain the same, there is less common mode voltage to differential voltage conversion with this filter.

I don't get this. If the frequency is low (no RFI), C3 is no more than an open circuit, and the circuit on the right is identical to that on the left. If frequency is high enough (RFI), C3 will appear to be a short circuit - there won't be any voltage potential across the two inputs. I don't see how C3 filters RFI other than zeroing out the inputs whenever the signal is influenced by a high frequency RFI.
Would someone explain how Figure 4-20 improved noise and RFI filtering? (I hope this is not a typo or misprint from an aged old text)


texts: Transformer maximum voltage rating specifications

texts:
I don't know how to interpret the voltage values found in datasheets for transformers. For example, in the datasheet below:

where it says 15v, 50mA near the winding schematic. Is this a maximum or a test condition or nominal value? Is there generally a maximum output voltage for a transformer other than the dielectric breakdown voltage which is in this case specified at 1500V? Do i have to respect something like not go above 50mA*15V watts? If i want to use this transformer at an output of 75-100V for each of the 2 secondaries will i run into problems? How can i make sure the output of a flyback converter using this transformer is not too high, using the information provided in the datasheet?


texts: How to know if a LED power supply will deal correctly with dimming

texts:
I have a led strip with its 24V own power supply (IKEA's Ledberg), and I want to make them dimmable. I've successfully done it with an arduino and a MOSFET, but I'm unsure if the power supply will deal with it correctly.

I know that some power supplies will monitor the output and try to provide a constant current, but I'm not sure about the Ledberg ones. Is there any way I can be sure?


texts: Does changing the gap between plates change the capacitor voltage?

texts:
Consider an ideal capacitor which has a length of \$\ell_1\$ between its plates. The capacitor terminals are open; they are not connected to any finite valued impedance. Its capacity is \$C_1\$ and it has an initial voltage of \$V_1\$.

What happens to the capacitor voltage if we make the gap between the plates \$\ell_2=2\ell_1\$ without changing the amount of charge on the plates?

My thoughts on this:

Increasing the gap will decrease the capacitance.

$$ C_2 = \dfrac{C_1}{2} $$

Since the amount of charge is unchanged, the new capacitor voltage will be

$$ V_2 = \dfrac{Q}{C_2} = \dfrac{Q}{\dfrac{C_1}{2}} = 2\dfrac{Q}{C_1} = 2V_1. $$

Is this true? Can we change the capacitor voltage just by moving its plates? For example, suppose that I'm wearing plastic shoes and I have some amount of charge on my body. This will naturally cause a static voltage, since my body and the ground act as capacitor plates. Now, if I climb a perfect insulator building (e.g.; a dry tree), will the static voltage on my body increase?


texts: I repaired a PCB trace with a conductive pen that I now want to remove without damaging the underlying copper.  Is there any solvent that will remove a nickel conductive pen trace?


texts:
I have a faulty Microsoft Surface power supply and I found a circuit diagram for it that I could use some help figuring it.

Specifications:

The LED is supposed to be on only when the Surface's Power On
Controller tells the connector it is charging (with the Surface receiving a 12V pulse every half second)
At all other times LED is supposed to be off
If however, there is any sort of problem with the power supply, the
LED will blink
Blinking means the pulse generator is causing the LED to blink, which
is somehow prevented when things are functioning properly

Can someone figure out what prevents the LED from blinking during normal operation, and more importantly, what flaw might cause it to blink?


texts: Why can't I put 110 V appliances on 220 V outlets?

texts: It's known that Power = voltage * current and it is also known that the voltage in the electric grid is fixed. So even though I know (from practical experience) that we cannot use 110 V devices on 220 V outlets, why does this happen? Shouldn't the electric current change in order to match the power required by the device?


texts: control speed of 12v dc fan with thermistor

texts:
As a learning exercise, I am trying to control a 12VDC/0.18A computer fan with a thermistor.  As I am planning the circuit (and I certainly can be wrong in my calculations), I plan to have a 12V power source (8AA batteries in series).  I am trying to use a PN2222 transistor to control the fan's speed.  According to my calculations, I would need 6mA into the base of the transistor to get the 180mA needed to run the fan at (or close to) full speed.  So, then to control the speed from there, i.e. clamp down the current going to the base to reduce the current into the fan, I have placed a 5-100K thermistor in line with a 2K resistor.

Connections:  Negative rail connected to Emitter and 2K Resistor which also connects through thermistor to base.  Collector is connected to negative side of fan.  Positive rail connects to positive terminal of fan.

I believe I have included all the pertinent information, but if I left something out, I'll be happy to add more.

So, the problem I am having is that the fan doesn't even turn.  I have connected the fan directly to the battery source, and the fan turns.  I have started some basic troubleshooting, but found that I am reading 0V across the 2KR (1.9K pictured).  So, I guess my question is what am I missing here?  Why can I not get the fan to turn in this circuit, and I am sure it is probably something stupid.


texts: Eagle CAD autorouter places tracks too close to vias. I tried to change some parameters in the design rules but without a good result.


texts:
JAMMA connectors are card edge slots that were common in arcade games before cheap SBCs. They are designed for fairly high current (5A) and are robust and cheap in a range of sizes from 8 to 72 pin.

I can't find a KiCAD footprint for any size of JAMMA connector. This doesn't surprise me, but I also can't find a comprehensive physical specification.

I know there is 3.96mm centre to centre for the pins, and 3.96mm between the rows. They use a flat pin with a hole designed for attaching a heavy wire, with an interstitial gap of 1.8mm. This implies a pin width of 2.16mm requiring a 2.2mm hole and a pad at least 2.5mm wide leaving 1.46mm pad edge to pad edge.

However, JAMMA connectors come in two flavours, the other one having wire pins. The diameter of the wire pins I do not know, and Chinese suppliers have not responded with diagrams. Centre to centre they have to be 3.96mm same as the flat pins with the holes. At a guess the pin diameter is about 1mm but it's hard to be certain until I receive them and use calipers.

I've never created a KiCAD component and it looks like a fair bit of work to do a good job of it. Any information, guidance, encouragement or assistance with KicAD would be appreciated, with the outcome being contributed to the KiCAD libraries.

In particular, can board makers do slots? It crossed my mind you could do a series of 13 0.9mm holes at 0.305mm intervals but I don't know how well the drilling machine would cope.

Even can it be done, slots may not be worth the bother. There isn't a lot of room for the heavy tracks associated with these big pins to escape between the pads (gap of 1.4mm) so I'm going to have to make heavy use of vias and layers anyway.


texts: How To Calculate kVA values in power analyzer meters?

texts:
I am using a Schinder Electric PM2120 power analyser meter.

I record values with it every 15 minutes.
When I calculate values in kVA manually and compare them with the recorded values, I notice that a difference appears. Please explain to me why this is happening.

I used \$Root 3\times VLL_{Avg}\times I_{Avg}\$ to calculate using kVA.

Spreadsheet link: record

The time, voltage, current, kVA, THD values are taken from the measurements made with the meter.


texts: How to measure battery charge and depletion over time

texts:
When using my various electronic devices, they always seem to know how much charge is left in the battery. They also know when the battery is completely charged.

Not exactly sure how this is measured, but I assume that it is based on the voltage of the cells. Is this drop in voltage linear? If it is linear, then how do iPhones and iPods still run at the end of the charge with so little voltage?

Edit: Bonus points for useful graphs.


texts: The advantage of using base biasing over emitter biasing?

texts: Can someone please explain to me what is the advantage of using base biasing over emitter biasing. Why is a 'feedback resistor' used in base biasing?


texts: thoughts on reading only one changing GPIO with accurate time amoung huge number of digital Inputs

texts:
I am trying to read a huge number of digital inputs (129 to 800 and maybe more) at the same time. the sampling rate should be around 500K samples per second but I only need to read one of these inputs if there is a signal change (interrupt?). I am stuck at this for a long time and would really appreciate the help.

should I use 16 bit PISO shift-registers IC and a simple MCU but it seems that I will have to check every bit looking for a high signal?.
should I use an IO expander IC with SPI such as  interface such as MCP23S17 but usually these have 3 bit address which mean I only could get away with 16*8=128 inputs. Another IO expander with greater IOs is MAX7301 but I am not sure how to use multiple ones and if it would affect the performance.
should I move to an FPGA for this sort of jobs given that I never touched one but I am ready confront my fears.
will multiplexers work or will they have their limits
could a hardware cascade of ICs solve this issue so I only recive the address of the changing bit with timestamp but how?

it is important to note that I need to keep the sampling time high in order to capture any change in one or at most 2 pins.
please point me to the right direction as I am clueless and don't know what to do.


texts: Export restrictions on components like FPGAs

texts:
I'm considering upgrading the FPGAs on a product of mine from small Spartan3A-200s to low-to-mid-scale Spartan6s. The Spartan6s are actually cheaper, and I've just about outgrown the 200. It looks like it'd be a mistake to design in another Spartan3A at this point.

My (oilfield related) product is shipped potentially anywhere. So, I really don't want to make a major mistake like putting controlled technology in my next design.

These FPGAs are based on technology that was absolutely state of the art just a couple years ago. I recall certain processors once being export-restricted, so I am concerned that the Spartan6s might somehow be restricted.

I've been searching for info on what FPGAs or components in general are covered by export restrictions like ITAR, without turning up anything definitive. It -looks- like it only applies to space-rated chips. (It's always mentioned in that context).

How am I supposed to tell what's okay to export?


texts: Why do some PCB designers put pull-up resistors on pins where there is already an internal pull-up?

texts:
I'm going to use a DP83848I Ethernet PHY chip and I have noticed that a lot of people put pull-up resistors on these pins:

LED_CFG
PWR_DOWN
MDC
RESET_N

Example:

Why?
According to the datasheet, there are already internal pull-ups on these pins. (Except MDC, The datasheet doesn't require any pull-ups on that pin. I = Input, PU = Pull-up.)

The datasheet can be found here: https://www.ti.com/lit/ds/symlink/dp83848i.pdf?ts=1612458047376&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDP83848I
Question:
Why do so many people put pull-ups on pins where the pin has already an internal pull-up?
Have I missed something?
This is my schematic:


texts: How to calculate R and C for AM Demodulation envelope detection?

texts:
How can I calculate the value of \$R\$ and \$C\$ for an AM envelope detection circuit.

Knowing that the carrier wave is \$20\mathrm{KHz}\$, \$1\mathrm{Vpp}\$ sine wave, and the message signal is a \$32\mathrm{Hz}\$, \$2\mathrm{Vpp}\$ triangular wave with a \$3\mathrm{V}\$ DC offset:

I used the low pass fillter equation (\$f_c=\frac{1}{2\pi R C}\$) to calculate \$R_1\$ and \$C_1\$ and it was fine ~100 duplicate. The result was this:

Is this the correct method to use?.


texts:
I need some help with the following circuit:

I simulate it using LTSpice IV and have this:

But I couldn't get that thinking. Of course, I know that it's possible that there's some DC voltage before the capacitor C2 if it's Ground on the other side, but I couldn't get that.

For example, I thought that, in Vnode, it had to be something like the characteristic curve of a capacitor discharging in a AC voltage.

Any help will be appreciated. Thanks!


texts: MOSFET burning out when attached to a solenoid

texts:
Apologies for the very poorly written previous question.

We have a circuit that consistently burns out our MOSFETs when we attempt to use them at full power, 250V, but they seem totally fine at 200V.

The circuit is used to power a solenoid to make a small robot kick a ball. At the top, there is a capacitor charged up to 250V, next the solenoid with a snubber diode (unidirectional zeener with a 330v breakdown voltage). The MOSFET is off until we want a kick at which point we turn the MOSFET on and allow the cap to drain through the solenoid.

The mosfet we are using is the STD18N55M5, this one, it is rated to 16A continuously and 64A pulsed. The Drain source breakdown is 550V. I don't know exactly why there is a resistor  or a diode alongside the MOSFET but I assume they are similarly for spike protection.

I am new to the project so I don't know a lot of the details but I have been tasked with trying to discover why our MOSFET keeps burning out above 200V. My initial instinct is that the 16A is just too low for 250V but I have no evidence to back this up. Another possibility is that the zeener is somehow breaking down at 250 rather than 330 and shorting the MOSFET between 250 and ground but that seems unlikely.

I don't really understand how one calculates the current through an inductor and MOSFET since there are no resistors in the path which seems like it would create infinite current which obviously isn't the case. Any insight or suggestions for things to try would be greatly appreciated. Thank you!

EDIT: the cap is 1500uF, 250V. The flyback zeener is this one digikey.com/product-search/en?vendor=0&keywords=F4115CT-ND and the mosfet is the d package with no heat sink

simulate this circuit – Schematic created using CircuitLab


texts: Double single-transistor logical inverter not working as expected

texts:
I had a 5V-powered circuit with a single-transistor (BC547) logical inverter in it, it worked wonderfully.
Then I also needed a "buffered" version of the signal that goes into that circuit, so I thought I'd just stick another identical inverter after the one I already had, essentially recreating the original signal, obtaining what you can see in the image:
The idea worked well as far as the "buffering" is concerned (i.e.: point B behaves as I need), but it disrupted the "midway" inverted signal (point A), which now only rises to ~1V when it should be 5V.
Is there any way to remedy this, and still get a 0/5V signal at both point A and point B?
Thanks in advance.
PS: Using a "proper" inverter IC is out of the question, for the moment.


texts: Powering 12V device from USB-PD port not supporting 12V

texts:
I would like to power a 12V 2.5A device using barrel connector from a 60W USB-PD capable thunderbolt 3 port. I have a few of those pd trigger cables (https://www.aliexpress.com/item/4000025832414.html) that seemed perfect for the job. However, from my testing the PD port supports 20/15/9/5V but not 12V.

Is there a way to get 12V from usb-pd port that does not support it? Or how can I convert 20V or 15V from the pd trigger to 12V?

I would ideally like to avoid soldering or exposed circuits since we are talking expensive equipment and I would probably do bad job soldering. So I preffer something plug 'n' play if its available and so far I haven't found anything like that.

PS. What I'm trying to do is power HTC Vive Cosmos from Akitio Node Pro eGPU dock to get rid of one AC power supply to make setting up easier when transporting.


texts: Why PNP transistor might be opened even though (almost) nothing is connected to the base?

texts:
I have a simple printed circuit board with simple circuit on it. Very beginner. No SMD.

As a part of this circuit I have transistor BC557.

If I don't solder the base pin of this transistor and test the circuit then transistor is closed (as expected) but when I solder it to a path on the board that has nothing else soldered to it (there were two resistors but I desoldered them) then the transistor is magically open now.

Transistor operates on voltages around 16V (on emitter) and on very small currents. The only load between collector and the mass are in parralel: 100k resistor and MOSFET gate-source.

Can printed circuit board be leaky in a way? Somehow allowing some current to flow from the base that's not connected to any other component?

Adding 1uF capacitor between base path and emitter path on PCB doesn't seem to help.

I noticed that if base is left unsoldered and I touch it with a screwdriver I'm touching with a finger then the transistor opens sometimes, even if I don't touch anything else in the circuit at the same time.

Can I somehow make it less sensitive?

This behavior didn't occur when I had same circuit powered by the same battery and tested with the same load but on breadboard.

The circuit I'm trying to build is that one: http://serwis.avt.pl/manuals/AVT746.pdf

And it worked on lower voltages (less than 9V).

I tried putting 100k resistor between emitter and +16V but it doesn't seem to help either, transistor still is open when base is soldered to unconnected path (but it caused MOSFET to overheat, even though the sorce-drain current is just 2A).

I also swapped the transistor for another one (same) to rule out damaged element.

BTW This circuit cuts the battery power to the receiver on the right after a delay roughly controlled by C2. It turns it back on after pressing the switch. Cool thing about this one is that it can turn on an off large currents (in theory up to 30A) and work with voltages from 6 to 16V.

I replaced switch with transoptor (+480 Ohm resistor in series) so I can control this circuit with another one.


texts: Limiting, scaling and biasing analog input (ADC) of microcontroller

texts:
I have current transformer coils to monitor a gas-powered AC generator output (A & B) and 4 load circuits.

The output of the T1 coil with a 1500 watt load is about 30Vpp.

Will this circuit properly scale the input to the AD converter?
Are these good values for the resistors?  (revised 12/24/12 to use 1k+100 )
How can I protect the AD input from exceeding 5V?

AD-GND      A         1k
-----,--@--------\/\/\/---------------------Ax-+
     |  T1                            100      |
     +------------------------------\/\/\/--Ay-+------- AD-input1
     |
     |       B        1k
     +--@---------\/\/\/--------------------Bx-+
     |  T2                            100      |
     +------------------------------\/\/\/--By-+------- AD-input2
     |
     ...
     |
     +--@-----  as above
        T4


texts: Generating a current with ionized water droplets (in a cloud)

texts:
Playing mind games with myself tonight; I know some of the windiest spots in the world are at the tops of mountains and often socked in the clouds. To measure meteorological phenomena at these locations is a difficult task, with rime ice eliminating mechanical energy generation and solar very limited due to clouds.

With occasional ionized cloud droplets, would it be possible to generate electricity "indirectly" by inducing charge on a conductor without any moving parts? Would this be possible even if there were equal numbers of positive and negative ions?


texts: How to convert high voltage DC at low amps to low voltage DC or AC at high amps?

texts:
How to convert high voltage 500 volts DC at very low amps to lower voltage  12 volt DC or AC at high amps? Must I use an electrostatic motor or can I use an op amp?

The reason I am posing this is a desire to send up a wire to convert atmospheric electricity to something I can use.


texts: How to choose high frequency inductors for high voltage line filtering?

texts: I saw these inductors 680 uH (RL-1294-680) in each power line like shown below. The line to line voltage is 480 VAC. The inductor used has a saturation current of 280 mA. So I suppose I shouldn't reach that point. What should I take into consideration when choosing inductors for this application? In this example, the designer chose 680 uH high frecuency inductors in each power line. How did he come to that conclusion?


texts:
I cannot find what is the ouput voltage the ESP32 ? I mean OUTPUT on the GPIO.
I'm a beginner with this technology and I don't find this information.

Thank you for your help !


texts: How can I convert a flow sensor's pwm output to logic level relay control?

texts: I have a flow sensor with PWM output and I can't replace it with a flow switch due to mechanical restrictions. Is there any simple way to convert the PWM output to a logic / or analog signal and trigger a transistor with that? e.g. something like a filter that converts the PWM output to voltage and then after a specific threshold turns on a relay?


texts: Solenoids causing Arduino to malfunction despite protection diode

texts:
simulate this circuit – Schematic created using CircuitLab

I have an Arduino Mega that I'm attempting to control some solenoids and LEDs with.

The LEDs are 3.3V, controlled through an open drain shift register
and MOSFETs

I wasn't sure how best to represent the Arduino in Circuitlab, so I used some switches to represent the I/O pins.

Basically, the problem is that, after I fire the solenoids a few times, stuff starts acting weird.  First, the shift registers will start resetting to random status sometimes when a solenoid is fired.  If I just push new data to them, they work fine again until another solenoid fires.  After a while, the Arduino will start thinking it's getting inputs (I have the internal pull up resistors enabled, so it's thinking it's input pins are being grounded when they're not).  If I power off the circuit and turn it back on, everything will work fine for a while more, but I have no idea what's causing this, and I'm worried I'm slowly frying the components somehow...

Also, whilst browsing similar questions, I saw one person say that you should try to put your MOSFET as close to the solenoid as possible.  Currently my MOSFET is mounted on the board with the arduino, but the solenoids are 2-3ft away.  Could that cause this?


texts: Resistor divider on current sense signal

texts:
I am building a step down converter using LTC3892. It will have 12V output sourcing 50A in each of two interleaved phases.

Problem is that LTC3892 has fixed current limit value at 75mV. This means that for 50A current limit, I would need a current sense resistor of 1.5mOhm which is a bit odd value.

I wonder whether I could use a 2mOhm resistor and then use a resistor divider to reduce the signal voltage from 100mV to 75mV? Has anyone had any experience with such method?


texts: Use of Cable Shield in Optical Rotary Encoder

texts:
I have an optical encoder with four wires: Green = A phase, white = B phase, red = Vcc positive power supply, black = V0.

Additionally, it has a metal shielding layer in the cable. Now I don't know what is the use of this metal shielding. Can anybody provide some information about it?


texts: I've created a MOSFET Differential Amplifier in PSpice, the schematic of which I've attached. However, when doing an AC sweep and adding a trace to do a Bode plot, the graph is a flat line, and I don't quite understand why. Shouldn't there be a negative response as frequency increases?


texts: Design circuit with two OP AMP and one voltage source

texts: I'm having trouble with this problem. I'm supposed to design this circuit in such a way that the value of R will make the current ix = 10 Amps. Any ideas? I have just no idea where to begin for this one.


texts: Does the Sallen-key filter require a buffer for low power applications?

texts:
I am designing a circuit which takes an 3uV at 10-10kHz input that filters, applies gain and integrates the analogue signal. I'm thinking of using the circuit below for the topology using two stages consisting of a Sallen-key filter and active RC integrator.

simulate this circuit – Schematic created using CircuitLab

Vin has a source impedance of 3.4Kohm.

In this low power level application, would a buffer be required to feed the sallen-key or would the circuit effectively operate in this system?


texts: What are some good logic simulators for experimenting with multiplexers?

texts: We've been tasked with showing the numbers on a 7-segment led display with dual 4x1 multiplexers and 3 variables. Our first try was a failure and we won't have the opportunity to experiment in the next few days, is there any good program for this kind of project? I've tried logisim but the cable on the selection variables(I don't know if this is the name in english) is always orange .-.


texts: Software to manage packaging all files related to a product (for hand off to customer)

texts:
I want to provide my client with a Product Lifecycle Management (PLM) and Product Data Management (PDM) style package of all the documentation related to the project (in house user manual for their technical writers to use as reference, board bring documentation, Test campaign docs, etc...), Hardware files (release verision of schematics, gerbers, etc..), datasheets and parts list (BOM), and finally release binaries.

Is there any good software geared towards small design studios (I have a 4 person group...with often only 2 people on a project). So far I have only found enterprise level PLM/PDM software that goes way over board for what I need.

And yes, I know, I could just make a folder with all that stuff and just zip it. But there are lots of reasons why that is not the greatest solution. :P


texts:
While evaluating the Libelium Waspmote board for wireless sensor networks, we discovered a strange communication problem.

We tried to set up a link between the waspmote and another board via UART at 115200 Baud using 8N1.

This is the resulting waveform on Tx for sending 9 times 0x55 (01010101b) :

The levels of high and low degnerate to the treshhold of detection: starting out with a High level of 3.3V, the peaks drop in to about 2.7V and the lows start out at about 1.1V and drop to 0.7V.

According to the target boards specification, the peaks should be > 2.3V and the lows < 1 V for correct operation.

It looks to me as if some capacitve behaviour emerges, but I have no clue why this happens.

I am in need of a clue on what is happening, what i am doing wrong, or what i can do to fix this problem.

Some additional info:

The microcontroller on the waspmote is an Atmega1281, and it's uart pins are directly connected to the communication link (no drivers in between).
I can not reduce the baudrate since the target board accepts 115200 baud only.

UPDATE 1

I made a detail shot of the signal. We are looking at a transmission at about 125kHz - which seems to be a bit far off the desired 115200 baud I'm aiming at.

UPDATE 2

I measure identical waveforms when I disconnect the traget board and put the oscilloscopes probe directly at the microcontrollers UART-Pin. This seems to rule out problems with the target board.
However, the measured baudrate is exactly 125000, which is an error ofabout 8% from the desired target baudrate of 115200. Since the UARTs specification limits the baudrate skew to 2%, I guess there's my problem. However, since the waspmote board is locked to 8Mhz clock rate, the Atmega1281 on the board can not produce a more acurate 115200 baud clock through the prescaler registers ( I checked the manual). I guess I'll need another board to communicate with my target board.

Thanks, everybody.


texts: How to add (all zero state) to the states of linear feedback shift register (LFSR)

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I need to add the state of all zeros to the states of an linear feedback shift register.

How can I do this?


texts: Completely different circuit response with 1000kΩ than with 1MΩ resistance

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I have the following circuit (a band-pass filter) and I cannot understand what's the difference of a 1000kΩ resistance to a 1MΩ as seen here:

With R223 = 1000k, my circuit outputs the expected theoretical results (for input signal of 32kHz at amplitude of 500mV, it retains indeed 500mV almost) , but when I replace it with a 1M resistance it outputs 74mV amplitude instead, which is totally illogical! Maybe I have missed something obvious here? But aren't those two resistors exactly equal? Isn't 1000k = 1M? And the weirdest thing is that the real circuit (not simulation) also outputs the "illogical" result of 74mV!


texts: I want to dim a 60W incandescent bulb using PWM on a MCU. The bulb is rated at 220-240V 50-60Hz at 60W. I am planning on using a optoisolater connected to the PWM pin. I want to run it on DC, so since the bulb is 60W and P = VI then am I correct in saying that I can get full brightness at say a voltage of 30V and current of 2A ?


texts: Need some help with identifying the primary on a power transformer

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So a friend of mine had an old amplifier which he didn't want anymore so i told him to give me the transformer before throwing it away since i might need/can use it in a future project. But since it is a surface mount/PCB type transformer i have a hard time identifying the primary since i get continuity on most the pins. And i know that the transformer is fine since the amplifier worked perfectly before taking out the transformer.

I managed to find the schematic of the amplifier:

https://docuri.com/download/hcd-rg330_59c1dc7cf581710b2868a7b5_pdf

Here is a picture from that schematic which shows the transformer and then some pictures i took myself of the one i have:

Any help is appriciated and if you need another picture of something specific please do tell.
Thank you!

New picture of the pins:


texts: DC analysis of common-drain NMOS amplifier

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The DC analysis is regarding the amplifier calculations, but that is not relevant to the topic. The equivalent DC circuit of the amplifier is:

The known values are: \$Rg1=300k\Omega\$, \$Rg2=200k\Omega\$, \$Rs=100k\Omega\$, \$k_n=25\frac{µA}{V^2}\$, \$\lambda=0.02V^{-1}\$, \$Vtn=1V\$, \$Vdd=10V\$.
Now the problem is to find the bias point (drain current - \$I_D\$, voltage \$V_{GS}\$ and voltage \$V_{DS}\$.

First, I calculated the gate voltage as:
$$V_G=\frac{Rg2}{Rg1+Rg2}Vdd=4V$$
Then, I assumed that the transistor is operating in saturation mode, and set up these equations:
$$I_D=k_n(V_{GS}-Vtn)^2(1+\lambda V_{DS})$$
$$V_G=V_{GS}+Rs I_D$$
$$Vdd-V_{DS}-Rs I_D=0$$

The problem is, I cannot solve those equations, as there always seems to be one element missing. Any ideas on how to solve this?


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For example in this 4th order transfer function how the damping ratio would be calculated?

in fact I` m encountered with this problem: If I didnt realize the concept of problem plz guide me:

problem: calculate gain magnitude (k) if damper ratio of closed loop system is 0.7 (it means zita=0.7):

.

open loop transfer function:

the expansion of open loop system fraction:

and now how much is zita?
quadratic faraction isn t standard form because there s a 's' in numerator, am I right?

how much is k due to the zita has a magnitude of 0.7?


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I'm designing a PCB with allium and after route all the nets, I put allium in 3D view. (My first Double layer PCB)

In 3D, it appears to me that the pads are not plated (connecting both sides of the PCB, through the hole), despite the option to plate the pads being selected in pads properties.

Is this a 3D view bug?

The right ones appears to be plated but the left ones looks like they are not.

Left Pads properties:

Right Pad Properties


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I am building a simple portable speaker using a DFPlayer Mini, but I think that's not entirely relevant to my question.

I am looking for a way to detect when an USB Drive is plugged in, so the player can start reading data from it. I haven't found anything on this issue on the internet, so what i came up with is this circuit:

I expect the USB to drain enough current to switch on the transistor, so the HIGH IF USB CONNECTED line is driven high. I'm not sure whether the resistor values are appropriate, but I didn't want to waste too much current.

In my mind, this should work, as the USB should be able to work up to as low as 3.3 V.

It just came to my mind that I don't actually need the voltage regulator, but where do I connect the 4.3 V on the Arduino board? To 5V or 3V3?

If you see any other flaws with my design, please let me know.


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After connecting a PD charger, I see 15V on the power lines. That means, the device asked for 15V and the charger switched from 5V to 15V. Can I just put two wires into the USB-C port on the device, giving it 15V without any warnings, or it must somehow prepare it's inner power system first?
If not, how can I tell the device it's OK to take 3A from the 5V charger (instead of non-PD 1A)? I've heard something about connecting resistors to proper pins of the USB-C.
I want to use either 15V 1A charger or 5V 3A charger, but both of them are none-PD. From running the device with a PD-compatible charger, I know it can use both of them.