texts: PCB challenges and breadboard feasibility

texts:
I'm building a system that contains several chips (Intel 8085, 4 shift registers, SRAM, 8255 I/O) all connected to a common address and data bus. The highest frequency signals in the circuit are on the 8 MHz SPI bus used by the PIC18 monitor to shift bits (address or data) into and out of the SIPO and PISO registers. The frequency is that high because I want to capture all 8085 bus activity if possible. The next frequency is the 500 kHz (at most) parallel A/D bus.

I just began component placing and routing in Eagle and I've found the task daunting. So challenging that I'm considering scrapping the PCB and completing the entire circuit on a large breadboard, especially considering the fact that the only PCB I've ever designed is a 6x4 keypad in KiCAD which is nothing compared to a system of this complexity. I can't afford to spend a week patiently designing, wait weeks for the board to arrive, solder costly components only to have the board not work. I know mentioning deadlines here isn't cool but I do have a deadline in 3 weeks.

I've asked a question related to this issue before and Chris Stratton said that crosstalk is an issue mostly in theory (also use short wires, bypass, etc) but what I'm looking for some confirmation ("Yes its very doable though...") or a definite no-no ("You can't do it. Go play with something else."). Specifically,

Has anyone else here designed something similar on a breadboard and it worked without glitches? No tricks to it but keep the wires as short as possible and bypass power on every rail?
What are the odds that someone inexperienced in PCB design could design such a circuit well enough for it to work perfectly the first time after fabrication (at some fab house)? That is, barring any issues with code.

I would test this myself with a breadboard but I'm just about to order the final components needed for breadboard testing or those needed for the final PCB (IC sockets and the like). Which ones I purchase depend on the answers I get from you guys.


texts: Capacitor bank for high powered appliance

texts: I have a vacuum cleaner which draws a little too much current only when it's starting up. This causes the trip switch in the home circuit to trip. Is it feasible to use a capacitor bank to provide this starting current so that the vacuum cleaner can continue to run on the normal AC power?


texts: How do I calculate the voltage at these locations?

texts:
I'm wondering how to calculate the voltage on the following charts (series circuit and parallel circuit). I'm interested in the math process involved, not the answer.

I'm mostly confused about how to find Vb as I believe Va will always be 5 volts and Vc will typically be close to 0. Any help and explanation is greatly appreciated.


texts:
I bought an electric toothbrush from Amazon UK and it came with a shaver plug. I’m trying to fix it to fit a EU socket. I've got a spare EU plug and I was thinking of cutting the shaver plug off and attaching that one.
I didn't pay attention in HS physics so I just want to run this by someone.
It says 2.5A 250V~ on the shaver plug and 220-240V AC 50-60Hz / 0,9W on the charger itself. Plugging that into a european socket should be ok right?


texts: STM32 value optimized out when reading from ADC

texts:
I'm trying to read my ADC pin but i'm getting strange results.
When my ADC input pin is connected to ground, the result from my ADC is definitely not zero. I know it's somewhere between 1000-2000. When i try to read the exact value within the debug window it says: optimized out. What could be the reason for this issue since i already had achieved this with the same chip/code?
I've measured the input pin and it's definitely 0V
I'm using system workbench for stm32 and CubeMX, programming trough an ST-link. Chip is an STM32f429zi
Here is my code, i use the value later in my code.

  uint32_t value = 0;
  HAL_ADC_Start(&hadc1);
  HAL_ADC_PollForConversion(&hadc1, 100);
  value = HAL_ADC_GetValue(&hadc1);
  HAL_ADC_Stop(&hadc1);

I hope someone can help me solve this issue. Thank you all!


texts:
I'm building a project that involves a raspberry and a small 3-6v water pump.
As the RPI and the water pump run on 5V I am using a single 110v-5v 2.5 Amp walwart to supply the power.

My question is, will I cause the raspberry pi harm as a variable current passes through the load? Initially the raspberry pi was not a happy but upon adding a flyback diode it seems to be OK. Are there other precautions I should take to ensure the RPI is not harmed?


texts: How can I control 128 (or more) solenoids?

texts:
I need to switch 128 solenoids either on or off individually, several times a second.  I'd like to drive this from either a PC, or an embedded device.

How would you recommend I do this?  Perhaps there is a way I can enable addressing of a group of (8 or 16) solenoids and send a turn on, or turn off command to them?

Considering what's out there, what is the easiest way to go about this?  What is the best or most preferred way?

I am looking at these solenoid valves that run at about $50 each. Do share information if you know of any cheaper/better ones.  The purpose is to control an indoor waterfall.  It's low-pressure so all the water drips downwards.

http://www.ascovalve.com/Applications/ProductSearch/ProductInfo.aspx?productid=8262H001AC120/60,110/50D&userAction=view


texts: Does a Crystal Radio coil require enameled wire or insulated turns?

texts:
When creating a coil for a Crystal Radio, why do I have to have insulated windings?  Why does it matter if the individual turns touch each other?

When it "shorts out" in this context, what does that mean, as in where did the charge go?


texts: X-ray back-projection for conversion to hard-field magnetic induction tomography?

texts:
This is a question about hard-field back-projection as used in x-ray tomography, applied magnetic induction tomography (MIT). Al-Zeibak and Saunders (A feasibility study of in vivo electromagnetic imaging, 1993) have shown that an x-ray filtered backprojection method, can be applied to an exciter and receiver coil, with a straight line of magnetic flux between them along the central axes of the 2 coils. Therefore this would take the place of a straight-line beam of x-rays, to scan and image the sample object (plastic container of saline solution).

In place of the summation of the x-ray attenuation coefficients (mu),

$$p_\theta(r) = ln \lgroup \frac{I}{I_0} \rgroup = - \int \mu(x,y) ds$$

( See: R. A. Brooks and G. Di Chiro, “Principles of computer assisted tomography (CAT) in radiographic and radioisotopic imaging.,” Phys. Med. Biol., vol. 21, no. 5, pp.697, 1976. )

they appear to detect the summation of voltages by the receiver coil:

$$p_\theta(r) = \int V(x,y) ds$$

Where V(x,y) is the voltage in the object at (x,y)

Would it be possible to convert this (Al-Zeibak and Saunders method) to a square Helmholtz-coil assembly, providing a uniform AC magnetic field (i.e. straight lines of flux) and a square array of air-cored inductors as the receiving/sensor coils. So that a metallic object being scanned would generate a summation of voltages for each approximate straight line of flux of the Helmholtz coils?


texts: Does anyone have advice on homemade EKG/ECG leads?

texts:
I'm not sure this is where it should be posted, so apologies in advance, but I'm working with an Arduino and Sparkfun's heart rate monitor AD8232 (https://www.sparkfun.com/products/12650) to gather ECG data for heartrate. I want to try to collect without "official" ECG pads, and maybe without the leg option (so basically, two on the chest, opposite sides of the heart). I have been trying with tinfoil, and I get some readings with the leg lead, but it's pretty sketchy and I have to often tailor the data I gather (I am using Matlab to process the data I get, copying and pasting from the Arduino. I know I can output to a file, but, that's another story).

So I'm curious if anyone has any non-gel and non-sticky options for pad options that work?


texts: Pin change interrupt won't toggle OFF my LED

texts:
Friendly Note: I am a beginner :)
Microcontroller: Atmega328p   LED = PORTB0    BUTTON = PORTB1
Aim: To have the button generate a pin change interrupt request which runs an ISR that toggles PORTB0 HIGH and LOW, therefore toggling the LED ON and OFF.
Current Problem: The LED toggles ON but does not toggle OFF.
#include <avr/io.h> // header file file for input output pins
#include <util/delay.h> // header file for delay.
#include <avr/interrupt.h>

#define F_CPU 16000000UL

int main (void)
{
    DDRB |= (1<<PORTB0); //SETS LED TO OUTPUT
    PORTB |= (1<<PORTB1); // TURNS ON PULL UP RESISTOR FOR BUTTON

    //Set button interrupt
    PCMSK0 |= (1<<PCINT1); // PIN CHANGE MASK REGISTER FOR BUTTON
    PCICR |= (1<<PCIE0); // ENABLES PIN CHNAGE INTERRUPT

    sei(); //ENABLES ALL INTERRUPTS GLOBALLY (REQUIRED FOR ALL TYPES OF INTERRUPTS)

    while (1)
    {
      //Empty while loop
    }
}
ISR (PCINT0_vect) // INTERRUPT ROUTINE
{
    PORTB  ^= (1<<PORTB0); // TOGGLES LED ON OR OFF
}

I have tried using a switch statement aswell but this had the same result (only toggling the LED ON):
    #include <avr/io.h> // header file file for input output pins
    #include <util/delay.h> // header file for delay.
    #include <avr/interrupt.h>
    #define F_CPU 16000000UL
    #define DEBOUNCE_TIME 25

unsigned char button_state()
{
  if(!(PINB & 0x02)) {
    _delay_ms(DEBOUNCE_TIME);
    if (!(PINB & (0x02))) return 1;
    }
   return 0;
}

    int main (void)
    {
        DDRB |= (1<<PORTB0); //SETS LED TO OUTPUT
        PORTB |= (1<<PORTB1); // TURNS ON PULL UP RESISTOR FOR BUTTON

    unsigned char n_led = 1;

       while(1) {

  if (button_state())
  {
   switch(n_led){
   case 1:
     PORTB ^= (1<<PORTB0);
   break;
   case 2:
     PORTB ^= (1<<PORTB0);
   n_led=0; // reset case number
   break;
  }
    n_led++; // next case
 }
}
 return (0);
 }


texts: Antenna VSWR value and impedance matching claims by the manufacturer

texts: Having larger value of VSWR is indication of improper matching. Eg. http://www.abracon.com/patchantenna/ACA-107-T.pdf this datasheet claims VSWR to be around 4:1 to 5:1 (which seems bad VSWR value to me). Also it claims that the antenna is Matched to 50 Ohm. Well, it appears that load impedance (here input impedance of the antenna) should be around 4 to 5 times higher or smaller than that of transmission line impedance in order to achieve this value of VSWR (i.e. either around 200 ohm or 12 ohm for transmission line of 50 ohm characteristic impedance). First question is, if it's such a bad VSWR, why do these manufacturers claim that it is matched with 50 ohm, Second question, are there any impedance converters which can be used to compensate for such improper matching, or should we just use passive RLC networks to correct the mismatch?


texts: Why can't potential divider be applied to calculate potential at Base Node in this circuit?

texts:
I have a self biased NPN transistor circuit as in the picture below and I want to calculate the base voltage Vb. The most common intuition leads me to apply potential divider and calculate the voltage, which in this case comes to be 3.529V. But whenever measure Vb, i get value near to 3.4V, which is less than what I calculate. Is there a simple explanation?

simulate this circuit – Schematic created using CircuitLab


texts: Modelling a LED Array for SPICE simualtion

texts:
I am currently looking to model a whole LED array within LTSPICE. I am working on all of hte logistics right now.

I currently have a LED array with about 300 LEDs on the array. Instead of modelling each LED, I figured that I get the IV curve of all of the LEDS when the array is turned on.

I currently have the data points and thus the IV curve of the LED Array. NOw what do with it.I thought that a simple solution would be to simulate the Diode part through the use of a look-up table.

In order to model the array, I was thinking that I could create a table of the IV points of the array (which I have have) and use a lookup table in combination with the VCVS. THE VCVS would use the look-up table in order to determine the output current of the VCVS.

However,  I was wondering if the VCVS is able to take a table as a parameter? I was thinking that I could use the table command but not 100% sure. Any guidance on the this matter is greatly appreciated. Thank you.

EDIT:

For clarity, I obtained a plot of IV curve from the LED array


texts: Voltage translation with resistor and LDO explanation

texts:
Could someone explain the voltage translation "Magic" that is happening in the circuit in the link below?

Voltage Translation Magic!

The YRPBRL78G13( blue on the left ) is a 5V design and the cc3000 module is a 3.3V design.

I can't understand how the arrangement of LDO and pullup (pulldown?) resistors would achieve voltage translation.

I've tried simulating this, and as far as I can tell this shouldn't work.

All help is appreciated!


texts: ESP8266-01 not working: red LED barely lit after reflashing from FTDI board

texts:
I'm trying to make my ESP8266-01 work with a simple FTDI board, wired like this schematic:

From here.

Everything works nicely when in "Flash mode" (even with ESP8266 NodeMCU Flasher or doing everything within Arduino IDE). But when I disconnect GPIO 0 from ground pin from FTDI, everything seems to freeze. Symptoms:

FTDI LEDs are all lit (both green LEDs and red LED).
ESP red LED is barely lit, almost completely turned off.
Nothing is recognized in my computer.

Notes:

I've tried plugging GPIO 0 into VCC. Nothing works too.
I'm powering the entire setup with USB current only.

What am I doing wrong? Could this problem be solved only with external power supply? If yes, how much current does the ESP8266 require?


texts: A warning on power pins of MCUs, explanation?

texts:
I came across with this warning:

  Most Chinese development boards do not have any kind of protection on
  the +5V rail. This means that the +5V pin of the USB connector is
  directly connected to any +5V/VIN pin on the development board. Always
  check if this is the case when you’re connecting your development
  board to an external power source while using the USB port.

I could not understand fully that what is the danger? What will be the consequences of this action?

Thanks.


texts: Two single-precision versus one double-precision unit

texts:
Suppose you are designing a floating point unit, and it is desired that it be capable of both single precision and double precision operation, in the former case not by simply expanding the single precision operands into double precision registers, but by performing twice as many operations per clock cycle.

That is, to be specific, say you want to have two options, if A and B are 64-bit registers, either perform the operation C=A*B, or alternatively C0=A0*B0, C1=A1*B1 where A0, A1 are the low and high 32-bit words of the A register.

How efficient is this? How practical or efficient is it to split a double precision unit into a pair of single precision units like this? I want to say, what percentage of the transistors can be dual-purposed, but I'm sure it's not as simple as that.

To be specific, how does the practicality/efficiency of this compare to the same dual-purposing of a fixed point multiplier unit?


texts: How to measure internal battery pressure?

texts:
Which unit is used to measure internal battery pressure?
And how can it be measured? (Does it change with battery age somehow?)

The internal battery pressure increases at high charging capacities and at high charging speeds, while a negative internal battery pressure occurs when the charging state goes towards zero, and discharging too quickly.
That's why batteries should be long-term-conserved at around 50% of charging level, to ensure minimum internal pressure.


texts: Triangular Wave Current input to a capactior, Voltage Response?

texts:
I am simulating a cap. When i give a triangular current input to a capacitor, I see an increase in voltage for both rising and falling side of current signal. why is this happening?

For a rising ramp I(t)=(kt), Voltage is kt^2/2
For a falling ramp I(t)= -(kt), voltage is -kt^2/2

But for a triangular wave, why is it an increasing voltage? it should decrease right?

Please help me understand


texts: Factors impacting propagation/gate delay

texts: I was just wondering how the change in transistor sizing, load capacitance and supply voltage affected the propagation/gate delay of an inverter.


texts:
I know a little bit about microcontrollers. I want to first say this question will be over my head but I'd like to do the project anyway...

I want to have a HDMI input, add effects to the sound, then output to HDMI out(all the while receiving the video, if there is any, on the other end). Through this guys post Microcontroller to process HDMI frames I learned I need a DSP. Can anyone step me in the right direction, I cannot find any tutorials or references online how to even get HDMI in to HDMI out on a board. If anyone has any references for that or even how to take the audio and effect it that would be very helpful.

I need to do more research on DSP's since I really just heard of them... but I'm having trouble finding HDMI components(for the in & out connection) and which type of processor or hardware would be used to process the sound...

I have seen the Raspberry Pi but I need an HDMI in & out and would like to find out how to do this strictly using the components rather than using a prebuilt microcontroller like that if at all possible.

Any information is very much appreciated!


texts: Missing contamination delay specification for a component

texts:
If IIUC: contamination delay (\$t_{cd}\$) is the time where the signal level on the output of a component starts to change in response to a change on the component's input, while the propagation delay (\$t_{pd}\$) is where this signal level change on the output stabilizes (i.e. becomes valid). Furthermore  \$t_{cd,min}\$ of a component must be bigger than the maximum hold time of a subsequent component connected to the first component's output.

While all component specifications I found provide \$t_{pd,max}\$ none of them provided \$t_{cd,min}\$. What is the reason for this? Can I assume in this case that \$t_{cd,min} = t_{pd,max}\$ ?


texts: Buying a regulated DC Power supply at home

texts:
I want to buy a regulated DC Power supply, I searched around in my local stores and I only have two options left (based on what I need and what I can afford).
Triple Output 0-30V & 0-5A
Triple Output 0-30V & 0-10A
The difference in the price is 1350EGP, which is a 50% increase in the price of the 5A model.
I do not know if it is worth it or not.
So my question is, what are the experiments that I would need a current that is greater than 5A at home?
Note: I am not a newbie in electronics, I already have an oscilloscope, a function generator and couple of DMMs, I know my way around microcontrollers, analog electronics and digital electronics, above all that I already built a 1A linear DC power supply, but so far I did not use anything beyond 3A (supplied from wall adapters).
If by any means you would like to check the specifications yourself, here are the links to the power supplies.

5A version
https://ram-e-shop.com/product/ps-rxn305d-ii/
10A version
https://ram-e-shop.com/product/ps-rxn3010d-ii/

Thank you all in advance.


texts: How does a cable insulator prevent energy loss?

texts:
So I was watching a recent video for TED-ED titled "How to practice effectively...for just about anything - Annie Bosler and Don Greene," and at one point the speaker said the following:

  Myelin is similar to insulation on electrical cables. It prevents energy loss from electrical signals that the brain uses...

I thought cables were insulated just to protect us from getting electrocuted or to protect us from leakage current... Can someone please explain?


texts: PID Control: Controller of the type \$\dfrac{1}{s+k}\$

texts:
In PID control an integrator action is represented by \$\dfrac{1}{s}\$

Does anyone know what would be the effect of using  \$\dfrac{1}{s+k}\$ instead of \$\dfrac{1}{s}\$, where \$k\$ is a constant? What would this controller be called?


texts: Use of clock in SDC style IO constraints for FPGAs

texts:
Question on use of clock in SDC style IO delay constraints

The intention of this write up is to cast some clarity on how an FPGA IO interface has to be constrained. As a preamble the two timing constraints which can be used for constraining an FPGA IO interface are:

set_input_delay

Usage:  set_input_delay  [-add_delay]  -clock    [-clock_fall]  [-fall]  [-max]  [-min]  [-
reference_pin ] [-rise] [-source_latency_included]
set_output_delay

Usage:  set_output_delay [-add_delay]  -clock    [-clock_fall]  [-fall]  [-max]  [-min]  [-
reference_pin ] [-rise] [-source_latency_included]

The set_input_delay constraint makes sure that an input to the FPGA from an external chip meets the internal setup and hold requirements. Similarly the set_output_delay makes sure that the data driven from an FPGA meets the setup and hold requirements of the external chip. The constraints use various timings like [tCO tSU tH] of the external chip, PCB trace delay, clock skew etc for the estimation. These stuff are pretty clear to me except the "use of clock". Here starts the confusion!

Both the constraints specify the delay values with respect to a clock. Now comes the concept of a virtual clock, a clock which feeds the external chip and not existent inside the FPGA. I have seen Intel FPGA(previously Altera) documentations prescribing the use of a Virtual Clock for constraining all IO interfaces. But it did not make complete sense to me till now!

Regarding the clocking, there are two cases I'm interested in. Please check the attachement for the drawings.

Case 1: If I have source synchronous interface like an SDRAM or QSPI interface the FPGA internally generates the clock for the external chip. In the figure clk_ext and data are sent from the FPGA. So should the SDC constrainting use a virtual clock or a generated clock from FPGA?
Case 2: There is an external clock synthesizer feeding the FPGA and the ASIC clocks. The clocks clk_osc_fpga and clk_osc_asic may or maynot be related as far as we are concerned. But there is indeed a data flow from the FPGA -> ASIC. Note that the data generation inside FPGA is done using clk_int which is not sent out! So is this where we should use a virtual clock? And how would the timing analyzer model the skews or frequency differences in the virtual clock with respect to the internal fpga clock?

I would appreciate any advice on this. And thanks for reading a really long question.

Update on the Question:

In one of the designs, I was able to estimate the latency of the clk_int with respect to the clk_osc_fpga. I found it to be around -1.3ns. So basically this means that the virtual clock or clk_osc_asic is propagated advance with respect to fpga internal clock clk_int.
The question is how do I constrain this latency? Should I use the set_clock_latency on the virtual clock? Or just adjust the phase of the virtual clock when using create_clock constraint? Also how to specify the sampling edge of the virtual clock?

Thanks again for the support.


texts: What happens to the windings on a transformer during tap changing?

texts: I'm trying to figure out what the windings do when a tap change occurs on a power transformer. The picture below is my understanding of how tap changing occurs when there is an increase in load on the TX. When the load increases and the volts drop on the secondary side of the TX. To compensate for that drop, either the Primary volts will need to increase or the primary winding will need to have some of its windings removed. In my calculations I removed a percentage of the windings to compensate for the volt drop. Does this picture explain correctly how tap changing occurs? Realistically I'm sure the primary volts gets reduced a bit as well but will it reduce as much as the secondary volts on load? I understand in the real world you would have a three phase either star and/or delta connected system, I just represented it as single phase for simplicity. P.S The value 10.75KV is just an arbitrary value chosen for the Vd. Thanks.


texts: How can I figure out the voltage in this circuit?

texts:
I'm supposed to use nodal analysis.

Node A is the left one, node B is the middle one and node C is the right one. The bottom one is my reference node.

So I got these equations:

Node A: \$ -5 + \dfrac{V_a-V_b}{20} + \dfrac{V_a-V_c}{50} = 0 \$

Node B: \$ -\dfrac{V_a-V_b}{20} + \dfrac{V_b-V_c}{30} = 0 \$

Node C: \$ -\dfrac{V_b-V_c}{30} - 0.01V_1 - \dfrac{V_a-V_c}{50} = 0 \$

\$V_b = 0.4V_1\$

I tried solving the system with these equations but I didn't get anywhere.

What am I doing wrong?

The answer is: \$V_1 = 148.15 V\$


texts:
I am building a "DIY Cellphone" project (http://2loo.com/ax). I have ordered all the components in the Bill Of Materials (http://2loo.com/ay). I put together almost everything when I stumbled upon a component that I don't know what it is. It is the component in the figure below (Taken from: http://2loo.com/aw). I think it says "D" or "0" on it. Is that a capacitor or a jumper?

According to the cellphone schematics (http://2loo.com/az), one capacitor and two coils are supposed to be there. However, those are missing from the bill of materials and are also missing from the figure above.


texts: using an "isolated DC/DC converter", what is the schematic?

texts:
I'm trying to use a "isolated DC/DC converter" (5v --> 12v converter)

(MEE3S0512SC, http://www.mouser.com/ProductDetail/Murata/MEE3S0512SC/?qs=%2fha2pyFadugniRNbNhQpOV6aGeFGH%2fTBs%252bIW10C7AdACaF1cHtE9jQ%3d%3d)

Reading the data sheet, I've connected as such:

pin 1 (Vin-): +5v DC from power supply

pin 2 (Vin+): GND from power supply

pin 3 (Vout-): voltmeter GND

pin 4 (Vout+): voltmeter +

I'm reading 30V on the voltmeter. What am I doing incorrectly?

Many thanks in advance,
Matthew


texts:
The aim of the circuit is to enable/disable power to an IC (U2) using a transistor (Q1) to enable/disable ground, controlled by an MCU (U1). However, when the ground is disconnected, it does not shut off the IC. I.e. U2 is behaving as it would if it was powered normally.

If the Rds of Q1 is measured (when power is applied to the board), it is low when the transistor is enabled (a few milliohms), but when Q1 is disabled, Rds is higher, but much lower than I expected (a little less than an ohm).

There are more inputs to U2 from U1 and these are all set to HIGH, in case there were any leaks that could cause a ground connection.

What am I missing here?

Thanks,

Components

U1: Atmel ATxmega32E5
U2: Laird BL600-SA
Q1 & D1: TI csd16301q2


texts: Voltage divider not functioning correctly

texts:
I have a Raspberry Pi connected to an MCP3002. It's power and Vref is taken from the Pi's 3.3V

I also took a two 1M resistors to form a voltage divider on the 5V connection to create 2.5V. Then on the pi I test the voltage using this code http://www.raspberrypi-spy.co.uk/2013/10/analogue-sensors-on-the-raspberry-pi-using-an-mcp3008/ but without the temperature conversion.

However, when I connect the voltage divider up to the ADC I get 0.7-0.75V

    #!/usr/bin/python

import spidev
import time
import os

# Open SPI bus
spi = spidev.SpiDev()
spi.open(0,0)

# Function to read SPI data from MCP3008 chip
# Channel must be an integer 0-7
def ReadChannel(channel):
  adc = spi.xfer2([1,(8+channel)<<4,0])
  data = ((adc[1]&3) << 8) + adc[2]
  return data

# Function to convert data to voltage level,
# rounded to specified number of decimal places.
def ConvertVolts(data,places):
  volts = (data * 3.3) / float(1023)
  volts = round(volts,places)
  return volts

while True:

  # Read the light sensor data
  ADC_volts = ReadChannel(0)
  digital_Volts = ConvertVolts(ADC_volts,2)
  print digital_Volts

simulate this circuit – Schematic created using CircuitLab

I've been doing this all morning, I recently put this back together, and it worked.
I am planning on using this to connect a piezo but I need to bias the signal with to centralize it.
Is it a problem with the code, or my set up.


texts: Create an audio cable with 100k ohm resistors

texts:
Please keep in mind I am a beginner.  Hopefully my terminology is correct.

I've purchased a new product called a Mighty, which is sort of like an iPod but it streams music.  It works great with a set of headphones, but I tried plugging it into my car's Aux input and nothing came out.  Doing a little research, I discovered that there is something with the impedance of the output jack.  it requires an aux cable with an impedance less than 300, which apparently a headphone provides but a stereo extension cable that you would plug into an Aux jack in a car does not.

Is it possible to add 100k ohm resistors to a standard Aux cable?  I'm trying to find a pic or diagram online on how to do this as it seems like something a beginner can accomplish, but I can't find one.  or am I totally wrong in thinking this would work?


texts: Why are my microcontroller and CAN transceiver failing?

texts:
I have a PCB with a dsPIC 30F6012a and a TI ISO1050 isolated transceiver. This is a combination of devices I've used regularly. The two chips' CAN TX and RX are wired directly to each other with no other components attached to those traces. I've had these boards operating correctly for weeks without issue.

In the last eight hours, I've seen two identical failures on two separate instances of my PCB. The TX line from the processor to the transceiver ceases to look like a series of pulses. Instead, it looks like a 5V rail with pulse excursions to 4V. When I cut the connection between the processor and the transceiver, the processor end is trying to drive pulses high to 5V and failing (I get ~1V pulses), and the transceiver end is solid 5V.

I've changed some of the firmware in the last day or so, but nothing concerning the CANbus rails. The hardware hasn't changed at all. Even if the code had some unanticipated effect, I don't immediately see how firmware could be causing this problem. Does anyone have any suggestions?


texts: Question about the accuracy of integrated resistors

texts:
I'm studying the implementation of resistors in integrated technology. In particular the books deals with the accuracy of the obtained resistors. It says:

Then it says:

"We observe that the value of the resistor depends on four parameters that are
achieved with independent technological steps. Therefore, to estimate their
accuracy we assume them to be statistically independent." and it comes out with the following equation:

The question is: what is the meaning of this equation? How is it mathematically derived?


texts:
Disclaimer: I'm not an electrical engineer, and most of what I've done so far has been from researching similar designs on the interwebs. I'm just a tinkerer with a soldering iron, so please excuse my lack of knowledge.
Objective: Replace 12V (10 x 1.2V NiMH) battery wand for Somfy motorized shade with 4S lithium ion (4 x 18650) battery pack. In order to prevent the new battery pack from over-discharging, I need to create a soft latching low voltage cutoff circuit to cut the power when the total voltage reaches 13.2V (3.3V per cell). The circuit should use minimal power at rest, and no power after it has cut the power to the pack.
Problem: Almost all 4S BMS boards allow the voltage to drop below 3V per cell which I consider to be too low. I have a circuit that works in LTspice as well as on a breadboard, but it doesn't work in practice. I'm guessing that when the motor is engaged, the voltage dips below the cutoff point and the circuit is cut. Here's the circuit:

Additional Info:

I'm not concerned about charging. The pack will be wired properly to allow me to charge and balance the pack properly.
Yes, I know that a 4S lithium ion pack is greater than 12V. See Bonus Objective 2 below.
If you feel strongly that I should allow the cells to drop below 3.3V, please explain why.

Bonus Objective 1: Is there a simple and cost effective way to cut the power based on the voltage of each individual cell rather than the entire pack? In other words, cut the power when any cell reaches 3.3V?
Bonus Objective 2: Even though the Somfy motor is quite tolerant of voltage over 12V, I'd like to include a buck converter in the circuit to provide a steady 12V output without draining the battery at rest.


texts:
Cleaning out some OLD (30-40 years) parts drawers, I came across a few of these parts:

14-pin DIP
package is 3 layers, black layer in between 2 white layers (ceramic ?)
marking says "STACKPOLE 14-13-1-R  1K" and "7711" perpendicular to that

Nothing useful googlable. Doesn't really matter - I'm just curious.   I vaguely remember it's integrated resistors of some kind.


texts: What is the impedance in a theoretical LC circuit?

texts:
While writing a paper about an experiment I am conducting, I was wondering how inductor-capacitor circuits theoretically behaved. In theory, we assume that wires and components that are not resistors have zero resistance. The resistance of the inductors and capacitors would also be zero. If we had an inductor and capacitor in series and an ac power supply connected which inputted, say, a sine wave, wouldn't the output to ground be a similar function with the same amplitude?

The reason I ask this is that the ac input function damps (decays to zero)when there is resistance in the circuit. And with these circuits, there exists no resistance to decay the function. Whether the circuit is underdamped or overdamped is not a problem, but the main question I have here is about the impedance in these circuits.

In theory (assuming superconductivity), since there is no resistance and thus purely imaginary impedance, would the signal oscillate forever between the inductor and capacitor in an LC circuit?

If I think about it myself, the answer would be yes. But I believe there is a nuance I am missing or a false fact I am assuming.

Thank you.


texts:
I've made a dual supply using two 9V batteries, and I want to make an on/off switch for it. I know how switches are connected with single batteries, but I'm not sure how is it done with dual supply. Here is a picture of the dual supply connection.

Any idea on where the switch should be connected?


texts: Inductive proximity sensor and target design

texts:
I am thinking of using the LDC1612 by TI to sense position over a 0 to 10mm range with an accuracy better than 100nm. I have been told this is possible by a TI engineer.

However, my question concerns relative dimensions of coil diameter and target. I am especially concerned with linearity of response, or the ability to linearize it either in circuit or mathematically.

Diameters - Is it best to have a coil>>target?

Does anyone here have any experience with this type of sensing?


texts:
I am developing a product using the BLE NANO (nrf51822).  Here is a pin out diagram:
I was following some tutorials and they said to use PWM out of an analog pin to make sounds with a buzzer (I was debating on using  po_29 for this).  Currently I am using a digital pin out for an LED though (po_28) and I thought I'd try hooking the buzzer up to that.  When I did the buzzer made noises just as expected.  So my question is: is there a reason to use an analog pin / PWM for a buzzer or is it the same as just using a digital pin?


texts: how to interface HCPL-3700 optocoupler to an input pin of ATmega16L

texts:
I want to detect logic of the mains supply (230VAC, 50Hz) and feed the output of HCPL-3700 into ATmega16L. I read through the datasheet but could not understand how to calculate the resistor values. Does anyone have an idea of how to go about doing this?

EDIT 1

I am referring to application note on HPCL-3700, page 5 under AC Operation With No Filtering

Assuming 60% criterion, 230 x sqrt(2) x 60% is 195V.
choosing closest whole value of 200V instead of 195V.

Rx = (V+ - VTH+) / ITH+
   = (200V - 5.5V) / 2.5mA
   = 38.9 Kohms.

choosing round figure of 40 Kohms for Rx. I can use two 22 Kohm resistors.

Calculating power dissipation in 22 Kohm resistors
P = (I*I) * R
  = (4.4mA * 4.4mA) * 22K     (where 4.4mA is Iin)
  = 426 mW

So, choosing 22 Kohm resistors with 500mW power rating.

How does this answer look? I think I'm wrong because there are few things that still don't make sense.


texts:
I'm designing a Colpitts oscillator with a single supply rail-to-rail opamp powered with 3.3 V. The positive input of the opamp is set to VDD/2 to offset the negative part of the oscillations so everything stays between 0V and 3.3V.

I have to make a few design considerations and I'm wondering which one is best and why.

What would be better and why, to attach the capacitors to the virtual ground or the real ground? Both circuits work (simulation) but I wonder which is best, I have a small preference to the second circuit because then the virtual ground opamp doesn't need to deliver much current.

I already read following post. Can oscillators be made from a single supply?

Virtual GND = VDD/2

Real and Virtual GND combined


texts:
This is the first time I am working with an image sensor. I have the datasheet of the ICX282AQ. But I don't understand much. What I would like to do is:

Can I drive this sensor with an Arduino board to send data to my computer? Any device/chip is needed more to drive this sensor?
Any tutorial to drive it, any open source, designed board?


texts:
I am working on a 140W class D amplifier for my subwoofer. I am familiar with its topology but have few questions.

The music source is a radio that ouputs 200mV peak-to-peak signal containing all frequencies (there arent seperate outputs for subwoofers and other speakers).

I have it currently set up like this:

source->op-amp preamplifier->ADC->microcontroller PWM signal out->H-bridge + LPF

1) Since this is an amplifier only for a subwoofer it only plays on frequencies from 20-200Hz. Do I need a LP/Bandpass filter:

Before the preamplifier
After the preamplifier
Or should I design LPF for H-bridge with cut-off frequency at 200Hz
Something else?

2) Microcontroller PWM signal will have a frequency from 30-50kHz. How should I go about designg LPF for H-bridge considering the speaker will play only frequencies to 200Hz?


texts: Can I power Ardiuno using buck converter IC 3485 or any other buck circuit?

texts:
A buck circuit lowers the voltage by generating pulses at a certain duty cycle. Is it okay to give this pulsing voltage to Arduino? Can Arduino work normally with this?

I have 12V battery and I want 6V from that.


texts: VHDL Counter does not update when desired

texts:
For a project I am working on, I require a counter whose value increases as soon as the increment control goes high (i.e. on the rising edge). However, I have had trouble implementing this in VHDL.

Here is some code that I have written:

IF Reset='1' THEN
        count := 0; -- Asynchronous reset
    ELSIF rising_edge(clock) THEN
        IF Enable = '1' THEN
            count := count+1; -- Increment
        END IF;
    END IF;
    q <= std_logic_vector(to_unsigned(count,12));

Here is the ModelSim simulation waveform:

As you can see, 'q' is only updated one clock cycle AFTER the Enable input goes high. I want q to increment as soon as Enable goes high. Is there a way to do this?


texts: Is there any way to generate the following exponential outputs in oscilloscope of multisim?


texts: Can i bypass the builtin rectifier and directly supply dc to my microphone preamp and reverb board

texts:
I currently have this mic preamp and reverb board that accepts 12-0-12 ac:

original

I have a 24v 10a switching supply and i found a way to create a 12-0-12 dc using this tutorial on youtube

Would it be possible to bypass the built in rectifier and just use my diy dual dc circuit? Thanks


texts:
Im working on TI based processors now and they have 2 types of Interrupt configuration(FIQ or IRQ).I have seen such interrupts before when i was doing a hobby project using a LPC1778 but since i didnt use interrupts i didnt mind them.
I need to use them now for a project and its essential that i find out the difference so that i can use them appropriately.
Both are interrupts but what makes them different such that they are identified with two seperate names?

Any help would be great.

Thanks.


texts: How to safely use a transistor to control fans

texts:
I'm working on a project where I control two 12V 80mm fans with an ESP32. I've taken inspiration from various blog posts about fan control on the Raspberry Pi with a transistor (e.g. https://fizzy.cc/raspberry-pi-fan/).
As depicted in this blog post, the transistor is used to control GND connectivity of the fan, to switch it on/off.
The resistor used to "protect" the transistor varies a lot depending on the source (from none, to 680 Ohm, to 1kOhm as used here).
I'll be using the power from a USB power supply (5V out) and a step up module (to ~7V) and control the GND connectivity via the ESP32. Now my problem is, that I find no explanation on how to calculate the appropriate resistor.
Question: How can I calculate the value for the resistor, to safely operate the transistor (BC547B, Bipolar Transistor, NPN, 45V, 100mA, TO-92, 3-pin)?
edit: I would also have a PN2222ABU transistor available.


texts: Problem connecting transistor, flybackdiode and relay

texts:
I am a new person with tinkering electronics as I am from Computer Engineering.
I am working on a project with arduino that consists of a relay, I researched from the internet and found out that a suitable relay configuration uses a transistor, a flywheel diode and a relay.
I used a 2N2222 transistor a 1N4007 diode and a 12V Relay (SRD-12VDC-SL-C).
I used the following schematic.

and here is my fritzing schematic.

When I connected the circuit accoring to my fritzing schematic the labelled NPN transistor blew up in smokes,and when I readjusted some wires next the transistor on the relay blew up in smokes.
Please help me the circuit diagram as I am not able to understand it properly and I guess that the fritzing schematic is wrong.
EDIT 1:
Blue Wire-Data line from arduino.
Red Wire-VCC.
White Wire-GND.


texts: What is the best Arduino Operating System?


texts:
The ATX specification includes a -12V (and an optional -5V) rail on the main power connector.

What are these negative voltage rail used for on the connected circuits?


texts: I recovered a few capacitors of this style from an old cassette player. As far as I can tell, it seems like Mylar film, but the “100⊖” marking has me wondering. Is this some peculiar shaped tantalum capacitor, or is the indicator not a polarity marking?


texts: Does MSP430 and AVR have internal pull-up on UART's RXD line?

texts: Suppose a device with MSP430 or AVR microcontroller and floating UART lines (e.g. to external connector). Need I add an external pull-up to the RXD line?


texts:
How would I configure an op-amp to filter out the negative portion of a signal. Would it just be to put the negative supply of the op-amp to ground? I wish to do this with the 200MHz EL1801 op-amp to remove the negative sync from a 75 ohm RGB video signal which will be atleast 150MHz.

Datasheet: look for video sync remover on page 10

http://www.intersil.com/content/dam/Intersil/documents/el81/el8100-01.pdf

Application note: explains how to restore dc level.

https://www.intersil.com/content/dam/Intersil/documents/an95/an9514.pdf


texts: Why use an external resonator with an ATmega microcontroller if it has one built in?

texts:
Why should I use an external resonator with an ATmega microcontroller if it has one built in?

I'm specifically referring to many of the 8 MHz Arduino boards. A lot, if not most, have an external ceramic resonator, but the chip has a built-in one so what's the benefit of using an external one?

Arduino Pro Mini


texts: What will happen if P-channel Enhancement type MOSFET gate kept open while connected as diode in real case

texts:
[

I am using MOSFET as diode for polarity protection of system. Vehicle supply of 12V is applied to drain & system is connected to source. Gate kept open purpose.
I have simulated attached schematic on LTSPICE with following graph as output.
It works as diode as expected even if gate is floating.

I want to know what will happen in real case if gate is kept open / floating?

I have modified circuit referred in Application Note to check how circuit works in simulation

Application Note: Infineon - enter link description here

Part No. (RRS140P03FRA) - P Channel Enhancement type MOSFET


texts: Bootstrap capacitor calculation - Which formula should I pick?

texts:
In order to calculate capacitance of bootstrap capacitor, I searched around and found two different formula from Ti and Infineon. The Ti version states:

while Infineon version say:

I think the basic idea behind these two formulas are same: dividing maximum charge may loss when high side MOS conducting, by minimum change of voltage. But I failed to figure it out on myself that why \$Q_g\$ was multiplied by \$2\$ in Infineon's version and again the whole numerator was doubled.

So far the Ti version makes more sense for me as \$Q_g\$ itself is the charge we loss in a switching cycle and also OnSemi seems to give similar formula (pg 5). But I believe there is some reason why Infineon engineers write this formula. I am currently studying how to design half bridge driver and I have selected IR2103 from Infineon. And that's why I want to ask which formula should be used and why?


texts: I amplify a signal which including AC and DC.Why is the output waveform changed when C1 is 0.1u?And how to decide the value of C1?


texts: If LEDs in a series begin to lose intensity and die is it too much voltage or too much current?

texts: If a series of LEDs I adapted to work off the 5VDC coming from a USB outlet start to lose intensity and a couple have died out, what has happened? Is the voltage too high for the series? Or is the current too high? And would putting in a resistance prevent the remaining LEDs to completely die out too? (I'm guessing that once LEDs start fading out, there's no way to turn back the damage already done.)


texts: BJT vs Mosfet, switching variable current battery powered device

texts:
I have a device that runs on voltage between 3v and 3v3 and consumes current anywhere between 4mA and 50mA. The device is powered from a battery with a 3v3 regulator.

I need to design a circuit that can switch on/off the device and I can not decide between a BJT and a mosfet for switching.

If I use a MMBT3904 npn transistor, I will have to keep base current at approximately 1mA so that It can drive the device at its maximum current consumption of 50mA (with a gain of 60). It seems like it would be very inefficient when only 4mA of current is required. Also there is the Vce voltage drop which the datasheet says can be 300mV at Ic=50mA. Voltage drop greater than 300mV will cause my device to malfunction.

As far as mosfet is concerned I can not seem to find a mosfet that can drive 50mA with Vgs of 3.3v.

My electronics is a little rusty and It does not seem to me helping me.


texts: Ideas to measure 2D position of an object constrained to X-Y plane

texts:
I am working on a project, and an aspect has come up where I would like to measure (track continuously) the X and Y position of an object across a 2D plane. The object is moved by a person, with the object's movement constrained to the 2D plane (so no Z-axis displacement).

Constraints:

I would like measured position resolution of 1 mm, ideally 0.5 mm or better.
The space over which the object moves is 30 cm X 30 cm.
Whatever method of measurement I use shouldn't significantly constrict the movement of the object.
Also, please just assume that the plane on which the object moves is air, and NOT an actual solid surface (for project-specific reasons that are hard to verbalize).
The good news is: The object is completely OK to be modified as necessary (LED on top, or string attachments, or anything else).

What might be a method to get that kind of resolution?

I am considering various approaches, but I don't know if any of them will fulfill the resolution requirement. Since there aren't many constraints on my existing system, I am OK with even a complex / bulky implementation, just as long as it's precise enough.

Here are a couple of my ideas so far:

(1) Infrared-based range sensors (only need two actually)

(2) Two long calipers/micrometers connected from the object to the sides

(3) Two strings, each connected from the object to a freely bending strain gage leaf on the side


texts: Cheap soldering flux causing QRE1113 circuit not working

texts:
Edit (months later): Coming across this silly question I posted months ago, I want to talk about what caused my problem actually. My cheap soldering flux did that. After being heated up, it would flow below resistor arrays, and short out the resistor pins because it is cheap and it will have low impedance after being heated.

And what I learned from this story is: buy good quality soldering flux and soldering wire, as they also have flux inside, if anyone want to solder small package chips. This problem, I believe, will not only cost a lot of time to figure out for anyone new in electronic but could hardly be corrected by others on the web as well. Which, of course, will make him/me feel sad because everything works in theory but not on PCB. That's the reason why you may want to spend more money on these clean free soldering flux/wire from big brand and save your day.

recently I made a prototype IR tracking board by referring SparkFun Line Sensor Breakout and here is pictures of the PCB.

(The three in the middle was not soldered because I want to see if they could improve performance later). After powering it up with 3.3V, I found things worked well and my oscilloscope showed nice waveform like that when I move my finger close to QRE1113.

However, things stopped working just in minutes. Although some output still lives, U1 will not go down to GND when I cover the sensor and pins relate to U5 ~ U7 output awful waveform like that

So far I am quite confused and do not know exactly how to locate the problem and how to debug my board. Thanks for any guidance.

My schematic:

p.s. I have uploaded my Eagle schematic and board files to Google Drive.


texts: ADS Gives Negative Input Impedance in Transmission Line Simulation

texts:
I am trying to get a very simple transmission line input impedance simulation right in ADS, but the result gives a negative real part of the impedance. This should be impossible. Any advice on how to fix this. Here are some screenshots.
enter image description here


texts: Understanding/analyzing a power supply circuit

texts:
simulate this circuit – Schematic created using CircuitLab

I'm having some problems with this exercise, it is given:

$$V_1=220V_{rms}/60Hz\\\frac{V_2}{V_1}=1/15\\C=0,5mF\\R_L=12V \text{ and }1200mW\\\text{Led: }I_F=15mA \text{ for }V_F=2V\\\text{Voltage Regulator: For }15V<V_i<27V \rightarrow V_0=12V$$

It askes for the graph of \$V_i(t)\$, the resistance \$R_{Led}\$ and the voltage amplitude in the capacitor. The diodes are ideal (0V drop) and despise the regulator consumption.

Now I'm having problems with the following:

1) What is the meaning of the two expression: \$R_L=12V\$ and \$1200mW\$, \$\text{Led: }I_F=15mA \text{ for }V_F=2V\$? For the resistor is it the power when the voltage is 12V? For I is it the current when \$V_f=2V\$? If it is it doesn't make much sense since \$V_0=12V\$ always. Could I just multiply by 6 to get current for 12V?

2) It seems that I have to calculate the voltage on the capacitor? If so (and even if don't), I know the formula for the voltage according to time \${\displaystyle V(t)=V_{0}(1-e^{-t/\tau })}\$ (charging) but I've only applied to circuits with one resistance, how to do it in the circuit above? I imagine that would something more complex than calculating the equivalent resistance in parallel or series.

Excuse me my english and I appreciate any help I can get.


texts: What kind of switch (SP4T) is ok for short periods (100-200us) of 85V, 16A?

texts:
I am looking for a switch that is a SP3T switch that can handle 85VDC and 16A.  The 85V, 16A reqiurement is only for short periods of time (100-200us). The switch I need to use will connect a PU, PD, and load (injector).

I am looking for something somewhat cheap because I found some that are close 125VDC and 15A, but these are like $80 a switch and I need 15 of them. I am not really sure if it is necessary due to the short on-times (specified above).


texts: Solar cell powered supercapacitor charger with strange output voltage regulator problem

texts:
I have a strange problem in a low power circuit design. I designed a buck-boost converter as a maximum power point tracking circuit (control the output of solar cell within a small voltage range within +/-5% of its maximum power point) for small solar cells (3.5V 0.2mA typical output in indoor light condition). The buck-boost converter works fine. The output is used to charge a supercap with 2F capacitance and 2.5V voltage rating.

Then I figured I need a regulated voltage at the output end (3.3V or 5V). So I used a TI TPS61221/2 boost converter as the output voltage regulator.  I found out that, for large capacitor such as the supercap, there is a problem during the startup. When I start to charge the supercap from 0V to 2.5V, the TPS6122x will try to start up when supercap voltage reaches 0.8V, but it will fail to start up and the voltage will fall to 0.6V. The oscillation will repeat over and over again, and never start up correctly.

So I decided to include a "startup" circuit using a MAX9064 comparator and a TI TPS22902 load switch. My idea is that it will only start to connect the supercap output to TPS6122x when the supercap (SC) voltage is higher than 1.5V. (There is hysteresis I set on the comparator for a rising edge 1.5V, falling edge 1.0V, but I didn't draw it in the schematics here. Input and output capacitors for TPS6122x do exist, but also not draw in this.) The min Vcc for MAX9064 is 1V. I connected (with diode) from solar cell, TPS6122x output and supercap to a "Vcc capacitor" in order to get C2 a >1V voltage during start up. Pull down resistor used on the output of MAX9064 to ensure a low on the TPS22902 enable. See the attached picture.

However, funny enough, this circuit sometimes works sometimes not! Which means it still have the strange oscillation at 0.8V when I explicitly disconnect it with a load switch. Nothing should happen before the supercap reaches 1.5V. But if it is always like that, I'm going to change the circuit. But then I found out, many times it works just fine! It goes to 1.5V and start up the TPS6122x. I'm very confused that is there a problem with the set up? What could cause this funny problem? Pull-down resistor? Load switch problem? Vcc? Or supercap itself?


texts:
We want to design a telecom compatible power entry circuit with 48V 20A rating for a student project (design of a telecom equipment with 48V DC input power) using PAN4820 devices.
The schematic diagram of the design is attached. All parts are rated for 200V.
The problem is that in the PAN4820 datasheet, the test voltage is 100V but in our design MOVs’ maximum clamping voltage is around 165V.
I would like to know whether PAN4820 supports surge voltages around 160V for short periods of time (8/20us) or not. I could not find such a thing in the filter’s datasheet.
Thanks in advance


texts: Unwanted switching noise on the output of the MCP16417 (DC-DC, step-up converter)

texts:
I want to use the MCP16417 step-up DC-DC converter for a low power battery powered project. Before implementing the design on a PCB I wanted to try the chip and built the circuit (top circuit on page 2 of the datasheet) on a breadboard (I use the MCP16417 in a MSOP form factor and soldered it to a adapter board). Unfortunately I get lots of noise on \$V_{\mathrm{out}}\$ (see pictures below).

Compare to fig. 2-31 on page 12 of the datasheet.
I used an axial inductor and an \$10\,\mathrm{k\Omega}\$ axial resistor as a load. All connections on the breadboard (and the leads of the inductor) were shortened as much as possible.
Why do I see switching noise on \$V_{\mathrm{out}}\$? What can I do to make smaller? Is it just a problem when implemented on a breadboard (parasitic inductance/capacitance & coupling)?


texts:
Trying to fix an old transmitter from some rc toy, I may have removed the crystal oscillator some 4~5 years ago so I can only guess it was either 27Mhz or 40Mhz.
I tried 27Mhz crystal oscillator (I don't have 40Mhz) but the transmitter didn't work on any toy that have an rc receiver (tried many), working transmitters read high (2.xx volts) on antenna, mine does not.
Transmitter uses SM6136B ic, very similar to TX-2B and have same pinout. I have seen circuits that use 27Mhz oscillators with these ics but the circuits are entirely different, anything I can do to make/modify it to work? IC appears to be fine as it does output voltage on SO pin (pin 8) when any of the switches are pressed.
Schematic: (Added missing ground and some fixes)

PCB Front and Back:

Congested part with components:


texts: Microelectronic Circuits Sedra Smith (drawing tool)

texts:
I'm looking for the tool used in the reference "Microelectronic Circuits" (or similar) to draw the circuits. e.g. For the n-channel enhancement-type (circuit symbol c).

Any help?


texts: What would be the output of A = 0100 and B = 0111 with S = 1 in a 4-bit binary adder-subtractor?

texts:
I understand S = 1 means subtraction and S = 0 means addition.  So then, the output would be the result of 0100 - 0111.  But since it's negative, I'm not sure how it would be represented.  I know the answer is -3, or -11 in binary, but what would be the output in the adder-subtractor?

I think what's getting me is what goes on in the circuit in the blocks labeled "FA", and what happens with the final carry bit (if it's 1 of course).  I do understand how to do binary addition and subtraction.

(source: kfupm.edu.sa)


texts:
My question is: why we say that   in  three phase system  total power delivered to the balanced three-phase circuit is the same at any instant?. This is how I understood that one phase at one point of time  gives all the power then the second and third and so again from the beginning I do not know if my assumption is correct and I would like to hear your opinion.

thanks.


texts: Sensor to rapidly sample light intensity of a small area at a distance?

texts:
I'm looking for a sensor or method of rapidly sensing light intensity of a 1-inch x 1-inch square of a LCD monitor at a distance of 1-1.5 feet away. Does anyone know if such a thing exists, or has experience with this challenge?

I've considered using a standard photocell with some sort of zoom-lense, but I don't have enough experience with senses to put one together, and haven't found anything pre-built.


texts:
I have a SmartPill DataRecorder with an SMD antenna connector inside (434MHz antenna.)
This is a photo of the SMD RF connector that I’m trying to identify:

Frontview:

Side view:

I tried to connect a 434MHz antenna with a UFL pigtail, but the pigtail of the antenna is too tiny for the SMD connector of the data receiver.
To me (but I’m not sure,) seems to be the same type of connector as the one on the antenna (U.FL (UMCC), IPEXMHF1), but bigger.
Can anyone help me identify the SMD RF connector and the relative pigtail mate?
The diameter of the connector is about 3 millimeters.


texts: How much current will I get from the 5V rail of a Teensy 3.2 powered over USB?

texts: The microcontroller in question is a Teensy 3.2. My understanding is that the most current that you can get from a standard computer USB port is ~180mA; how much of that will current devices attached to the Teensy's Vin (+5V in the case of USB power) receive?


texts: Reverse of referencing everything from ground

texts:
Say we live in a world where p-type carriers just have more mobility and therefore switches faster than n-types, so we'll favour PNP's and PMOS's. So in such circuits, we reference everything from the supply with more positive electric potential, instead of ground. What kind of system to we call those types??

I've been Googling for techniques with that sort of system, but it's coming out with nothing.

EDIT:
In case anybody asks why I needed to know, I simply need to invert an analog signal from Vx voltage from ground to same voltage difference in reference from Vsupply. I'm working with MOSFETs and please don't ask me to use a Common Source or a ready made Opamp.


texts:
I need to implement a circuit but Im having some trouble since Im novice on electronics.

I have 4 inputs. A being ON/OFF switch. B is an Inibitor. C is an Emergency and D is not an adequate ocasion.

In order to turn off the lamp I have to meet 2 conditions.

Condition 1: Switch is ON (A), Inibitor is OFF (B) and the ocasion must be adequate (NOT D).
Condition 2: Emergency is ON (C). This one is independent and will always turn on the light as long as it is activated.

simulate this circuit – Schematic created using CircuitLab

I did this schematic. NOR only outputs 1 when both are 0, which means INIB off and D is adequate. Then join with On from Switch with AND and light is ON.

This is represent by A(NOT)B(NOT)D. Now I only need to add the C variable which is independent.

The final equation is A(NOT)B(NOT)D + C. Am I thinking right? Sorry if this sounds stupid but Im still learning and a bit confused!

Thanks in advance.

\begin{array} {|r|r|}\hline C & A & B & D & X \\
 \hline 0 & 0 & 0 & 0 & F \\
 \hline 0 & 0 & 0 & 1 & F \\
 \hline 0 & 0 & 1 & 0 & T \\
 \hline 0 & 0 & 1 & 1 & T \\
 \hline 0 & 1 & 0 & 0 & F \\
 \hline 0 & 1 & 0 & 1 & F \\
 \hline 0 & 1 & 1 & 0 & T \\
 \hline 0 & 1 & 1 & 1 & T \\
 \hline 1 & 0 & 0 & 0 & T \\
 \hline 1 & 0 & 0 & 1 & F \\
 \hline 1 & 0 & 1 & 0 & T \\
 \hline 1 & 0 & 1 & 1 & T \\
 \hline 1 & 1 & 0 & 0 & F \\
 \hline 1 & 1 & 0 & 1 & F \\
 \hline 1 & 1 & 1 & 0 & T \\
 \hline 1 & 1 & 1 & 1 & T \\
 \hline  \end{array}


texts:
This has been very long since I left electronics but recently I restarted taking interest in it as hobby.

I bought some PIR sensors from Aliexpress and found it is very simple to implement if I have 5V DC supply on breadboard. I am not sure how I can hook it up to bulb (CFL or 230V LED bulb) as a complete unit.

Can some tell me, should I use 5v DC normal AC-DC step down power supply enclosed everything in small box and mount it near the bulb or is there any other way to do it. I will use 5V relay and relay driver using NPN transistor.

I am asking this because all the tutorials I have seen uses breadboard power supply or 12V DC adapter and 5V regulator IC. I did not come across with real life application using 5v drawn from mains supply.


texts:
I made a custom board using STM32F103VCT6 MCU as shown in the attached schematic below. I soldered all the components as per the schematic and powered it on. The board worked for sometime and stopped working. We found that the 3.3V line was shorted to ground which was due to internal shorting of the MCU.(It was also heating up).

Note: The main MCU, CP2102 and USB headers were SMT assembled by the board manufacturer.
So for the 2nd board i started slowly and soldered only the programming header, HSE clock, boot select, reset switch, 3.3V regulators and probed for a test signal (PWM on PA15). It was working fine. We added the circuit for CP2102 and send a test msg via UART (to CP2102) which was successfully read from a COM port on the PC. The problem began when we tried to read data directly from STM32 (CDC configuration)through the other USB header port(PA11 and PA12).
The test msg was being sent out for 5 seconds and hanged up. An error popped saying usb device was not recognized. The CP2102 was also not recognized. I was not able to flash the board too after that (using st-link utility) which sent a message that the core was held under reset. Upon probing the reset pin the voltage was held at 0.7v. The reset pin was latched at the above voltage. After allowing the board "rest" for some time , the reset pin was unlatched and i was able to flash again. But the stm32 was still not recognized as an USB device. In the device manager it says that the device descriptor request failed.
Later i soldered an external CP2102(breakout board) and was able to communicate through it(USART1 - PA9 and PA10). But the CP2102 on the board was still unresponsive () and the USB_CDC is also not recognized
The board is supposed to read sensor inputs and send them via USB_CDC(PA11 PA12)
Note - (the cp2102 on the board was only to flash programs directly via usb).
Current status of board :

USB_CDC device descriptor failed (sometimes it shows up as COM6 but disconnects after 10seconds)
On board cp2102 was recognized as COM5 and was communicating for more than a minute and suddenly
disconnected. Later attempts at reconnecting recognizes the cp2102 but when trying to connect
immediately disconnects.
External CP2102 is working fine.
PWM was working too.
Probing D+ & D- of USB CDC has yielded the below waveforms. These waveforms were only detected when the USB was detected as a COM port.

My questions are as follows:

Is the schematic right
What caused erratic behaviour of the reset pin
Does connecting through usb cause the erratic behaviour of the board
How to check if the MCU's USB circuitry is fried

I am using CDC_transmit_FS command to send the message via USB.
HAL_Delay(200);
HAL_UART_Transmit(&huart1, msg, 3,HAL_MAX_DELAY);
HAL_Delay(200);
CDC_Transmit_FS(msg, 3);
HAL_Delay(200);
HAL_UART_Transmit(&huart2, msg, 3, HAL_MAX_DELAY);


texts:
Let's consider a transmission line (which drives a generic load ZL) connected to an AC voltage source.

If we know that the peak voltage of the source is equal to Vp, how can we evaluate the peak current (is it Vp/Z0? Vp/Zin?)? Moreover, is it possible to evaluate the peak power by knowing only the peak voltage and current?


texts: Why the shape of rotor-poles of salient pole synchronous machines are designed as sinusoidal in shape?

texts: I knew that this is done to eliminate harmonics. But I couldn't get its reason. So I am confused whether my conclusion was right or wrong.


texts:
Do USB connectors come in protected versions suitable for damp, vibration prone environments?  If so, what terms should I use when searching for them?

If not, what are my options for meeting the USB wiring and connectors standards without standard USB connectors?  Can I use different cables and connectors and "make up" for the electrical differences by terminating the ends differently?


texts:
what I want to do

To switch composite video signal inputs to one output.

conditions

4 inputs to 1 output
all inputs and output are composite video signals with RCA connectors
12VDC used for power supply
Arduino used for switching

I've been wondering which stackexhange site to post this question, https://electronics.stackexchange.com/ or https://arduino.stackexchange.com/. But this one seemed rather "electrical" to me so I chose this community.

details

I'm trying to install video cameras and a LCD monitor to my car. Something like checking rear view image when I'm going backward would be helpful. But Commercial video switchers are not cheap and touching a mechanical switch while driving is not very safe. So I'm trying to find a solution for this.

After hours of searching, my crude solution was below.

simulate this circuit – Schematic created using CircuitLab

transistors used for switching
Arduino analog port used for switch signals
a momentary switch is connected to Arduino. You push the switch to cycle through video input signals (e.g. input1 -> input2 -> input3 -> input4 -> input1 -> ... for each push)
only one transistor is "turned on" at a time. When you want to switch to other inputs, all the switch signals are turned off then the target switch is turned on.
The grounds of the inputs, switch signals and output are the same.

However, this is too primitive. So I started searching again. Here is a list of articles I checked.

How to switch composite video signal inputs to one output - Electrical Engineering Stack Exchange
audio - Switching RCA composite video, under uC control - circuit ideas & suggestions - Electrical Engineering Stack Exchange
Arduino controlled video switch - Electrical Engineering Stack Exchange

In the third one, I found out there's a such thing as video switching IC. After further searching, NJM2595 (data sheet) seemed good to me.

5-input 3-output
Operating Voltage ±4.0 to ±6.5V (I'm going to use 12V-5V DC-DC converter)
not so expensive (around $1)

Here is a circuit I'm going to implement.

simulate this circuit

EDIT : checked  @mguima's answer and revised circuit diagram

(Sorry about the messy diagram. I just tried to put inputs to the left, outputs to the right, power supply to the top and ground to the bottom.)

Note

digital output pins of Arduino used
Vin+, - at the left top are external video signal inputs.
NJM2595D (pin shape : DIP16) used instead of NJM2595M (pin shape : DMP16) due to easy mounting on PCB.
a custom built PCB used with a flat and big ground pattern to reduce noise.
resistors and capacitors around the input and output pins. I got this idea from the Application Circuit section of the IC datasheet.
decoupling capacitors after video inputs and 5V supply placed less than 0.1 inches away from the IC pins to AC couple the signal and reduce noise.
75 Ohm series termination resistor placed less than 0.1 inches away from the IC output pin to reduce the parasitic capacitance and inductance effect

Is it feasible? If not, what would be an solution for this?


texts:
In a boost converter during switch on time inductor build magnetic field and during off state magnetic field collapse.My question is during off satte inductor is connected to source voltage,so why not it building magnetic field

?


texts: What is the most popular embedded serial bus?

texts:
I'm designing an embedded device that I would like to make interoperable with third party peripherals through a serial bus. Should I choose SPI, I²C, or some other bus?

The peripherals will be pretty low bandwidth (some sensors that communicate over the bus, polled periodically) and most likely within a metre or less of the controller. The controller's sole task is to collect the sensor data, package it in some way, and then send it off to a wireless module via another bus (although the sensor bus could potentially be reused for this too).


texts:
I am looking at buying a NetDuino for some fun home hobby projects.

Have any of you used it and how was your experience?

Should i look at the Arduino or FreeDuino range instead(or something totally different)?

I decided to stick to the NetDuino due to my C# knowledge, but that is not a requirement.

Thanks

PS. I am not sure if this belongs to the community wiki or not (guidance appreciated).


texts: Circuit stable in the Bode diagram, unstable in step-response

texts:
I am designing a simple current control circuit and trying to simulate it in LT Spice. The circuit is not optimized for some real-world application, it's more a learning method for me to get grip on stability analysis.

The circuit consists of a voltage controlled MOSFET M1 and a simple diff. amp U4 for voltage measurement. The measured voltage is compared to set voltage (VSET) and the comparator control the MOSFET gate.

For AC analysis I followed the instructions from this LT Spice video, and inserted an AC stimulus V4 at the high-impedance input of U2. I ran some simulation with varying capacitance for C1 and got this nice and stable Bode:

where my gain margin was 18dB and phase margin 132°. No resonance peaks, all nice and clear. According to the theory I'm familiar with, this should be nice and stable circuit. But the moment I remove the AC stimulus and insert the DC pulse at VSET, I get the step response like this:

Now, I'm quite confused. What sense does it make to have two opposite stability outputs? Aren't trasient and ac analysis compatible?


texts: How to disable battery charging in an inverter?

texts:
I installed solar retrofit to an already existing inverter battery setup.
Now during daytime,inverter will be in battery discharge mode by converting DC from battery to AC for appliances use.While battery gets charged from solar panels during daytime.
During night, solar retrofit will not be working and inverter will work as usual. That is,inverter charges battery (AC to DC) from the grid and every appliance connected to inverter uses grid and there is no solar charging. Only when there is a power outage,battery will be used to power appliances connected to inverter (DC to AC).
Are there any ways to charge battery only by solar and not by grid?
Thanks.


texts:
I'm new the ATtiny series of Atmel MCUs and I've been trying to build a DC-DC boost converter with an ATtiny85-20PU recently.
To get started I've been trying to control the brightness of two LEDs by mapping the readings obtained using two 1k potentiometers. However only one LED responded and the other LED stays OFF the whole time.
So I did a minimal test and found out that whenever I try to use PB4 or PB2 to obtain an analogRead, it doesn't work for some reason. I'm able to get an analogRead only from PB3. The datasheet says that PB2, PB3 and PB4 are ADC channels
I'm using my Arduino UNO as ISP to program the ATtiny85 and I'm uploading the code using the Arduino IDE. I've tried looking up the datasheet and I was particularly going through the data given on the ADC unit and tried using the following.
According to the datasheet,

17.13.1 ADMUX – ADC Multiplexer Selection Register
• Bits 3:0 – MUX[3:0]: Analog Channel and Gain Selection Bits
The value of these bits selects which combination of analog inputs are
connected to the ADC.

So I tried including this in my setup,
ADMUX |= (6<<MUX0); #  this was  the bit configuration given for using PB3 and PB4 as the input channels

but had no luck.
This is my code:
int feedbackPin = 2; //Using 2 or 4 won't work.Only 3 works
int gatePin2 = 1;

void setup() {

pinMode(feedbackPin,INPUT);
pinMode(gatePin2,OUTPUT);

}

void loop() {

int v1 = analogRead(feedbackPin);
int del2 = map(v1,0,1023,0,255);
  analogWrite(gatePin2,del2);

}

I would appreciate any help in setting up the two analogReads correctly.


texts: Power Electronics for 3.3v or lower MSP430 + 10v sensor

texts:
After asking around I realized that switching regulators should be used to regulate the power going to the MSP430. I'm wondering (I'm not very informed in the topic of power electronics) how can I power the MSP430 with 3.3v or lower and a 10V load cell on the same PCB from the same power source if possible?

I've considered a combination of a switching regulator (TPS60313) with a separate battery and a linear regulator (LM317) to power the load cell with a power source of 12V or more. However that would mean that I would have to have 8 AA-batteries to run the LM317, which is a little ridiculous in terms of packaging. Also I have to consider the voltage drop off of these batteries.

Another option is to use two switching regulators: one TPS60313 for the MCU with a seperate battery (one AA battery), and another step-up switching regulator for the load cell (have not determined a specific one yet, but I have done research pointing to this list)

Just to wrap it up, my question is, which would be a better route? Pointers would be great!


texts: hc-05 arduino getting rssi value problem

texts:
Hi I am trying to get RSSI value from my HC-05 bluetooth module that is in master mode. I wrote some code but it did not work. Terminal shows nothing. Can you help me get through this? My HC-05 is in AT command mode and I am trying to get RSSI caused by another HC-05 module across the room. After I get whole RSSI entry I will parse required part somehow. I read other posts about this and they will not be of help to me.
Code:
#include <SoftwareSerial.h>
//master device 2
SoftwareSerial BT(5, 6); // RX, TX
String data;

void setup() {

Serial.begin(9600);

Serial.println("Enter AT commands:");

BT.begin(38400);

}

void loop(){

BT.write("AT+INQ\n\r");
while(!BT.available()){}
data = BT.read();
Serial.print(data);

delay(5000);
}


texts: Virtual display for simple GPU development

texts:
Related: Where to start when considering making a GPU?

I'm a pretty strong programmer, but I'm very new to hardware design, so apologies if I use strange terminology.

My long-term goal is to write a custom GPU, but I'm starting out with a basic framebuffer to get comfortable with hardware design. Here's a rundown of what I'm expecting to do with my project:

Receive a frame of pixel data on a bus
Store frame in a stack on the hardware
Output frames at the monitor refresh rate

I can figure out #1 and #2, but I've never done anything like #3. I'm thinking the optimal development setup would be to have a virtual display that connects to the output pins of my design (VGA or DVI) and displays it in a window on my computer. I could probably do this with an FPGA and a small LCD, but I'm thinking it will be easier for development (esp. travelling) to have it all simulated.

Is there already a solution for this? If so, what can I search for to get more information about it? If not, what is the usual development setup for something like this?

I'm developing on Linux using Icarus Verilog, so a solution that works with that would be preferred.


texts: Making conducted EMI measurements in the presence of building-wide ground-fault protection for personnel?

texts:
As is documented here among other places, the Line Impedance Stabilization Networks used to make measurements of conducted EMI as per CISPR 22, FCC Part 15, and suchnot contain large line-to-ground capacitances that cause significant mains frequency current to flow to the equipment grounding conductor (my computations show this current is in the vicinity of 15mA steady-state).  This means that they cannot be plugged into outlets that are ground-fault protected for personnel (5mA differential trip current as per UL 943 Class A).

In a building where GFCI protection of this nature is provided everywhere (using the NFPA 70 406.4(D)(2) GFCI retrofit provisions to compensate for missing equipment grounding conductors in an older building, for instance), how can I measure the conducted EMI of my designs, given that simply plugging a LISN in guarantees gloomy sadness?


texts: Why does the current in autotransformer motor starting gets reduced squared in relative to the voltage?

texts:
Say, relatively, the motor's full voltage rating's voltage, current and torque are 100, 100 and 100

Why does when the autotransformer tap is set at 80%, the motor runs at

80 64 64

65% and 50% as follows:

65 42 42

50 25 25

And not operating in direct proportion to the voltage?

Edit: The motor is just a 3phase AC induction motor in general


texts:
I have spotlights which go on 12V/24V distributor but every time I plug one in there is a spark, they still do work fine but it's a bit scary and just annoying when all the other ones flicker every time I plug one in (I have 8 spots connected total) and the others flicker when there is arc.
I found they have this plug for rc cars and then they can plug and there is no spark.
https://aliexpress.com/item/32784910994.html
the rating seems okso I guess they work what do you people think? Is it worth doing 16 plugs of them for all the lights and then they would be fine? Or do I just need one of them on the distributor and then nothing can spark?


texts:
I am using TWR-S08DC-PT60 board which has a MC9S08PT60 microcontroller.

I am trying to disable the watchdog timer in my application, just for ease of development. After configuring it in the software, it is disabled in the first run after programming, as wanted. However, after a reset occurs, either by reset button or power down, it is automatically enabled by itself. This happens when I debug, run or flash using CodeWarrior 10.4.

Here is how I disable it:

  _WDOG_CS1.Bits.UPDATE = 1; // Enable changes to WDOG.
  WDOG_CNT = 0xC520; // write the 1st unlock word
  WDOG_CNT = 0xD928; // write the 2nd unlock word

  _WDOG_CS1.Bits.EN = 0; // Kill the dog.
  _WDOG_CS1.Bits.INT = 1; // Enable WDOG interrupt.

From the reference manual:

  23.3.2.1 Reconfiguring the Watchdog

  In some cases (such as when supporting a bootloader function), users may want to reconfigure or
  disable the watchdog without forcing a reset first. By setting the
  WDOG_CS1[UPDATE] bit to a 1 on the initial configuration of the
  watchdog after a reset, users can reconfigure the watchdog at any time
  by executing an unlock sequence. (Conversely, if the WDOG_CS1[UPDATE]
  remains 0, the only way to reconfigure the watchdog is by initiating a
  reset.) The unlock sequence is similar to the refresh sequence but
  uses different values.

When I debug the application, I can see that UPDATE bit is set and the watchdog timer is disabled, also, it behaves as desired when I reset using the debugger. However, in case of a reset by the reset button or power down, watchdog timer is enabled again and reset the MCU, since I do not feed it in the main loop.

Also, it doesn't create an interrupt before resetting the MCU, although its interrupt is enabled. I can see, by the help of SYS_SRS (system reset source) register that the MCU is last reset by watchdog timer.

Commenting out 2nd and 3rd line (WDOG_CNT=...) does not help.

Here is my full code:

main.c
init.h
init.c


texts: Help identify this component (part of switch de-bouncing?)

texts:
I found this component in parallel to a switch and 100nJ capacitor. My guess it that it is part of the de-bouncing circuit. Can somebody tell me what it is?

The blue disc has a diameter of about 8mm.

In case it helps:

this was part of a 12V circuit.
the mechanical switch may activate either a relay coil or a semiconductor switch
the label reads to me like "HEL (weird 7-like symbol) D560K"


texts: Circuit in picture is a simple regulator. I need to add 3.3V output delay-off for about 30ms. The reason for this is the battery can momentarily detached from the its contacts. I want to avoid a reset during this time. Any suggestions?


texts: Calibrating an AD592 temperature transducer

texts:
This transducer outputs 1uA/K. To convert it to a voltage I've put it in series with a 1k 5% resistor and a 220R trimmer to adjust for the 5% variance, tested with the multimeter to make sure I'm getting exactly 1k, then take the reading from between the transducer and the resistors (I should be getting 1mV/K). I'm using 3.3v from my arduino. I've got the thing set up in my computer room and I wrote a little C# program to get the reading from the arduino over serial and do the calculations to display °C and °F. It does respond to temperature changes. For example, I touched an ice cube to it and the temperature dropped, and I held my lighter next to it and it went up, but it settles in at exactly 68.2°F and doesn't change when there's nothing around it. First off, I think my room feels warmer than 68.2° F, and secondly I'm finding it hard to believe that the temperature in this room is so perfectly stable. I'm wondering how I might go about calibrating the thing.

The datasheet says that it has a range from -25° C to 105° C (248.15 K to 378.15 K). Since water, while liquid, can't be below 0° C and above 100° C (under normal conditions), would it work to wrap the transducer in heat shrink and dunk it in ice/boiling water for a minute or so to test that it's reading 0/100°C? I don't want to damage the transducer, or short it/the arduino out in water, so I'm asking. If I can calibrate those two temperatures I can determine the swing between them to figure out an ideal reading for ambient room temperature, right?


texts: Need help identifying replacement components on PCB

texts:
I have outdoor speaker that has leaked over the years and now the passive crossover inside has become corroded and the tweeters no longer work.  This is a dual voice coil speaker, so it takes both channels.

I'd like to replace the non-working components on the board but I need help identifying them so I can find suitable replacements.

The path to the 8" woofer passed through the large coil and that still works, so I will leave that be.

Following the traces on the PCB, the path to the tweeters is as follows:

Yellow capacitor
White resistor
Fuse

From my searches this is what I think these components are:

Yellow circle:
Polypropylene Film Capacitors, 2.2uF J 100V Axial

White square:
Ceramic capacitor 5w 4ohms and the J is 5% tolerance

Flat capacitor looking thing:
Seems to be a resettable fuse, JK60 065

Looking for these products on Mouser, I can't seem to find the filters that produce the right combination of requirements.

Have I identified these correctly, is there something commonly available that can be swapped in?


texts:
I am trying to connect arduino and usb lancard

In the datasheet, there is USB transceiver interface, containing symbol, type, pin number, description (usb D+ or D- signal).

However, the datasheet (about 20 pages) includes no information about what pin (out of 4) and what value to send to make anything work.

What reference should I refer to?

Thanks!

(I am a hardware beginner, sorry for dumb question)


texts: Why does an RTD sensor circuit use a reference resistor that is 4x the RTD value?

texts:
I'm using an Adafruit MAX31865 board to measure the resistance of a PT1000 RTD. The board comes with a 4300-Ohm resistor.
I'm trying to model the amount of noise (in degC/sqrt(Hz)) that I expect out of this circuit. But in order to do that, I'm trying to determine how the circuit does the measurement under the hood. One of the things that I don't understand is why the optimal reference resistor has a resistance 4x that of the RTD (e.g., 400 Ohm for a PT100, 4 kOhm for a PT1000). The MAX31865 datasheet says this (see also):

The reference resistor current also
flows through the RTD. The voltage across the reference
resistor is the reference voltage for the ADC. The voltage
across the RTD is applied to the ADC’s differential inputs
(RTDIN+ and RTDIN-). The ADC therefore produces
a digital output that is equal to the ratio of the RTD
resistance to the reference resistance. A reference
resistor equal to four times the RTD’s 0 degC resistance is
optimum for a platinum RTD. Therefore, a PT100 uses
a 400 Ohm reference resistor, and a PT1000 uses a 4 kOhm
reference resistor.

(emphasis mine)
Can someone explain why "A reference resistor equal to four times the RTD's 0 degC resistance is the optimium for a platinum RTD"?


texts: 2EDN mosfet driver burns out when connected to PWM signal

texts:
Good day everyone, I am building a motor controller for a 250W DC motor.
Today I was testing a part of my design, but somehow the MOSFET driver did not work. The Arduino send a 50% square wave (4kHz) to the optocoupler. The optocoupler produced a clean square wave from 0V to 12V, just as expected. The driver, however, did not output such a signal. The output of the driver was around 0V, without any recognizable square wave or any wave whatsoever.
When I replaced the driver, I disconnected the output of the optocoupler from the input of the driver. I soldered a jumper to the input of the driver and manually connected it to 0V: Output of the driver was 0V. After that I connected the input manually to the 12V source: Output of the driver was 12V.
Being confident that the circuit would now work normally, I reconnected the square wave from the optocoupler to the MOSFET driver. Again, 0V on the output of the driver and a broken driver.
Below will provide my circuit diagram.

Can someone please help me out?

parts:
Mosfet Driver: 2EDN8524FXTMA1
Optocoupler: TLP781F

Thanks!!


texts:
In the circuit below, I have to calculate \$V_u\$.

simulate this circuit – Schematic created using CircuitLab

By applying the voltage divider between the series resistances below, I get $$V_u=V_e\frac{R}{R+R}-V_e\frac{R}{R+R}=0$$
However if I apply the voltage divider to the two elements above, I get $$V_u=V_e\frac{R}{R+\frac{1}{j\omega C}}-V_e\frac{\frac{1}{j\omega C}}{R+\frac{1}{j\omega C}}$$

The solution gives directly:

$$V_u=V_e\frac{R}{R+\frac{1}{j\omega C}}-V_e\frac{R}{R+R}$$

Why? How did it apply the formula?


texts: Texas Instruments fully differential op amp app note: I'm having difficulty understanding an equation (single ended to differential video conversion)

texts:
I am developing a circuit to convert single-ended video to differential, based around the TI article "Converting single-ended video to differential video in single-supply systems" by Jim Karki. The article describes how to bias a FDA using a Thevenin equivalent to eliminate offset errors in the output.
Conceptually it all makes sense, and I can make sense of everything except for Equation 4 on the 3rd page (see the included image). The equation states that the gain of the circuit is G = 2 x (Rf/Rth)x(Rt/(Rs+Rt)). What I don't understand is why the second term, Rt/(Rs+Rt) is included here, when it already is included in the calculation of Rth (the Thevenin resistance) along with the video input's source resistance. It isn't as simple as just saying that the effects of Rt & Rs cancel out the 2x at the beginning of the equation (as would be the case with most video systems), because Rt and Rs are not the same resistance in the final solution.
Part of me thinks I can see the logic, but I can't formulate a consistent explanation. Because the circuit I am designing is slightly different, I really need to understand all of the steps rather than lazily copying what is in the paper!
EDIT: I corrected the erroneous Rs to Rt in one of the equations as pointed out by one of the commenters
Here is a link to the full article:
https://www.ti.com/lit/an/slyt427/slyt427.pdf


texts: lcd "random fruit" built in function for pic

texts:
I'm trying to display a random fruit on an lcd and I was wondering if there's a built in function in the MikroC PRO for pic v.6.4.0 library that does so.

I drew the fruit using the lcd custom character tool and I'm using the generate code option.I would really appreciate your help. Here's the generated code:

 void fruit1(char pos_row, char pos_char) {
  char i;
    Lcd_Cmd(64);
    for (i = 0; i<=7; i++) Lcd_Chr_CP(fruit[i]);
    Lcd_Cmd(_LCD_RETURN_HOME);
    Lcd_Chr(pos_row, pos_char, 0);
}


texts: Use of Norton theorem to find short circuit current

texts:
In the given circuit, while finding Norton or Short circuit current, we short terminal A and B. So I have assumed that is(t) = short circuit current.
Is it correct to assume so?
I did it because as terminal A and B are short circuit, all the current is(t) has zero resistance path to ground. Is my analysis correct?


texts: How do I multiplex many signals into my sound card?

texts:
I'm looking for a recipe that will allow me to...

Hook 24 piezos to a box that will "multiplex" their output into a single signal that I can connect to the microphone input on a PC soundcard.

The purpose of this is to build a cheap and portable contact-microphone/midi-drum-trigger setup.  Essentially I just need to get a low-resolution signal from all 24 piezos into the single soundcard input, which probably responds to frequencies between 20Hz and 20kHz.  Each of the 24 signals must be coming into the PC full-time, not "sampled" once every nth step in a sampling cycle; I'm just looking to compress each signal into a small band of the total frequency band of the soundcard.  But it is important that each signal be compressed such that they can be compared 1-to-1;  i.e. given a situation where each piezo is identical and receives identical environmental input, each signal on the PC should be identical, albeit "transposed" to one of 24 frequency "bands".


texts: What is the voltage drop across a TIP41c when it passes 2.9A for long durations?

texts:
simulate this circuit – Schematic created using CircuitLab
I'm having trouble understanding from the datasheets what exactly happens when I put a circuit as follows:
The two 20W LED don't have a specific current description but they are 12V so I assume they take between 1,5 to 1,7 Ampere to run. My idea is to use a resistors and potentiometer to make a current regulator that allows currents up to 2.9A to under drive the LEDs and hopefully make them cool enough to last.
So I have multiple questions:

What is the voltage drop across the TIP41c that I need to take into account when it passes continuously 2.9A? Is the back of the TIP41c connected to one of the pins? Is it ok to connect it to ground?
Am I ok with the limitations of the LM317?
I plan to use 3W resistors for R2 and R4. What is the minimal Wattage rating for the potentiometer I should use?
Would 1K potentiometer be enough for dimming the LEDs fully? If not, what rating should I use for a good linear dimming using a 1 turn Potentiometer?
Am I overlooking anything in design?
I didn't understand the hfe part of the TIP41c datasheet.
\$h_{fe}=\frac{i_c}{i_b}\$?
How do I use that to know if R1 is good or not?

Many thanks
Second revision of my question:
I tried to learn from the first go and found a video that I want to adapt:
https://www.youtube.com/watch?v=soygy1rnLcs
Here is the circuit,

simulate this circuit
Now there are many things I'm not sure about:

Am I right to use the cap to reference to ground? What should its rating be?
am I forgetting resistors that need to be put to protect the transistors?
I still want current to be in the range of a few mA to 2.9A for all the LEDs. Is this a good way to achieve that (and I just need to find the right resistor values) or did I get the video wrong, and what am I doing wrong?
If I'm using 20W LEDs that are rated at 12V like that and I'll underdrive them since some Voltage will go to the circuit I'm trying to build here, is it really a bad idea to limit the total current of all 4 LEDs and assume they are the same and will use the same current? I know I'm using 1 opamp in the LM358, is it possible and better if I check on the individual nodes N1 and N2? How would I do that?

Again, thank you
Ok let's forget the LEDs for a sec.
I'll try to copy what is in the video and fit it as closely as I can to just have the regulator:

simulate this circuit
If I start with setting the current I still have the problem using a \$R_{shunt}=0.1 \Omega\$ so that at the maximum current of 2.9A only 0.29W will be lost as heat, and if anything goes wrong it'll be 4A that run through it which is still ok for a 3W resistor.
Is there a transistor (Q3) that can handle 1.5A  and will work with that small \$V_{be,sat} = 0.19V\$?
Thank you


texts: CNC USB keep randomly disconnect while plug Computor notebook to wall plug

texts:
My CNC Machine used Mach3 USB board, Switching PSU (for stepper) and inverter fpr spindle.
When notebook run from battery, every work fine until battery run out.
After thatr, I plug computor notebook adaptor then USB keep connected and disconnected continueusly.
My question what cause these problem (USB connection unreliable when using ac plug for both device and PC) and how to prevent that?
Note Mach3 USB Board powered by USB. Also my PC run win10 (maybe that can cause problem)


texts: How do proportion current for components?

texts:
I am making a mini-fridge. On one side is a 150mmx150mm aluminium plate. It has been roughed up to increase surface area. On the other side it has an aluminium CPU cooler which can survive the tdp of the peltier.

I have:

2 x TEC1-12706, 4 x Fan 12V @ 0.2A

A TEC1-12706 is a peltier thermo-electric pad that emits cold on one side and hot on the other. This operates at 12V and at max, 6A. Hence the 12 and 06.

Say if I had a 12V dc power supply, how would I proportion the correct amount of current to these components? So if I want 6A each going to the peltier cooler and the remaining 1A for the fans.

I was thinking a potentiometer will do it but it would not be the best and efficient way.


texts:
It is true that an ideal transformer can not exist (but we can approach it as closely as want by improving the engineering behind it), but I think they may be mathematically inconsistent. To illustrate, consider these two circuits:

In case-1, I have a \$V\$ volt battery attached to a resistor, then the power drawn is given as \$P=VI\$, this is pretty standard and one of the first things any one who has done introductory circuit theory will learn.
Now, in case-2, we have a transformer consisting of two inductors and metal rod interior (the thing you use to keep their fluxs linked), so the coil in second circuit acts as a battery for the resistor R. Now, for an ideal transformer, the power in the input circuit is the same power in the output circuit. Hence, the voltage and current are predetermined by the power conservation equation.
If we say \$I_1\$ is the current in circuit on left in case-2, and \$I_2\$ as current with \$V_2\$ as voltage for circuit on right, then we have the equation:
$$ I_1 V_1 = V_2 I_2$$
For the resistor in the second circuit, it must be that the current is determined by voltage through it (ohms law ) but we already have a predetermined current by transformer power conservation. Now, this leads to two possible current values! Which is right?[ we can isolate equation for current by relating ratio of voltage with number of turns of coil]
And, what was the mistake in my logic which lead to this contradiction? It seems like even if we account for power losses of the transformer, that is introduce a multiplicative factor \$\kappa \$ in to the power conservation equation as so:
$$I_1 V_1 = \kappa I_2 V_2$$
We still have the same contradiction.
Related question

An explicit calculation:
Suppose that we have by turn ratio:
$$ \frac{V_1}{V_2} = \nu$$
Then by the power loss accounted transformer equation:
$$ I_1 \frac{\nu}{\kappa}=I_2$$
Now, for he is the 'strange' part, by Ohm's law , for the resistor:
$$ V_2 = I_2 R$$
Hence, we get:
$$ \frac{V_1}{\nu} = I_1 \frac{\nu}{\kappa} R$$
Or,
$$ R = \frac{\kappa }{\nu^2 I_1} V_1$$
This equation we can isolate for \$R\$, now as V and I changes it seems that R must take multiple value but it is that R is only one single value!