texts: Why is there a power drop in a serial circuit, but not in a parallel circuit?

texts:
I performed an experiment to compare the power dropped on a combination of a motor (small fan) and a lamp. I got the motor and a lamp from a lab, they are very old and all labels on the elements are gone. I connect them to a 3 V battery in both serial and parallel circuit as follows:

simulate this circuit – Schematic created using CircuitLab

In the top circuit, when the fan is spinning in full speed, I see that the lamp is very dim until I slow down the fan. In the bottom circuit, the brightness of the lamp will not be affected by the fan. I am trying to analyze this two situation in the following statements.

In the serial circuit, the voltage drop on motor and lamp add up to 3 V, but the current on both elements are the same. I am guessing the resistance of the lamp is much smaller than that of the motor so the voltage drop on the motor dominate. Most power is drop on the motor; I think that's the reason why the lamp is so dim. But what I don't understand is why the lamp becomes so bright if I hold the motor to stop the fan. Will stopping the fan cause the voltage drop on the motor?

In the parallel case, the voltage drop on lamp and motor are same. I know the current are different on elements. But in the case of using a battery as the power supplier, how is the current output determined?

I am thinking the total current output from the battery depends on the lamp and motor, in each path, the current is provided so to satisfy the power of the element. So it will try to output enough total current for each element to make the lamp bright and the fan spin fast. Is this correct?


texts: Why does the ADC require 3 wires instead of 2?

texts:
I'm very confused about ADC. I do apologize if these questions sound silly. I use ATMEGA328P for ADC.

Why is the negative terminal required for ADC to take measurements, if the ADC pin is already negative by itself?
Why does the ADC only take measurements when resistance is present between the ground and the ADC input pin? If I remove the 1k resistor, then measurements no longer work, why doesn't ADC pick this up, unless a resistor is present?

If I take the VCC and GND wire between my fingers in separate hands, and let the ADC wire 'float', I get a wave:
(no photo-cell, just bare wires, GND in my left hand VCC in my right hand and ADC input floating in the air)

What is this wave representing? If I don't hold the VCC and GND, then the ADCH is just showing random output, so the wave doesn't occur by itself. My vref is set to AREF of 4v.

If I connect the ADC to an aluminium jar, I see what appears to be square wave, is that possible that I'm picking up some kind of signal from  random device, like for example wifi chip? or not without op-amp?


texts: Resistor values for a non-inverting op-amp with gain of 2

texts:
I'm trying to build a circuit that uses a non-inverting op-amp to double the voltage in the circuit. The op amp I'm planning on using is: http://www.farnell.com/datasheets/2258629.pdf , and I think it needs to be set up in this configuration: https://upload.wikimedia.org/wikipedia/commons/4/44/Op-Amp_Non-Inverting_Amplifier.svg. My question is what should the value of resistance of these resistors be? I know they have to be equal in value but am unsure about the absolute size of the resistance.
For reference the voltage going into the op-amp will be between 0-5V coming from an Arduino Uno power rail and varied through a potentiometer.
Thanks
Edit:
The current circuit is as below, my thinking in response to the points raised about the voltage across the op-amp, is to put it in parallel to the proportional servo valve, hence running it off the 24V supply. My concern is that the current in that is 0.5A, which I understand wont all go into the op-amp, but the data sheet says the op-amp has a 2mA max limit. Does it have a feature built in that stops it accepting more than this, or will it try to accept more than this if given the opportunity and I'll end up breaking it?


texts: Find current flowing over an element given charge as a function of time

texts:
This should be pretty basic but I want to clarify some:

I = dQ/dt, so that means that I is the derivative of q(t) right?

So if I'm given q(t) = (7t^2 - 2t +3) pC and told that time is dimensionless for simplicity.

So to solve it I would take the derivative and get 14t-2 (units? pC/time?) Am I doing this right? How would I determine the unit for the answer if t is dimensionless?


texts: Power sequencing two +5V rails without a voltage drop

texts:
I'm new to power sequencing and wanting input on the best way to solve this problem.
I have two separate +5V rails on my PCB coming from a rectified wall source and USB. Due to back powering issues, I only want +5V on each rail when both power sources are present. My initial attempt (pictured) was to use discrete MOSFETs as shown, but with nonzero threshold voltages, I'm dropping >1.5V across the FETs. The loading requirements are up to 100mA on the rectifier rail and up to 30mA on the USB rail, with a voltage drop <500mV (although ideally less) on either rail.
Does my design have any potential, or should I be approaching this entirely differently?


texts: How to distribute power to multiple devices on a PCB

texts:
I am new to hobby level PCB's, but looking at taking my projects to the next step moving from breadboard. The part I do not know how to do, or see on tutorials is how do I take a single 5V line (or any voltage line), and distribute it across multiple devices/sensors.
So for example, I have a single regulated 5V line (coming from a 12V to 5V converter), and I want to send it to the PCB, and then from the PCB I want to take the 5V line and send it to my arduino (5V GPIO in), Rasperry Pi (5V GPIO in), and a couple other devices.
Do I solder across joints, seems like asking for trouble? Is there a component, or techinque for doing this?


texts:
Alright. I was given the task to design an analog design board which contains lots of opamps, some CMOS switches and some ADCs/DACs. It also contains 4 separate power supplies (each supplying +5V and -5V (+5VA1 .. +5VA4, -5VA1 .. -5VA4, AGND1..AGND)) plus some 3V3/ DGND logic.

Space was an issue so I was limited regarding placement and routing. I decided on 8 layers, wheras 4 of them are power planes (all of them are split planes). I designed them like this:

Top Layer (Signals in all directions, components)
MidLayer1 (Signals in horizontal direction)
MidLayer2 (Signals in vertical direction)
Power Plane 1 (AGND Plane): AGND1..AGND4
Power Plane 2 (POSitive Plane): +5V (digital!), +5VA1..+5VA4
Power Plane 3 (NEGative Plane): -5VA1..-5VA4, +3V3
Power Plane 4 (DGND Plane): DGND (required in large areas)
Bottom Layer (Signals in all directions, components)

Now I wanted to know what would be the "optimum" layer stackup. Signals are not high speed, just some rather low speed analog, relatively precise signals. Often, signals will pass from Top to Bottom (this was required because of the limited space), yet usually signals between OPamps will stay on either top or bottom layer.

Top and Bottom are given, now I was wondering if I should embed the middle layers within power pairs, or if I should put both GND planes into the middle.

Any ideas on this? There is some digital logic on the board as well, but it's mostly low speed communication.


texts: I want to use a charge pump to convert 5V to regulated 3.3V output. The charge pump I want to use has the switching frequency of 1200 kHz max. Do I need to be concerned about this switching frequency to avoid EMC issues? How is the EMI from charge pump in comparison to inductor-based regulators?


texts: Are these UV-C tubes meant to be run only on pure AC ballast?

texts:
I’ve this portable small T5 4W UV-A 300-400nm black light tube lamp with me. I’m trying to see if it’s possible to use a 4W UV-C lamp in the same fixture. But I noticed that the lamp has the violet glow only to one side which makes me think the supply is pulsed DC likely. But I noticed that the tube has started to darken on both filament ends as shown in picture.

Anyone has any idea what might be causing this or is this tube Int meant to be run on an AC type ballast.


texts: How to set by software interrupt of USART in NVIC? - in fact emulate it

texts:
After putting data into STM32 USART register DR, data is being transfered and interrupt occurs(TXE,TXC). NVIC jumps into my IrqHandler code. How to set this same interrupt by software(and run IrqHandler), without inserting data into DR.

I have software CTS/RTS handling in my IrqHandler. I would like to have all tranmission management inside interrupt routine. Send function will be only used to prepare SendBuffer and byteIndex for transmission.


texts:
I want to initialise a register of an external component with a FPGA. The data is latched by the external component at every falling edge of the clock signal.
You can see in the diagram that the SDATA line is somehow delayed. The falling edge of the clock signal lines up with the SDATA bits center. Could someone give an VHDL code example how I could write into a register some data bits?


texts: Transmission distance with AM2320 temperature and humidity sensor

texts:
I'm about to work with a temperature/Humidity sensor, this sensor has to be wired more than 5m and less than 10 m to my PCB board, I was going to use the SHT3xx sensors, these sensors work with I2C output protocol. I read that I2C has a reach of 2m more or less, so I left behind the SHT3xx option.
I started to consider the DHTXX line of sensors in the datasheet they assure 20 m of transmission distance, furthermore, looking for a DHTXX accurate I found the AM2320, that sensor has I2C output but I'm afraid that the 20 m of distance that (ASONG manufacturer) says in the datasheet, probably not achieve with I2C.
Has anyone worked with the AM2320 and tested the transmission distance?
If I use the I2C of the AM2320, will I get more than 5 m of transmission distance?
thanks.


texts:
I'm building a multimode analogue filter for a synth project I am working on. I've been following some schematics I found in the wild.

The project is working nicely on the breadboard so far but I have to use a mechanical SP4T rotary switch to patch any one of my 4 outputs (Notch, HP, LP, BP) to my audio output.

I'd like to do away with the rotary switch and replace this with a single momentary push button. Each press of the push button will switch to the next output and keep going for every push. I would then use 4 LEDs to indicate which output was in use.

I'm reasonably new to all of this and really must read up on my logic IC's and their applications.

I'm thinking this would be done with an octal latch maybe? Any ideas?


texts: Switching the leads of a high current motor

texts: I'm trying to create a circuit that will allow for switching the direction of a wheelchair motor. I originally was using a regular relay to switch the motor on and off, but after killing 3, I determined that the motor drew too much current (I'm running it at 12V DC). I have since used a starter solenoid, which has worked fine, but these are expensive and are only SPST. Now I need to be able to switch the direction of the motor, and I am having a hard time figuring out a way to do this. Any thoughts? Thanks.


texts: Dual power sources (PV cell and battery)

texts:
I have a small IoT project with a 280 mAh Li-ion battery. My intention is to plug in the device and charge the battery when it dies, but I wanted to extend the battery life and have been thinking about adding a small PV cell since the device will be exposed to sunlight frequently.

In most circumstances, the battery will be able to output more mA at the system bus voltage (4V) than the PV cell, but I want to increase total system runtime. Is it possible to use the PV cell and the battery at the same time to power the system bus? If the battery is doing less, that's still a win (even if it's not charging).


texts: Arduino Mega ADK demo kit on Xoom and Nexus S

texts:
I have an Arduino Mega ADK board. I am trying to make the sample project that is distributed with the ADK, but I can's seem to get any devices to detect my board.

I have installed the firmware on the ADK board with arduino, and it compiles and transfers with no errors.

I have the DemoKit application installed on device (tried both Xoom and Nexus S). I never get past the first screen that says please plug in the adk board.

I have tried powering the board via USB and with a 9v, didn't make a difference.

Beyond installing the android apk, and the arduino firmware on the board is there something else I need to do in order to get this sample program working?


texts: ESP32 microcontroller generates noise on microphone

texts:
I am trying to build a device for monitoring ambient noise in a room.
I am using SparkFun ESP32 Thing MCU together with SparkFun Sound Detector(electret mic + opamp LMV324m).
Nothing fancy, just read output from microphone with ADC.

My debuq/measurement setup(connected to breadboard) tried with and without L1, R1, C1 and C2:

I have two problems:

High prority: when ESP32 is running, it creates a lot of noise on the microphone's AUDIO output.
Most significant are spikes every 100ms. As you can hear on recording or see below. These spikes are also present on ENVELOPE output.
Lower priority: When ESP32 is turned off, or if it is connected alone to +5V USB without esp32,
there is still lot of noise from the microphone module itself. As you can hear on recording when I turned off esp32.

Output from AUDIO recorded using laptop:
(0s - 5s   : esp32 ON)
(5s - 10s  : esp32 OFF, I pushed and hold RESET button)
(10s - 15s : esp32 turned ON again)
https://instaud.io/236W

Spikes every 100ms on AUDIO output

AUDIO FFT, ESP32 OFF (LEFT), ESP32 ON (RIGHT)

I have tried to:

use L1, R1, C1 and C2 components as you can see in schematics (all combinations of them)
create primitive shielding of microphone modul using copper plate and tin box connected to GND.
separate esp32 from mic to approx. 1m distance (used longer cable)
use thick ass copper cables instead of cheap chinnese breadboard ones

with no success


texts: Is it possible to get two low-voltage interrupts pins on a Atmega328?

texts:
Caution: Noob at work :)

I'm trying to get one of two 1.5V-2V signal inputs to trigger an interrupt routine on an Atmega328 (Doc PDF). By using the analog comparator interrupt, I gather I block the analog-digital-converter interrupt and vice-versa.

I had a look at the ADC Auto Trigger Logic:

I cannot understand what free running mode does. It runs continually and if it value is true, it will trigger an interrupt routine for me?

Footnote: I could have also done this with external components, but I didn't have the parts at hand and thought I'd take it on as a learning experience in microprocessor use.


texts:
I am designing a transformer in FEMM and I was wondering about the polarity of the windings. The following figures illustrate two cases.

When I run the simulation, the magnetic field in the first one is significantly bigger than in the second case so I guess the first one is the right.

Am I wrong? What parameter defines the polarity of the windings.

EDIT: There is a small mistake in the pictures. The 24 AWG / 1000 turns is the primary winding. There is a mistake with the name.


texts:
I have AVR Atmega328p which I want to blink for 5 secs every 16 secs (to test the watchdog interrupts).

I have the following code, which keeps restarting, and the last line is:

test_blink(2);

Which I know because the led on PC2 is always on.
Where did I wrong? I re-checked the WD settings for 10s times already..

#define F_CPU 128000

// LED Definitions
#define LED_PORT PORTD
#define LED_PIN PD6
#define LED_DDR DDRD
#define LED_PWM_PCNT 50

// Watchdog definitions
// counter = 2*8 = 16 seconds
#define WD_COUNTER_MAX 2

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <stdint.h>
#include <util/delay.h>
#include <avr/wdt.h>

// Global watchdog counter (for wake-up counts)
volatile uint8_t watchdog_counter;

// Function declarations [may split to files]
void reset_pins();
void led_blink();
void sleep_me();
void setup_init();
void test_blink(int pin);
void setup_watchdog(uint8_t state);

void led_blink()
{
    LED_DDR = (1<<LED_PIN);
    LED_PORT = (1<<LED_PIN);
    _delay_ms(5000);
}

void test_blink(int pin)
{
    reset_pins();
    DDRC |= (1<<pin);
    PORTC |= (1<<pin);
    _delay_ms(300);
    reset_pins();
}

void reset_pins()
{
    DDRB = 0;
    DDRC = 0;
    DDRD = 0;
    PORTB = 0;
    PORTC = 0;
    PORTD = 0;
}

void setup_watchdog(uint8_t state)
{
    // Watchdog:
    // Clear WD reset flag
    MCUSR = 0;

    WDTCSR = (1 << WDCE) | (1 << WDE);
    if (state == 0) {
        WDTCSR = 0;
    } else {
        WDTCSR = (1<<WDP3) | (1<<WDP0) | (1<<WDIE);
    }
    wdt_reset();
    test_blink(2);
}

void sleep_me()
{
    ADCSRA = 0;
    reset_pins();
    PRR = 0xff;

    // Set sleep mode to POWER DOWN
    SMCR |= (1 << SM1);
    // Enable SLEEP
    SMCR |= (1<<SE);

    // Enable global interrupts.
    sei();

    // Disable pull-up resistors
    SMCR |= (1<<PUD);

    test_blink(2);
    setup_watchdog(1);
  sleep_cpu();
}

void setup_init()
{
    watchdog_counter = 0;
    setup_watchdog(1);
}

// watchdog interrupt
ISR(WDT_vect) {
    setup_watchdog(0);
}

int main(void)
{
    cli();
    setup_init();
    test_blink(4);
  while(1)
  {
        cli();
        // Disable SLEEP
        SMCR &= ~(1<<SE);

        if (watchdog_counter >= WD_COUNTER_MAX) led_blink();
        else sleep_me();

        watchdog_counter++;
  }
}

I am using the following fuses, and avrdude command:

avrdude -B 250 -c usbtiny -P usb -p m328p -U lfuse:w:0xD3:m -U hfuse:w:0xDF:m -U efuse:w:0x07:m -U flash:w:watchdog.hex:a


texts:
I faced with a problem of checking ferrite bead with parameters:

The measurements for two reels of this component have difference in Resistance and inductance:

  Reel 1: Resistance: 170 mOhm, Inductance: 2.5 uH (10kHz)

  Reel 2: Resistance: 460 mOhm, Inductance: 9.9 uH (10kHz)

Can You assist with next questions:

Why there are such difference in Resistance and Inductance between two components from different reels? Does this difference matter?
Why in spec don’t specified inductance?
Why on Characteristic Curve no value of impedance 1000 Ohm? Because I guess that curve for Z should be with Impedance value near 1000 Ohm.


texts: I have read somewhere that a TVS is nothing else than a robust Zener diode. My application requires using 300V zener diodes (that may exist but do not pop up so easily), but TVS at 300V are very common and inexpensive. My question is: can TVS diode be used to regulate the voltage in reverse mode like a usual Zener diode would do ?


texts:
How do you make XBee send its RSSI value to another XBee?
I am working on a project which involves sending the RSSI value of one XBee to another XBee which sends that data to an Arduino. The Arduino processes the RSSI values received from three XBee modules to track its position.

I don't know how to make the XBee send the RSSI value to another XBee.

Also, is there a way to send data from XBee without using Arduino or other low cost microcontrollers?

Thank you.


texts: Primary battery dies after 5 months instead of 25

texts:
We have designed a PCB with ultra low power Bluetooth module with the objective to run it on batteries for about 2 years.
We have measured the power consumption, it is 400uA on average with 20ms peaks at 3mA every 500ms.

We choose to put 3 C alkaline batteries rated for 7'200mAh in series. Our working voltage range is between 5V to 2V. Therefore we are expecting 18'000 hours of autonomy, i.e 25 months.

The problem: after 5 months being powered on, the system stopped to work. We found out that one out of the three batteries is completely dead while the other two still have some power (1.3V for alive ones and -0.6V for the dead one). We measured the impedances between batteries connectors, nothing below MOhm.

The question is: why are these batteries dying after only 5 months? Are we just unlucky with these batteries? not very probable because it happens on about 5 devices. It doesn't look like there is any unwanted power consumption, we measured it either with an amp-meter in series with an external power-supply, and also by adding a 330 Ohm resistor in series of the actual batteries to be able to see the peaks using an oscilloscope, results were consistent. What are we missing?

simulate this circuit – Schematic created using CircuitLab

Edit: More details on the current measurement

A first measure has been done replacing the 3 cells with a power supply and an amp-meter in series. with this, we were able to easily change the supply voltage to see how the current was changing. It was as expected i.e. about 400uA with 4.5V and about 600uA with 3.3V which should represent most of the time with actual cells.

A second measure has been done by adding a 330 Ohm resistor in series of the cells and we observed the voltage on the resistor using an oscilloscope. We did the measurement either with actual cells and a power supply. Same averages were found than with previous method. and we were able to see the 3mA peaks. We observed the signal for about 15 minutes without any irregularities. See oscilloscope screenshot below for details.

simulate this circuit

The device is running in the exact same state and environment during these measurement than actual usage in which we discovered the short battery life.


texts: UPS vs Surge Protector regarding short circuits and quality of power

texts:
I did research before posting and it seems a UPS filters power so that it is constant and “filtered” additionally it seems to be able to protect against short circuits. Does a surge protector have these same benefits except for the fact that it can provide power during an outage!

This is what I found regarding UPS and short circuits:
“ Uninterruptible power supply (UPS) systems ensure critical loads have continuous and quality power. ... Proper coordination of protective devices in the UPS distribution system means that only the fuse or breaker directly upstream of a fault (short circuit) will operate to clear the fault.”

Is this paragraph accurate and does this fact apply to surge protectors except the power, during power outages?

Do surge protectors filter power so that it does not have spikes and makes the power filtered and constant?


texts: TPA6111 Stereo power amplifier to mono setup

texts:
I have a TPA6111 stereo audio power amplifier part (http://www.ti.com/lit/ds/symlink/tpa6111a2.pdf) that has this typical application (from the datasheet):

My application requires a mono signal amplification and I'd like to know if there's a way to sum the audio input&output signals. Alternatively I could use just one channel I think.


texts: Why does SendChar code of UART different between IRQ and Polling?

texts:
Now I'm trying to analyze STM32F103 Cortex-m3's UART code in IRQ and Polling mode.

Ans I found 2 types example code such as the below.
This is IRQ.

/*------------------------------------------------------------------------------
  SenChar
  transmit a character
 *------------------------------------------------------------------------------*/
int SendChar (int c) {
  struct buf_st *p = &tbuf;

                                                  // If the buffer is full, return an error value
  if (SIO_TBUFLEN >= TBUF_SIZE)
    return (-1);

  p->buf [p->in & (TBUF_SIZE - 1)] = c;           // Add data to the transmit buffer.
  p->in++;

  if (tx_restart) {                               // If transmit interrupt is disabled, enable it
    tx_restart = 0;
    USART1->CR1 |= USART_FLAG_TXE;                // enable TX interrupt
  }

  return (0);
}

This is a Polling method.

/*----------------------------------------------------------------------------
  SendChar
  Write character to Serial Port.
 *----------------------------------------------------------------------------*/
int SendChar (int ch)  {

  while (!(USART1->SR & USART_FLAG_TXE));
  USART1->DR = (ch & 0x1FF);

  return (ch);
}

But I can't understand why do they have difference code?


texts: Should I use a permanent magnet inside a solenoid for an electromagnet shuttle?

texts:
I'd like to make some kind of actuator/vibrator but much stronger. I thought of using a static, tubular solenoid, driven with AC current. Inside it would be a mobile permanent magnet cylinder (magnetized along the axis of the cylinder). One end of the permanent magnet would be tied to a membrane and the current would make it vibrate.

-Will the magnet core rock back and forth in a much stronger way than a classic iron core would?

-Will the magnet core require a spring, like an iron core would ?

-Any comments on the conditions such device would work or not are appreciated.


texts:
I need some help understanding a little (I guess) thing here.
I was trying to understand a constant current source but something happened that I can't understand.
When I did a simulation in LTspice and I applied 16V or more, like 30V or even more, it works fine I can get around 10mA or very close (at 50V I have 11.2mA for example) but once my Vsource starts to decrease the voltage under 16V I got a bad stability, my (Vbe) starts to drop drastically.
Can someone explain why?
Check images below
*Circuit designed by owel.codes


texts: Logic level for system lower than IC's recommended logic level

texts:
My system has a logic-level and logic-supply-voltage of 2.4V. I want to use a particular IC in it (which basically operates as a shift register), and the datasheet says the minimum recommended logic supply voltage is 3V (see image below).

Would the IC still operate and communicate in the circuit... in other words: could I get away with it? And if so, what problems might i encounter or be more likely to encounter?

Cheers.

Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX6921-MAX6931.pdf


texts: Why is the transfer function of this non-inverting low-pass filter wrong?

texts:
I came across this block in a larger circuit:

With a transfer function (in pole-zero form) of;
$$
H(s) = \frac{s+30000}{s+5000}
$$
which was found using KCL on the inverting terminal of the op-amp.

As I am not used to finding transfer functions using conventional circuit analysis and I wanted to find the "pure" transfer function (i.e. the general function not the pole-zero representation). However I found that substituting my transfer function in the place of the pole-zero, with a step response is not quite the same. (It also does not match simulation outputs compared to the pole-zero function)

My calculations are as follows:

$$
V^{+}=V_{in}=V^{-}=V_{out}\times\frac{R_{2}}{\frac{1}{sC}||R_{1}+R_{2}}
$$
$$
\frac{V_{out}}{V_{in}}=\frac{\frac{\frac{R_{1}}{sC}}{\frac{1}{sC}+R_{1}}+R_{2}}{R_{2}}=1 + \frac{\frac{R_{1}}{sC}}{R_{2}(\frac{1}{sC}+R_{1})}=1+\frac{R_{1}}{R_{2}}\times\frac{{sC}}{{sC}}\times\frac{1}{1+R_{1}Cs}
$$
From this I found the final transfer function to be:
$$
H(s)=K\frac{1}{1+R_{1}Cs},\:\:\text{where}\:\:K=1+\frac{R_{1}}{R_{2}}\:\:\text{and}\:\:\omega_{p}=\frac{1}{R_{1}C}
$$
The K value was derived from the DC gain of a non-inverting amplifier and the pole frequency equation was derived from the relationship shown here: https://en.wikipedia.org/wiki/Cutoff_frequency

For the transfer function of the larger circuit; this block's transfer function is multiplied with another (an RL filter is connected to the input of the op-amp);
$$
T(s)=\frac{s}{s+\frac{R}{L}},\:\:R=80\Omega,\:\:L=10\text{mH},\:\:T(s)=\frac{s}{s+8000}
$$
$$
H(s)\times T(s)=\frac{s(s+30000)}{(s+5000)(s+8000)} - \text{Using pole-zero function}
$$
$$H(s)\times T(s)=\frac{30000s}{(s+5000)(s+8000)} - \text{Using transfer function}
$$
The transfer function was then given a step function \$ \frac{0.6}{s} \$ and then simplified with partial fractions:
$$
H(s)=\frac{5}{s+5000}-\frac{4.4}{s+8000} - \text{Using pole-zero function}
$$
$$
H(s)=\frac{6}{s+5000}-\frac{6}{s+8000} - \text{Using transfer function}
$$
Here is the graph of the two inverse laplace functions' step response:

My question is this; is the "pure" transfer function I derived wrong or is there some error made afterwards that results in an incorrect final graph compared to the pole-zero one? The pole frequency equation is correct and the general form of the transfer function matches a low-pass so I am most confused.


texts:
How does one measure the power factor?

$$\text{power factor}\equiv\frac{\text{power}}{|V||I|}=\frac{R}{\sqrt{R^2+(1/\omega^2C^2)}}$$

for an RC circuit driven with \$V(t)=V_0\cos{(\omega t)}\$.


texts: implications of difference between RMS and mean in rectified and non rectified graphs

texts: I have a project relating to EMG signals and i did a full wave rectification to zero for the graphs before calculating mean and RMS of the graph. My question is, would it make more sense to find the mean of the rectified graphs and the RMS of the non rectified graphs to compare. If so, what would the difference between the mean and RMS values show or imply?


texts:
I'm laying out a stacked PCB where I have 3 or 4 boards stacked on top of each other with signals propogating down with female/male headers (think Arduino shields), shared control signals are propagating down from the top (logic) board to the lower daughter boards, with certain runs being 12 inches or more between the logic out and logic in.

Is it necessary to buffer TTL signals, and is there a maximum trace/path length before when its important?


texts: How to get 460.8KHz from 1.8432Mhz oscillator using counters?

texts:
I need to supply 460.8kHz clock to IC (NCR20C12). However, I can only get 1.8432MHz Oscillator. How can generate clock divided by 4 from it? I have a couple of SN74LS393 counters and want to ask, is it possible to divide clock with counter and how to do it? Can't find solution on google, may be because of messing some terminology.

Is the following circuit correct?

simulate this circuit – Schematic created using CircuitLab

Sorry for my bad english, stupid question and thanks in advance.


texts:
I would calculate the transfer function of this circuit.

I have the following questions:
I can do the series resistance (R + L) and then make the parallel with the capacitor.
Finally make the voltage divider with the resistance R).

It would be changing the value of Vo(s)?
In this case changing the value, someone could help me solve it?

I also attached a photo of Laplace transformed circuit.

Thank you.


texts: Measuring the impedance of a transmission line

texts:
I designed a Tem Cell and I need to measure its impedance which I have no idea how I can do that. I have tracking generator, signal generator and 50 ohm terminations. So how can I measure the impedance of this transmission line?
P.S: Can you explain it like explaining it to a beginner ( I am one).
Another P.S: I am not a native speaker so feel free to edit the question.


texts:
I have the following transmission gates circuit.

I have some difficulties understanding the purpose of this circuit. It has the same structure like a flip flop but works differently.
This is the equivalent circuit when CLK is 1 or 0:

I would be grateful if someone could clarify me.


texts: Connecting buck converter to 10mF 40v filter capacitor

texts:
I have a very well made custom-made lab supply given to me by a friend. It is capable of 1.6A max and 32V DC voltage.
I want to add a secondary output to this supply but I have a hard time figuring what point in the system I should choose as input to this buck-boost module.

simulate this circuit – Schematic created using CircuitLab

C1 capacitor has 32V across it.
The Variable Switched Supply look like this converter or something similar. This module is actually controlled by a voltage pot and a current limit one.

I experienced the full power of the cap when I tried to rush the discharge with a screwdriver.
This makes me wander:
Q1: If I were to add the buck converter directly to this cap would it be sufficiently safe? Could I get electrocuted if there was a direct path from the cap to me?
Currently the buck-boost is connected to OUT1 and OUT2 DC outputs which I consider safe (the module I added is capable of step up and step down transforming). The problem with this configuration is that at about 3.5V on the standard output the  module triggers the short circuit protection and never recovers. I have to cut the power, wait a few seconds and only then does the output voltage recover.
Q2: Why is the module shortcircuiting? I presume the IC has some undervoltage protection. Is this normal behaviour?


texts: How do you simulate voltage noise with LTSpice?

texts: Is there a way to setup a voltage supply with voltage jitter/noise? I want to experiment with filtering out noise on various voltages etc. but not sure how to configure LTSpice to create a noisy voltage supply.


texts: Transistor part number selection software

texts: I know there are online/offline softwares for finding equivalents or known transistor datasheets but is there any software that works inversely? For example that I can ask the software for a transistor with VCEmax  or cutoff frequency equal to some value and the software gives part number suggestions?


texts: Measuring noisy signals: Does wrapping the test lead through a ferrite reduce common-mode noise?

texts:
Let's assume we have a test set-up involving an oscilloscope and a unit we are testing. we measure the voltage between two points using a standard scope lead and see significant noise, I now take out a clip on ferrite wrap 2 or 3 turns around this ferrite and close it. The noise on my scope is visably reduced. What have I done?

We should note here that the scope is plugged into the wall and so connected to mains earth.  The scope return lead is tied to earth via the scope and the UUT may otherwise be floating or tied to earth by a different route locally (same building).

My personal understanding is I have effectively added a common-mode choke in series with the signal and so I am filtering out at least some of the common-mode noise.

There is at least one user on this site who has a different opinion on this.

The last thing I want to do is start a flame war but I am sure in this case that we are both able to discuss this calmly and both keen to learn if we have misinterpreted things.

So does wrapping a scope lead around a ferrite reduce noise because it cuts down common-mode noise or some other method?


texts: Overvoltage and reverse polarity diode protection - capacitor across "reverse" diode?

texts:
I've stumbled across a schematic as shown in the picture. It is an over-voltage and reverse polarity protection before LDO. V1 is input voltage of 12V, but it doesn't matter for my question.

What surprised me is the use of C1 cap of value of 100nF. R1 is a part of the design, R2 is only for simulation (load). I am kinda confused, since I've never seen this additional capacitor across D1 and cannot figure out its purpose. In my humble opinion, it should not be used at all. Am I missing something? Can someone explain to me this peculiar circuit? :)


texts:
I'm using a dsPIC33F (Microchip) to sample a 555-timer signal. I've tried square, triangular, and "sinusoidal" signal shapes, but always have the same problem: the ADC samples the waveform correctly, but the result is always half of the expected frequency.

For example, my input is 440Hz, and when I plot what the ADC writes to the buffer, I get:

Without the lines it is:

On the oscilloscope I read it as 440Hz.  My sampling frequency is 8kHz (which I checked with the oscilloscope by toggling a pin), and as I change it, the sampled values change to reflect that, so I'm almost certain I'm using the correct timer to trigger the ADC.  Since each point represents 1/8000 = 0.000125s, the above graphs show a waveform with a period of 36*.000125=0.0045, or 222Hz.

I feel like the conversion time should have no effect, as long as it's shorter than 0.000125s.  I'm confident that it is, and have tried different conversion times with no change.  I know it's not the most efficient way of doing things, but to start I also convert only one sample at a time before triggering an interrupt and writing to the buffer.  I'm not sure if that would matter.

If anyone has any ideas, I'd be grateful.


texts: Why do we declare the inputs of our design as reg in testbench and outputs as wire?


texts: Can I replace a general-purpose electrolytic capacitor with a low-ESR capacitor?

texts: I have a dead PSU. I opened it up, and I found three bulging 1000 µF general purpose-type crappy electrolytic capacitors. I've replaced capacitors like this on several motherboards in the past, so this will be fairly trivial to do, but the only capacitors I have handy are low-ESR types. Could a swap like this work out, or should I grab a few general-purpose capacitors from a supplier?


texts: Issue with "Simulink does not support code generation"

texts:
I have something similar to this simplified  following block diagram on Simulink. It looks rather messy.

I want to replace a 3-point summing block with a function block, while keeping the same output.

First I started by placing the code inside the function block:

function y = fcn(u)
   sys1 = tf(0.5,[1 0 0 4]);
   sys2 = tf([3 0.5],[1 0 15]);
   sys3 = tf(1,[1 1]);
y = sys1 + sys2 + sys3;

However I was greeted with an error saying that Simulink does not support code generation.

  "The 'tf' class does not support code generation."

I then came across a similar problem here: https://nl.mathworks.com/matlabcentral/answers/74770-is-there-any-way-to-disable-code-generation-in-simulink

I am trying to implement an extrinsic function or'wrapper function' with some difficulty. I created a new script called myWrapper.m, containing the same code:

function y = myWrapper(u)
   sys1 = tf(0.5,[1 0 0 0 4]);
   sys2 = tf([3 5],[1 0 15]);
   sys3 = tf(1,[1 1]);
y = sys1 + sys2 + sys3;

and the MATLAB Function edited to:

function y1 = fcn(u1)

y1 = myWrapper(u1);

The error persists.

I somehow want to access myWrapper.m file from the MATLAB Function block. Any pointers on how this should be done? Following the previous link given and the official docs I am ending up with something like this in my MATLAB Function block:

function y = fcn(u)coder.extrinsic('myWrapper')

y = myWrapper(u);

The last code above is syntactically incorrect and I am at a loss on how it should be done. MATLAB automaticaly corrects the above code to:

function y = fcn(u,coder,extrinsic, myWrapper )

y = myWrapper(u);

which is not what I want.

Any tips and/or suggestions on how this could be done would be appreciated.

A similar question was asked on the MathWorks forum here, two years ago, with no response.


texts: What is the difference between commutation number and pulse number in?

texts:
My question is about bridge rectifiers in power electronics.
I guess the jargons are too vague, so i quote the exact definitions from my book which i don't understand at all:

  m represents the commutation number. This is the number of commutations per period in a group commutating cells.For the Graetze bridge, m = 3 for both left and right diodes. In most cases, the commutation number equals the number of phases.

and here is the definition of pulse number:

  The pulse number is the total number of non- simultaneous commutations per period.5 For the three-phase bridge, p = 6 as the commutations of the upper and lower diodes are not coincident. In general, for a bridge rectifier with m odd, p = 2m. For a bridge with m even, p = m holds

It would be great if someone can clarify the definitions above.


texts: Altium Designer 19 net name hidden on tracks

texts:
In Altium Designer 10, the PCB file will show Net Names on Tracks and designator on footprint, like this picture:

but in Altium Designer 19, the Net Name and designator are both hidden:

Does someone know how to set Altium Designer 19 to show Net name and designator?


texts: Best transistor to use for audio amplifier

texts:
This term, we will be designing an audio amplifier. So far in our lecture, we are still at BJT and based from what I've heard, FETs will just be partly discussed unlike the thorough one on BJT. Anyway, I would like to have an idea this early so I can plan on what transistor to use for best audio amplification. I have read some threads how the other transistor (BJT/FET) is better, but other forums say that the performance relies not on the component but on how the transistor is properly biased and how the circuit is properly designed.

In designing an audio amplifier, which of the four subtypes of transistors is the most efficient? (NPN/PNP/JFET/MOSFET)

By the way, the requirement of my professor is just this: impress me. Right now my group haven't decided yet on the specifics of the circuit (wattage, impedance, etc).


texts: Why doesn't page mode write operations exist?

texts:
I'm learning about the different memory access modes for SRAM. (Specific datasheet available here.) As I understand, there is "asynchronous mode", "page mode" and "burst mode".

Page mode is an extension of asynchronous mode to efficiently deal with adjacent read accesses. Page 12 says that such a page mode does not exist for write accesses.

Why do we not have page mode write accesses? Are there any fundamental restrictions for such write accesses?


texts: Using an Arduino to measure wire capacitance

texts:
I wanted to use an Arduino as a capacitance measurement device for a coaxial wire. I started at measuring the wire capacitance using digital multi-meter UT58B. I turned the knob to 2 nF and then measured the capacitance depending on the wire length. These are the results:

After the measurements I got the function (y = 0.0032x + 0.0268) on how the capacity changes depending on wire length. Now I wanted to use the Arduino to measure the capacitance and then calculate the wire length depending on the capacity. I tried following a guide to make the Arduino be able to measure the capacity.

Now the problem. I tried calculating the needed resistance using R = TC/C for one seond and got:

R = 1/(0.019*10^(-9)) = 52631578947.37 ohm

As you can see the resistance is too big. My questions:

Should I decrease the time constant? And how small could it be so that arduino can still measure the time? What maximum resistance can you suggest?
Maybe I wrongly read the multi-meter values? (the 2 nF scale)
Maybe there are other solutions you can suggest to measuring capacity with Arduino?


texts:
I want to ask how is right to connect enable in ICs and digital communication between ICs.

Take for example this:

want to ask about this 3 examples:

Should I use a resistor and how I choose it value?
It's an error to connect a decoupling cap? (I suppose it's good if I want to have a stable EN but I'll have some delay before  EN goes down after my pin5 pull down)
What is difference between I2C connection and a simple connection between 2 pins? I see the first have a resistor connected to Vcc and second to Gnd, why this difference?


texts:
It seems obvious that the mirrored symmetry in current between IR2 and IG must be displaying the same phenomena, but I admit that while learning LTSpice and running simulations for a future circuit.

It is confusing as to why it is displaying a \$3\mu A\$ spike for the gate readout, and a negative for the resistor. I understand that there is current needed to achieve gate charge for threshold, but why is R2 negative?

The explanation may be simple, but it's been a long day and I'd like to understand what's happening.


texts: How to Modulate Current without an Arduino

texts:
I am looking to turn current "on" and "off" extremely fast without the use of an Arduino. With an Arduino, I understand I would be able to do that in code. However is there another way of doing this?

The main reason for doing this is, I have an electromagnet. And I would like to modulate the frequency of the magnetic field. To do this, I would need to allow and block the current from passing through at a certain rate.

Note: I am still getting a hold of the correct terminology. Therefore, please excuse any concepts/terminology used incorrectly.


texts: Regulate FAN voltage from another potentiometer (Different voltages)

texts:
Currently i have a 100w LED been powered from a 14.4V lipo battery. I use a Voltage Booster to boost voltage up to 33V. I have modified the voltage booster with a pararel potentiometer to change LED intensivity on the go (From 24V to 33V)

Also i have a 12V fan to heatsink and i use a step down buck converter to lower and regulate voltage to 12V. Now i want to reuse my installed potentiometer to regulate fan voltage and LED at same time without the need of having 2 potentiometer. Since potentiomter is receiving a different voltage from LED how can i wire the hardware to make it work?

LED Min Voltage from POT: 24V
LED Max Voltage from POT: 33V
Desired Fan Min Voltage from POT: 8V
Desired Fan Max Voltage from POT: 12V

Last image shows my configuration for the potentiometer and voltage booster


texts: 1-dB Gain Compression Point in Amplifier

texts:
An amplifier has small-signal gain 15 dB and 1-dB gain compression at an input power of 13.2 dBm. The amplifier is used to amplify four modulated signals of equal power. To avoid problems with intermodulation products, the amplifier will be operated at least 5 dB below the 1-dB gain compression point. What is the maximum output power of each signal?

My workings:
1-dB compression point: 15 dB - 1 dB = 14 dB
5 dB below this value: 14 dB - 5 dB = 9 dB
5 dB below the input power: 13.2 dBm - 5 dB = 8.2 dBm
Divide by 4 input powersL 8.2 dBm - 6 dB = 2.2 dBm
Max output power: Gain + input power = 9 dB + 2.2 dB = 11.2 dB

Is this correct?


texts: Powering an old RC servo - Can't find the datasheet

texts:
I'm testing my arduino with servos, and my sg90 works fine for testing purpouses.

I would like to use something stronger, and my father (that in the 80s used to work with RC autos) gave me this old but promising servo.

I know I can't supply power with arduino if I want it to survive august, and I know all the servos work around 4.8-6v.

The problem is I can't really find any datasheet for this servo, and I would like to know at least the current drain to dimension my external power supply (or how can I misure it. All the wires are black, making it even harder).


texts:
Say we have 2 audio lines, one is driving an LED via an opamp circuit, and one is driving a speaker. Feeding the same pulse signal to both, are we able to detect latency between the time it takes for the speaker to engage and the LED to emit?
Thanks in advance

cheers


texts: "Stacked" NAND flash memory; 2 chips on a single circuit?

texts:
Sorry if this is a stupid question, I'm a newbie just getting into the actual hardware side of things.
Obviously I'm starting small, just a simple re-balling of a BGA chip to build my own Single Board Computer and wanted to know how to do all of that. Anyway, I'm wondering if it's possible to put two NAND flash memory chips onto the same circuit to double the memory (i.e. 8GB chip + 8GB chip = 16GB chip). Tried Google, but it's bloated with millions of useless blogs that bury any useful information.
Something like this (except obviously all connections are connected):

If not, what would theoretically happen? My guess is it would write the same data to both chips (which may prove useful), but I really don't know.
Thanks in advance :)


texts: Explanation of Source-Absorption Theorem Example

texts:
In the section on the Source-Absorption Theorem, my textbook has the following example:

I was wondering: If the voltage $$v_\pi = - v_e,$$ then why do we get $$g_m v_\pi = g_m v_e$$ instead of $$g_m v_\pi = -g_m v_e$$?

I would appreciate it if someone could please take the time to explain this.


texts: VLSI Fabrication: Why Aluminum and Copper used for metal layers?

texts:
In usual VLSI fabrication process, why Aluminum was used for metal
layers although copper and gold got better conductivity?
What does lead to trending toward copper for metal layers in recent years (instead of aluminum)?


texts: How to design sequential circuits using JK flipflops from output sequences of LED pairs?

texts: How do I solve problems like these where I'm given an output sequence of LED pairs and I have to design sequential circuits using JK flipflops? what should be my approach? where would I even begin?


texts: Conceptual question regarding the Laplace transformation

texts:
In preparation for an exam in linear signals and system my instructed handed us a couple of conceptual questions that should prepare us. I ran into the following:

Which statements regarding the Laplace transformations are true?

Multiplication of two signals in the time-domain corresponds to convoluting the signals in the Laplace-domain.
A differential equation can not be Laplace transformed if the roots in its characteristic equation lie in the RHP.
Opposite the Fourier transformation, the Laplace transformation of the system response includes both zero input response and zero state response.
The Laplace transformation of a system's step response gives the systems transfer function \$H(s) \$.

My attempt at reasoning
1 is wrong. It's true that \$x_1(t) *x_2(t) = X_1(s)X_2(s) \$, but \$x_1(t)x_2(t) = \frac{1}{2\pi j}X_1(s) * X_2(s) \$, so it is not equivalent.
2 is wrong. If the poles lie in the RHP doesn't mean that a Laplace transformation \$H(s) \$ doesn't exist, but it means that the system is unstable, the frequency response doesn't exist and \$H(j\omega) \$ is meaningless.
4 is wrong. It is the Laplace transformation of the impulse response \$h(t) \$ that gives the system transfer function \$H(s) \$.
3 I believe is correct. I just think of transforming a capacitor with an initial voltage to the Laplace domain, which will result in an impedance \$Z_c=\frac{1}{sC} \$ in series with a voltage source \$\frac{V_c(0)}{s} \$. So both the zero input and zero state response is taken care of.
However, the only answers available for this question state that either all of the statements are wrong, or that at least two of the statements are correct, which doesn't agree with my reasoning. Can someone spot a flaw in my reasoning?


texts:
I was looking at the development board layout for the MMZ09312B and I had a few questions:

datasheet: http://cache.freescale.com/files/rf_if/doc/data_sheet/MMZ09312B.pdf

Are large polygon pours away from the signal path a good practice? For example in the test circuit the top left and right corners are polygon pours of the signals at pins 3 and 7 respectively which are far away. Doesn't all this extra copper end up picking up a bunch of noise (even if there is via stitching)?
Since I want the traces of my input signal and output signal to have the same impedance as the SMA connectors (50 Ohms characteristic impedance) the trace width will depend on the distance between the signal layer and the ground layer among other parameters. With a standard 2 layer board (distance between layers approx. 60mils), my trace widths would be >100mil. With a standard 4 layer board (distance between layer 1 and layer 2 is approx. 10mils) if I set layer 1 as signal and layer 2 as ground I can use a trace width of ~15mils. But if I use the 4 layer board, what should I do with layer 3 and 4? Leave them empty?

Picture of dev board for reference:


texts: Source for parts to make a BlinkM I2C bus cable? (from todbot blog)

texts:
I came across this post on the todbot blog about controlling BlinkMs over an I2C bus:
http://todbot.com/blog/2008/06/17/get-on-the-blinkm-bus-with-a-blinkm-cylon/

I LOVE his connectors, but cannot find a good source for the ribbon cable/push through connectors...

Has anyone seen where I can get these easily? Its such an elegant solution.


texts: Optimize my power button circuit to make it more robust

texts:
I have the following schematic with the power switching part of my circuit.

It is possible to turn on the device when you hold your finger on the contacts of the button S1 and it seems that the problem is gone, when I change the value of R106 to something around 3.3k.
But why does this problem happen? My first attempt is that the resistor R106 is too big so it is not possible to keep the charges in the gate of T103. But I´m not sure if this idea is correct.
And my second problem is: When I reduce R106 the current during the on phase (when T105 is switched to hold the device) increased, because the resistor is smaller. So my idea would be to add a new resistor with around 90k on the collector of T105. Together with changing R106 to 3k3 this will result (hopefully) in a better interference immunity for the switch (so I can´t turn on the device with my finger) and the same current consumption, because of the higher resistance of the circuit when the device enables his hold function.
Would this work and is this a good approach?


texts:
I have some slight confusion about voltage drop across electronic components.
If the current before and after the resistor is the same, why is there a voltage drop across the input and output terminals of the resistor?
Voltage drop is the joules of energy lost when moving 1 coulomb of charge across 1 ohm.
So its essentially a force which acts on electrons at a point.
If the current is the same before and after the resistor, why is there a difference of electromotive force?
The only other thought i have may be that the drop is compared to when the resistor is not there
Can anyone clarify these concepts please?>


texts:
I have an audio mixing circuit that in a simplified diagram looks like this:

Sounce source A goes straight to the headphones (impedance ~300 ohm). Sound source B is buffered and amplified before being mixed.

I have a circuit that can shutdown/mute the buffers for sound source B because I need to prioritize sound source A into the headphones. Sound source B should mute is signal at the mix contains the signal from source A. However I am trying to figure out a way to tell them apart in order to reliably operate this function.

I cannot buffer sound source A, it is a closed system. The overall system that source B is connected to has its own power supply and is allowed to fail but shall not interfere with the operation of source A into the headset.

Hint: Use of a microcontroller and embedded software is a valid solution if it helps determine the signal differences.

update: I agree with @transistor's answer that a ducking circuit will achieve what I am looking for. However, the question is, is it possible to set up a reliable trigger to engage the ducking circuit to mute signal B when signal A is present given the layout in the picture above?


texts: switch 3 references voltage for my servo position

texts:
I have some positioning servo driver and servo with pot feedback.
Now I try to build circuit to switch between 3 positions. For testing I just use 3 way switch and 3 pots as voltage reference, but in my destination project my switch will by 10 meters away from servo and driver so current circuit may be noisy. So can I build this without passing ref. voltage thru switch? Or using buttons?


texts: Which end of a barrel connector is positive

texts:
I am having trouble understanding barrel connectors. From what I read online either the inside or the outside can be positive or negative depending on the direction of the current.

SO which end is the positive and which is the negative. Any useful advice or articles of this would be great.

This is the kind of connector I am talking about:

Thanks, Dan.


texts: Gunn vs. VCO in terms of phase noise and THD

texts:
I am trying to compare the THD and noise phase of a Gunn oscillator and a VCO. I conducted an experiment where I measured both parameters for both devices and came up with the following results:

(1) THD: VCO's was 4.03%; Gunn's was 14.3%

(2) Noise phase: VCO's was between -85 dBc/Hz at 10kHz and -110 dBc/Hz at 100kHz; Gunn's was -70.8 dBc/Hz at 50kHz.

It should be noted that the Gunn was operating at about 8.6GHz whereas the VCO at about 1.6GHz. Also, the Gunn was connected to the SA using a 10dB attenuator.

Here's what I am unsure of - why are the VCO's THD and noise phase significantly lower than those of the Gunn? Is it because the Gunn's central frequency was much higher?

Furthermore, is it to be expected that the precision and stability of the VCO will be better than those of the Gunn?

I'd appreciate some feedback.


texts: I am designing a circuit in which Vdd=3.3V. I have checked datasheets of hex inverters 74HC04 and 74LVC04 and both of these can work good at 3.3V logic circuits. If I have to select one of them then which one is recommended?


texts:
I want to build a hand sanitizer on my own. Like these, you can buy for enormous prices.
I need a proximity sensor (like the ones, which use infrared to check if someone is there).
And I need a small (!) valve to dispense a few milliliters (!) of the liquid (I found valves, which can pass dozens of liters per minute, that is too much). It will be a liquid comparable to water. I do not need a pump (gravity will do the trick), so I do not have a lot of pressure to open a valve. Would be great, if this valve can run on 3 or 5 V, so I can power the whole thing with a few batteries. If this valve is silent, would be even better.
I think, I will not use any microcontroller for that, just a few basic components like resistors, transistors and such stuff.
Any ideas for the proximity sensor and the valve? Did not find anything so far....
EDIT: I do not want a recommendation, where to get these things. But, searching on Google did not give me any usable results. My question is more like "Do you know an IC, which I can use for a timer" -> NE555. I am not searching for a specific product.
So my problem is: How can I open a tank for a short period of time? I do not need a pump, but I do not have a lot of pressure to open a valve.
To get a proximity sensor is the easier part of the problem.


texts: Design a BJT Amplifier to meet all the given specifications( Using LTSPICE)

texts:
Given Parameters: 1KHz 10mV sine wave as excitation(Vin)

Specifications to be matched:
Input Resistance(Rin) = 18 KΩ,
Current gain = 33 dB,
3 dB Bandwidth = 425 KHz
We are allowed to vary R2,R3( refer 2nd figure below) and Capacitor values to meet the specifications.
My attempt: I started with Rin and to match it, I varied R2 values using LTSPICE and got it to be 31.73K

Now the problem is when I try to meet ideal current gain or 3dB bandwidth specifications by fixing this R2=(31.73K) and by varying R3 or the capacitors, my Rin is bound to deviate from given specification I just matched, so I'm not really sure as to how to go forward and match other specification after the first one.
Fresh attempt: I took a different approach and only varied R2 and kept R3 fixed.  I varied R2 values to match current gain of 33dB and got 46.22Kohm.  and when I tried to match Rin, I got 29.19Kohm but then I realized on changing the C2 value to say 706n the gap between the two R2 values gets bridged and I get 35.209Kohm for matching current gain and 32.92Kohm for matching Rin and 3dB bandwidth isn't affected much and is nearly 416kHz  but I do not have a concrete way to vary C2 ( except randomly changing it) whereby I can simultaneously check which two R2 values gives required current gain and Rin and actually bridge the gap between the two.
EDIT:
Model to be used-

As for the Voltage gain spec, we aren't required to meet any so we just have go as much closer to only the three given specs.


texts: will i need header file "atxmega128.h" for porting from IAR to GCC?

texts:
i have a  code for avr that write with iar, and have a header file,"ATxmega128A3.h.
if i want to port this code to GCC (i am working with atmel studio),will i need to call this header file, or this header file just for IAR compiler?


texts: Operating a 0.08 amp fan using capacitor

texts:
I am developing a hot air blower made out of 40w heater, 25mm fan and 12v power supply.
I want to be able to keep the fan working in case that the power supply is cut off, so in case the heater is still hot, the fan will cool it.
This should be 5-10 seconds fan operation.
Is that possible with a capacitor or should I use a battery?
The fan's specs is 12 volts, 0.08A
Thank you


texts: Voltage regulator circuit increasing voltage when I connect a lower impedance load

texts:
I found this topology for a voltage regulator using a LM 317 and a "current booster" PNP transistor:

So, I tested this same topology with a little change: I used a TIP36C for the transistor and used a 100 R resistance instead to avoid heating of the LM 317 regulator (and make the transistor conduce sooner). I used it with a 19 V source.
But, I found a problem that I couldn't yet reproduce in simulations: The voltage in the output is RISING when I connect a load. Why could that be?
For instance, if it's at 11 V and I connect a 11 ohm load it will rise to around 12 V. And I'm under the impression this rise takes a reasonable amount of time, like 0.5 s.
I already checked everything and nothing seemed wrong, except from the transistor itself.
When I measure it with a multimeter, I'm finding a 2.6 V base-emitter reverse breakdown voltage (while the forward voltage is around 0.7 V).
This seems off, I thought it should be around 5 V at least.
Could it be the transistor is bad and causing that behavior?
I tried considering that but still couldn't imagine how could this cause such behavior.


texts:
I have a 8 MHz oscillator that I run to two CPLDs on my board. The trace lengths are less than 1.5 inches. The traces do you have vias in them, so they do change their impedance. But I was hoping that with such a slow oscillator, I wouldn't be having an excessive ringing as you can see in the image below:

This image shows a closeup. The rise/fall time are about 4ns.

I am not terminating the clock but the system has worked quite well so far. But on the next revision of the board I'm considering increasing this clock to a frequency of about 20 MHz. I gather I will need a proper termination scheme then.

My question is, why am I seeing so much excessive ringing when the signal has a rise/fall time of 4ns and the length of the trace is less than 1.5 inches?

MORE INFORMATION REGARDING MEASUREMENT

The probe is connected directly at the pin of the oscillator. I soldered a small wire onto the ground pad and I connect the ground clip there. This is VERY near where I'm probing.

The scope is a 50MHz Rigol and indeed the if I look at the square wave calibration waveform it's extremely clean. It's exactly what you'd see in a textbook. So I don't think it is calibration that's at fault.


texts: Can Power be absorbed by large transformers?

texts:
Nearby our house is a transformer for underground power lines. It sort of looks like this:

When I take a telephone pickup coil, and amplify I hear the 60hz hum through a speaker. I am wondering if there is enough magnetic field around this to pick up some power and light a LED or some low-power-draw device. If so, how would I do this, would I just hook a coil to an LED?  Do these transformers leak magnetic fields in enough quantity to pick up anything?


texts:
I was looking at a reference design and I saw a symbol I didn't recognize:

So I looked up the part. It's a dual Schottky rectifier like this:

What is the purpose of having two diodes in parallel in this case?

Thanks


texts: Why output voltage becomes less when beyond resonating frequency?

texts:
In a class C amplifier (Figure A), every time the transistor turns on in every "pulse", the collector current becomes saturated. This charges the capacitor to its maximum (Vcc). This capacitor will always get charged to its maximum, independent of the input signal frequency.

So why does the output voltage reduce when the frequency is below or above its own specific resonating frequency? (Figure B)

I mean, whether the input frequency is in resonance or not, the capacitor will always get charged to the fullest when the transistor turns on, thus swinging the tank circuit to peak Vcc. So why is the output voltage damped when it is  beyond the resonance?


texts: Comparing dynamic range of a CD versus an analog phonograph

texts:
As far as I understand, when we talk about the dynamic range of an ADC we are referring to the ratio of the biggest signal it can handle to the smallest signal it can resolve.

On the other hand the dynamic range is defined as the difference (in dB) between the maximum input level and the noise floor of the ADC. If we neglect the noise floor, we can obtain the formula of such system as 20*log10(2^n) where n is number of bits.

In many forums I found that they are making comparison between old analog players such as vinyls and digital players such as CDs. They are making the comparison by documenting their dynamic ranges in dBs

But how is dynamic range for an analog audio device such as a phonograph or cassette player is obtained?


texts: Simulation of parallel port but without a parallel port

texts:
I've been working on a project in my faculty that requires me to use a parallel port, but as I see my laptop doesn't have one!

I've been searching for a way to simulate the parallel port on my laptop, like when I send some data to the address 378H, the program that's like the simulator will give me an indication that he has received them and so on...

I found this website but it wasn't useful. Also have been googling all the night , but didn't find any ....

If you needed any more information I will be more than happy to provide them

I'm using Windows 7


texts: How to safely charge a capacitor with a GPIO pin of an Arduino/Raspberry pi/ESP8266/Attiny

texts:
I know that the question should be explained in more detail, but there is not really anything more to be said about the above-mentioned question.
Thanks for your suggestions


texts: Is one big via better than multiple small vias when changing power traces and ground between layers?

texts:
I'm confused about the via placement in power traces either to change layers as part of routing the main supply or to get to component pins from a layer different to where the power trace is located, and from components such as decoupling caps to the ground reference plane.

I read here "Many small via vs few bigger via" and here "https://www.ultracad.com/articles/viacurrents.pdf" that having multiple vias is better but both sources talk more about the thermal benefits of having multiple small vias as opposed to one big via.

My confusion is when I look at this from an inductance standpoint since small vias have higher inductance and high inductance is definitely not a good idea in a power distribution network.

So my questions are. Is it better to have two, or more, 10 mil vias or one large 30 mil or 40 mil via on decoupling capacitors?

And, is it better to have multiple 10 mil vias or one large via to connect VCC top layer to bottom layer and the power supply GND to the GND plane?

I'm not concerned about the heat but more for power integrity. I just want to be able to switch layers without introducing much inductance and have effective decoupling.


texts: 24V failsafe switch that cuts power untill power is removed and reapplied

texts:
Does anyone know of a device that when current is applied it will stay on for a certain period of time then turn off until current is removed and reapplied?

Basically I have a float switch that, when fluid gets low, it flips on 24v current which flips on a solenoid valve until the fluid fills up enough to turn the valve back off.  The problem is that if the fluid does not fill up enough of the valve sticks then the solenoid stays on and after a while gets extremely hot.  The fluid I am using gums up when under heat so the solenoid then becomes stuck and it is a HUGE mess to fix.  I am hoping that there is a simple device that I can put in line between the power so that after say 15 seconds it will cut the power until power is removed and reapplied again.

Any ideas are greatly appreciated!!


texts: Why do the 2N2222 and PN2222 avalanche differently?

texts:
I've been experimenting with a 2N2222 transistor (in the TO-18 metal case) and using it as an avalanche transistor -- by not connecting the base and having the emitter and collector connected in reverse (so maybe I'm actually using the reverse mode, I'm not really sure)... basically it avalanches and continues being on until current drops to zero, then resets itself undamaged.

I (mistakenly) thought that all X2222 variants would behave the same, such as the BT2222A (an SMD package) that I was about to order.

Now, experimenting with PN2222 (TO-92) and it's not avalanching the same way (if it really is doing so). if it's avalanching, it tops off to a certain voltage (around 9.15V on a 16V supply, with voltage drops on a few other components, of course), then very, very momentarily avalanches just to go slightly under 9.15V, then stops the avalanche. then it repeats the cycle... or at least I think this is what it's doing.

Why is this, and what can I do to make PN2222 behave more like 2N2222?


texts: What could be the reason for failure in using a single-phase full-bridge square wave inverter to drive a coil for wireless charging?

texts:
I am working on a wireless charging project that needs a three-phase inverter. I built the inverter (with flexible wiring using connectors) myself and tested it as a single-phase full bridge converter at first. The inverter worked fine for resistive load (although there were so many noises in the waveform), but when the coil was connected, the voltage across the coil was totally distorted (not a square wave and I don't know what is that). I would like to ask what could be the possible reason(s) for this?

Inverter test for coil (left) and for resistive load (right)

This is the circuit of the inverter test for coil. For resistive test, the circuit was just similar to this one but with R1 being removed and L1 being replaced by resistor.

-Coil inductance = 3.9uH
-Switching frequency = 128kHz

At the moment of switching, there was no secondary coil. The coil connected to the inverter just acted like an inductor.
Thank you!


texts: How to find out which certificates (FCC, CE etc.) are necessary for a product?

texts:
Is there any way to find out which certificates are necessary for an electronic device to be sold / imported into US / Europe / Asia?

FCC and CE are common knowledge, but then there are other certificates absence of which can cause problems (like CEC for example).


texts: Op-Amp Input Common Voltage Range for specific gain

texts:
This is the circuit I am working on.

I am using this instrumental amplifier AD623 with a gain of 100 using a 1k resistor between pin 1 and 8.
(https://www.analog.com/media/en/technical-documentation/data-sheets/AD623.pdf)
Based on this, my input voltage can swing from -0.05v to 0.05v.
When input voltage is 0.05v the simulation works without problems as I post on the image.
The problem I am having is that when input voltage is -0.05v I get error on simulation and I think is because I exceed specs of the input common voltage of the ic.
I need to understand how can I get correct output voltage based on the input voltage I mention.
(If input voltage is -0.05v output can be any value <5v without problem in this circuit design)


texts: Connecting a MIDI device with a USB B connector to an iPad

texts:
I'm trying to connect my digital piano (a Yamaha Clavinova CLP-440) to my iPad, to be able to use apps which utilize MIDI input (piano training and such). The iPad only has a Lightning connector input, and the piano only has a USB B female connector labeled "USB to Host". I have a USB B male to USB A male cable, which won't plug into the iPad.

One advice I found is to use a "Lightning to USB camera adapter" from Apple, which is a USB/A female to Lightning adapter. But I can't obtain that quickly, and it's also expensive. Instead, it occurred to me that I might use the regular charging/synchronization cable I have for the iPad, Lightning to USB A male, and then buy a USB A female-to-female adapter, to work like this:

Piano (USB B female) -> USB B male to USB A male cable -> USB A female-to-female adapter -> iPad charging/synchronization cable -> iPad.

Will that work? I'm not sure how the details of USB host/device identification work with respect to using the charging/synchronization cable. Will it allow the iPad to act as a host to the piano? Any other simple solutions I'm missing?


texts:
I think I got too ambitious with an earlier post, so lets back it up a bit.

I would like to use a 3.3V output from a Raspberry Pi to high-side switch a 12v load.  I thought this was possible with a combination of PNP and NPN transistors following the example here, but I'm not sure if this can be adapted to 3.3V base and 12v collector.  Is it possible to replicate this with 2N2222 and 2N2907 transistors, given a load less than 800mA?

If that's not an option, then I guess I should follow this post and go the route of using a MOSFET here, but it's not entirely clear what properties I should be looking for in a MOSFET.  Do I need a drain down current greater in magnitude of my load (ex, will a -3.7A drain down current be sufficient for a 800mA load) and a gate source voltage lower than my base (ex, 3V)?

Thanks


texts: Li-Ion/Li-Polymer Battery Charger mcp73871-2cci/ml Issue

texts: Hope someone can help.  I have designed a pcb board based on the mcp73871-2cci/ml. No matter what I change there is no current draw and all the indication LED’s remain on. I have seen some example schematics, some have pull down resistor and others do not. I also changed the 10k NTC THERM to a 10k resistor and there is still no change. Any ideas?


texts: How to minimize the size a microcontroller implemented on an FPGA?

texts:
I have 1500 lines of 16-bit data that need processing. I designed a microcontroller to execute some data processing algorithm on the dataset. It does well when the number of lines is small (< 100), but quickly explodes as it increases.

How do you normally deal with large amount of data while maintaining a small area? Bear in mind I have limited experience in FPGA implementation in general.


texts:
I have a lascar LCD volt/ammeter that has 10 pins. What I want to do is design a simple PCB that has a few resistors, connects to a battery and  an aircraft then send off a Gerber file to a manufacturer to have about 10 made.

The problem is I can't seem to find a simple PCB program that lets me make a few holes for the resistors and LCD pins, then lets me connect them with a few copper tracks. All the programs I have used want me to make a full schematic before I can design the board which is unnecessary. Then they show me a parts list with thousands of parts that I don't need.

I literally want to make some holes with pads around them so I can solder the resistors, etc and have a few copper tracks. Does anyone know of a simple program that can do this and export the board to a Gerber file?


texts:
simulate this circuit – Schematic created using CircuitLab

I'm using a HC-SR501 PIR sensor and a 12V relay to switch between green (NO) and red (NC) on a LED strip, everything being powered by a 12V power supply.

Without any motion in the room, the LED strip changes color from red to green and back to red, every 24 and 45 seconds respectively, with the relay jumper set to LOW. If the jumper is set to HIGH, the strip has the red light turned on and no motion will make the relay to switch to green.

Testing the PIR sensor separately I get a normal 3.3V on the output channel for 19 seconds when motion is detected.

Can you please tell me what am I doing wrong?


texts: JK flip-flop: What is the difference between clear and J=0, K=1, rising clock?

texts:
I'm trying to create a Program Counter using some JK flip-flops.

I have two different way to do that:

Use some 74LS73 (dual JK flip-flop with clear):

Use both 74LS10 (triple input NAND) and 74LS00 (double input NAND):

Using the first integrated circuit will be easier, but this isn't the problem.

My doubt is about the Clear pin in 74LS73: I know it will reset the flip-flop but also the combination J=0 and K=1 on a rising clock edge should do it...

So, what is the difference between the Clear pin and J=0, K=1, rising clock?


texts:
Can someone explaine to me how dose this overcurrent protection works and how to calculate it?
BQ297xy Schematics


texts:
Is it possible to pass data from Matlab to ClearSCADA software?

On their forums I found this:
http://telemetry.schneider-electric.com/id3/forum/messageview.cfm?catid=51&threadid=973 but this description is unclear to me.

Any experiences with interfacing Matlab/ClearSCADA ?


texts: P-channel MOSFET switch - very high Rdson

texts:
I am trying test my p-channel mosfet (IRF9Z34) high side switch on load. On circuit simulator I get the result I expect, Rdson (VM1) is low and load current is 1.4A. (In the target system the gate will be controlled, here the mosfet is always on for tests). T1 - P-MOSFET IRF9Z34.

In the real circuit current is max 0.9A, so I have very big Rdson, I don't understand why. Vgs > Vth, The power supply has a current effiency > 2A.


texts: Was the term "shield" in use [for daughterboards] before arduino became popular?

texts:
The first time I heard the term "shield" in connection with arduino [some years back], I had to google it. So, I'm curious if this term—which seem to me to translate roughly as "daughterboard" in pre-arduino terminology—was in use [roughly with this or a similar meaning] in some other EE context before arduino became popular.

(This question actually came to me while I was reading our meta-thread about the arduino tag, in which someone noticed that arduinistas seem to use at least some terminology that's not common in EE at large.)


texts: Can manage to read device ID from an AVR only once

texts:
I'm using an ATmega48 device and my debugger is the Atmel ICE. I manage to connect to the device only once, the 2nd time causes a "failed to enter programming mode" error. Cycling power to the device enables me to re-create this as many times as I wish. I lowered the communication speed to 8KHz but that does not perform any different than 50KHz, for example. The device is new so it runs from the internal oscillator so even 50KHz should be a very reasonable speed.

Any suggestions to what is going on here?


texts: Micro controller to set 'dial knob' mode on multimeter

texts:
Can a microcontoller be used to replace the "dial knob" function in a   'off the shelf' multimeter(10A max AC/DC). Is it easy to scale and micro control multiple identical multimeters using one microcontroller?
All multimeters operating mode is to be set using one centre dial which the microcontroller reads. The rest of the multimeters simply stack behind the top most device with their shell/case taken off.This will save on the bulk of the device shape and "streamline" whatever blob comes out in the end. DiY x-Channel Multimeter - Hope it's a clear visual :)

The dial itself works by simply bridging between many pads on a PCB(check photo). Can the dial(mechanical) be bypassed by micro controller with ability to set the full range of combinations that the dial currently bridges?

The microcontoller would have to remember the active settings for each individual multimeter dial position and maintain them independently.

Would be good if there is a way to only power the micro controller upon need to change settings and power off immediately after setting the relevant multimeter board IC. Saves battery (1x9v)

It is desirable to have everything readable in one glance and therefore all LCD displays are to be lifted off the multimeter PCB and placed to sit all next to one another on the top surface of the combined device.Allows for easy tracking of everything in one place without losing sight of the work area.

How far can the LCD be lifted off the PCB? as the photo shows the LCD is a generic type component... Has anyone tried separating the LCD from a PCB? What max distances can be done?Is 10 cm a possibility?

can this work ?


texts: How can I prevent my DC-DC converters from exploding?

texts:
I'm an electrical engineering student at TAMU working on a project for my first internship: a signal recorder for an experimental helicopter. For context, here are some of my requirements:

19 DC analog inputs ranging from 0V to 6V (but could be as high as 24V)
Must be powered by 24V supply (5V=Teensy, 5V=TLC1543, +/-24V = LM324)
Must NOT effect the input signal in a noticeable way

To do this, I've designed an Op-Amp Buffer using LM324s and a voltage divider to bring the (potentially) 24V signal into the 5V range. I'm also using a PDM1-S24-D24-S and a SPU01N-05 to try to power the +/-24V for the Op-Amps and the 5V for the Teensy and ADCs, respectfully.
Unfortunately, my design has a major problem: The +/-24V DC-DC converter explodes after a few moments connected to power.
I think it is because the capacitors within the PDM1-S24-D24-S cannot discharge and eventually explode. When I check the resistance between the positive and negative 24V output pins on my circuit, my multi-meter oscillates between a small value (~500 ohms) and an "open loop" message - suggesting that either the resistance is massive or that there is no connection at all.

simulate this circuit – Schematic created using CircuitLab
Above is a rough schematic of what I've currently designed, for brevity I've omitted the other 17 Op-Amps but the pattern of connection continues.
It seems to me that the loads are in parallel, and therefore should have a smaller value (potentially too small, i.e. a short), but my measurements suggest otherwise. I tried adding the 10k resistors to solve this, but the results were the same. Can someone help me identify the problem causing my DC/DC converter to explode? And suggest a solution?
I recognize there are other problems with my design at the moment, but I will ask for help with those on a separate question. But I will happily hear any suggestions that aren't related to the question.
An additional question: Is it bad practice to use a different DC-DC converter to supply the ADCs that will read the signals here? Could it also cause problems with the +/-24V DC-DC?


texts: Is it safe to implement a split power supply from two identical AC/DC adapters?

texts: If I have two identical AC/DC adapters(Such as laptop adapters) can I achieve this as in the following illustration? Would it be safe?:


texts: Why are there no 256-bit or 512-bit microprocessors?

texts:
In an 8-bit microprocessor its data bus consists of 8 data lines.  In a 16-bit microprocessor its data bus consists of 16 data lines and so on.

Why is there neither a 256-bit microprocessor nor a 512-bit microprocessor?  Why don't they simply increase the number of the data lines and create a 256-bit microprocessor or a 512-bit microprocessor?

What is the obstacle that prevents creating a 256-bit microprocessor or a 512-bit microprocessor?


texts: pic16f877a problem in timers with proteus simulation

texts:
I used PIC16f877A at proteus to do timer interrupt.

The code is pretty simple it has nothing to do rather than setting the timer1 registers , the while(1) loop is empty , the timer setting is as below.

When I run it the frequency of RB0 is too low it's just 32 Hz while it should be much greater than that, I sat the clock frequency both on fuses and proteus to 16 MHz, pre and post scalers 1:1 , but it still extremely low, I believe the is something wrong with ISIS it self , any ideas ?

main.c :

#include "config.h"
#include <stdint.h>

void main()
{
    // -- [[  IO Configurations ]] --
    TRISB0 = 0;
    TMR1 = 0;
    TMR1CS = 0;
    T1CKPS0 = 0;
    T1CKPS1 = 0;
    TMR1ON = 1;

  // -- [[ Interrupts Configurations ]] --
    TMR1IE = 1; // Timer1 Interrupt Enable Bit
    TMR1IF = 0; // Clear The Interrupt Flag Bit
    PEIE = 1;   // Peripherals Interrupts Enable Bit
    GIE = 1;    // Global Interrupts Enable Bit

    while(1)
    {
        // Stay IDLE ,, Timer Interrupt Will Handle Everything For Us !
    }
}

// Interrupt Service Routine - ISR
void __interrupt() ISR (void)
{
   // Check The Flag Bit
   if (TMR1IF)
   {

        RB0 = ~RB0;
        TMR1IF=0;
   }

}


texts:
I am trying to design a development board with a dialog micro. I am trying to remove the need for a programmer on this board. So that the user could simply plug in a usb cable and be able to communicate with the chip and boot it.
I have seen the arduino uses an additional micro (ATMEGA16U2) to do usb to uart and this feeds into the arduino's actual micro (ATMEGA328P-PU).
Apologies if the following comes across very stupid but for my own clarifications I have 2 questions:

Firstly, how is the first micro programmed to begin with? I'd imagine the chip comes empty so if I plug a USB at first it wouldn't see anything?

Secondly could I use an FTDI usb to serial chip to do the same thing? Would that not have been a simpler solution?

I am guessing once the communication between my laptop via usb to my micro via uart is initiated, I could then use any IDE to program this chip.

I have very basic prior experience working with micro's and would like to take this opportunity to improve on that.


texts: How to connect 3-digit display and suppress leading zeroes?

texts:
I searched a little and it told me to use with more than one display, connect  (Ripple Blanking Output) from most significant 7447 to the  of the next 7447.

Which number would be most significant?

Connect  of the least significant 7447 to 5v unless you want the diplay to turn off when the number is 0. How will the RBI come to play, to remove leading zeroes?


texts: Powering dual-voltage board from AA batteries

texts:
I'm building a board (simple toy) that needs two power voltages. The first part has MCU and sensors and can use anything from 3.3 to 2.6 volts. The second part has an audio amplifier and servo motors; it needs 5 to 5.5 volts. The total current is ~50mA on average, with short spikes to 80mA when the speaker is active.
I currently use 4 AA cells and two linear regulators (5V and 3V3), but this has unwanted drawbacks:

lowering 6V to 3V3 wastes almost 50% of energy;
it only works with fresh batteries. As soon as the power pack voltage drops below 5V, the first regulator stops working, and the 5V part becomes underpowered.

My next best idea is to use 3 AA cells, a boost DC-DC regulator to power the 5V part, and a linear regulator to get 2V8. This way, I can use batteries until dry; they should go about 1V each in the end.
Is it a good design, or is there a better one? This is one of my first boards, and I don't have a good intuition, even less knowledge.


texts: Pseudo-differential DAC output to single ended

texts:
I have a Cirrus Logic CS43198 DAC with pseudo differential outputs.

Is there a simple passive circuit to change them to single ended outputs?


texts:
I have radial capacitors with markings 235 RCN on one side and 333 C5K on the other side. How do I interpret these?

Front side:

Back side:


texts: Damaged OLED LCD voltage regulator replacement

texts: I have a 128*32 OLED LCD that is used with an Arduino. I recently damaged the voltage regulator and was hoping to be able to repair the board by soldering off the damaged component and replacing it with a new component. What should I replace it with? The datasheet can be found here: https://www.waveshare.com/wiki/0.91inch_OLED_Module


texts:
I plan to work on this field in the future (I'm still very new to the engineering world). I got some time free now and I would like to invest in learning more. Will I need any programming language in the design of integrated circuits? If so, in which should I focus?

Thanks, excuse my bad english.


texts: Selectively measuring AC magnetic fields with a Hall sensor (and getting an accurate Tesla reading)

texts: Is it possible to only measure AC electromagnetic fields in the 40 Hz — 120 Hz range with a resolution of 0.01 µT using a Hall effect sensor? If so, how would one go about doing it, and what particular Hall effect sensor should I be using?


texts:
What is the cutoff voltage for 18650 3.7V Li-ion batteries?

Since there is an internal regulator board on these how can they accurately be measured? When they reach their cutoff voltage will this circuit simply shut them off providing 0 volts to the load from that point?

I would like to debunk some of these Ultrafire batteries coming with crazy high maH capacities. I have a dummy load to drain them down, just not sure which voltage level qualifies officially for "depleted".


texts: All of the tube amp designs i see have the tubes exposed to air. Is this a design feature for heat dissipation or is it simply because some find it pretty?


texts:
I am desperately seeking the real type of this branded 44-pin microcontroller.
Does anybody know this pinout?

I already checked many thousands of 44-pinners on Digikey and Mouser.

A 16MHz crystal is connected to pins 8 and 9.

There is a good chance it's a Japanese brand, the PCB is manufactured in this country. Already checked Renesas, Mitsubishi, NEC, Hitachi, and the rest.

Maybe pin 1 location is shifted to another corner?


texts:
So my Xbox one PSU died and microsoft doesn't sell official ones yet, so I bought a third party one and the fan that is in it is a 12V blower fan with 2 wires running right to the board (it says 12V right on the fan). So obviously one of the wires is ground and the other is 12V. So I need help determining what would be the best method to lower the voltage to around 7-9V.

(The reason I'm trying to drop it is because this thing is extremely loud and pretty much unbearable, it runs cold all the time so I do not think heat will be an issue here, if it is I'll buy a new PSU)

So here is a photo of the set up: Album with pictures in it

How do you think I should go about doing this (resistors, diodes, I have no problem installing or trying anything, I was thinking a 25 ohms resistor with a rating of at least 5 watts).


texts: Use diode in parallel to increase current

texts:
I just realized that some diodes I have are rated for 1A only. I'm planning to wire a l298 chip to some stepper motors that are rated for 1.7A.

The datasheet seems to recommend to connect each phase to VCC and GND in reverse order. Something like this:

simulate this circuit – Schematic created using CircuitLab

My guess is that the current passing in those diode should never be really that high and must happen when phases are reversed as it seems to feedback current into the input.

Though the question is:

Will the 1A diodes be enough (IN4004).
If not, can I wire 2 diodes in parallel to spread the current accross 2 diodes instead? In other words, instead of using 8 diodes for 4 outputs I'd use 16.


texts:
I'm trying to control the current going into my hot glue gun which in turn allows me to control the temperature of it.

Saw some online diy projects doing it with a dimmer switch, but I'd like to have the knob on my hot glue gun, and the dimmer switch wouldn't possibly fit into it.

I'm guessing a variable resistor could do the work, but are there any variable resistors out there that wouldn't blow on 240V?

EDIT : So the variable current with a dial part now couldn't do, I'm thinking to add a slide switch (or some other type of switches that might work better in this scenario) which I'll then be able to choose a multiple of fixed current. Other that the diode method Steve G suggested, are there anyway I can reduce to a fixed current? Could resistors work at such a high power? My hot glue gun is rated at 60W.


texts: Question with solving for complex power, S, for each component

texts:
simulate this circuit – Schematic created using CircuitLab

Hi!

So I have a couple questions that I have already tried to solve that I think I am going in a little bit of the wrong direction with.

So at first I am suppose to find the source current \$i\$:

What I have tried to do seemed too simple. I made it so \$t=0\$. And so the voltage source was \$2\$ V. Then I did a KVL and got \$i = 1\$A. But I feel like I should've used impedances.

I know the impedances:
Capacitor = \$-10j\$
Inductor = \$10j\$
Resistors = \$1\$

How do I find the complex power of each component with the impedences?

Also side noting:

How do I change \$2\cos(10t)\$ to Vrms?

Thank you :)


texts: Can every voltage source accept fly-back diode's current?

texts:
A diode is used parallel to the motor (or inductive load) in order to prevent damage to the switch because of back-emf voltage.
Now, that back-emf voltage actually produces a current and by using a fly-back diode, that current is going into the voltage source which maybe a battery.

1- Is there any consideration one should take into account because current sometimes goes into the source?
2- What kind of sources or battery chemistries can and can not tolerate such current?


texts:
In all the textbooks the shown inputs to Op-Amps are AC.

Could one use Op-Amp to amplify a DC voltage? if the answer is no, why not?  Why only transistors can be used to amplify DC, aren't Op-Amps made of transistors?


texts:
I am currently trying to design a circuit on a Mac (some might say therein lies my problem).
My goal is simply to design a rudimentary implementation of the circuit which I can visualise working
I have tried:

Tinkercad circuits
the Falstad JavaScript (or desktop
version) circuit simulator
downloading LTSpice for
Mac.

The problem with 1) and 2) are that as soon as I start working with larger arrangements they start to bog down and stutter, both become unusable.
In terms of using LTSpice I am keen but I cannot find any suitable models for components such as a shift registers, 7 segment displays etc.

One point of intrigue with respect to this problem has been the NXP SimKit but I cannot even start to decipher whether it would work with LTSpice for Mac, can anyone help?


texts: Best way to find delay between receive data from USART

texts:
I write a code (for Atmega168P) for receive data from USART interrupt as below:

ISR     (USART_RX_vect)
{
    unsigned char count=0;
    unsigned char coder[13];
    int over_uart=0;

    for (count=0;count<13;count++)
    {
        while (!recive_485)
        {
            over_uart++;
            wdt;
            if (over_uart>=20000)   {
                coder[0]=0;
                count=14;
                over_uart=0;
                break;  }
        }
        coder[count]=UDR0;
    }
}

Each time that i receive 13 byte of data and put in coder array.

I use a variable over_uart for calculate time between each of received byte. if over_uart>=20000, means that:

The receive progress is start but we have problem in lines that do not get next byte in 20000ms And terminate the last command and look for new 13byte that will receive from line.

Any body know a optimized way that find delay between receive data from USART (without help of over_uart variable)?

  EDIT:

I correct the problem in my code and remove put delay in ISI as blow:

ISR     (USART_RX_vect)
{
    coder[count]=UDR0;
    if (coder[count] == 20)
        UartFlag=True;
    else
        count++;
}

And in Main function:

while (1)
    {
        if (UartFlag)
        {
            DoSomthing();
            count=0;
            UartFlag=Fulse;
        }
    }


texts: Why do I get "[Synth 8-5788] Register in module is has both Set and reset with same priority" WARNING in vivado and how to solve it?

texts:
after synthesis in xilinx vivado, I am getting the WARNING:

  [Synth 8-5788] Register next_state_reg in module example_code is has both Set and reset with same priority. This may cause simulation mismatches. Consider rewriting code.

why am I getting this warning and how to solve it without changing the logic in the below code sample ?

always @(posedge clk or posedge rst)
begin
    if(rst)
        state <= a;
    else
        state <= next_state;
end
always @(posedge clk or posedge rst)
begin
    if(rst)begin
        count = 1;
        wt_refresh = 0;
    end

    else begin
        case(state)
            a: begin
                wt_refresh = 0;
                if(in_put)
                   count = count;

                else if(count < hold*30)
                   count = count+1;

                else begin
                   count = 1;
                   next_state = b;
                   wt_refresh = 1;
                end
               end

            b: begin
                wt_refresh = 0;
                if(in_put)begin
                    count = 1;
                    next_state = a;
                    wt_refresh = 1;
                end

                else begin
                    if(count != 20)
                        count = count+1;

                    else begin
                        count = 1;
                        next_state = c;
                        wt_refresh = 1;
                    end
                end
               end

            c: begin
                wt_refresh = 0;
                if(in_put)
                    count = count;

                else if(count < hold*15)
                    count = count+1;

                else begin
                   count = 1;
                   next_state = d;
                   wt_refresh = 1;
                end
               end

            d: begin
                wt_refresh = 0;
                if(in_put)begin
                    count = 1;
                    next_state = a;
                    wt_refresh = 1;
                end

                else begin
                    if(count != 20)
                        count = count+1;

                    else begin
                        count = 1;
                        next_state = e;
                        wt_refresh = 1;
                    end
                end
               end

            e: begin
                wt_refresh = 0;
                if(in_put)begin
                    count = 1;
                    next_state = a;
                    wt_refresh = 1;
                end

                else
                    next_state = e;

              end
        endcase
    end
  end


texts: What library version is bundled with which version of the Arduino IDE?

texts: There are several libraries bundled together with the Arduino IDE. I wonder if there is a list which shows exactly which library (and bugfixes, code changes) where bundled with which Arduino IDE.