texts: STM32 send from UART3 and receive on UART2

texts:
I thought to create a simple test to send and receive a buffer via UART. I succeeded in sending bytes from my PC to the nucleo bord and receiving them in blocking and non-blocking mode. But for some reason I can't succeed to send data from UART3 and receive the bytes on UART2.

I have a nucleo-f103rb and have the following pins setup:

UART2: tx=PA2;rx=PA3
UART3: tx=PB10;rx=PB11

And then the following code:

  while (1)
  {
    /* USER CODE END WHILE */
    /* USER CODE BEGIN 3 */
    if (HAL_UART_Transmit(&huart3, send, 2, 1000) == HAL_OK)
    {
        if (HAL_UART_Receive(&huart2, receive, 2, 1000) == HAL_OK)
        {
            HAL_GPIO_TogglePin(GPIOA, LD2_Pin);
        }
    }
  }

All the boiler plate is generated using cube mx. So the UART 2 and 3 are all default, same for the button pins.

I connected the transmit pin of uart3 to the receiving pin of uart2
I connected the receive pin of uart3 to the transmitting pin of uart2 (while not used in this trivial example though)

What am I missing here?

Update

As comments and answers suggested, I shouldn't be using the blocking mode approach. So I rewrote it slightly to rely more on interrupts.

I attached a callback to the nucleo blue button

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
    if (GPIO_Pin == B1_Pin)
    {
        HAL_UART_Transmit_IT(&huart3, (uint8_t *)send, 2);
    }
}

And I added a callback for receiving stuff over uart

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
  /* Prevent unused argument(s) compilation warning */
  UNUSED(huart);

  /* NOTE : This function should not be modified, when the callback is needed,
            the HAL_UART_RxCpltCallback can be implemented in the user file
   */

     // Toggle the pin to see some proof that I received something
     HAL_GPIO_TogglePin(LD2_GPIO_Port, LD2_Pin);

     // Resubscribe uart2
     HAL_UART_Receive_IT(&huart2, (uint8_t *)receive, 2);
}

In the main function I call the interrupt so that the callback is active.

while (HAL_UART_Receive_IT(&huart2, receive, 2) != HAL_OK);

__NOP();
while (1)
{
}

Again, when debugging through I do end up in the button released callback, but the callback on the uart receive isn't triggered. When I send stuff from the PC, it does. So it seems that sending stuff via uart3 isn't working. So I guess that must be the wiring.

But I really can't see what I am missing here, the pins are clearly defined in the pinout here: https://os.mbed.com/platforms/ST-Nucleo-F103RB/.

I hope the photo is clear enough, but this is how I connected them.


texts: What is the significance of the OR gate in this Full Adder circuit?

texts:
simulate this circuit – Schematic created using CircuitLab

I don't understand the significance of the OR gate in the Full Adder because I don't think its input AND3 and AND2 will both ever be 1.

One of the requirements for an OR gate to produce (1) is if both of your inputs are (1,1), so AND2 and AND3 need to produce (1). For AND2 to produce (1) you need to have A2 and B2 to be (1). For AND3 to be (1) you need to have your XOR3 output have a (1) and your AND1 to output to be (1).

I can understand how AND1 can produce (1) but I don't understand how XOR3 can produce a value of (1) to feed AND3 without compromising the (1) value of AND2.

Because if A2 and B2 are given the values of (1,0) or (0,1) to produce (1) for AND3, then the value of AND2 will never be (1) because A2 and B2 need to both be (1).

Am I missing something?


texts: Separate PICAXE Download board Serial In pull down resistor

texts: I have a PICAXE (20M2) project that I am working on and I have two separate boards one programs the chip, the same chip then gets transferred to the other board, to which the peripherals (LEDs, Servos, Switches) are connected, for the PIC to do its work. On the second board (the non-programming one) I have read in the documentation that the serial in pin cannot be left floating and should be pulled down. Does anyone know what size resistor should be used between the Serial in pin and the Ground. Going on the below diagram (which is the schematic for the download board) I am guessing a 33K resistor (10K+22K rounded to the nearest value resistor I have available). Thanks in advance!


texts:
I've bought this 12V to Magsafe 2 85W car adapter so I can charge my MacBook Pro off of my auxiliary batteries without having to keep the inverter on (more efficient). If I understand correctly, this is using a DC-DC step up converter to take the voltage from 10-14V up to 20V. The problem is it gets HOT, especially if the computer is under load. The charger's own internal temperature protection kicks in and it stops providing current until it cools off. Is this just because it's a cheap / defective product or because 7A is too much for a 12V cigarette lighter style outlet? Can I expect the same heat to be wasted if I build my own DC-DC converter as outlined by this DIY article?
Some insights would be great, I just want to understand what's going on :)
UPDATE: I tried to build a heatsink for it that I stuck onto its metal back. It did not work. I took it apart and found that that the metal cap is connected to nothing internally explaining why the heat sink did not work. In addition, all of the electronics were encapsulated in foam, which I'm sure did not help with the overheating. I am now going to build my own like in the article linked but I have another electrical question.


texts: Does the per unit change in voltage   on secondary of a transformer depend only on the power factor of load and not the value/magnitude of load connected across the secondary?


texts: Is there anything wrong with my current setup for LED

texts:
I'm planning on building my own 5W high power LED Lamp, and this is my current setup:

Circuit

My power source is going to be 3 Li Ion Batteries in series, giving 14.8 volts for most of the time.

I then have the positive wire hooked directly to a Single Pole Single Throw switch, so if I have the circuit open there will be no current flowing, i.e. 0 power output from the battery.

These wires then lead to an adjustable buck boost converter with CC/CV, which I will set to a Constant Voltage of 12V and a Constant Current of 350mA as required by the LED

The output then goes through an adjustable PWM Dimmer with a potentiometerwhich then finally leads to the LED

This is my question - Is there anything wrong with having the PWM dimmer AFTER the Buck Boost converter?

I also want to know whether the entire circuit is going to be using 5W (exluding inefficiencies) all the time, regardless of whether I set the PWM dimmer to a duty cycle of 10%, 50%, or 100%?

Should I move the PWM dimmer BEFORE the Buck/Boost converter, so that I control the duty cycle before the power is sent on?


texts: Why do we use an opamp to produce a voltage output above 1V in this circuit?

texts:
I wonder what advantages (regarding noise or other important factors) the opamp circuit:

holds over a circuit consisting of only a photodiode and a resistor (the resistor has to be placed where the voltage (V) is):

The math should be the same:
$$ U_{out} \propto R * I_{photodiode} $$

I'm curious what your ideas are.

P.S.: I want to use a circuit to pass a voltage proportional to the photodiode current to the ADC of an µC.


texts: Measuring resistance with ohmmeter over resistor and capacitor in parallel

texts:
In "Teach Yourself Electricity and Electronics, 6th Ed."  [Gibilisco] (2016) a test question reads as follows:

A DC ohmmeter will give us a correct reading for a component in isolation (not connected to anything else) if that component"
(a)  contains inductance and resistance in series.
(b)  contains capacitance and resistance in parallel.
(c)  contains pure resistance.
(d)  contains pure inductance.
(e)  Any of the above.

The correct answer is claimed to be (e).
My question pertains to (b): Assuming a large capacitance inside the component, wouldn't it take some time before the correct reading could be obtained, since it would take some time for the voltage across the capacitance to creep asymptotically towards the voltage of the internal battery of the ohmmeter (during which time the ohm-reading would be too low, because of higher-than-final current through the internal ammeter of the ohmmeter)?
EDIT: When posing the question, I was unaware of the different ways of measuring resistance, e.g. keep voltage stable and measure current OR keep current stable and measure voltage, the LATTER being the preferred method in modern multi-meters. I naïvely assumed stable voltage.
With my question I was asking for confirmation that the resistance reading can take some time to settle to the actual value. This has been confirmed by the accepted answer to be the case, regardless of the type of ohmmeter employed. (With a large internal capacitance in the measured component and an ohmmeter using a small fixed current, presumably the measurement could take a LONG time to settle to the resistance value of the resistor.)


texts:
I am building a power supply circuit, and the switching regulator (L4963) calls for a low-ESR output capacitor. The capacitor in question is C3 of the evaluation board circuit.

What does "low" mean? How low?

Also, how do I find or calculate the ESR for a capacitor whose datasheet does not have a parameter called ESR?


texts: How to synchronize 2 PCBs with only 1 pair of clock?

texts:
I got a TX and a RX now, on 2 PCBs, between which I want to establish communication. The problem is, first I only have one pair of differential clock from the clock generator, but both of TX and RX need one.Also, I think they need same-frequency clock to work properly, so using 2 different clock generators is not perfectly reliable.

Now I am thinking of designing an extra PCB, on which the clock to be used is bifurcated to provide 2 clocks. The clock can be running as high as 10GHz, so impedance continuty has to be considered at the bifurcation.

I want to know if there is any other better way to deal this, like using a single-to-differential chip? Or any problem or concern with my method?


texts: How to simplify the actual function using K-maps?

texts:
So I'm trying to learn how to use Karnaugh maps. I've found what are the rules of simplification and how to apply them but every tutorial or lesson I find uses some generic function like "Here's how to do Karnaugh maps for three variables" and someone just does the truth table for A, B, C and then creates a map. But what if I wanted to simplify some specific function, say F=AB+A(B+C)? I can't just make a truth table for A, B, C and their sum because it's just not enough. So how should I solve it using Karnaugh maps? Should I make a "typical" truth table, i.e. for A, B, C, AB, B+C, A(B+C)? But how should this help me in drawing the map and simplyfing?

Could someone please tell me a little about it or point some direction? I'd really like to learn this but just can't get a grasp of it.


texts: Hardware For Emitting Specific Sound Frequency

texts:
I need a battery-powered hardware setup for emitting  a specific frequency or a range of frequencies, in the range of 17kHz-20kHz. It should be picked up by microphones from at least 8 meters away (not sure how to convert this to Dbm).
The strength of the signal has to be relatively stable for at least one hour.

I have several questions:

Is there a hardware solution that does this?
If I would want to make one myself, what would I need? Let's say I use Arduino with a buzzer, what buzzer and battery would you recommend?
Any other suggestions or considerations I did not provide and should consider?

Thanks!

Edit:
I fixed 17-20Hz to 17-20kHz. Do waves in this Frequency still come out squared when toggling buzzer input?


texts:
As S1 is 1 (5v) and S2 is 0 (0V) then D1 is conducting D3 and D4 is reverse biased D2 is conducting. Q1 is switched over and shuts the output to 0V via D2 and S2.
Etc. All states. Someone will explain the rest
Thank you
the first pattern is good and the second pattern is bad.


texts: I have a relatively simple question on the grid voltage. When we say the voltage from the wall is 220 Vrms is that the line-line voltage or is that the phase voltage. ie are the two output lines from a socket both hot (in which case each line’s magnitude would be 220/sqrt(3) Vrms)  or is one hot and the other neutral?


texts:
I would like to identify this connector in order to buy it
This is the same size as DB25 but this is not with pin like on the parallel port

[![enter image description here][1]][1]

[1]: https://i.stack.imgur.com/az0Tz.jpg


texts:
I am currently devising ways to shut off different circuit sections in an embedded circuit. Here is a breakdown of what I am doing and my initial idea. Currently I have a micro controller which is sampling multiple analog sensors and in between sampling it goes on to sleep mode, but know due to the low power constraints in the specs, I would like to shut off some of the individual analog circuit sections (equivalent to each sensor circuit), my current Idea is through the use of Op Amps and ICs with shutdown support, however I am also wondering whether I can actually use an "IC" to cutoff the power to a circuit section based on a digital output or via a digital interface (I2C, SPI... ETC) which will allow me to completely isolate that section from the circuit, but is this possible?

Any Feedback or if you can point me to application notes, design notes, research papers, links... I would greatly appreciate it.


texts: Measuring touch-weight resistance in piano keys

texts:
Piano technicians, such as myself, use an old, labor intensive way of measuring touchweight resistance in piano keys.  I would like to automate this process electronically.

This is an explanation of the manual process I'm trying to automate.

A piano technician places successive 2 grams weight increments on top of a piano key until it begins to move downward.  Then at the moment it begins to move downward he records the gram weight value, usually 25-50 grams (this is the downweight).  Then he takes off some weight until the key rises again (this is the upweight).

Here is a explanation online - with a video. https://www.youtube.com/watch?v=HAYnD1CWwjA

How would you go about making a project which charted these two values and did it electronically?

What would the electronic action of "key pressing" look like? How could I approximate the manual procedure?

How should I start a project like this? what do I need to know, other than what I've already found out below?

This is what I currently know or have researched.

It should measure the downweight and the upweight through the keystroke (usually between 3/4 to 5/8 inch key dip).

According to what I've researched, I would use some kind of strain gauge / load cell, and perhaps a servo or solenoid to press down the key electronically.  This would presumedly be connected to an arduino, or raspberry pi which would be programmed to interpret the results.


texts: Why does my PWM Arduino loop not working as intended?

texts:
I have a Arduino sketch I am trying to use to control a DC motor using PWM. It seems it it just running the motor as if I the PWM was set to 255 (100%). I intend for my sketch to start the motor slowly (0) and increase every 30ms to 255, then back to 0. However it just seems to run at 100%. Any thoughts? Here is my code.

int con = 5;
int amm = 0;
void setup(){
  pinMode(con, OUTPUT);
}
void loop(){
  analogWrite(con, amm);
  amm = amm + 1;
  if (amm = 255) {
    amm == 0;
  }
  delay(30);
}

Am I missing something? I don't code alot in C so maybe I did my loop or variables wrong? Thank you for your help!


texts:
I have dell laptop D600m. I have a charger for it but the charger does not work properly meaning that it can power the laptop but does not charge the battery of the laptop.

I opened the charger and saw the circuit of the charger and found a problem in a transistor at the end the circuit which two legs are connected but the 3rd one is free. The transistor no is Dallas 2501+0447D3+170AA. I live in peshawar Pakistan, I searched in different electronics shops but could not find anywhere.

How can I replace that transistor with some other which is available in shop easily. I bought two other chargers but after some time they had the same problem.


texts: Circuit with reverse polarity data lines

texts:
let`s say I have 2 Microcontrollers and I want to connect them to send data between them. I have one dataline and GND (datarate or how to sync is not part of this question). Is there a possibility that I create a circuit where it doesnt matter which way I connect the the 2 Lines so that one MCU detects which Rail is GND and on which rail to send the data?

Both of them have to be connected to the same gnd right?

I have seen some Bussystems where it doesn`t matter how the 2 Lines are connected. How is this archieved?

Thanks in Advance

EDIT

would it be a good idea to implement some kind of twisted pair communication?


texts:
Im trying to draw up a circuit with two bulbs and two spdt switches.
In this circuit one of the two bulbs must always be on, and both switches must be able to swap which bulb is on.

So to avoid any confusion: Both lights must change state (on to off or off to on) when either switch is used, One light must be on the other off, I only have two single pole double throw switches and must use both.

This is seems like a simple circuit like but i am having a very hard time working this out. Thanks for your help.


texts:
Regards to all

I'm totally new with electronic and I need help with some schematics.

I find one circuit that fits my needs: simply instantly turn on the LEDs with press of a switch and dims them on release. Now I want to use IR photogate instead of a switch but when I combine another web based circuit of a IR photogate in Circuit Wizard software, dimming effect from first circuit is lost.

Am I on a right track and what am I doing wrong?


texts: Why modern oscilloscopes use hardware triggering?

texts:
I've been learning how DSOs work for the past few days. As far as I understand, digital storage oscilloscopes have trigger circuitry, which usually consists of an analog comparator and a DAC. A voltage, corresponding to the trigger level is generated with a DAC and compared with the amplitude of the input signal. Once the input signal passes the threshold level, the acquisition starts.

My actual question is: why can't this all be done in software? Wouldn't that be easier to constantly acquire data from ADC and store it into a circular/FIFO buffer and compare the values with the given trigger level?


texts: What should I use for powering a Raspberry Pi at near space altitudes?

texts:
I'm planning a high-altitude weather balloon project (to around 100000 feet) some time down the line to take video and pictures of near space altitudes and I have some questions I need to ask before doing so.

I've decided to go with a Raspberry Pi B+ with a Raspberry Pi camera module to record 720p/1080p of footage from the edge of space. However, I'm not sure what to use for powering it. I'm thinking of using this 10400 mAH / 2.1A
Xiaomi Power Bank to power the electronics including an Arduino, GPS transceiver and various other sensors. Will this be a safe bet to work at the edge of space? What alternative power supply options are available for this application?


texts:
So I just bought and installed a new fuse for an analog multimeter I scored for free and now it works like a charm.  The new fuse is the same rating as the blown one I found inside, which is 0.5A 250V.  The meter has a warning symbol  consisting of a little triangle with an exclamation point inside it and says 500V.

I'm completely new to electrical engineering, because I am a Computer Science student.  My question is, besides accidentally passing the Ω or kΩ settings while hooked up to a power source, what other things should I avoid doing to prevent the fuse blowing or any other damage to the meter or myself?


texts: Soldering leads/pins to SMD/SMT for solderless breadboard prototyping?

texts:
Background:
I just began with electronics and I'm looking to build a 12v to 5v converter circuit.  My plan is to use a Murata 78SR-5 to power either an Arduino or Rasberry Pi.  I'm studying electronic design on my own as a hobby so I may not have adequate circuit design as of yet, but I have noticed that there are few available for purchase capacitors with leads|pins on them which can be used on solderless breadboards.  I can't find a capacitor with the specific voltage range with leads already existing for use with solderless breadboard prototyping so I turn to SMD/SMT type.

Question:
What details are needed to know, if soldering leads/pins to SMD/SMT capacitors or resistors practiced?  e.g. temp, wire size, wire alloy, etc.


texts:
I have an issue where I want to count how many times I hit a switch using an interrupt. I tried placing the count variable inside the main but it claims that count does not exist. I put count inside the pragma but I know that will reset the count value to 0. How should I approach this problem?

I'm using the STM8S003K3

volatile int count = 0;

#pragma vector = 8
__interrupt void EXTI_PORTD_IRQHandler(void){
   count++;
   PD_ODR_ODR3 = !PD_ODR_ODR3;
}

void main() {
   __disable_interrupt();
   PD_ODR = 0;             //  All pins are turned off.
   PD_DDR = 0xff;          //  All pins except PD4 are outputs.
   PD_CR1 = 0xff;          //  Push-Pull outputs.
   PD_CR2 = 0xff;          //  Output speeds up to 10 MHz.
   //
   //  Now configure the input pin.
   //
   PD_DDR_DDR4 = 0;        //  PD4 is input.
   PD_CR1_C14 = 0;         //  PD4 is floating input.
   //
   //  Set up the interrupt.
   //
   EXTI_CR1_PDIS = 2;      //  Interrupt on falling edge only.
   EXTI_CR2_TLIS = 0;      //  Falling edge only.
   __enable_interrupt();

   while (1) {
       __wait_for_interrupt();
   }
}


texts: How should I understand FPGA architecture?

texts:
I've been given the task to make a 2-bit adder by programming a FPGA. The FPGA is seen below:

However, I don't even know how to begin this task, because I don't understand what I am looking at.

What are all those green lines supposed to do, and what about those green and red shapes?

I hope someone can clarify this for me, since I really want to understand it.

PS: I don't know if it is essential in understanding what's going on, but this figure was included in the problemsheet as well:


texts: IR led extremely slow to turn completely off?

texts:
I'm working on a project where I'm simply reading the amount of light emitting from an IR led with an IR sensor.
For some reason, after the IR led reaches full luminosity, it takes a minimum, whopping 500ms for the IR sensor's readings to drop from 65536 (16 bit resolution) to ~0.

This is my circuit:

simulate this circuit – Schematic created using CircuitLab
Figure 1. OP's schematic redrawn by @Transistor (for verification).
This is my code:
#include <ADC.h>

ADC* adc;

int ir_led = A8;
int ir_sensor = A9;

void setup() {
    Serial.begin(115200);
    configureADC();
    pinMode(ir_led, OUTPUT);
    pinMode(ir_sensor, INPUT);

    delay(1000);
}

void loop() {
    digitalWrite(ir_led, HIGH);
    delay(10);  // wait for ir led to reach full luminosity

    int start_time = millis();
    digitalWrite(ir_led, LOW);
    while (adc->analogRead(ir_sensor) > 50); // wait for LED to turn completely off: a reading of 50 out of 65536 is equivalent to 0 with environmental noise
    int end_time = millis();
    Serial.print("DELAY TIME (ms): ");
    Serial.println(end_time - start_time);

}

void configureADC() {
    adc = new ADC();

    adc->setAveraging(16); // set number of averages
    adc->setResolution(16); // set bits of resolution
    adc->setConversionSpeed(ADC_CONVERSION_SPEED::HIGH_SPEED_16BITS);
    adc->setSamplingSpeed(ADC_SAMPLING_SPEED::MED_SPEED);

    adc->setAveraging(16, ADC_1); // set number of averages
    adc->setResolution(16, ADC_1); // set bits of resolution
    adc->setConversionSpeed(ADC_CONVERSION_SPEED::HIGH_SPEED_16BITS, ADC_1); // change the conversion speed
    adc->setSamplingSpeed(ADC_SAMPLING_SPEED::MED_SPEED, ADC_1); // change the sampling speed

}

Serial output:

Plotting the sensors readings:

Some delay is expected, but 500ms does not make sense. Can someone help me figure out where this delay is coming from and why?


texts: Excessive voltage drop from LiPo battery

texts: I am using a 750mAh 25C 3.7v LiPo battery for a custom electronics project which currently draws ~1.5 amps, far below the rated operating current of (0.75 * 25 = ) 18.75 amps. However, at the battery terminals (before any PCB traces) I am noticing a drop from 4.03v to ~2v, below the 3.3v I require for my MCU. Why is this drop so significant? Is the battery bad?


texts: How would I properly develop a current rating for this system...?

texts:
I have a system that I have recently developed for in house (manufacturing) equipment testing. Transformers rated for 80VA (264V, .303A) are used in series and rectified using a full-wave diode bridge. The signal is leveled out by capacitors to produce a DC bus voltage. A fuse is placed in series with the windings of the transformers and rated for .315mA.

Should the system be rated for .303 mA (the rating of the transformers), .315 mA (the rating of the fuse) or higher (more current possibly pulled from the bus caps)?

here is a schematic of the system:

Voltage ratings were easy to figure out. I turned on the system and turned the input variac as high as it would go.


texts: Modification to Arduino 12V Detection Circuit

texts:
I'm upgrading the interior lights on an older model vehicle. The plan is to tap into the very simple lighting circuit (always hot with a switch for on-off-door) to detect each scenario. Light switch on, stock lights come on = Arduino does something; Light switch in door position and doors open = stock lights come on, Arduino does something different.

In response to a similar question a few years ago, Phil Frost uploaded the following diagram, which uses a pull-up resistor before the optocoupler:

I would like to modify this circuit, such that current only flows on the Arduino side if it is also flowing on the 12V side. Here's what I've come up with:

There are a lot of other details to this project, but the questions I have are just regarding this circuit:

Will this work just as well as the original?
Is there any benefit to using the modified version over the original?


texts: What is the state space model for a BLDC motor

texts:
I wanted to model a brushless DC motor so that I can add controllers(PID ) to correct the transient state behaviors. I started to model my BLDC and I found some model. Then I used specs from MAXON motors to verify my model by  supplying my model with nominal voltage and looking at the no load speed. The problem is that the no load speed I found from my state space is not the same as the one on the data sheet. It led me to believe that my state space model is wrong. But I could not find out what is wrong. I scoured the internet for answers but still could not find a usable model. I need to find out where I am wrong so that I can correct it. I will explain how I modeled the motor.

TRIAL

The first is the BLDC schematic.it is a 3 phase motor so we are going to have to work with wye or delta connection.i started with wye connection of stators, and assumed it is balanced. There is an inductance of \$L\$ per phase and resistance of \$r\$ per phase. The figure shows how I converted wye to delta so that I can some how convert the 3 phase scheme to a single phase one.

Each line voltages are going to be triggered one after the other for electrical commutation. The idea is that even if  this lines are commutated one after the other, each  current values and voltage values should be the same except for phase changes, so I can take one line voltage circuit and work as if it was a brushed dc motor( this assumption might also be the source of error, if it is please correct me ). So the circuit for one line is:

Now from this model, I got my state space model to be:
states

$$\begin{bmatrix}(\omega)\\(I)\end{bmatrix}$$

inputs
$$\begin{bmatrix}((v)\\(Tl)\end{bmatrix}$$

\$ Tl \$ is the load on the torque , since I want to verify it at no load it is zero

outputs

Are the states themselves

state space

$$A=\begin{bmatrix}(\frac{-R}{L})&(\frac{-ke}{3L})\\(\frac{kt}{j})&(\frac{-bm}{j})\end{bmatrix}$$

$$B=\begin{bmatrix}(\frac{1}{3L})&(0)\\(0)&(\frac{-1}{J})\end{bmatrix}$$

$$C=\begin{bmatrix}(1)&(0)\\(0)&(1)\end{bmatrix}$$
$$D=0$$

The specs I used to verify the model is for maxon motor which has the following characterstics:

I plugged in my \$k_{t}\$ (torque constant), my \$k_{e}\$ (speed constant ) and finally my \$bm\$ (torque speed gradient). Using matlab the output plot at steady state is about 4170 but from my data sheet it should go to 16700 rpms and my current from state space is 2.5A but my data sheet says it should go to .723A. So what seems to be the problem with the model.


texts: Address Sent bit is not set on STM32F4 Disco

texts:
I am trying to interface my STM32F4 Discovery board with a sensor that works over i2c, since the sensor required a specialized i2c protocol, I decided to implement my functions using registers. But when I am trying to send a byte and check the BTF bit of the SR1 Register if the byte transfer is finished, it never seems to get cleared and my code hangs in the while loop indefinitely.

        while (!(I2C3->SR1 & I2C_SR1_BTF)) ;

And if I manage to pass that while loop commenting that out  then it stuck while waiting for the address transmission bit.

while (!(I2C3->SR1 & I2C_SR1_ADDR))  // Read Request Adress set

Whole snippet :

unsigned int axI2CWriteRead(unsigned char bus_unused_param, unsigned char addr,
                        unsigned char *pTx, unsigned short txLen,
                        unsigned char *pRx, unsigned short *pRxLen)

extern I2C_HandleTypeDef hi2c3;
HAL_StatusTypeDef status;
uint8_t t;
*pRxLen = 0;
memset(pRx, 0, 2);
uint8_t rxData[255] = {0};
uint8_t index = 0;

    I2C3->CR1 |= I2C_CR1_START;
    while(!(I2C3->SR1&I2C_SR1_SB));
    I2C3->DR = 0x90;
    while (!(I2C3->SR1 & I2C_SR1_ADDR))
        if (I2C3->SR1 & I2C_SR1_AF)
         return I2C_FAILED;

    t=I2C3->SR2;
    while(index < txLen)
    {
        unsigned char a = *(pTx+index);
        I2C3->DR = a;
        while (!(I2C3->SR1 & I2C_SR1_BTF)) ;
        index ++;
    }

    index = 0;
    I2C3->CR1 |= I2C_CR1_START;/* Generate Start */
    t = I2C3->DR;
    while(!(I2C3->SR1&I2C_SR1_SB));// Wait until SB is set
    I2C3->DR = 0x90|0x01;

    while (!(I2C3->SR1 & I2C_SR1_ADDR)) //Wait for flag ADDR=1
        if (I2C3->SR1 & I2C_SR1_AF)
         return I2C_FAILED;

    t = I2C3->SR2; //Read SR2 for deleting ADDR

    while(!(I2C3->SR1&I2C_SR1_RXNE));
    rxData[index]=I2C3->DR;

    uint8_t messageLength = rxData[index];
    while (index <= messageLength)
    {
        while(!(I2C3->SR1&I2C_SR1_RXNE));
        if(index == messageLength)
        {
            I2C3->CR1 &= ~I2C_CR1_ACK;
        }
        else
        {
            I2C3->CR1 |= I2C_CR1_ACK;
        }

        rxData[++index] = I2C3->DR;
    }
    I2C3->CR1 |= I2C_CR1_STOP;

        *pRxLen = rxData[0] + 1;
        memcpy(pRx, rxData, *pRxLen);

if (status != HAL_OK)
    return I2C_FAILED;

return I2C_OK;

When I check the i2c bus, I can see Transmission of the address was done correctly but data byte has never been written on the SDA line.

Do you have any idea what might cause the data not being sent or what might cause the Address sent bit of I2C_SR1 not being set ?

Note :I am using 6.8k pull up resistors


texts: I purchased a few of these units and have no idea what they are. Is there anyone that might have some suggestions?

texts: The item measures 1" wide and 1-1/4" high nad about 1/2" front to back


texts: Guitar signal preamplifier - ADC input to STM32F4

texts:
This is for a DSP project. I am trying to prepare my guitar signal for as best as possible ADC response in order to detect harmonics to the 5th of the highest note of the guitar (1175 Hz for 22 frets), which is about 5875 Hz. This means that I need to be sampling at about 58.75 kHz, which is possible with the microcontroller and it's DSP functions.

I am using an STM32F407 Discovery board.

So far, I have not come across any solutions that I am happy with.

Considerations that are important:

Guitar output impedance: about 1M ohm.
Anti-aliasing for the ADC
Guitar signal of 500mV Vp-p max
ADC input range 0-3.3V
5V single supply
Frequency range from 82Hz and 5875 Hz

Does anyone have any suggestions of a circuit that I can use? I have TL082, LM358 and LM741 opamps available, but I am open to other suggestions.

The goal of this element of the projects is to be able to use the first 5 harmonics and a sampled period of the guitar signal for further DSP.

This is what I have come up with so far - although I believe it's far from ideal.

This is a closed loop bode plot of the system. Couple of things that worry me are the massive phase differences at the corner frequencies, and the slope of the low pass filter and it's stop frequency. The cutoffs are at 10Hz and 10kHz

Any tips would be greatly appreciated.


texts:
Below is the complete circuit for a PWM control output:

(please left-click to enlarge)

"Out" in the schematics will be directly connected to PWM input of a 3-wire or 4-wire DC fan.

Since I don't know the input impedance of the fan, I decided to use a PNP transistor at the output of the LM393 comparator.

Here is the output waveform of the comparator:

And here is the final output after the PNP (there is like 0.9V offset):

(please left-click to enlarge)

As you see using a PNP is introducing offset to the output signal.
Is there a technique or another coupling way to fix this issue without using another opAmp?


texts: Loop Filter cutoff frequency of an all-digital PLL

texts:
I am trying to implement an all digital PLL for FM demodulation on an FPGA using VHDL. I built all the blocks needed, i.e the NCO centered at 100kHz, the phase detector(simple multiplier) but now I am struggling with the loop filter. What should the cutoff be for the loop-filter so as to have a good output signal ?
I am trying to implement the follwing :

I have not yet closed the loop. This means that the NCO is stuck at 100kHz and I am varying the input signal with a function generator. WHat should be the final cutoff frequency of the loop filter so as I could see the phase error as a stable DC signal at the output of the loop filter ?

Thanks.


texts:
I found a question to practice so I can increase my experience in RTL design. I am trying to come up with a generalized design which can support all these requirements.
Here are the details:
Black-box details:
Name: tag_replicator.sv
Design-time parameters: DATA_PARALLELISM -> (1, 2, 4, 8)
Run-time parameters: n_l -> (1, 2, 3, 4)
Flip-Flop-stages: 1
I/O interface: AXI-streaming
// Input Interface
input   logic [2:0]                   n_l;
input   logic [DATA_PARALLELISM-1:0]  i_data[1:0]; //(data tag)
input   logic                         i_valid;
input   logic                         i_last;
output  logic                         i_ready;

// Output Interface
output   logic [DATA_PARALLELISM-1:0]  o_data[1:0];
output   logic                         o_valid;
output   logic                         o_last;
input    logic                         o_ready;

White-box details:
DATA_PARALLELISM = 1

DATA_PARALLELISM = 2

where 'X' indicates back-pressure. T is a 2-bit tag which, according to the specification, tells the mode of operation.
Any solutions/suggestions are welcome.
Edit: To answer what this design is about?
Answering w.r.t relaxed 5G communications terminology.
N_L is the number of MIMO layers. Each Resource Element (RE) in an OFDM symbol may contain N_L number of complex modulated (QAM) IQ samples. This utilises multiple transmit antennas for spatial multiplexing. Now, in order to match the throughput of the downstream modules. Each tag which tells the type of RE, needs to be replicated for each IQ LLR. I hope this helps to understand the bigger picture.
Also, I already have a solution to this which I may give as an answer if nobody has any new ideas in the next few days.


texts: how can I motorize hand cranked standing desk

texts:
I already have a hand cranked sit stand desk, which I would like to motorize without too much damage to the existing mechanism and (for not too much money). As it is hand cranked, there is an existing lifting mechanism.

Details on the desk: Manufacture's website

The crank requires 14.7N (1.5Kg) at 16cm away from the center of axle:

And the connection in to the lift mechanism is a 6mm hex hole:

I was thinking of using a stepper motor to replace the crank as it would give good acuracy and was easy to control with an arduino (or something like that).
Up til now I haven't found anything with the correct amount of torque suitable for this application (I was going off ~2.5Nm).

The mechanism does not lock


texts: Allowable ripple current οf battery charger

texts:
The ripple of the charging current is pretty important for the aging of an electric battery. So, the current ripple should be as less as possible. In order to reduce the current ripple, we have to use bigger values of inductances (For instance in a boost converter). So, there is a takeover between current ripple and the value of L.

I would like to ask about the maximum value of the current ripple (DI %) that it is chosen in a real application (such as Electric vehicle battery charger). A value of 2.5% current ripple is acceptable?


texts: How to connect same signal pads in Package Editor in Eagle?

texts:
So, I'm trying to make a circular pad for a project:

To try to make my life easier when changing inner and outer diameters I created a package which consists of 2 pads: one horizontal, which connects one "fin" to the next one, and a vertical one, which is the fin itself.

The "origin" distance is the radius of the pad.

My problem is, I don't want the "unrouted" yellow connection between the pads since they're already touching, and the Package editor doesnt have the route command.

Is there a way that does not involve using the "wire" command and trying to guess the pad center? (I'm not sure if even this would work).

p.s.: I know if I just ignore the request to route it, I'll probably be fine. But I'd like to know if there's a proper way of doing it.


texts: What to look for in desoldering/rework equipment?

texts:
I am considering purchasing a desolder/rework station for through-hole work. I'm a hobbyist and don't often repair boards, but do sometimes remove components from things for reuse.

I recently repaired a motherboard by replacing damaged electrolytic caps, and after struggling with a 30W iron and a spring-loaded vacuum tool, I took the board to a friend who had a Pace rework station with a vacuum nozzle. What a difference the right power and tool makes.

So now I'm on the lookout for purchasing a similar station for my workshop. But the array of features and manufacturers is confusing, and most units are priced out of my budget (which, ideally, would be less than $500).

Does anyone know of the type of solder/desolder station a hobbyist should look for? What features can I safely ignore, because I do not do production work on a daily basis? Conversely, what should I opt for that will make things easy and are worth the cost?

For example, I've looked a Hakko FM-205 which seems like a good idea, but I'm wondering if its requirement for shop air is going to be a huge headache. (I do have a compressor.) Should I opt for one instead with a built-in pump?

I want something that can be used for soldering and desoldering both, to replace my worn-out RS pencil irons.


texts: Channel 4 in STM32 Advance Timers TIM1 and TIM8

texts: There are advance control timers in STM32 family as in STM32F407 and these are specially suited for 3-phase (or 1-phase also) motor control applications using full H-bridge. These timers provide complementary output signals to drive the upper and lower h-bridge switches. This much is understandable from the datasheets. But there is a 'Channel 4' which is also available in these timers without the complementary output as shown in the image. I wonder what is the purpose of this timer?


texts: I have a smart card that is used with a Respironics CPAP machine.  I need to read the data off of the card.  I have the Windows software for the card but I don't have a card reader just yet.  Many people say you need a specific MAKO DT3500 card reader which costs 60-160.00.   In the manual it says that you don't need a driver if you use a serial smart card reader.  My question is: Are serial smart card readers able to access data on most any/every smart card out there?  Is it like a SD memory card reader where pretty much anyone I buy will be able to read the card?  Is that the same for the USB versions?  If I buy a newer USB reader and load the drivers that came with it, will the Respironics software be able to see it.  I know this might be hard to answer but in the experience of the smart card users out there do you generally need a specific card reader for a specific card?


texts:
I am working on a circuit that contains CD4043 R/S latch. The design on the breadboard works and everything is great, as soon as the PCB was manufactured and components were soldered, an issue with the latch arose.

I use the switch-button on the SET input to initialize the latch and for the restart. But somehow on the output, I always get 0 with no matter what is on RESET input. The exception is when the button is actually pressed, then I have 5V.
However, as I said before, there were no problems on the breadboard.
What I did, but it doesn't help:

All the unused latch inputs connected to the ground.
Decoupling capacitors across VCC and ground.
The design itself based on logic components. Calculated delay times, there should be still enough time for the latch to recognize 5V from the switch, but it somehow doesn't 'hold' it.
First used SPDT switch, then replaced it with single pole switch + resistor, to avoid open circuit state at the moment of switch.

Nothing has helped :'( :'( :'(
Please advice. If you need extra details I am ready to provide.
EDIT 1: I attached the actual electrical circuit to make it clear.

EDIT 2: I need the latch output to depend not only on the input signals (A and B in U3), but also on its own output, i.e. if at least one of the input signals is off, the latch goes to 0. As soon as input signals are back, the latch should stay in 0 state until it's initialized with the switch S1.


texts: How to select the setup time and Hold time for the DDR3/4 SI analysis?

texts:
I am performing SI EYE analysis for the DDR3 interface.
Following are my consideration for the DDR3 SI analysis:-
Data rate= 800MHz/ 1600 MT/s
Data UI = 0.625ns = 1/800MHz
Address, command and control UI = 1.25ns = 1/1600MT/s
But I am little bit confused in selecting the exact Data setup time and Data hold time values
and
add,cmd , ctrl setup time and hold time
May I know the perfect way to select the setup time and hold time for the DDR3/4?


texts: How to find the resonant frequency of a human body?

texts:
I've read that the human body has resonant frequencies somewhere around 50MHz. I also think it would be interesting to look for values in other ranges like 10-100 kHz. I'm wondering how to build a device which can measure these frequencies and track them as they change.

I was thinking about using a circuit designed for a crystal oscillator, and just putting a human where the crystal would be. However, I'm not sure about the various ways in which the analogy could fail. Also, usually circuits for crystals specify a very specific oscillation frequency. I might be looking for a circuit where, for instance, I specify a wide range like 20-40 kHz, and if I connect it to some parallel LC circuits with a resonant frequencies of 15 kHz and 34 kHz and 100 kHz, then it will oscillate at 34 kHz because that is where the impedance is minimized within the specified range.


texts: Underground cables and resonances in range of frequencies

texts:
Is that true that underground cables with no power factor correction have resonances
in range of frequencies which leads to multiple zero crossing distorted waveform?

But why? Is that is because it work as a band-pass filter?

From the book Electrical Power Systems Quality:

  While they may cause interference with low-power electronic
  devices, they are usually not damaging to the power system. It
  is also difficult to collect sufficiently accurate data to model power
  systems at these frequencies. Acommon exception to this occurs when
  there are system resonances in the range of frequencies. These resonances
  can be excited by notching or switching transients in electronic
  power converters. This causes voltage waveforms with multiple
  zero crossings which disrupt timing circuits. These resonances generally
  occur on systems with underground cable but no power factor correction
  capacitors.


texts: Ultrasonic dual transmitter-receiver circuit

texts:
I am building an ultrasonic flow sensor, based on piezoelectric actuators from cheap HR-SR04 modules. I need to measure the speed of sound back and forth. Schematic like this is good to send pulses:

But then I need to switch this transmitter and receiver actuator. How to do this? Use mux? Or there is some generic driver schematic, which combines high-voltage sender circuit plus input amp?


texts: I am trying to understand what a rated voltage/current/power mean for a machine. when I google it, I typically get information on how to find it from nameplate, but I am trying to understand it conceptually. Say, I manufacture transformer. I take certain wire and do 100 windings in the primary, then take the same wire do 20 winding in the secondary. Now, if I were to write the nameplate, how would I do so? Ideally, the conductors should conduct till it melts and core can intake more flux till it saturates. On what basis, can I tell a particular voltage/current to be rated?


texts:
I am working on a project on image tracking on MATLAB, by moving the mounted camera on a servo motor controlled by the Arduino Uno board, the data is serially sent to the arduino using USB according to which the servo motor changes its angle, but there a problem at start the motor initializes to its RESET position that is 0 deg, but after passing an angle serially its does not move back to RESET position when I send 0 as a angle again.

#include <Servo.h>
Servo myservo;
int incomingByte=0;
void setup() {
  Serial.begin(9600);
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
}
void loop() {
  if(Serial.available()>0){
    incomingByte=Serial.read();
     Serial.println(incomingByte,DEC);
    Serial.write("readvalue");
    myservo.write(incomingByte);
  }
}

It also doesn't response to some of the angles which are sent serially. I am using a SG90 servo motor, here is its datasheet.
Thanks.


texts: Firmware & Circuit of ATtiny45 direct USB 2.0 Connection

texts:
I want to make my own modular USB device using an ATtiny45 that simply sends data to the PC over USB. I'm not reading data, so a single way ( ATtiny -> PC ) connection would be completely okay.

I am using an Arduino Uno as ISP with the standard ArduinoISP sketch loaded from within the Arduino Software. I'm thinking of using AVRDUDE to programm the ATtiny45 with the Arduino as ISP because I want to be able to use C code compiled to HEX since it is more advanced than the Arduino Programming Langue.

My basic thoughts of the circuit:

As you can see, I want a "direct" USB connection.
So far I know that i have to use a software based solution for this.

I've managed SoftwareSerial to work with my ATtiny45. For this I've used the Arduino Software to Programm the ATtiny45 with following code:

#include <SoftwareSerial.h>
#define rxPin 3
#define txPin 4
SoftwareSerial serial(rxPin, txPin);

void setup() {
    pinMode(rxPin, INPUT);
    pinMode(txPin, OUTPUT);
    pinMode(led, OUTPUT);
    serial.begin(4800);
}

void loop() {
    serial.println("1");
    delay(1000);
}

Please note that I don't use Pin 3 ( yet ) but I need to define it for SoftwareSerial.

This way, using SoftwareSerial, i was able to send data from the ATtiny directly into the TX pin of my Arduino UNO that had a blank sketch loaded onto it for this test.
I was using the Serial Monitor of the Arduino Software to read the data on COM4 ( in my case ) because my PC didn't recognized any device ( COM port ) as I've tryed to hook the programmed ATtiny directly to a USB cable.

Unfortunately I only got strange unicode characters in the Serial Monitor. I think it's because the data is in hex format or so.
So I've noticed that I need to connect a USB/Serial Converter betewwn the USB and the ATtiny45... I've searched for such converters, but I don't want to use any pre-made boards, since I want all my components on a single board.
I think an FTDI chip would be way too "much" for my project, isn't it ? ( It has too tiny pins to solder... )
V-USB was then my second approach, since it doesn't need a USB/Serial converter ( as i know ). So to use V-USB I would need to use AVRDUDE as I mentioned earlier.

I've found this nice example V-USB EasyLogger. It contains a circuit design and example firmware. ( C / C++ / HEX )

The only thing I want to know is: Do i really need to make my circuit look like shown in the example ? ->

What else do I need to know about this kind of USB connection ? ( Why do I need a USB / Serial converter ? Can I just hook up the +5 & VCC ? What components do I absolutely need ? what kind of signal do i need to send via TX ? bits ? hex ? what voltage does it needs to be ? )

Thanks for all of your answers.

UPDATE

Here are some aditional links that really helped me in some points. But I still didn't understood it fully...

the first one -> http://www.ernstc.dk/arduino/tinycom.html

and the second -> http://www.re-innovation.co.uk/web12/index.php/en/blog-75/227-attiny-arduino ( scroll down to the "Serial Output" section )


texts:
As we are developing our application based on the PIC18F66K22. We need to interface LCD with it. We have the LCD working with it but the problem that we are getting is that the LCD initialization takes around 10 Sec and only after that the LCD starts till then even microcontrooller does not execute any commands.But after initialization it works as expected without any delay. What might be causing the problem ? The LCD controller is ili9163C. The datasheet can be found at https://www.displaytech-us.com/sites/default/files/driver-ic-data-sheet/ILI9163C_DS_V010_2011_0118.pdf .

The following is the initialization code.

void LCD_init()
{
Send_Command(0x11); //Exit Sleep
delay_ms(50);
Send_Command(0x26); //Set Default Gamma
Send_Data(0x04);
// Send_Command(0xF2); //E0h & E1h Enable/Disable
// Send_Data(0x00);
Send_Command(0xB1);
Send_Data(0x0C);
Send_Data(0x14);
Send_Command(0xC0); //Set VRH1[4:0] & VC[2:0] for VCI1 & GVDD
Send_Data(0x0C);
Send_Data(0x05);
Send_Command(0xC1); //Set BT[2:0] for AVDD & VCL & VGH & VGL
Send_Data(0x02);
Send_Command(0xC5); //Set VMH[6:0] & VML[6:0] for VOMH & VCOML
Send_Data(0x29);
Send_Data(0x43);
Send_Command(0xC7);
Send_Data(0x40);
Send_Command(0x3a); //Set Color Format
Send_Data(0x55);
Send_Command(0x2A); //Set Column Address
Send_Data(0x00);
Send_Data(0x00);
Send_Data(0x00);
Send_Data(0x7F);
Send_Command(0x2B); //Set Page Address
Send_Data(0x00);
Send_Data(0x00);
Send_Data(0x00);
Send_Data(0x9F);
Send_Command(0x36); //Set Scanning Direction
Send_Data(0xA8);
Send_Command(0xB7); //Set Source Output Direction
Send_Data(0x00);
Send_Command(0xf2); //Enable Gamma bit
Send_Data(0x01);
Send_Command(0xE0);
Send_Data(0x36);//p1
Send_Data(0x29);//p2
Send_Data(0x12);//p3
Send_Data(0x22);//p4
Send_Data(0x1C);//p5
Send_Data(0x15);//p6
Send_Data(0x42);//p7
Send_Data(0xB7);//p8
Send_Data(0x2F);//p9
Send_Data(0x13);//p10
Send_Data(0x12);//p11
Send_Data(0x0A);//p12
Send_Data(0x11);//p13
Send_Data(0x0B);//p14
Send_Data(0x06);//p15
Send_Command(0xE1);
Send_Data(0x09);//p1
Send_Data(0x16);//p2
Send_Data(0x2D);//p3
Send_Data(0x0D);//p4
Send_Data(0x13);//p5
Send_Data(0x15);//p6
Send_Data(0x40);//p7
Send_Data(0x48);//p8
Send_Data(0x53);//p9
Send_Data(0x0C);//p10
Send_Data(0x1D);//p11
Send_Data(0x25);//p12
Send_Data(0x2E);//p13
Send_Data(0x34);//p14
Send_Data(0x39);//p15
Send_Command(0x29); // Display On
}

This is the main section

void main()
{
OSCCONbits.IRCF0 = 1;   //HFINTOSC 16MHz with PLLEN
OSCCONbits.IRCF1 = 1;
OSCCONbits.IRCF2 = 1;
OSCTUNEbits.PLLEN = 1;
delay_ms(5);
while(!OSCCONbits.IRCF2);   //wait for HF-INTOSC oscillator frequency is stable
delay_ms(5);
    Config_IO();
    lcd_reset();    //LCD reset
delay_ms(5);    //LCD reset complete delay`
    LCD_init();
font_init();

    TRISBbits.TRISB3 = 0;
TRISCbits.TRISC2 = 0;
RELAY_EN = 0;

FillFullLcd(WHITE);
//LCD_image (0,33,159,96,(unsigned char rom *)benchmark);
// sprintf(&FirmVerText[6],"%d.%d",FW[0]-0x30,FW[1]-0x30);
// setfont((void *)font_Calibri_10);
// LCD_OutText(50,97,FirmVerText,BLACK);
setfont((void *)font_Calibri_10); //added by shailesh
    LCD_OutText(50,99,FirmVerText,BLACK);//added by shailesh
    LCD_image (0,33,159,96,(unsigned char rom *)benchmark);
    delay_ms(3000);
    FillFullLcd(BLUE);
    Hstart = 0;
    Vstart = 0;
    radius = 5;
    Hend = 100;
    Vend = 75;
    color = BLUE;
LCD_draw_round_corner_box(2,33,157,96,75,LOGOC,1);
//LCD_Rectangle(2,33,157,96,LOGOC,1);
LCD_OutText(35,55, productstr,WHITE);
    delay_ms(2000);
    calibration();
    while(1);
    }

Here in this code it takes around 10 sec to paint the entire screen blue. but after that all the lcd operations are working perfectly fine and without delay. What might be causing the problem here ?


texts: Choice of resistor in half wave rectifier

texts:
I found following schematic of a half wave rectifier (from here) and I was wondering how to choose the resistor, and I have following questions:

Is it correct that this resistor is basically functioning as a pulldown for when the AC is in the reverse polarity (top negative)?
When connecting the output of this rectifier to the input of another device I think we would lose current across the other device when R1 is too small, so my guess is that we have to choose R1 at least as large as the input impedance of the connected device (or even a lot larger), is this correct? And if so, is there a more precise way to compute a value?

simulate this circuit – Schematic created using CircuitLab


texts:
Do current sources exist practically or is it just a concept?
If there exist a practical current source, can you give some examples.


texts:
I have an old Siemens motor with this specification :
220V
80W
0.65A

I need to reduce the speed (slow down) of this motor.

I know it's easy with something like an inverter, but I'm just wondering how about with just a resistor? If it is possible what are consequences? Is it bad for motor (damage or crash?)

If no, let me know how to slow down with resistor or something you suggest, please.


texts: Rate of change of parameters through L and C

texts: While solving numericals on initial conditions we deal with rate of change of parameters like di(0+)/dt=100A/Sec or dv(0+)/dt=1000V/Sec etc. Instead of such a huge parameters why circuit doesn't get burst or why we don't feel any electric shock?


texts: How to efficiently charge 48V battery-motor system with solar panels

texts:
I'm wondering how to efficiently charge and use the following system with standard 18V solar panels:

48V lead-acid battery
1kW electric motor

To charge the battery with either PWM or MPPT, the solar panel voltage should be more than 48V, if I understand correctly. Thus I can either boost the voltage to more than 48V (inefficient), or connect multiple solar panels in series (e.g. 3x18V=54V). The panels will not necessarily be oriented in the same direction, and shadows may be cast on individual panels, so I guess connecting them in series will make the whole array highly sensitive to the environment.

Alternatively, would changing the battery-motor system be an option? The 48V battery is made up of 4x12V packs, so I could connect them in parallel to form a 12V system that could easily be charged with the 18V panels. But I guess I'd require a new motor, right?

Any tips are appreciated!


texts: Confusion over sign convention for power

texts:
We are given this electrical circuit:

At the last line, they put a 'minus'.

My question is, why is it a minus?


texts: How "well regulated" must the input voltage to a DC-DC boost controller be?

texts:
According to its datasheet, the TPS43061 "is a low Iq current-mode synchronous boost controller with wide-input voltage range". My intent is to use this controller to boost and regulate the stepped-down and rectified mains voltage from 12.6 V to 15 V, supplying up to 6 A output.

Under "Power Supply Recommendations" in Section 10 of the datasheet, it says that "[the] input supply should be well regulated." How regulated is "well" regulated? There doesn't appear to be a line regulation parameter in the electrical characteristic section.

My guess is that the "well regulated" part means that the input voltage ripple should not exceed some designed amount, and indeed the minimum input voltage is used in calculating the values for various external components.

Can I assume, living in the United States, that the mains voltage will be stable enough to follow this recommendation, assuming that the output of the rectifier has enough capacitance?


texts:
Following the previous post
Output of XOR gate with high-impedance input

I am interested further how four-valued logic of SystemVerilog gets eventually implemented in hardware.

Could someone correct / confirm my next observations?

Consider

assign LED = (select) ? value1 : value2;

Observation 1:

  select ? value1 : value2

in four-valued logic is not equivalent to

  (select & value1) | (!select & value2)

When

select = u; value1 = 1; value2 = 1;

during simulation and in hardware value of LED will be one, whereas

(u & 1) | (!u & 1) = u | !u = u | u = u;

(note, in SystemVerilog undefined value u is represented as x)

What is the semantics of (a ? b : c) expression? What about semantics of case and if statements?
Observation 2:

X value after synthesis is initialised to 0 by default.
For example:

select = x; value1 = 0; value2 = 1;

turns the LED on, whereas

select = x; value1 = 1; value2 = 0;

keeps the LED off.

If in hardware x is 0 by default, why is extra value required during simulation, wouldn't having 0, 1 and z be enough?
Observation 3:

The hardware behaviour when

select = z

is super-weird. In this case LED is on if and only if

value1 = 1; value2 = 1;

What is happening in this case (c.f. observation 2)?


texts: negative current for discharging capacitor

texts:
So I was trying to derive the exponential decay equation for a discharging capacitor and realised that I would only get the correct answer if I used a negative current, that is to say the direction of the current opposes the direction of the voltage applied by the capacitor?(this is probably where the problem is).
Here is the equation:
$$Vc(t) - (-RC\frac{dVc(t)}{dt}) = 0$$

I have also visited links to similar questions and saw that the negative current means that the discharging current is opposite to the charging current. But what if I start with a charged capacitor? In this case am I not free to define the direction of the current in which ever way I want?
In short, I would like to clarify whether there is a potential gain or a potential drop at each of the elements(a capacitor and a resistor).

To elaborate:If I have a circuit with only a charged capacitor that is discharging and a resistor, and I perform KVL around the loop in the direction of the actual current, following passive sign convention. Do I not end up with the equation:

$$Vc(t) - (RC\frac{dVc(t)}{dt}) = 0$$
why is this equation not valid?


texts:
I'm sorry I am very specific here, I have a problem with the charger of my motorbike dashcam and I hope you can help me fixing it (see picture and video test with multimeter).

I really have no idea of the various PCB components, I was thinking maybe to "bypass" it using the wires but before I try this extreme procedure, maybe you can help me fixing the problem in a less destructive way.

Link to Picture and Video!


texts: Is this NPN with base grounded and collector at negative voltage functional?

texts:
I am an engineering student and this question is one of my assignments this week and I need a more professional opinion.

I don't see how the transistor is even operational with the base connected to ground. With no voltage applied to the base to overcome barrier potential both collector-base and emitter-base diodes will remain reverse biased. Also collector current (\$ I_{C} \$) is labeled on the emitter side and emitter current (\$ I_{E} \$) is labeled on the collector side.

I'm not sure if this is a trick question or if I am over looking something. Am I wrong about my assessment of the question?

  For the circuit shown in Figure 3 below, draw the DC load line and locate its quiescent or DC working point. Show all work.
  week 4 assignment diagram C


texts: What are two typical threshold voltages for a flash FET?

texts:
I have a simple question for you all: what is a realistic approximation of a pair of threshold voltages for a flash transistor? I am working with NAND flash, 45nm, with VDD = 0.8V. I can find lots of information on the basics of flash, and scientific papers on applications etc, but no mention of specific threshold voltages used.

Any tips you can give me to help solve this problem would be greatly appreciated!


texts: What is the idea behind the ingenious Widlar current limiter?

texts:
For a long time, I had the idea of this circuit as a short circuit protection. I first saw it in the output stages of the Widlar's 301 and Fullagar's 741 op-amps... and knew it was Widlar's invention. I was satisfied with the classic explanation that "if the current through R9 is excessive, Q15 turns on and diverts Q14 base current"... but later...

My interest in this circuit solution grew after I saw that it was also being used as a current source (sink). I began to feel that there was some "devilish" trick here... like in all Widlar's implementations...

Then I asked myself, "What really does this circuit of two interconnected transistors? What is it - current limiter, current source or both? When does it act as a limiter and when as a source?"


texts: Why do I get a compiler warning with "int __attribute__((address(0x3000))) x;"

texts:
I am trying to understand why I get the following warning

#include <xc.h>

int main (void)
{
     int __attribute__((address(0x3000))) x;

     while(1);

     return 0;
 }

  PIC24_Attributes.c:13:5: warning: ignoring address attribute applied to automatic x

I know __attribute__address((address(0x3000))) x means store the variable of type int x in DATA SPACE address 0x3000

When I download the program, and debug it, I see that the address of x is 0x856

but when I put it globally the warning disappears, and when I debug, the address of x is 0x3000.

I googled the warning I got, and I found someone with the same warning as me, but with the space attribute instead  (http://www.microchip.com/forums/m351172.aspx)

From what I understood was __attribute__ only works for static variables, and automatic variables (don't know why it is automatic, it is an int) are allocated dynamically.

Can someone explain this please, as I understand that `attribute((address(...)))' means store the following variable at a certain address.

Microncotroller: PIC24FJ1024GB610 (Microchip)
Debugger: PKOB (Explorer 16/32 Development Board)


texts: Need help identifying an SMD component - top marking PJt

texts:
I'm wondering if anyone can help identify this component, with top marking PJt.

It's a 6-pin package and it's connected to a phototransistor. The collector is connected to pin 6 and the emitter is connected to pin 5 via a 10 kΩ resistor. Pin 1 is gnd, pin 3 goes through a 330 Ω resistor into pin 2 then through a 2.6 kΩ to gnd. Pin 6 goes to a 10 kΩ resistor. Pin 5 goes through the diode to gnd.
I'm thinking it's a comparator to give a high/low output from the phototransistor, but I can't find any comparators with a similar pinout.


texts: Ultrasonic sensor without micro controller

texts:
I have been researching how ultrasonic proximity detection works and I believe the HC-SR04 would be a decent fit for a project. The sensor unit looks like this.

I would like to know is if this schematic would function as I imagine it or a flop. The premise is based from the datasheet for the HC-SR04 here.
Datasheet

The sensor works by sending 8 40KHz pulses when the trigger pin receives a 10us pulse. If an object is picked up by the receiving sensor, the "Echo" pin goes high between 150us-25ms (38ms if no object detected). I was thinking for the fun of it, to use a pwm signal from a 40106 to a 4017 counter. If I could activate the 4017 for whatever the Echo pin signal width time would be, I could output a fractional voltage which could be sent to an ADC etc. Here's is the working idea. Assume output 3-9 continue the fractional voltage. I left them open to not bog down schematic.

The pins on the spice model are confusing, however assume R=reset, C=Clock inhibit. When "Echo" pin from HC-SR04 goes high, 4017 is initiated and reset. The outputs will toggle from the 263Hz which should cycle based on min-max Echo signal time. Since the trigger would only be activated once every few seconds (to scan), whichever 4017 output was high when Echo pulse ended would freeze until the next sensing pulse; ideal for using that voltage for other applications. Here is the idea behind the Trigger/Echo function.

Any and all feedback is welcome. Just an idea, not sure if it's feasible or missing important variables. Thanks for viewing. Cheers.


texts: Questions regarding AFG3000C function generator

texts:
I have a new function generator - model  AFG3000C.

I am having difficulty in understanding certain terms related to this function generator.

I have tried online searches, but I couldn't get what I was looking for. Being a newbie, I request you all to help me understand my queries in simple terms.

Could you please explain my queries below :

In this function generator, we have the option to set "LOAD IMPEDANCE" as 50 ohms, load and high Z.

What does each mean? And where to use each one? I guess, it is related to the transmission line characteristic impedance. But where should we use the load option, 50 ohms and the high Z option?

Can we set the impedance using the function generator according to our needs?
This function generstor only provides output voltage right? Can someone impress voltage on the function generstor channels? If so, how and how to check how much voltage can the FG withstand? And what about the current parameter?


texts: Need to build a circuit resembling fluid flow through porous media

texts:
I am trying to use electronics analogy to build a model that describes fluid flow in a porous media. For example I consider voltage, current and resistance to be equivalents of pressure, flow rate and permeability (inverse of resistivity), respectively. I need some help on how to choose more elements for my circuit to accurately model the fluid flow. Since I am not an electrical engineering student and I do not have a strong background in it, I would really appreciate the answers which start from the basics and move towards more complicated explanations.

Here is a list of things I need to know how to do:

I need to be able to control the time it takes for the current to travel from one point to another point. For example if points A and B are connected with a wire and A has a higher potential and I somehow increase its potential, theoretically there should be an immediate increase in the current flowing at point B. Is there an element I can put in between which controls the response time of point B to change in potential at point A?
I need to be able to model a variable permeability condition (i.e. variable resistance). I know if I use a resistor in my circuit it will have a CONSTANT resistance, so it will not help. Also, I want the changes in resistance to be proportional to the amount of current that has been flowing through that element. Like what happens when a capacitor is being charged, dQ/dt term is proportional to Q and it exponentially decreases to zero by time. But what if I don't want it to be decreasing exponentially? What other elements can I use to force the changes to be an arbitrary function of time/flow, for example a second degree polynomial? (if it's possible at all!) Also, is there a way to do the exact opposite i.e. the resistance decreases with time?
I am not sure if it is the same as part 1 or not, but how can I model the distance between two points in space? (The further the distance the longer it takes for it to respond to changes in another point of the circuit.)


texts: Do infrared photodiodes vary their resistance according to the strength of infrared radiation they receive? Or do they simply have some sort of HIGH and LOW state, meaning that they either let current pass or not.


texts:
simulate this circuit – Schematic created using CircuitLab

I need to find the voltage at node 3 considering all the diodes ideal. I tried the Superposition theorem to find the result.

When V2 will be shorted, then node 3 voltage should be 0 volts.

When V1 will be shorted, 'D2' will be turned off and the voltage at node 3 should be:
\begin{equation}
\frac{10}{10+5}10 = 6.667 (approximately)
\end{equation}

So, the voltage at node 3 should be 0+6.667= 6.667 volts. But the result is provided 3.3 volts (approximately).

I did a simulation too.(Diodes of simulation causes 0.27 volt drop)

So how do I solve it ?


texts: Measuring low ripple on a power supply with an oscilloscope

texts:
I'm building a 3.3V 400mA power supply around an ultra fast buck reg (3 MHz or 1.6 MHz, LM2734Z/X.) According to simulations, the ripple will be <2mVp-p. The noise floor of my scope is about 500µVp-p on 5mV/div (the minimum setting), so how do I measure such a small signal?

I'm thinking I'm going to need an amplified probe of some kind, but I suspect these will be very expensive.

I was thinking of fine tuning the trigger and using the averaging function to remove the noise from the signal, but would this be adequate for power supply ripple? Scope is a HP 54501A, 100 MHz -3dB b/w, 10 MS/a digitising, quite an old scope but only cost £150.


texts: On purpose shorted capacitor in schematic

texts:
I've come across this schematic from an RF device where I've spotted some weird configuration of capacitors. There are, all around the schematic, some shorted capacitors which I can't figure out what are for.

You can see, for example, in the images below, that C306, C307 and C308 are shorted.

Any clue of what are they for?

Regards.


texts: AC adapter more wattage than required issues

texts:
Many say it is safe using an AC adapter exceeding the required current.
But this source says:

  a power adapter that can provide more current than the load requires will sometimes work, but if the current difference is very large (say 30 to 50%) be aware that "ripple voltage" on the adapter output may be higher than ideal, and a filtering capacitor may be required to smooth out the DC output voltage of the adapter.

So, is it better to stick closely to the required current?
(obviously assuming the specs are reliable)

EDIT: in my case i'm considering this 90W power supply for a 45W load.


texts:
I am busy with Dynamic Range of an ADC including Programmable Gain Atmplifier. I try to calculate maximum Dynamic range level of my measurement system. How can i calculate Dynamic range? I have read these equations:
"SNR (dB) = 6.02x(ENOB) + 1.76 (dB)"   ENOB: (efficient number of bits) also
total DR can be found by this formula; DR = SNR of ADC (dB) + Gain of PGA (dB)" According to these formulas where is the nyquist frequency? I don't understand how can Nyquist Frequency increase SNR? Can anyone explain me?


texts: I need a device that can protect a 3–phase induction motor from high currents and overheating.


texts:
I'm a developer and I want to have a bit of fun with electronics. I don't know much about it so I have a bit of a question. I'm pretty sure this can apply to Netduino, Arduino or any other one.

I want to use the Netduino like if it was variable resistors.

I would connect the Netduino to a helicopter remote control by removing its variable resistor from the remote's board and connect Netduino's output.

The question is how can I do that? How can I wire it and do I need additional components?

Some Links/Pictures

http://sharetext.org/C3PS


texts: How did this capacitor survive having a nail driven through it?

texts:
How did this metal film 1 uF 630 VDC polystyrene capacitor survive having a nail driven through it while under a voltage of 122 VAC? It is part of UL testing for potential X or Y grade capacitors, which it MUST pass to be put on UL's approval list. The starting value was 980 nF. After being pierced by a nail, the capacitance was 956 nF, so some damage was done.

Thanks to Alexander for tracking this down. UL tends to be very secretive about such details.

  UL 1449 REV 09162013, SURGE PROTECTIVE DEVICES Effective March 11,
  2016
  Third Edition

  59F. New section added;

  Capacitor Failure Test

  59F.1 If required by the Exception of 25.3,
  capacitors employed in Type 1 SPDs shall be permanently mechanically
  (driving a nail through the capacitor where the nail should not short
  out the capacitor to ground nor reduce spacings to other electrical
  paths) or electrically (as specified in 10.2.2 of UL 810) failed and
  three samples tested at the short circuit current rating of the SPD in
  accordance with the Short Circuit Current Rating Test procedure
  covered by Clauses 39.2.1 to 39.2.4.

  Permanent failure of a capacitor
  is demonstrated by the flow of short circuit current until interrupted
  by an overcurrent protection device or for 3 full cycles.

  59F.2 Capacitors rated 1 uF or less may be failed in accordance with
  59F.1, or may be replaced with jumper wire having a minimum gauge size equal
  to the capacitor leads. The jumper wire shall not open during testing.


texts: Will this passive non inverting anti-log circuit work?

texts:
The potentiometer on the left of the circuit below is actually the output of a digital potentiometer designed for audio volume control, so its outputs are internally configured to offer 64 logarithmic steps, from 0dB to -64db. I can't change that. Now as it turns out, I need to use the output to control an audio amplifier that has an internal DSP processor, which accepts 0-3.2VDC to control its audio volume. That amplifier currently gets that voltage from a  linear potentiometer, so it is internally doing its own linear to log conversion. So using the circuit shown without the diodes,  with just R11 and R12 used as a simple voltage divider to convert my 0-12V to a 3.2V range, it works but the response is less than ideal. Since the output of my digital pot is advancing the voltage in 1 dB steps, the "steps" become audibly noticeable in that amplifier's output level, especially as the higher volumes are reached. So what I need to do is convert the logarithmic steps  to some approximation of linear, meaning I need an anti-log function.

So I'm thinking of approximating an anti-log curve with a couple of diode networks as shown. Basically, the output voltage will initially follow the input voltage, but then rise progressively slower as D2, and then later the D3-D4 pair begin to conduct. It seems to work well enough to make the volume control sound more responsive, but somehow the circuit just seems to be a "hack" to me. Can anyone suggest a more eloquent solution that doesn't involve a huge amount of additional parts?

Addendum... After playing trial and error with the above circuit all day, feeding it with a linear ramp and comparing input to output, I decided it was too difficult to optimize. Should the max reference voltage (12 V in the above) change at all, too many resistors have to change to duplicate the desired response. But on a whim I came up with this. I honestly have no idea if I'm really approximating an anti log (or log) response with this configuration, but I found it very easy to "tune" to a desired response, as long as the max input reference voltage was at least 2 or 3X the desired final output max. The gist is, as the input POT was adjusted higher, the output would gradually diverge from the input, so that input changes had progressively less affect on the output. The final test of course was to actual try it with an audio signal through the voltage controlled amplifier, and I thankfully found the digital POT control to be much more natural.

I'd still welcome comments on why this seems to be working so well, whether I am indeed approximating the non inverting log curve I'm after, and whether it could be done simpler. But bottom line, if anyone else runs into a similar problem, this does seem to work VERY nicely... at least to my ears!

Another addendum: For the benefit of anyone following this in need of a similar circuit, I need to point out the the LM324, despite being a common choice for single supply OP-AMP circuits, turned out to be a poor choice for this otherwise good circuit. The reason being, this OP amp is based on internal BJT transistors, and so it really can't "drive" any output below 0.6 volts. In my case, even though I didn't need the LOG response curve to start below that point, the circuit still needed to output 0-3 volts into an existing circuit that had a small positive bias current, and so I was not able to adjust the output down to zero, even if I grounded the final OP amp used as a buffer). So I will likely replace the quad OP amp with something like the Texas Instruments TLC274, because being FET based, its output Voltage Range actually does Include the Negative Rail


texts:
I decided that I will be soldering airwire to one of the pins of existing SMD devices directly (e.g. to capacitor terminal) - there's no space for through-hole wire mounting pad, and soldering to terminal soldered to pad should be more mechanically reliable than soldering wire just to its dedicated SMD pad.

If I give same name to signal at each side of airwire I will have airwire in the board editor, and I want to eliminate it. If I give signals different names, while "output" side of airwire passes ERC properly, another side is having input only, and gives an error. I of course can accept this error, but looking to the way making it "clean".

I tried to make SMD pad terminals for each side of airwire, but putting it onto the resistor/capacitor pad logically gives "overlap" error. Is there any other hacking way I can tell EAGLE that it should not draw airwire?


texts: Why are linear systems poor oscillators?

texts: Given a linear system with initial conditions. If you have conjugate poles in D(s) that lie right on the jw axis, you should, in theory, be able to get sustained oscillations that do not grow unbound nor damp with time. Why would it not be a practical solution? I guess most linear systems would have damping which would imply the oscillations would die out. I tend to think it has something to do with sensitivity of the system's ability to oscillate. For example, if initial conditions are just not perfect when you start the oscillator up, it will not oscillate.


texts: What is Bus capacitance in I2C? How it limits number of devices can be connected to the bus?

texts:
Bus capacitance limits number of devices that can be connected by I2C. What problem is encountered if one tries to exceed this limit can anyone explain this in detail please.

Thank you


texts: Alternatives to the PS223 power supply monitoring IC

texts:
I am repairing a power supply that (among other faults) has a dead PS223 chip. This chip monitors the output voltages for over/under voltage and over current. It also outputs a "power good" signal to the motherboard.

The problem is that I cannot get that chip locally. I can order it on eBay, but it would take a long time to arrive.

However, I doubt that this chip is unique in its function - maybe there are other chips (that I can hopefully get faster) that do the same function with minimal modifications to the circuit?


texts: What do the numbers on motors mean (How do I read them?)

texts:
I salvaged from an old microwave, the motor that spins the food tray. I'm trying to figure out how much voltage I need to apply to it in order to get it to spin, but I cant make any sense out of the numbers on it. It's a Synchronous Motor.

This is what's on it:

100/120v~  50/60Hz  4W
4/4.8r/min  CW/CCW

I can guess that it rotates from 4 to 4.8 rotations per minute? but other than that, I'm clueless. What do these other things mean? Thanks so much!


texts: Emitter follower voltage regulator misbehaving

texts: To make a crude voltage regulator, I've made a simple emitter follower using a BD139 transistor. When the 0.5A load is connected, the circuit behaves as expected: the voltage across the load sits at about 0.8V below the voltage at the base. However, if I increase the load impedance, or disconnect the load, the output voltage rises to equal the voltage at the base. That's a problem, because I want the output voltage to be constant despite variations in output current. Any ideas, please?


texts:
simulate this circuit – Schematic created using CircuitLab

(a) In the circuit on the right I think I understand that:

$$
i = \frac{V_o - V}{R}
$$

(b) But in the circuit on the left I don't understand. Personally I would say that:

$$
i = \frac{V}{R}
$$

(c) But from what I have read it is wrong, because it is:

$$
i = \frac{V - V_o}{R}
$$

Is it (a) right? And what is correct: (b) or (c), or none? And why?


texts:
What is a scratchpad memory?
I mean I get the article in principle, but I can't figure out how it exactly differs from other memories e.g. L1 Cache.
It

is a high-speed internal memory used for temporary storage of
calculations, data, and other work in progress.

is no explanation for me. From my pov this could be applied to almost each kind of memory.


texts: how to determine if system is matched in system

texts:
I'm concerned about matching. If you look at the pictures, there is a certain tracewidth optimized for 50 ohm that is then changed to fit the pad of the rf component. How would I measure the amount of reflection in an already built system?

Situations: The RF board is already built, there is another component that generates the rf signal on the other side of the board, making the attachment of an sma connector to hook up a network analyzer not so likely. Even if it wasn't there, the trace is far from the board edge (maybe a right angle sma connector and unloading the rf generator?).

Additionally, it would be nice to test this for every board that comes through production (making attaching components not an option). Is there a way to test it with an rf probe (just a cable that you touch the tip of the cable to the trace) or some other method to ensure accurate matching?


texts: BJT Analysis how to find collector current

texts: This is a quick drawing of a circuit that I am trying to analyze. Basically, I want to know how to go about finding the collector current, to start. Is it possible to create a Thevenin equivalent circuit for the resistors in this model? If not, how do I start on finding the voltages?


texts:
I'd like to make this chandelier:

But before I embark on this quest I've few questions.

Cleverly titled "edison chandelier", this thing has 10 incandescent bulbs so energy consumption will be over the board with approx: 10*60w=600w. More than half of my houses total consumption at any given moment. What can I replace this with? Are there economy version of these bulbs? Transparent LED imitation of edisons bulb or something?
How do I choose a wire?
How do I connect wires at the base?
What about using arduino with wifi shield to wirelessly shut of portions of the lamp?


texts: How to find replacement LED for TV backlight

texts:
My TV has a damaged LED in its backlight. The LED had started flickering like 2 weeks ago and finally the whole backlight stopped working. Nothing obviously unusual on the LED driver board, the MOSFET and the sense resistors seem to be okay, no short, body diode working, no visible burn marks.

So I want to replace the damaged LED, but by which model? With a battery (8.2V) and a 400 Ohms resistor a single LED shows 2.69V @ 15 mA. There are 22 LEDs in total (two rows with 7 LEDs and one row with 8 LEDs), all in one series circuit. Each SMD-LED has approximately 3mm by 3mm body with <=1mm height and a circular radiative region.

I have no idea what could be the maximum rated current or the color temperature. Is there any chance of finding a right one? Are SMD LEDs of TV backlights somehow standard types?


texts: Can old vintage quartz crystals handle more power?

texts:
Old crystals are very large compared to present day devices. Vintage transmitter circuits did not have many valves in their line up.

I have seen a 2 valve 50 watt CW transmitter for 80 meters in a 1950s electronics magazine.  When transistors arrived RF types were more expensive than the valves they replaced, so in the 1960s the number of transistors in the transmitter strip was kept to a minimum.

The transistors had less  power gain than the valves,  but it was normal to make a 5watt HF CW transmitter with only 2 transistors.  The crystal oscillator in these cases is called upon to deliver significant power.

Surely the crystal drive power must be quite high.

Would new small crystals have a short life in these old circuits?

Would the frequency stability be bad when present day easy to find  small crystals are used?


texts:
I want to build a mobile charger that is battery operated and found this diagram. At first glance, this diagram looks kinda simple and I thought that this won't work. I'm a newbie on making this kind of projects and its look like a simple one so I want to know how and why this diagram works. If this diagram really works I really need help in converting it into a schematic diagram.

and also what is the diffference between the two in charging power?...

thanks..


texts: MOSFET Driver increase maximum duty cycle

texts:
I have a piece of test gear I am working on designing, in which there I need to drive a number of N channel mosfets, (3 high side, 2 low side)

I found there is a very large range of gate drivers intended for driving 3 phase motors, and thought this would be a good option as it would provide the drivers I need in a cheap, & space efficient package.

The design I ended up using was the Allegro A4919GETTR-3-T to drive NTMFS4C029N mosfets.

I am roughly aware of how the bootstraping circuit works, and the limitations it places on maximum on time. However I expected be able to generate longer than I am. I would like to be able to generate pulses at least 200ms long, but with the current setup only seem to be able to manage about 5ms before the Bootstrap voltage monitor kicks in.

I am running with a 15V supply, and my bootstrap capacitors are 0.1uF

Searching through the datasheet I did find "GHx Passive Pull-Down Resistance" specified at 400kΩ this seems pretty low to me but would potentially explain my problem.

I assume this property is intrinsic to the device and cant be changed, is there anything I can do to increase my maximum on time.

The only thing I can think of is increasing my bootstrap capacitor size(and correspondingly Vreg capacitor). However I don't know what controls the sizes I can use, can I just throw a 20uF capacitor in and call it a day or will this fry the bootstrap diode.

As a further down the road backup option (requiring a PCB redesign) what factors would need to be considered before switching to something like a TMC6200 with an integrated charge pump to allow 100% on time operation.


texts: How to put in Voltage Dependent Current Source in LTSpice

texts:
my post lab question asks me to simulate a circuit using LTSpice. I am having trouble implementing it.
The circuit looks like this:

My issue is with the little diamond thing on the very right. I don't understand how it would be connected in LTSpice, because it looks like this:


texts: How does using a DC-DC step down converter save power?

texts:
I understand how DC-DC buck converters save power when compared with a linear regulator, but do they save power when compared to not using power conversion all together? In my specific case, I have a microcontroller that outputs 3.3V to a sensor device which could run at 2.5V. If I step down the voltage from 3.3V to 2.5V, am I saving power and allowing my battery to last longer? Or does the overall power use remain the same?

Edit: The device is a custom made infrared sensor


texts: I'm having a little trouble with my boolean algebra and I was hoping you all can help me out.  I've been given the task of designing a circuit that takes in a binary 4 digit number (X3X2X1X0) and returns '1' if the number entered was even.  I'm fairly certain that my truth table is correct, but if someone could look at my algebra for my 'Y' value, it would be greatly appreciated, as I am somewhat unfamiliar with boolean algebra.  Thanks in advance!


texts: What exactly is this question asking us to do?

texts:
Based on the model and circuit shown in Fig. 2, draw a circuit model of the path of current through the human body for a person touching a voltage source with both hands who has both feet at the same potential as the negative terminal of the voltage source.

Is this how the diagram will turn out?

Is this how the two feet will be connected to V-?

Alright. Done. But the head resistor is still not connected anywhere.


texts: Transistor audio amplifier with dual voltage supply

texts:
There are lots of similar topics, but I can't find answer that will satisfy me. So, basically I am trying to do a transistor audio amplifier with dual voltage supply (+/-12V). I found circuit like this on some topic:

But it doesn't seems to work for me.
Here are LTspice circuit with Vout wavegraph:

Maybe anyone, knows where is the problem or can show me some simpler circuit with out differential transistor (maybe single transistor with push-pull output).

Best regards

Also, when I finally run this circuit, do You know how to  rise the amplification of this circuit(?), for now it is like 30 V/V.

When I add a resistor that simulate speaker, the output waveform starts to get messy again and literally don't know why.


texts: What's the easiest way to remove the power rails of a breadboard?

texts: All of the breadboards I get come with an adhesive backing that, while keeping the metal rows inside the breadboard in, keep the power rails connected to the breadboard. I want to remove the power rails off of a few boards to make a common data bus, and this has proven difficult. It seems like there is an easier way then ripping off the whole adhesive pad or just cutting the adhesive. Is there and easier way?


texts:
I need to implement a diode, which only operates, when enabled by external signal. Specifications:

When the enabling signal is off, there is no current irrespective of voltage (positive or negative, up to 40 V).
Enabled signal is on, after which the diode behaves normally.
I have searched a lot of alternatives: JFET, Mosfet, Bipolar transistor etc. but with no luck so far, except one having a two-way switch and diode in series (see attached picture). But I feel there must be simpler way.

Perhaps JFET could be used with suitable biasing and somehow allowing negative voltages in drain? Or, perhaps bipolar transistor enables this by some special arrangement?


texts: Adding microphone/amplifier to Gumstix Overo Earth COM?

texts: I am new to hardware hacking in general.  I have a Gumsitx Overo Earth COM and a Palo35 expansion board with audio in/audio out capabilities.  According to Gumstix's wikipage on audio input, the Palo35 board has "stereo audio in," but not a "stereo headset jack."  I know that I am going to need an amplifier if I want to add a microphone, but I am not sure how to actually integrate an amplifier or microphone onto the board.  I have searched for answers on Google for how to do this but I have not found many helpful results.


texts: 3 Wire Fan Tach, why using only one wire gives a signal?

texts:
I have a Sparkfun Power Shield for 12v fan powering, controlled with a BeagleBone Black. As I haven't been able to read the RPM with this setup, I added an spared Arduino Uno to do this, and also I will be using it for some 5v sensors I have, and a small SPI Oled Screen for debugging purposes, all connected to the BeagleBone using serial.

This is the wiring layout:

I did to measure the RPM, and while it's working as intended (it reads accurately the rpm), when I connect the 12v ground from the power shield to the Arduino, the fan starts, as it seems the open collector could power the fan, or somehow the circuit is closing and I'm not able to see it.

The strange thing is, as I was moving some cables to see if the layout was ok, I removed the ground from the power shield, and then I enabled the fans from the BeagleBone, and it started to measure the RPM, on one wire..

I know there are "one wire sensors", but I don't know why I didn't found some similar layouts on the web, as it seems to work perfectly, and using only one cable it's great, at least for me, because of the fear of burning something with the open collector tach..

This is my first question on a stackexchange website, please tell me if I should make any amendments to the question. Best regards.

This is the schema, I just removed the ground connection between the arduino and the fan. Note: I hope the selected components are ok, as this is my first schema. Note 2, 8Khz square signal estimating 4 cycles per RPM, 2000 RPM average.

simulate this circuit – Schematic created using CircuitLab


texts:
with System information Type 1 and Immediate Assignement, How can I find frequency of hopping channel in GSM?

So I'd like to print frequency of hopping channel


texts: What to plug in first to usb charger when charging: wall outlet or cell phone and why?

texts:
When I charge me cell phone or notebook or whatever what should I plug in first? Should I at first plug in usb charger  to the AC wall outlet and only then to the cell phone or vice versa ? What are the precise physical arguments for this?
 I think it is safer to plug in wall outlet first because of peak charge. What is safer for the cell phone circuits?
 Thanks in advance.


texts: How can we calculate the force of attraction between a coil and a ferromagnetic object?

texts:
As the question states I’m trying to figure out how I can calculate the force of attraction between the magnetic field of a solenoid (coil) and a ferromagnetic object. I suppose we should somehow calculate the force between the magnetic field of the solenoid and the induced field of the ferromagnetic object if I’m not wrong? So far I have not found any formulas online able to do this.

Let’s take an iron rod with a diameter of 12 mm and a length of 4 cm as an example. We are talking about a DC solenoid with lets just say, as simple values: 25 windings of AWG 12 wire and just a single layer coil. There will go a current of 2000A through the coil. The object is placed horizontal to the coil with a distance of 2 cm.

Any help on how to tackle this problem would be appreciated!


texts: Another question about Lighting up Vacuum Tubes

texts:
Hi Can anyone tell me if the 4-400 on my vacuum tube means 4 volts? & how do I tell what voltage the large RCA tube is as there are only RCA 105 written on it.
I'm making them into lights & want to make them glow. I understand that I connect the heater pin to the Ac/Dc adapter of the correct voltage. Thanks
Craig


texts: VUSB / +5V selector to safely power KNX project

texts:
I'm working on a board that will include a TP-UART IC + an ATMEGA328-AU on the same device.

I'm now facing the potential risk of damaging the host computer or the TP-UART IC if I'm mishandling the power source of the board.
The device can be powered through the KNX bus (typically 30V) and the TP-UART IC has its own built in regulator and will output 5V or 3.3V for an host MCU.
The thing is that I want to be able to power the device from VUSB (when I'm not connected to the bus) and I also want to be able to debug my firmware (so tied to the KNX bus AND the VUSB from the programer / computer)
I've seen some potential solution using P-channel mosfets / some autoswitchinp power mux (TPS2112) or even just opamp, but I really don't know what would be the safest and if there isn't any risks of back feeding 5V from VUSB to the VCC pin of the TP-UART IC
Edit: @akwky pointed out that if the board is powered by both P1 and VUSB, the internal on-chip regulator may have a slightly different voltage from VUSB. So I edited the schematic by adding a Zener diode Voltage Regulators (1SMA5918BT3G) to hopefully clamp the voltage to 5.1V going to VCC/VIF. Maybe I should have put this diode only on PIN 7 of the TP-UART. What do you think?


texts: Finding manufacturer of product based on certifications

texts:
I really do not know where to ask this question so I am starting here. If you believe there is a better place let me know and I will gladly move post.
I bought an induction cooktop from amazon and trying to figure out who is the manufacturer of this cooktop. The cooktop is a Warmford 240V, 3500W. However, there is no company named Warmford or company associated with a brand called Warmford (at least that I could find from an extensive search). Interestingly, enough more search results appear when you search Warmfod. I nearly gave up trying to find the manufacturer when I saw this sticker on the bottom of the cooktop.

My thought was that maybe I can find the company if I am able to look up their certification details. After doing some googling, I came across the website for Intertek which has a product directory. I went to the ETL directory, but even after going through this method I was unable to find the manufacturer.
This leads me to three possible thoughts:

This sticker is fake and they are not actually certified.

I am looking at the wrong place or have a wrong understanding about the certifications. If this is the case I am hoping someone could possibly take a look at the directories and point me in the right direction.

There is no way to find the manufacturer of this induction cooktop the way I am going about it. If this is the case any ideas of a direction that I could take would be appreciated.