texts: My country does not have grounding system, How can I protect myself?

texts:
I live in Egypt where the neutral wire is grounded. The ground wire is not separated from the neutral wire. A wall outlet has two holes only (live and neutral), The third whole (ground) does not exist.

According to this question, I can NOT use neutral wire as a ground:

Why don't we use neutral wire for to ground devices and earth wire for closing the circuit?

So, How can I protect myself from the weak electrical shocks that happens when I touch the metal case of an electric device? Such as: The metal case of a personal computer or a washing machine.

I have one more question, What makes the shock too weak?
I accidentally touched the live wire before and it was horrible.

If the live wire touches the metal case and then I touched the metal case, What makes the shock weaker? And If the live wire does not touche the metal case, What is the supply of the metal case? What causes the weak shock?

Thank you very much,


texts: Generating plasma flame with neon transformator

texts:
I'm trying to create plasma fire with 10kV neon transformer, as shown below. The name is SIET METALBOX (10kV 30mA). How do I diagnose the problem? All wires are ok.

The issue is that the setup doesn't work as expected after connecting to an outlet (50Hz 220V). Black wires are for high voltage output, white are inputs. I expect small plasma fire at the ends of the black wires pair when the ends are sufficiently close.


texts: Made a simple mono amplifier (LM386) circuit, and it stopped working. How can I debug individual components?

texts:
Note- I'm a programmer, not an electrician.

I'm replicating the circuit found here: https://www.youtube.com/watch?v=4ObzEft2R_g&t=04m50s (circuit @ 4:50)

I've soldered two identical PCBs, and when hooked up to a speaker, both worked great! However, I was testing the functionality by loosely touching the speaker input to the output of the 1000uF capacitor on one of the boards (and it was working!), when my finger slipped and I think the speaker input wire grazed some other component on the PCB.

I heard a small pop in the speaker, and when I hooked it back up, it didn't work anymore (silence).

I tested the speaker with the other PCB, and it's still working fine.

What might be wrong with my circuit? How can I debug this without essentially just re-soldering it all from scratch?

I already swapped out the LM386 with a fresh one, and it still doesn't work (I guess there's a chance I grabbed a dud LM386?). Visually, the chip/capacitors/resistors all look identical to the functional PCB.

I have a multimeter, and have access to an oscilloscope. I just don't know what to look for.

Where can I start?


texts: Calculating resistor for LEDs with different Forward Voltages in series

texts:
I need to work out what resistor I need for a series circuit containing 3 LEDs of 2 different types, and a 9v battery.  I can do the maths, but I need to check I'm doing it right as I'm trying to learn this from what I can google!

LED1 VF = 3.2V @ IF = 20mA
LED2 VF = 2.2V @ IF = 20mA

Both LEDs have a Forward Current of 20mA at these Forward Voltages.

The circuit will contain 2x LED1 and 1x LED2.

So, using R = (VS - VF) / IF, do I calculate the total VF as 3.2V + 3.2V + 2.2V, therefore VF = 8.6V?

Using the figures I have, I get:

(9 - 8.6) / (20 / 1000) = 20 ohm, so I'd need a 20Ω resistor?

Also, can anyone advise what type of resistor would be best?


texts: Does it make sense to plot resistor current vs input voltage in this circuit?

texts:
simulate this circuit – Schematic created using CircuitLab

I'm a bit confused by a question which asks me to plot current through R1 as a function of Vin using a constant voltage model for D1. I'm a bit confused by this. Given the model, even if I considered Vin to be the voltage over the current source, wouldn't it be V_Diode_on once I_in*R1 = V_Diode_on? Does this make sense or is this likely a typo and I should be plotting V_R1 as a function of I_in?


texts: Is C20 the same as 20C for battery ratings?

texts:
My current understanding is that the C20 capacity rating of a battery is the number of Ah that is supplied by a battery to a load that will fully discharge the battery over a period of 20 hours.

Is 20C the same as C20, or does a 20C rating mean that the battery is discharged in 1/20 hours and the current being drawn is ~20 times the rated Ah capacity of the battery?

Edit/clarification: I'm looking at battery specifications and this question is in the context of a battery having different nominal capacities at C20 and C100, rather than trying to determine the maximum allowable load that can be from the battery.


texts: Can I send data to my computer from the serial port on an Arduino/ATTiny?

texts:
I am using an Arduino to program an ATTiny like in this tutorial. My question is:

How can i send data to my computer on the serial port? Is it possible ?

Any ideas are welcome.


texts: N-Channel Mosfet to switch a -48V to -54V Power Source

texts:
I have recently been tasked with the rebuilding of a resistive load center we use at work for testing telecom power supplies we have serviced. It currently has a series of relays that continually weld the contacts together due to being grossly underrated. I am currently sitting on roughly 80-90 new APT5010JN N-Channel Mosfets that I would like to use for this application but cannot seem to get a circuit I found on this site once (It was in post "NMOS FET with a negative drain"). I Believe it would serve my purpose allowing me to utilize the N-Channel Mosfets I already have in stock. What I am trying to accomplish is replacing the EMR Relays with Mosfets so that I can switch on and off 30A branches in my load back which is connected to a power supply that is producing -48V to -54V. We currently have a control box that is used to switch the existing relays with coil voltages of +12V. The schematic I am having trouble scaling was provided by member alexan_e and looked like this:

Any assistance would be greatly appreciated.


texts: Sorry for the general nature of this question. But I have always asked myself what makes solder fumes smell of incense.


texts:
I am trying to turn on a LED for 5sec every 12 hours.
I tried:

#include <mega16.h>
#include <delay.h>

void main(void)
{
    DDRC.0 = 1;
    PORTC.0 = 0;

    while(1)
    {
       unsigned long i;
       unsigned long j;
       PORTC.0=1;

       for(i=1; i<432; i++)
       {
          delay_ms(100);
       }

       PORTC.0 = 0;

       for(j=1; j<100; j++)
       {
           delay_ms(50);
       }
    }
}

but the LED was on for about 2 hour every week.


texts:
I have two device ( ISL83485 + STM32), and they connected on RS485 line.
I want to send some UART signal to RS485 line with a tranceiver. I am using ISL83485 tranceiver for this purpose, I am using stm32f4 proccessor. When I transmit data under UART2, I can see the data in UART_TX pin of the tranceiver with the osciloscope. If the both device send data to line, I can see RS485 signal on the line, but if the one of them send transmit and another listen or quiet, I couldnt see any data on the RS485 line.
When the other device listen mode, I configured to DE pin as a RESET. But it didnt work.
My Connections details:
ISL83495 | STM32
  RO       USART2_RX
  DI       USART2_TX
  RE       PD3
  DE       PD4
  VCC      3.3V
  B/Z      RS485-TX-N line
  A/Y      Rs485-TX-P line
  GND      GND

between the A-B line I have 120ohm
Source Code:
uint8_t rs485TxBuffer[2]={0xAA,0xBB};
uint8_t rs485RxBuffer[2] ={0x00, 0x00};
..
int main()
{
..
    while(1){

            RS485_Set_Transmit_Mode();
            while(HAL_UART_Transmit_IT(&huart2, (uint8_t*)rs485TxBuffer, 2) != HAL_OK)
            {
                // ...
            }
            uartReady = RESET;
            while (uartReady != RESET);
            uartReady = RESET;
            RS485_Set_Receive_Mode();
            while (HAL_UART_Receive_IT(&huart2, (uint8_t*)rs485RxBuffer, 2) != HAL_OK)
            {
                  // ...
            }
            while (uartReady != RESET);
}
void RS485_Set_Transmit_Mode(void)
{
  HAL_GPIO_WritePin(GPIOD, GPIO_PIN_4, SET); // DE pin
}

void RS485_Set_Receive_Mode(void)
{
  HAL_GPIO_WritePin(GPIOD, GPIO_PIN_4, RESET); // DE pin

}

void HAL_UART_TxCpltCallback(UART_HandleTypeDef *UartHandle)
{

uartReady = SET;
}

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *UartHandle)
{

uartReady = SET;
}

HAL_UART_TxCpltCallback working correctly and I can see the dataon UART_TX line but I couldnt see this data in RS485 line. What is the problem here?


texts: 24V supply run 12V 3014 LED strip in series; help with resistors for series

texts:
i need help with wiring up some pieces of a 12V LED strip in series to run on a 24V 150mA supply. i want to add resistors , to help keep the strings evenly balanced. i don’t know if it is necessary, especially because the ones in each LED series; But i don’t think so, from looking around the internet. i think it matters and i am not entirely sure why, but i think it keeps them even in power distribution, and hopefully keeps burn out from occurring as easily.

i am puzzled because i had found a video that said to use 20% more watts than your LED strip was rated. i don’t like that though.

i don’t know what it’s rated anyway , only
that the LED set is 3 regular 3014,

likely FM-3014WLS-460T-R80 (or the 70 CRI one FM-3014WLS-460R-R70 which has the same specs) from Nationstar (it’s the warm white LED strip )

~3 V (3.2 VF) 30 mA (35 mA max) in series with a 100 Ohm resistor (code on surface mount resistor on board is “101”)

each LED being a 0.1W diode? and a strip being 12V 0.1W if i understand correctly. so parallel (as they are in a strip) that looks like 1.8W on one strip in series with another 1.8W ; so, 18 LEDs (6 units of 3) on one strip in series with another 18 LEDs, but this is wrong, due to the resistor in every unit, and could maybe be approximate (but this isn’t the point of the question. i want to know) to 18/4 ~ 4.5 units so i guess, 4 units of 3 LEDs with a 100 Ohm resistor, is maybe 1.8 W / 16 things ~ 0.1125 W per thing, but that’s rubbish but also gives room to dump energy in the resistors before the positive and negative leads and maybe in between the LED strip, as they are linked in series ?

so i am asking for help in these calculations which are over my head, and to understand how to do them
(i would eventually love to learn about zener diodes, but this is a logical baby step, and i also don’t have any zener diodes :)

i am not sure if that will even work. for example, i have no clue what actual resistance each LED is giving, being that the range of volts and amps it is passing changes the resistance. (and i don’t have the volt and amp curve graph even if i could use that, the data sheet doesn’t include it or a wavelength efficiency chart)

so without that data there is only the 100 Ohms to use (unless i use 6 Ohm per LED for the heck of it because i saw it on a circuit lab LED value. but, assuming i didn’t  ,

if a theoretical unit was set to 12 V , then V = I * R , 12 V= X * 100 Ohms, is 0.12 A which is high

, and V * I = W, 1.44 W for 3 LED and a 100 Ohm resistor.

i don’t know what i am getting wrong here right now.

a 0.1 LED would imply that 1.44 W - ( 3 * 0.1 W ) = 1.14 W of a resistor.

that doesn’t make sense; it’s way more energy than the LEDs. i must be doing something wrong.

i had figured that 3.2 V + 3.2 V + 3.2 V leaves 2.4 V to be filled by the resistor
and 3 V + 3 V + 3 V leaves 3 V to be filled by the resistor

i also tried to do with V = I * R for the resistor

one case :
2.4 V = 0.03 A * X (if LEDs at 30mA) , X = 80 Ohm => No
2.4 V = X * 100 Ohms , X = 0.024 A (24 mA)

second case :
3 V = 0.03 A * X , X = 100 Ohms
3 V = X * 100 Ohms , X = 0.03 A

it correlated with :

i had used an equation i found that said
I LED = [ V source - 3 * V LED ] / R
so,
I LED = [ 12 V - 3 * 3.2 V ] / 100 Ohms
I LED = 0.024 A
and
0.03 A = [ 12 V - 3X ] / 100 Ohms, X = 3 V
and even more disappointing was
.035 A = [ 12 V - 3X ] / 100 Ohms, X = 2.83333 V, which the curve that should have been on the datasheet would rule out.
the 100 Ohm resistor really seems to put a damper in everything , so i don’t know what further ones will do

But anyway, please help me understand the error of my calculations and lack of understanding.

thanks !


texts:
If you go to this link you see a nice laser driver for a small laser...didn't he mean to put that diode in series with the + and - or is it supposed to be parallel and I"m just not understanding for some reason?

http://www.rog8811.com/LM317%20components01.jpg?0.35312663627278806

also his reasoning there:
http://www.rog8811.com/laserdriver.htm

Plus isn't the diode possibly unnecessary since the laser is a diode and assuming it can handle the voltage?


texts: Understanding max and min propagation delay in flip-flops

texts:
I've been working my way through Digital Design and Computer Architecture, but am very confused by the equations for time delay - what each of the variables are, and how to conceptualize these equations.

Assuming no clock skew, the book gives the following two formulae:

$$t_{pd} \le T_c - (t_{pcq} + t_{setup})$$

$$t_{cd} \ge t_{hold} - t_{ccq}$$

What I understand so far is that contamination delay is the minimum amount of time that will pass before an inputted value will start to change, and the propagation delay is the maximum amount of time that will pass before the output is sure to be resolved.  I also understand that the setup time is the amount of time before the rising edge of the clock that an input must have stabilized, and the hold time is the amount of time after the edge that we wait before we can be certain that the output is stable.

Assuming this understanding and no further, can you please explain and help me conceptualize the two above equations?


texts: Resetting 555 via Transistor - RESET PIN LOW TOLERANCE

texts:
I have a circuit with a NE555DR timer that generates a pulse. The reset is held low and lifted when a voltage of 5 - 24V is applied to P0-3.

A PNP transistor MMBT5401 that pulls pin 4 to ground when inactive.

The Simulation is correct for the voltage at pin 4, this is 0.68V on the PCB. The problem that I have is that the DR555 Ti Timer has a low pin tolerance of 0.3V. the 0.68V is not low enough to reset the timer on the PCB.

The current on Pin 4 is 0.5A, I have not been able to get the voltage lower than 0.3V.

How do I get the voltage <0.3V on pin #4 of the NE555DR timer for it to be inactive?

I found this question, however, it did not address the voltage tolerance on the reset pin.

https://electronics.stackexchange.com/questions/369138/resetting-555-via-transistor-optionally-driven-by-touchplate-piezo/369143#369143

Circuit simulation with P0-3 at 0V


texts: How can I preserve battery lifespan on an always-on harvester/charging embedded device?

texts:
I'm using a GSM device powered by a battery, charged from energy harvesting from a low current source (0 to 200mA, the most of the time 20mA @ 9V.)
To charge the 8000mAh 4.2V battery, I'm using a TP4056 with previous buck (after some tests with buck-boost charger I found this configuration more efficient,) and the device is full most of the time if device works as expected.
Right now the TP4056 chooses when to charge: would it be better if I will force discharge a little bit more before charge? What can be the estimated battery lifespan retaining full battery all the time (with a few charge/discharge?)
Edit: Here are the waveforms of the battery voltage, the current through the battery shunt (charge or discharge), and the gas gauge.

Would it be any better if I limit (lower) charging current?


texts: How to test circuit with AC mains voltage?

texts:
From my experience, testing circuits with a lab bench power supply is great because it protects the circuit and itself from over current or short circuit when anything goes wrong.
I wonder how I can do that with AC main voltage (230 V).
My circuit is a 230 V BLDC driver using a diode bridge to rectify 230 V AC to 325 V DC (Approximately) then using microcontroller and IGBT to drive the motor.
When something goes wrong it might really dangerous.
What should I do?
These are some risk of my circuit that I think of.

High voltage jumps across some gap.
Shoot through via half bridge (short circuit)
Some controller error might cause over current (fault current controller)


texts: Overshoot/undershoot in non-minimum phase system

texts: I read some practical examples and see that in non minimum phase system the initial response of a system works in the opposite directions as the long-term response of a system. However, I don't see that behavior in the non minimum phase system with transfer function (s-1)/(s+2). I tried to plot the unit step response and see if there is any overshoot or undershoot (as the behavior of non-minimum phase system). If you look at the plot attached below, there is no overshoot/undershoot. Can anyone explain why?


texts: I am unsure if I have simplified this circuit correctly, therefore I am unsure how to write Vo in terms of V1. Please let me know if I have simplified this correctly.


texts: Why is the same MOSFET model give very different output for this circuit?

texts:
I have this MOSFET and as you see below it works fine when I try as inverting switch :

But when I try this on breadboard with three 2N7000 only one of them is like the simulation. If I try with the other two the Vout becomes only zero to 4V instead of zero to 5V.

What could be happening here? Everything is the same I just replace the MOSFETs from the same package.

Here is the breadboard wiring of this circuit:

(yellow is gate input, brown is Vsupply)

And below is scope screen for the same circuit with 5V and 4V output:

[]

Note: I also tried with R1 100 Ohm, nothing changes.


texts: Calculating power requirements of RGB LED strips

texts: Is there any formula or rule of thumb for calculating power requirements of 'typical' RGB LED strips? Say x amps per # of lights? or are there too many other variables involved(specific make, etc).


texts:
The channels are CAN_H (red), CAN_L (blue), and CAN_H-CAN_L (brown).

It can be observed in the diagram below that CAN_H-CAN_L has an acceptable signal shape. However, both CAN_H and CAN_L look poorly to me. And actually the device is not running in a noisy environment. I have two questions:

Do you think signal integrity is an issue here?
CAN_H-CAN_L sometimes has high voltage level of 1.65 V (left side part), while sometimes it has a high level of 2.06 V (right side part). Do you think this is a problem?


texts: On-Board connection of ethernet transceivers

texts: Is it possible to connect two 1000-BaseT transceivers with each other? I have two transceivers, each of them has 4 twisted pairs that actually are meant to be connected to an RJ45 connector including magnetics. Is there anything wrong with making on-board connections between ethernet transceivers?


texts:
I have a "stick lamp" that has a pot/twistable dimmer with photocell. It works fine with a 24w Sylvania CFL bulb but won't light this 22w dimmable LED bulb (http://www.ikea.com/us/en/catalog/products/80306780/). The LED bulb lights fine in a regular lamp. I read that maybe the lower wattage of the bulb or way the dimmer circuit works is causing issues.

Here's the dimmer:
http://www.ceilingfanswitch.com/product/lamp-dimmer-zing-ear-ze-02se/

I don't really care if the photocell works and I'm open to the idea of replacing the whole dimmer piece but not sure what to look for.


texts:
I am in the process of making a kill switch for my car and after doing some research I couldn't find the answers that I needed to start the project.
One of the biggest questions I have is how can I use a USB flash drive paired with an adapter board to act as a toggle switch? I was planning to keep a USB thumb drive on my set of keys and have a USB Type A adapter board hidden somewhere in the cabin which connects to the fuel pump/ignition/main relay. The idea is one or all of those components listed wouldn't work unless I plug a USB drive into the port, better yet, if anyone has an idea as to how I can get the car to start with only that USB drive I would love to hear it.
Any help or suggestion is appreciated.


texts: Powering cmos invertor from battery charging line

texts: I use MCP73831/2 for charging a battery. But now I have to power a logic gate from the same line (I mean connect gate's vcc directly to the battery and to charger output). Is it a good idea? Could the logic IC be damaged somehow by charger current? The rest of my circuit is disconnected from the battery with a mosfet while charging.


texts: MCU push button triggered by electrostatic discharges

texts:
In a simple project based on an STM32 microcontroller, I needed a couple of extra push buttons. So I connected each button between a pin on the STM32 and GND, configured the pins as input and activated the internal pull-up resistors.

It seemed to work well at first. Pushing the button pulls the pin to GND and triggers an interrupt. But a problem soon became apparent, which was that the setup was extremely sensitive to nearby electrostatic discharges. If I touched a piece of metal several feet away, it would cause the interrupts to trigger.

The STM32 is on a Discovery demo board which has a push button on it. That button does not have the issue, so I looked up the schematic (included below).

So there are 3 resistors, a cap and connections both to VCC and GND (and maybe the internal pull-up is used as well).

Will I need to add all that for my push buttons to be reliable? If not, which circuit do I need? What is the reason that the internal pull-up resistor is not enough for filtering out noise from nearby electrostatic discharges?

Update 1:

I have verified that the internal pull-up resistors are active. If I disable them, the buttons trigger randomly every few seconds. To activate the pull-ups, I use:

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;

And to disable them:

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

Update 2:

I changed my push button circuit to match the schematic (with R20 and C22 removed, R22 replaced with wire) and disabled the internal pull-up. It did not change the sensitivity to electrostatic discharges.

Update 3:

Turns out that I was using the schematic for the wrong Discovery board. I've included the correct one below. This new one does have all the components fitted and the circuit is very likely to resolve the random triggering issues.


texts: How to get started knowing how to power my robot?

texts:
I have been a software engineer for many years writing code for websites/servers etc. I recently became intrigued with the idea of building land drones. I have decided to build a small tank that has a raspberry pi on it and can drive itself around and do stuff. In the beginning I will start off with only powering a raspberry pi and the turning of the wheels of this tank. I will put python code into the raspberry pi to make it do this. Down the road I will add a camera and potentially another small computer such as a Nividia Jetson Nano. I have the skills to do all the coding to make it work but I lack an electrical knowledge. The main problem I see that I have right now is what power source do I need to be able to power all of these things? I would like to buy some sort of a rechargeable battery that could power all of the things listed or just the raspberry pi and the wheels if I never get to adding the other stuff. I have read that the raspberry PI operates at 5v and the wheels of my tank operate between 7-12v. I have also read about the drive controllers that you can attach to the raspberry pi and how they can control dc motors. I haven't looked in too much detail about what will be required of the camera and some of the other possible items I will add as I am hoping to build incrementally.
Rather than ask for a solution to the above mentioned problem I would like to ask what is the recommended way to get my feet wet with this problem as well as any other problems a beginner robotics person like myself this kind of robotics would have?
I know I can go on amazon and look for books but I was hoping to ask the community for help in case there is a go-to resource that the community would recommend. Thanks in advance for any help.


texts:
I am going to implement a MAX10 remote update. Unfortunately, in Altera's documents i only see a NIOS implementation and everything looks very big and too complex. Also i already have a reliable communication channel, so i only need to store the data. I am still sure i can implement everything i need in VHDL, but i have some questions (and altera's documents are not very helpful):

Is it enough to just address CFM, like user flash?
What are relevant addresses? What is the image start?
How do i start reconfiguration after flash is ready?
Which file should i use for download?

Thanks!


texts:
I am in the process of adapting an old phone to be used as an Bluetooth phone. I am currently testing the ringer circuit, which I build using the schematics provided by Sparkfun.

I wired up the stuff as follows:

Almost exactly as they have done it, apart from a few minor changes (I use a different H-bridge and only had a 150uH inductor lying around).

For the H-bridge I use the SN75441ONE, and the DC-DC converter is the MC34063.

RING1 and RING2 are connected to my Arduino, and the 1000ohm ringer is from the old phone I have lying around.

Now, when I hook up just the right part of the schematic to a 3.5V source (Vcc), I get a nice 45V on the output (with a steady current draw of about 130mA). But as soon as I connect this to the ringer part, I measure an output voltage of only about 7 volts. Increasing Vcc keeps the '45V'-voltage at about twice the Vcc.

I have to turn up Vcc to about 9V to get the '45V'-voltage to about 18V, and then  phone rings if I set RING1 and RING2 alternately to high (alternating at roughly 20Hz). It is not very loud, but it does work.

My question: why do I measure a lower voltage at the 45V output when I connect the ringer circuit? Why does this drop to a lot lower values? I don't want to need to provide 10V to the schematic, for what I know it should run on 3.5V.

(I hope I have provided enough information. Here is a picture of the actual implementation:)


texts: Do you know any tools which perform design rule checking for Gerber files of PCB and are suitable for using in batch mode on a remote server? Something similar to what BatchPCB or FreeDFM uses (I asked BatchPCB but they haven't answered yet.)


texts: Technology "dielectric constant" information

texts:
OK, so when working in a technology, say Bipolar, to build a high frequency amplifier, can I trust that the dielectric constant info for the various films contained in the electrical design rules, are measured at the frequency of the transistor Ft(6GHz)?

What do I mean?  So the dielectric constant formula has a frequency component, but it is often meaured on optical measurement tools operating in the 500nm, which would be great if my design operated at 600THz.

Do I need to do a conversion to capture the correct dielectric constant of the films related to the frequency?


texts: Finding steady state response of LTI, dissipative systems

texts:
The input, \$x(t)\$, and output, \$y(t)\$ of a linear time invariant, dissipative system are related via the differential equation

$$d^4(y(t)) + 6d^3(y(t)) + 14d^2(y(t))+14d(y(t)) + 5y(t) = - d^2(x(t)) - 9x(t)$$

If \$x(t) = \cos(t)-\sin(t)\$, determine the steady state response.

Now, I know

$$H(iw) = \frac{-(iw)^2 - 9}{(iw)^4 + 6(iw)^3 + 14(iw)^2 + 14(iw) + 5}$$

But I'm having a hard time understanding how this transfer function will help find the steady state response. Especially since there is no circuit given.


texts: Voltage build up in induction generator and its working principle

texts:
I had some  doubts while reading about  working of self excited  isolated induction generator .

If principle of operation of  self excited isolated induction generator  is similar (in a sense that in both cases initial excitation is due to residual flux and after that fields interaction takes place) to DC self excited generators, then why it needs capacitors to operate while in  DC
generators there is no such requirement?

And which connection we preferred in case of induction generator, stator and rotor winding in series with load or (stator winding and load) in series and parallel to rotor winding?

(A mathematical explanation would be better or even any answer which does not talk about reactive power is good for me because I read from many websites, and everywhere I found that we need capacitor to provide reactive power but this explanation to me is far from intuitive).


texts: How do I refer the transfer function of a system from its Laplace equivalent?

texts:
I have a problem, I know how to analyze circuits in Laplace domain to get the transfer Laplace function.
However, I don't know how to translate the answer to "real life"

  Suppose that I have a transfer system with Vout=1/sC, where C is a capacitance (say of 10uF). And suppose now that I give the system Vin = 2*sin(pai/2 + 2pai). How do I determain the output signal from the laplace form of my transfer function?

Thanks!


texts: What parts/sections of a CPU take the biggest number of transistors?

texts: I was surprised to hear CPUs only have a number of ALUs. What are most of the transistors in a CPU dedicated to?


texts:
I'd like to start with a couple DIY experiences into solar panels.

My question is regarding the inverter wattage.

I mean, if I pretend to make a cheap solar panel with a maximum possible wattage of 150w, connected to a 12v 20Ah battery. Should I buy a specific inverter for medium-small size projects?? Or could I buy, let's just say, a 1000w one? because gradually I'd like to increase the size of my projects in the future (and save some money)

Thanks in advance


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I am trying to figure out the best approach to convert a 480V 3-phase AC to a 12V DC. I am thinking of first converting the 3 phase to a single phase AC then using a transformer and rectifier shown in this link Transformer and rectifier to get 12V DC.

Is this the right approach or can anyone suggest better approach?
To Convert a 3 phase to single phase can we use one of the phases and a neutral wire in a 3-phase 4-wire system and give it as an input to the above transformer and rectifier or is this a bad idea?

Thanks


texts:
On my mini quadcopter I have a 2.4 GHz quarter wavelength monopole antenna that is close to defective (due to crashes and therelike) and that I need to replace. This antenna is used to recieve control input and send back telemetry data, so it is sending and receiving at the same time.

The ground plane of the quadcopter does not seem to be too good, so I was thinking about replacing the monopole antenna with a dipole antenna, e.g. from an old WIFI router.

Is it possible to use a dipole antenna in a monopole design? Can I just connect the second half of the dipole antenna to ground?

If I build the dipole antenna myself from two pieces of wire, do both halves of the antenna need to be aligned directly in one line or can I place the halves apart from each other to where they are convenient on the board?

Is there anything else I need to know about that topic?


texts:
I wanted to learn to use SPICE through text files, (no GUI except for notepad/notepad++) but I am not capable of setting this up myself. I found some spice2/spice3 downloads from Berkeley's but that's about as far as I get. I know that I need to run "spice < myCircuit.cir" in cmd, but it is an unrecognized function. I have tried all day with Visual Studio and some strange things I gathered from searching the internet, but no success.

Oh, and I am using Windows 10.

To make things more clear, I was following this walkthrough https://www.allaboutcircuits.com/textbook/reference/chpt-7/fundamentals-spice-programming/ but failed miserably. In the link, beneath the example CMD line "spice < example.cir" it mentions "(providing that the SPICE software has been installed on the computer!)." The walkthrough doesn't mention how to install, so this is where I depart onto various internet threads and I haven't found a working installation procedure.


texts:
I have the following N-JFET DC circuit for which I must find the output voltage \$V_{out}\ = V_D\$ (the drain voltage with respect to ground) when a PWM signal from \$-10V\$ to \$0V\$ is applied to gate. I can solve the circuit when the signal is at \$-10V\$ so I will focus exclusively on the \$0V\$ part.

The circuit is simulated with the PWM signal at \$0V\$ applied to the gate of the JFET, thus explaining the connection between the gate and the source to ground.

I know that \$I_{DSS} = 10mA\$ and the pinch-off voltage \$V_p = -4V\$ and I found that when the PWM signal is at \$-10V\$ the JFET is blocked so \$V_{out} = 10V\$, but I don't understand how I can find the output voltage when PWM signal is at \$0V\$.

I found that if \$V_{out} = |V_p|\$ when \$ V_{GS} = 0V \$ then \$ I_D = I_{DSS}\$, but doing so would result in an impossible voltage drop of a hundred volt on my \$10k \Omega\$ resistor, so I conclude that \$V_{out}\$ must be less than this, thus my JFET should be somewhere in the ohmic region. However, I cannot find the value given by the simulation.

Other given values are \$\lambda\ = 0V^{-1}\$ for the channel length modulation parameter and a temperature of 25 Celsius degree.

Any help would be greatly appreciated.


texts: Handling large numbers of input contacts

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I'm trying to interface a large number of contacts (<=1024) under velostat with an arduino DUE.  I have a large array of pads and I want to detect when any one point goes high (think of this as a super low-resolution single-input touchscreen).

What is the best option for interfacing with these inputs?  Are there any encoders that are large enough to handle this?

Thanks!


texts: What device has this marking M7CK 825 with size 3mm x 3mm, so I can purchase a replacement? This is a Garmin echomap 50s sonar circuit board. The outboard gave overcurrent and this broke down, as did one capacitor. Here are two boards Thanks.


texts: I am clear with the problem and its solution. But I am curious if it is possible to calculate all possible solutions.


texts: Infra red remote control very short range

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I bought a house that has a few LG split air cons.

Whenever I want to use them I need to get like 2 meter close to them for the remotes to work which feels too short and annoying. These units are 10 years old and I already changed the batteries for all remote to try if it would solve the issue.

So my question is what could have happened over these 10 years to reduce the range of the remote controls? Is there anything I can do to improve it?

I thought maybe the plastic in front of the IR sensor got opaque? Any change the remotes or the receiver start to loose power over time?


texts:
Are there any problems that can be caused by using resistors of large resistances (in the order of megaohms)?

I'm designing a feedback network that is just a voltage divider, and I want the feedback to drain as little current as possible from the circuit. The only thing that matters is the ratio between the resistors. So my question is: is there any reason why one would pick, for example, resistors of 1 and 10 Ohms instead of 1 and 10 MOhms?


texts:
I hope this is an easy question for you.

I am using a plastic box as a watertight enclosure for a single board computer and some accessories. I will be using an AC power source coming in through a 3 wire wet pluggable bulkhead connector. It is then converted to DC in the box to power the components (like the SBC, a serial-to-usb converter, etc). The AC/DC converter (Mean well brand) has a place for attaching a ground.

My question is: will using the ground screw on the AC/DC converter be enough to ensure this box is safely grounded? My gut says yes, especially since the box is plastic, but I am going to be using this in a saltwater environment. I really don't want to kill myself so I'd like to be extra sure before I deploy this baby.

Thanks much!

EDIT: Unless the ship goes down, this box will not be submerged. It will only be exposed to saltwater spray during cleanup.


texts: Calculating throughput of BPSK channel with roll-off, error correction code, packet loss

texts:
A digital signal is transmitted with packets of:

240 bytes of information.
control header of 10 bytes.
reference signal of 700 μs/packet

BPSK modulation.
rolling factor of 0.25
1 MHz band.
coding rate of 3/4.
probability of packet loss of 10%.

What is the throughput rate?

My efforts so far:

Baud rate = (Band)/(1 + rolling factor) = (1 MHz)/(1.25) = 0.8 MBd
Bit rate = 0.8 MBd * 1 bit/symbol = 0.8 Mbps
Considering packet loss = 0.8 Mbps * (1-packet loss rate) = 0.72 Mbps
Useful bit rate = 0.72 Mbps * coding rate = 0.54 Mbps

I am struggling now on how to consider the pilot signal on the calculation... could anyone enlighten me and give me a hint on how can I complete this calculation?

thanks!


texts: Could power cycling a modem 24 times a day for over 3 years (>30,000 times) cause the modem to lose its settings?

texts:
Could power cycling a modem 24 times a day with it being on for 10mins at a time for over 3 years (>30,000 times) cause the modem to lose its setting and revert to factory?
This modem.


texts: Switch type for electrical generator bonded to floating neutral

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I have an electrical power generator and for it to properly work with it connected to the house it must be converted from bonded neutral to floating neutral according to these instructions. I was thinking of attaching a switch to be able to easily change from bonded and floating without having to remove the cover and wire each time I want to use the generator connected to the house or when using standalone.

I haven't found a simple toggle switch that can hold the max amp and voltage. I was then thinking of an isolation switch used on cars for batteries. I've seen some that can withstand 500 amps, but at 12 DC Volts. Would that work?
I want something small I can attach inside the housing.
Any recommendations and what specifications I should look for?

My Generator produces a max of 50 amps at 240 AC Volts.

The bonding cable is the top right white cable.

Battery isolation switch


texts: How calculate and chose the right BJT that comands a relay

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I was projecting a simple circuit that, from a digital OUTPUT from an Arduino zero (3.3 V) switch on a BJT that is connected to a relay.

The base of the BJT must have a current of about 5mA or less. Is this configuration enough to run a relay?

I have simulated this circuit and Ic is about 49mA; if I change the relay, Ic increases or it's fixed?

I'm not really good at this thing

simulate this circuit – Schematic created using CircuitLab


texts:
I need 5v, 12v, and -12v in my circuit. What would be the best way to get this from a 12v, 5A supply?

For 5v, I could use a regulator. Not too sure about -12v.


texts: How can I get a broad overview of the world of electronics?

texts:
(Feel free to edit the question's title. Wasn't sure of a good one liner for my question)

I'm a university student who has found a love for electronics and circuit design. I have a solid knowledge of the basics of logic design (worked with logic gates, created ALUs, created registers, stuff like that). I found this SE site and started reading a lot of the top voted questions, which helped a whole lot. However, when reading most of the questions here, I find myself completely lost.

I think this is because of my limited scope and knowledge of the world of electronics. There are a lot of acronyms thrown around (IC, FPGA, MCU, etc) and most of them have little relevance to what I already know. I think hardware programming is awesome, but where does it happen? What do you program?

So, I guess my question is this: How can I visualize the world of electronics and where is the next logical (no pun intended) step for someone at my level? Where does circuit logic (NAND, NOR, etc) fit into all this?


texts: Darlington Transistors ULN2003APG Base Voltage

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I want to control a 30x1 array of pins through a raspberry pi B+.  On a breadboard, I set up a series of shift registers (74HC595) to an array of 2V leds, which I can control as intended. After the leds, I'd like to increase the current from 4mA to 25mA.  I installed a series of darlington transistor arrays (ULN2003APG) to do this. I had read that such transistor arrays require 1.4V at the base in order to activate.  Since I have connected to the Pi's 5V output, I used 460 ohm resistors (the closest to 400 ohms I had).  However, the test leds that I'd placed downstream of the transistor arrays won't turn on.  Thinking that I had overestimated the base voltage needed, I cut down on the resistance - eventually scrapping both the leds and resistors altogether. I still received no output from the test leds. What's wrong here? Any help would be much appreciated!

On the left are the five transistor arrays.  They are oriented downwards (with the indentation at the bottom).  As situated, the common is top left, the ground is top right.  The common is connected to the Pi's 5V through a 100 ohm resistor (I will need 2.5V and 25mA post-transistors).  The ground connects back to the Pi's negative terminal on it's 5V port.

On the left are shift registers, which are wired to the Pi.  They are working appropriately. Not shown, but previously configured, was a wire leading from the transistor's output through a 125 ohm resistor to the test led bulb.


texts: Please identify this 8-pin SMT device - markings P636F FDS 6690A

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Please assist - I cannot identify this device. I try to label all my SMT components, but this one has slipped through the net.

It appears to have a "f" as a logo; the text blocks are P636F; FDS and 6690A.

Also, as a more general question, what resources are recommended for tracking down such items?


texts:
I am working a stepper motor and I don't understand why the current going into the two windings are behaving as shown in the oscilloscope screenshot.

Stepper motor: :FL42STH47-1204A (4 wire) Driver: ST L6208

The driver is setup to run in full step mode and fast decay, 1.2A at 24V. Motor is running at 700rpm.

BLUE/GREEN: Winding current sense nodes RED: Step YELLOW: Winding

At lower speed, the currents are charging/discharging up following the normal exponential fashion, but as I increase the speed the currents start to show this strange behaviour. Initially I thought that this was due to the driver not able to cope with the current demand but the same result was obtained with a more powerful driver. This leads me think that it down to basic inductance physics but I can't figure out what is causing this. Has anyone idea of what is going on? Thank you.


texts: Would a four terminal mosfet work equally well if the source-drain polarity were switched?

texts: I noticed a question regarding mosfet polarity asked here and wondered whether a four terminal mosfet would behave the same way under reversed polarity. Since the four terminal mosfet has no internal diode (I think), I do not see how there could be a distinction between source and drain. Is this true?


texts:
I am trying to build a communication system over a power line using FSK. I want to stay within the frequency band A of the CENELEC protocol which goes from 3 to 95 kHz. I am trying to determine suitable modulation frequencies for the space and mark signals. The bitrate should be 2kbps.
I'm looking for trade-offs which I should consider when choosing this frequencies but I can't seem to find anything really specific (in theoretical or equation form), other than the bandwidth.
Do you guys know of any other considerations when choosing these frequencies, other than that the demodulator should be able to demodulate the signal, such as signal to noise ratio, bit error probability, etc?


texts: How do we explain the voltage doubler operation by analogy?

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The idea behind the Greinacher voltage doubler is so clear and intuitive that it can be explained, like any brilliant circuit idea, in a very simple way. I did it yesterday in a similar question where I visualized in a geometrical way the invisible voltages by means of voltage bars which lengths are proportional to voltages.

But this presentation technique is still a little abstract. So I asked myself, "Can't we visualize the circuit operation at startup using well-known life analogies - hydraulic, pneumatic, thermal, mechanic, information, etc?" They will be a good addition to the main question because the deep understanding of phenomena comes from looking at the same problem from several sides.

What would be the most appropriate analogy for this clever capacitor circuit?


texts: Why are two 555 timers in separate sub-circuits cross-talking? (Poltergeist in the Breadboard)

texts:
As an introduction to electronics, I am following Charles Platt's Make: Electronics (2nd edition).
Every circuit worked as expected, until Experiment 17: Set Your Tone.
In circuit on figure 4-37 (page 163), two 555 timers are used in astable mode (as oscillators). The first timer (low frequency) output is wired to the control pin of the second timer (audio frequency), as to generate a siren sound... at least supposedly!
Minimal example
I have been facing different "surprising" behaviours with this circuit, and while trying to work my way out of this situation, I extracted the minimal example below:

This circuit is two 555 timers in astable mode mounted as separate sub-circuits on the same breadboard. (I call them separate because, as far as I can tell, they only share the power rails). The left timer should have a frequency ~1/10th right timer (thanks to the left discharge resistor being 100K, compared to 10K on the right)
This behavior is what I observe if I only provide power to one timer at a time. But if I connect both at the same time (as shown in the picture above), then something I cannot explain happens:

They both start flashing in sync, at a high frequency (but not exactly the second timer frequency, something a bit higher).

I cannot see how those two separate sub-circuits can talk... And from my understanding of experiment 17 in the book, they are not supposed to.
Questions

Is there a malicious being living inside the breadboard, and how should I name it?

Otherwise, what is the rational explanation behind this behavior?

Additional details:

I provide 9V via some universal transformer which provide quite stable voltage.
The timers are marked 99AG7ZM NE555P
The ceramic capacitor in series with the control pin is 0.01μF (marked: 103), as recommended by the book.
The electrolytic capacitor is 10μF 25V
I tried replacing both timers with other timers (exact same model), resulting in exactly the same behavior.
Initially, I built the two sub-circuits very close, and tried another build with more distance (as the pictures in the post).

Measures
Measuring the voltage across the electrolytic (timing) capacitor gives a value oscillating between ~3.1V and ~6V on each sub-circuit, which is exactly what is expected. It is true when only one sub-circuit is connected to the power bus.
Measuring the voltage of the same capacitor in the left subcircuit when BOTH timers are connected to the power bus gives a stable voltage ~3.27V (barely oscillating between 3.265 and 3.275). I cannot explain that either (yet I do suspect this is all the same problem).
Close-ups
Here is a closeup of the left subcircuit:

And the right subcircuit:


texts: Reverse polarity protection using back to back NMOS

texts:
Designing a circuit to measure short circuit current of a power supply every second. Measurement will be on for about 50ms every second. Heat design has been made for this about of time not constant current flow. Current can be up to 15A and the voltage up to 60V when in voltage source.
Want to provide reverse current protection in case the user connects polarity wrong so the components don't overheat. If this occurs I have tested the board and it goes over 180º. In normal mode no component goes over 45º.
Have designed following circuit but it does not work. Works fine in forward mode. In reverse polarity mode once I switch ON both MOSFETs and its fine but I cannot switch them back off even if the gate is set to GND and heat rises drastically.

Any thoughts what could be wrong?

EDIT: Built new circuit but its failing when V1 is higher than 50V


texts: What's the precision of a quartz crystal?

texts:
Crystal datasheets usually list the following parameters:

  The Frequency Tolerance of a crystal is defined as the allowable
  deviation from the specified Frequency when measured at 25°C or room
  temperature.
  The Frequency Stability is defined as the allowable deviation over the
  rated temperature range.

In the context of precision vs accuracy, how should I interpret the Frequency Tolerance?

If I take two consecutive measurements of the same crystal assuming constant temperature. Can I expect the frequency error to be the same on both measurements (or at least lower than the Frequency Tolerance)? Or should both measured errors be assumed independent?

I'm analyzing the accuracy bounds of a GPSDO built with a MCU's PWM peripheral. The Idea is to avoid the need of a VCO if the required time-base quality is achieved. Slow frequency drift changes would be manageable through an FLL loop, so the distinction is important.


texts: Replace broken 79M12 and 7805 voltage regulators?

texts:
I have an old computer, an ABC80 from the late seventies or early eighties, in which I have reason to believe one or more of the voltage regulators are broken.

Now I wonder, what may be suitable replacement parts?  I know that similarly named parts are still produced, but I am not sure about the details.

What about this for a 7805 replacement?


texts: How to disable a microcontroller port once enabled?

texts:
I'm using MP430 series microcontroller. The functionality of the code is to do a specific task and then don't do anything (sense the tilt and glow an LED in a fixed amount of time). But due to some bug in the code, I'm noticing that a port pin gets '1' after some time.
So now I want to disable all the ports once the task is completed. How can I disable these ports which initially I defined as Input and Output ports.

And my 2nd question is: if I'm disabling these ports then are there any chances that the output port (now disabled) will stay floating and generate some noise or something and trigger my output LED? This question is for all the microcontrollers (MSP430, PIC, AVR, etc.)


texts: Negotiation fails on KSZ8895 Micrel Switch IC

texts:
Why does the negotiation with the network fail? The only common issue I found is the voltage gets a "load" which drops the pulse peak for a short time.
Here negotiation fails:

Here negotiation is ok:


texts:
I'm trying to implement at fuel cell in LTspice, using the lookup table function and a Arbitrary Behavioural Voltage Source (ABVS).

I specify the I-V relationsship from the datasheet as:
V = table(I,i1,v1,i2,v2,....)

This is quite cumbersome for multiple reasons.
1) There are a lot of points for the nonlinear I-V curve
2) Values are added in the "table" as i, v, i, v,... (alternating), which gets hard to keep track of when reading and/or adding/correcting.
3) It's a lot of work whenever I need to add another I-V curve.

It there a better way to add I-V lookup table functionality to LTspice? Can I load a .csv file with the data or something similar, istead of entering it manually into the GUI.

N.B. I've tried nonlinear regression to curvefit and add as a function, but that does not make things easier...

EDIT:
Thanks for the feedback, both of you!
A fuel cell is simply a source of power. The I-V characteristic determines the operating point, w.r.t. the remaining circuitry and power draw - i.e. voltage is determined based on the current draw, and current is dermined by the voltage.

So the PWL file is not an option, as it assumes a predetermined transient (time) behaviour, which I don't have, prior to the simulation, this is the outcome - altough the PWL file is close to what I am looking for, but without the time dependency.

A fuel cell has a linear region for moderate current, and is nonlinear for low and high currents.
So for the middle region, you can model it as a voltage source with a series resistance. But I'd like to add another layer to the analysis.


texts:
I'm using rf-tools.com LC filter designer to design a passive 4 pole filter for an active subwoofer.
The response is not what I expect, it's not showing any attenuation which seems to be good to be true with the input and output resistors.
Maybe the resistors are not included in the simulation for some reason?
I would like to keep the input impedance of filter as high possible to minimise load on the source, as long as the resistor values are kept equal it doesnt seem to add any attenuation, only inductor value increases which will be the limiting factor.
Inductors are something I dont understand very well and I know they can store energy so would like to confirm what's going and If i'm interpreting the sims incorrectly.


texts: 3 wire load cell and HX711 weight compensation

texts:
in my project I use 3 wire load cell (like this (3wire 50kg) but mine are purchased from ebay) and HX711 for weighing.

My wiring is like this (but i use Arduino mini pro 3V3):

Apparently it should be a full-bridge circuit where the temperature is fully compensated and temperature changes are minimal. However, my last-day charts are like this (is loaded statically with 18kg).

The graphs show that the weight varies with temperature. Therefore, I put all temperatures and changes from the calibration value into a graph and from this came out this graph. Where the X-axis is the temperature and the Y-axis is the change from the known value (18KG).

This chart showed me that the weight is probably not ONLY dependent on temperature as the first charts might seem.

I'm really frustrated about it because I've tried everything, but the result is always the same, even though this wiring should compensate for itself.

Has anyone encountered anything like this?

Thank you for any advice!

Edit 1:


texts:
I am trying to design a brushless DC generator system for portable use of charging batteries and if suitable possible hybrid power system of an aircraft.

The "BLDC" motor/generator will be connected to a 1.5KW, 2.011HP and 10,000RPM Max water cooled engine. The reason for a brusheless motor is due to its ratios of weight to power and many are water cooled to make further use of a pre-existing cooling system already in place.

The brushless motor i have found that seems to be best suited to the specification and water cooled is this Turnigy AquaStar 4084-620KV Water Cooled Brushless Motor on Hobby-King the voltage is desire is 12V DC if i use the engine specifications of 1.5kW = 1500Watts we can say 1500Watts / 12V = 125Amps this is a lot of current to handle.

The motor/generator is rated for a maximum voltage of 37 Volts and 105 Amps that is 37 x 105 = 3885w or 3.9kw which is slightly overrated for my engine, to drive this I intend to use a pulley system to drive the generator at 21,700 rpm which will generate approximately 35v (obviously kv = rpm/volt is not exact but pretty close and less when in use as a generator) I then intend to transform this to a 12v dc at 125 amps or as close as.

Obviously if anyone can improve my calculations above and design you are welcome to input but my question is what is now the best method to transform to my desired output with regulation so that engine speed is proportional to current not voltage if possible.

Idea 1: A dc - dc buck converter could be used but either multiple or a large unit would have to be used to deal with the high current and will be expensive.

Idea 2: use a 3 phase transformer to convert to 12 volts before rectification  however this will not add any regulation.

Obviously the 1.5kw of my engine is mechanical power and my estimated values may get me less as losses add up through rectification, heat, copper losses ect.


texts: How to proportion hydraulic flow using potentiometer and MOSFET

texts:
I am working on solving a problem that we generally deal with in a mechanical fashion. We have a hydraulic system with a dumb controller and a dumb valve stack. We can change the valve stack solenoids to a type in which you can vary the current. From here we would like to able to vary the current, set the flow proportions using a potentiometer and a MOSFET, then lock the box containing the potentiometer and related electronics. The solenoids draw a max of 3 amps, the current shouldn't need to go lower than 1 amp, and the entire system runs on 12 volts. I am wondering if control in this nature is not only possible, but is it wise?

I'm aware that a diode should be installed with the solenoid to protect the MOSFET.


texts: Isolated DC/DC Converter - Purpose of Capactor connecting two GNDs?

texts:
I've been looking at board mount isolated DC/DC converters to use in an application. I found this rather reasonably priced for my needs. Here is what I'm confused about, what is C103 doing here? Isn't it breaking the isolation?

Or, is it because it's DC it won't break the isolation?


texts: Why is low inductance important for stepper motors?

texts:
I’m building a CNC style device and am in the process of choosing the right stepper motors.

I read that it’s important to buy steppers with maximally 5mH of inductance.

Why exactly is that the case?

Is it because higher inductance means having to run them at higher voltage to achieve the rated holding torque?

In some forum I picked up this formula for stepper motor voltage:

Voltage = Sqrt(inductance) * 32

Is this formula correct? Where does “32” come from? So does that mean that a stepper rated with 3.0A and 5.6 mH phase inductance must be driven with 75 volts and chopper drivers set to 3A in order for it to perform optimally (yield the rated holding torque?)

Also,  inductance is sometimes written diffently in the sheets. Sometimes it’s “inductance/phase”, sometimes it’s “phase inductance”, but sometimes there are also two inductance ratings, one for “unipolar” and one for “bipolar."

Which is which and what rating does the above formula apply for?

Additional question:

Is there any way for me to compute the torque at a specific speed?


texts: Ethernet Communication with Microcontroller

texts:
I am trying to make Ethernet communication with MCU. To make this happen, I need MCU(in this case AT89C2051), Ethernet Controller ( ENC28J60), and a RJ45. However the microcontroller that I selected doesnt have SPI, hence I need to bit-bang it to act as substitute for dedicated hardware SPI.
This was intended to be implement within a specific device so that i can create a master/slave connection.
So here is my question:

Does my concept to create a master/slave connection correct?
Is it possible to write bit-bang code in C language/ Assembly language?
If i intend to create a software that interacts with the Master device and
control all the slave device, does it mean that I need to use socket
programming ?


texts: How can you predict the power an electrical generator (alternator) produces?

texts:
We have to design an electrical alternator in a multiphysics software, but we can't seem to figure out how to deduce the power it will produce. We need to charge a capacitor to 1000 joules (at 2000V) with it and want to know how long this will take. However, we the only output from Comsol is the induced voltage.
To go to 2000 Volts we attached the following stages to our generator:
Alternator --- full-bridge rectifier --- 5V-12V step-up --- 12V-2000V step-up --- Capacitor
How can we calculate the power that is produced to deduce the charging time of the capacitor?


texts: How to select a 2.4GHz chip antenna for a space-constrained environment?

texts:
I need to use the DA14580 BLE chip for my project. The problem is for the antenna. The reference design provided for the antenna is only PCB trace that's is too big for my project:

I don't know how to choose a chip antenna instead. The DA14580 need to communicate with my smartphone, as a wearable. So the distance is not really big.

I see that some device use the DA14580 with chip antenna, but I don't find any information about the antennas used for.

I think of using this chip (even if a little big) :

  ANT-2.45-CHP-x

Do you think that will work ?

How to choose a chip antenna for BLE ?


texts: What type of motor should be used to handle a static torque (blocked shaft)?

texts:
For the purpose of DIY robotics, I would like to have an electric motor, which is best for providing torque while not rotating. I imagine my robot will maintain a static balanced torque while maintaining pose, while movements will be implemented as guided disbalancing...

I think I can make the desired motors from one of conventional ones.

First of all, I don't like conventional DC motors, because I think they will overheat if blocked, and also they have a complex relationship between current and torque. Also it is possible the torque can have "jumps" on the relationship plot when the commutator changes coils.

So, I imagine, that the best option is 3-phase (3 dipoles) motors with permanent magnets. I will be able to control the current in each dipole and therefore will be able to orient magnetic field as I wish.

What are the motor types that best fit this description so that I can include them in my design?


texts: Xbox 360 Controller to Nintendo 64 Console

texts:
The goal of this project is to create a working adapter between a wired Xbox 360 controller and a Nintendo 64 game console. The signals from the Xbox 360 controller USB port data pins (Data+ and Data-) will be picked up and modified appropriately by a microcontroller; the modified 32-bit output signal will feed into the console. I am not going to inquire on how to perform the bulk of the tasks, rather a means of surpassing a roadblock that occurred during preliminary testing.

A computer running a Windows 7 OS is typically capable of locating drivers for the controller, which then allows the controller to communicate with the PC. Rather than plugging into a USB port, however, I have provided 5V directly from a power supply across the VCC and GND terminals on the physical male USB stick appended to the controller. This was partially a success in that the light indicating power is received turned on; but only momentarily, for about a third of a second. The light then turned off until I reconnected the DC signal. In other words lifting a lead from either GND or VCC and then reconnecting caused the light to blink again - for about a third of a second each and every time it was tested.

I presume there is a particular sequence of data that needs to be sent in through the two data pins, that the Windows driver would know how to communicate with. In this way a computer with the drivers installed will power the controller on and then immediately initiate some sort of coded signal through the data pins to keep the controller powered on indefinitely. It is at this point that I believe the controller can send data through the USB data pins, to the computer, though which the signal will vary based on the combination of buttons being pressed. Because I cannot get the controller to stay on I cannot even begin to test this, so it is all theoretical to me.

Could anyone shed light on what I may be doing wrong in powering the controller? Am I required to send data in the same way a Microsoft driver would to get the light to stay on? If so, how can I know the required signals to be sent? Am I potentially missing something else? I could not find a datasheet for the Xbox 360 controller that contains any information on how to intercept its signals and provide power (no shock there), so I have addressed my question here in hopes that someone has knowledge in this area.

Not looking particularly for a quick reply, just one that may concretely address these low-level questions.


texts: How does this linear actuators know absolute position of their carriages?

texts:
As title, I can't find out how main system of this linear actuators knows each carriage absolute position. This system is iTRACK from Rockwell, but there are some other brands that do this.

Here an image of the system:

As it's possible to read from their system description, each carriage have just a magnet on internal side of the linear.

I never read about "reverse" linear encoders where stator is actually the sensor and mover is passive.

I've tough about Capacitive and Inductive PCBs on each module, but as I know this system are not very fast (and in some case precise). On system description there's +/-0.5mm and some +/-0.15mm at speed of 2meters/s to 5meters/s.

Maybe there's also possibility to place a lot of hall sensors and interpolate their results, but the complexity and price of components will be incredibly high.

Someone can explain me how this is possible and how this system works? (or references)
Is this position technology something that is largely applied and commercial?


texts: Circuit to run a 3 phase magnet generator as motor?

texts:
I am trying to convert a wind generator to a brushless motor.

As you can see at the image, it has 16 magnets and 12 coils. The coils are connected as 3 phase, star connection, so I have 3 output wires to play with. The fourth which is the common connection is buried in epoxy and its unreachable.

I already tryed a BLDC Three-Phase Sensorless Brushless Motor Speed Controller, but it doesn't run smoothly, it makes a vibrating noise, like its not synchronized and it feels like it brakes its self. So the speed is ridiculously slow (like 60 rpm at 12v).

Is there any circuit to run it properly as a brushless motor? Thanks!


texts: Fundamental question about circuits and grounding

texts:
I understand that voltage is relative and that the hot wire in house mains is a nominal \$\pm\$ 120v in reference to the neutral wire. I also believe the ground wire is connected to the neutral at the breaker box and then connected to a metal stake driven into the ground. So here's my question:

If the hot wire was to connect to the frame of an appliance like a toaster let's say, and the toaster frame was not grounded, what happens when I touch the metal frame of the toaster, I don't understand why that is a dangerous situation. I mean, I don't see the circuit path. If the hot is say at 120v above neutral (at that moment in time) and neutral is connected to ground at the power box so the hot is therefore 120v above earth ground, how am I involved even if I am well connected to the earth (standing in water for example)? My mind says this, the current flows from hot to the short at the frame of the toaster to me to earth but I am nowhere near the metal stake in my yard and so how is the circuit complete? So I really have two questions:

Q1: Is there a completed circuit here that I just don't understand?

Q2: Does the frame of the toaster have some build-up of charge that is in excess of a neutral body and therefore imparts a discharge like a source to a sink (even if that neutral body was floating off of the surface of the earth)?

Actually, I have one more question. How does the ground wire protect someone from this situation inasmuch as I don't see the circuit path in it anymore than I see it when I am the "ground wire".

Thanks


texts: When doing calculations regarding diodes (in half wave rectifiers), is the peak value of the sinusoidal source used, or is the rms value used?

texts:
For example, in Vdc = 0.318Vs, is Vs the peak voltage, or the rms voltage. Likewise, how is the PIV determined, e.g. in part (e) of this question:

  4.65 Consider the half-wave rectifier circuit of Fig. 4.21(a)
  with the diode reversed. Let vS be a sinusoid with 12-V peak
  amplitude, and let R = 1.5 kΩ. Use the constant-voltagedrop
  diode model with VD = 0.7 V.

    (a) Sketch the transfer characteristic.
    (b) Sketch the waveform of vO.
    (c) Find the average value of vO.
    (d) Find the peak current in the diode.
    (e) Find the PIV of the diode.


texts:
Do seasoned designers tend to do a fair amount of calculations or are large parts of circuits designed intuitively? I'm asking because it seems like design engineers tend to have a sense of what value cap you want to have here, resistor there, for common parts of circuits. If that's the case is it because they're just recycling designs?
To the novice this is mind blowing. Though, books like the Art of Electronics seem to encourage the approach of making approximate calculations on the fly.


texts: USB female type A that "floats" on a PCB

texts:
I'm looking for a USB-connector that "floats" in line with the PCB. See my very crude drawing to see what I mean:

I know these connectors exists for USB micro (like this one) but I am unable to find it for type A-female.

Do they exist, and what search terms should I use to find this type of connector?


texts: Switchgear vs. power distribution center (PDC) vs. motor control center (MCC) - what's the difference?

texts:
Here's what I've observed so far:

All three contain circuit breakers. All three supply power to motors, although switchgear and PDC-fed motors are obviously higher-voltage, larger motors.

Switchgears are higher voltage than PDCs, and supply power to the transformers which feed the PDCs.

PDCs are higher voltage than MCCs, and supply power to MCCs. From what I've seen, PDC housings contain the transformer that feeds the PDC. (Is this always the case?)

Are there any other important differences/details that I've missed?


texts: Target  of concurrent assignment or output port connection should be a net type

texts:
I am trying to implement Fast Fourier Transform in Verilog for 32-point sample and have written the following butterfly module:

module bffly(
input wire signed [15:0] xa_r,
input wire signed [15:0] xa_i,
input wire signed [15:0] xb_r,
input wire signed [15:0] xb_i,
input wire signed [15:0] w_r,
input wire signed [15:0] w_i,
output reg signed [15:0] ya_r,
output reg signed [15:0] ya_i,
output reg signed [15:0] yb_r,
output reg signed [15:0] yb_i,
output reg ready,
input wire clk,
input wire enable
);

// ya = xa + xb*w
// yb = xa - xb*w

// ya_r = xa_r + xb_r*w_r - xb_i*w_i
// ya_i = xa_i + xb_r*w_i + xb_i*w_r

// yb_r = xa_r - xb_r*w_r + xb_i*w_i
// yb_i = xa_i - xb_r*w_i - xb_i*w_r

wire signed [31:0] temp_r_32;
wire signed [31:0] temp_i_32;

wire signed [15:0] temp_r_16;
wire signed [15:0] temp_i_16;

assign temp_r_32 = xb_r*w_r - xb_i*w_i;
assign temp_i_32 = xb_r*w_i + xb_i*w_r;

assign temp_r_16 = {temp_r_32[31], temp_r_32[28:14]};
assign temp_i_16 = {temp_i_32[31], temp_i_32[28:14]};

always@(posedge clk)
begin
 if (enable)
 begin
    ya_r <= xa_r + temp_r_16;
    ya_i <= xa_i + temp_i_16;
    yb_r <= xa_r - temp_r_16;
    yb_i <= xa_i - temp_i_16;
    ready <= 1;
 end

 else ready<= 0;
end

endmodule

The butterfly module is working properly. I have checked it with th test fixture.

In the fft module, I have made several calls to the butterfly module. Here is a code snippet of the fft module:

module fft(
 input enable1,
 input clk,
     input [15:0] a0,...,input [15:0] a31,
     output [15:0] br0,..., output [15:0] br31,
     output [15:0] bi0,..., output [15:0] bi31,
     output wand ready,
     output wan enable3
);
wire [15:0] wr0, etc. stores the twiddle factors.
reg [15:0] tr0;...,reg [15:0] tr31;
reg [15:0] ti0,...,reg [15:0] ti31;

bffly z12(.ready(enable2),.clk(clk),.enable(enable1),.xa_r(a3),.xa_i(16'b0),.xb_r(a19),.xb_i(16'b0), .w_r(wr0), .w_i(wi0),.ya_r(tr24), .ya_i(ti24),.yb_r(tr25), .yb_i(ti25));
bffly z13 (.ready(enable2),.clk(clk),.enable(enable1),.xa_r(a11),.xa_i(16'b0),.xb_r(a27),.xb_i(16'b0), .w_r(wr0), .w_i(wi0),.ya_r(tr26),.ya_i(ti26), .yb_r(tr27), .yb_i(ti27));

For all such calls to the butterfly there is an error as follows:

Target tr24 of concurrent assignment or output port connection should be a net type.

Target tr26 of concurrent assignment or output port connection should be a net type., respectively

When the target is assigned as a wire and not as a reg, then it works fine.

What do I do in this case ??


texts: Reverse voltage on MIC5225 in particular and other LDO in general

texts:
This question has been asked many times before, for example about LD1117, MCP1703, LM78M05CT, MIC2920A, ADP7142 etc. Why am I asking it again?

a) From reading all those topics it seems that the answer depends mostly on the design of the particular LDO, specifically whether the regulating element is FET or BJT. Not all datasheets have internal schematics available.

b) Most of the modules on the market have 5 to 3.3V LDOs nowadays. Not all of them are adequately designed. Case in point: in our product we are using Adafruit OLED display, which has on board 150 mA MIC5225 LDO for a panel that consumes up to 200 mA with all pixels white.

c) Pure 3.3V systems are now ubiquitous and they often have power management (e.g. via EN input on LDO or DC-DC) implemented. Adding separate 5V switch for the modules that use 3.3V internally anyway seems to be bad idea.

So, here are my questions:

Is it safe to permanently apply 3.3V to the output of MIC5225, which has IN and EN pins connected together but floating otherwise? The datasheet has examples for IN floating/EN grounded and for both grounded. In either case the "reverse leakage protection" seems to be limiting current to about 5 µA.
Would grounding both IN and EN (as in datasheet) be better than leaving them unconnected? Just as in previous question, when I say "safe" or "better" I mean no magic smoke, additional battery drain or stuff like that.
Is there universally suitable way to bypass unnecessary LDO on the pre-made modules (assuming there is an access to 3.3V output but no easy way to modify schematics)? This is obviously quite common problem (see the links in the beginning), so I think it deserves a definitive answer.

For the latter the opinions are rather conflicting. Here are some of them:

Let it be. The worst that can happen is capacitor on the input will be charged to output voltage;
Add bypass diode / ideal diode / MOSFET if LDO has BJT output, otherwise see (1);
Short-circuit input to output. I must admit, this one seems most compelling to me, with a benefit of re-using input capacitance for decoupling. However (at least in my case) this could be bad, since EN pin becomes powered too.


texts: How to remove the below error when doing FPGA implementation of program that use RAM using Xilinx block generator?

texts:
I wrote a code that use RAM (created by Xilinx block generator). It's size is 10X10 (total 100 data) .

I used INSTANTIATION as below:

RAM1 RAM_NAME (
  .clka(clka), // input clka
  .wea(wea), // input [0 : 0] wea
  .addra(addra), // input [6 : 0] addra
  .dina(dina), // input [7 : 0] dina
  .douta(douta) // output [7 : 0] douta
);

I am able to do synthesis but when i am doing implement design. It is giving error:

ERROR:NgdBuild:604 - logical block
'Leena/U0/xst_blk_mem_generator/gnativebmg.native_blk_mem_gen/valid.cstr/raml
oop[0].ram.r/s3a_init.ram/spram.ram' with type 'RAMB16BWE' could not be
resolved. A pin name misspelling can cause this, a missing edif or ngc file,
case mismatch between the block name and the edif or ngc file name, or the
misspelling of a type name. Symbol 'RAMB16BWE' is not supported in target
'spartan3e'.

What are the cause of above error and how can i correct it?


texts: BJT Bitonal Astable Multivibrator, can someone explain me how this circuit works?

texts:
I've been analyzing this circuit and so far I think it divides in two separate oscillators, but I still don't have a clear idea on how this two work together.

I'm leaving a picture of the circuit, any help will be appreciate it


texts: What to check for when buying an electronic component or module?

texts:
This has been raised as a canonical Q and A for future reference

How can I acquire electronic parts/items/modules and ensure that there is minimal risk of them being unsuitable for my project or design?


texts: Why does the voltage of vinegar batteries in series not equal the sum of the individual voltages?

texts:
I'm working on an in-class demo / hands-on for my sons primary school class, and I've made some small batteries with New Zealand 10 cent (copper coated) coins, and zinc washers, and vinegar soaked cardboard.  Each individual cell is measuring about 0.96 volts, but when I put 4 of them together, I only get out about 2.6 volts.  I'm wondering if there is something I'm unaware of about the nature of these batteries that makes them not add up.

Also, even at 2.6 volts, the same voltage as I'm getting out of a pair of eneloop AA's, the LED is not very bright at all -- compared to hooking it up to the eneloop AA's, where the LED is quite bright.  Is this because of the low amperage of the vinegar battery?  Would putting more in series make it better (or do I need to make a second one and hook them up in parallel?).

I'm a bit of a noob with electronics, mostly learning it now as my son is very interested, so having some fun learning it with him.

Thanks for any tips.

I've attached a picture below showing the intended final product (I squeeze the top and bottom of the led wires to complete the circuit, as a simple switch).  On the right is what I'm using for my cells (minus the vinegar, and without the cardboard being cut to fit the coin.)


texts:
I am using PIC32MZ2048EFH064, MPLABx3.40, XC32 V1.42, Harmony V2.01b. And my PC app is using MS Visual C++ 2010 Express.
  Instead of using microchip's Pic32 downloader I want to build my own downloader and, I want to download my custom encrypted firmware using PC host application. Now problem is, I am able to connect and download the bootloader firmware using my custom app, but CRC verification (i.e. program verification) is failed. Because the CRC calculated (and sent) by firmware doesn't matches to the CRC calculated by my custom app for the hex file. Now my observations are :

Both are using same address range and same program length over which CRC is calcuated.
Address range is : 0x9FC00000 - 0x9FC0FFF4.
Both are using same CRC table, CRC routine to calculate CRC.

I want to ask that, whether calculating CRC should include config register area also?


texts: Are there any ATxmega chips with bi-directional SPi ports?

texts:
I searched the datasheets shown for the ATxmega chips in the Microcontroller Selector, shown on the left side of http://www.atmel.com/products/microcontrollers/default.aspx, for any ATxmega chips with bi-directional SPi ports, but I was unable to find any.

I know ATmega chips have bi-directional SPi ports, but I want to take advantage of the features in the ATxmega chips for my solar car project.


texts: What happens if I put two batteries in series with different amperage?

texts: I have two LithIon battiers.  Both are 3.7V but one is 1000mAh and the other is 850mAh.  What happens if I put both in serial to power a device?  I should get 7.4V, right?  But what is the amperage?  Am I at risk at damaging either battery or the device I am connecting to?


texts: Mechanical Switch Causes Transients from AC-DC Power Supply

texts:
I'm having trouble getting rid of output transients from this Mean Well PSU right after the AC input is switched.

https://www.meanwell.com/Upload/PDF/RPS-500/RPS-500-SPEC.PDF

The PSU is a RPS-500 27VDC with fan.  The 120 VAC is coming from an industrial power strip and the switch is a mechanical DPST bat handle style.

The switch transients are showing up on all the outputs: 5Vsb, Power Good (PG), and 27VDC output.

I captured some scope shots from the 5Vsb pin w/out load.

Occasionally the transients aren't noticeable.

Would a multi-stage AC/DC EMI filter and perhaps a NTC resistor (to limit inrush) get rid of this?

My guess is that these are due to inrush current or the switch making contact at different phases of the AC input.

Edit 1:

Bench setup schematic

RPS-500 block diagram

Edit 2:

Scope captures from an MSO4054B using TPP0500B probe with spring tip ground.  Measured at 2mm double-row connector, no load (for now).

These are showing the 5Vsb ramp and the voltage transients when the switch is toggled.


texts: how to show a picture on monitor through VGA from basys3

texts:
I must find a picture and upload it into my basys3 board then I must show it on monitor through VGA cable.
I dont know how to do that.
What are the steps I must take?


texts: What fuses can I use for branch circuit protection above 600 amps?

texts: My present understanding is that not just any fuse meets the paperwork qualifications of "branch circuit protection". In particular, I want to protect a variable frequency drive, so J-type fuses are my go-to. But no manufacturer I've seen makes J-type fuses above 600 amps. I need 700-amp fuses. What should I do in this situation? Use some other fuse not rated for BCP? Is there another class of fuses I should look at that is rated for BCP?


texts: Voltage / current from Van De Graff generator vs. voltage / current from AC wall sockets in homes

texts:
The Van De Graff generator can generate voltages in the kV and MV range.
I have read that if I touch the Van De Graff generator producing, say 50kV, with one hand (myself being insulated from ground by plastic stool) and the other hand to the grounding rod, I don't get shocked because the current passing through me is small.
But if I grab live and neutral wires in each hand from a home AC electric service, which carry 120V or 220V, I might get fried because even though it has low voltage, it delivers high current.
My questions:

What factor determines the current flow through the human body in the case of the Van De Graff generator and of the AC wall socket?

Why is the current less in the generator case and why is it high in the AC wall socket case? Doesn't high voltage mean high current? And low voltage mean low current? What am I missing here? Is the missing thing the internal resistance?


texts: How will unmatched lithium-ion cells in parallel react?

texts:
We are stocking a portable power pack for USB charging. We tested them when they first arrived and found no issues but after 3 months we tested some of the remaining stock and found about 50% of them were dead. I took a few apart and found the cells were 2.5v (+/-.1v) There are two lithium-ion cells connected in parallel.

I charged a few of them back up a little and tested them every few days. They self discharge back down to 2.5v and then stop.

I believe this is because of poorly balanced cells and at 2.5v the stronger battery no longer has enough energy to overcome the internal resistance to charge the weaker battery so rapid self-discharge stops.

Our manufacturer is claiming it was a fault in the circuitry and they changed a capacitor to solve the problem. I do not believe this because it seems like any circuitry problem would keep discharging the cells.

Am I correct in how two unmatched lithium-ion cells will behave in parallel? Will they self discharge to a point and then stop?

Also what are the potential dangers of this? Is there increased risk of fire from charging batteries that are not well matched?

Is this an obvious case of mismatched cells or could it possibly be a circuitry issue?

Thanks!


texts: Finite State Machine Handling Timers Gracefully?

texts:
I've been working with mostly 8 bit MCUs, where most RTOSes are too much overhead.

Most of the applications I've worked one have just been a periodic interrupt with if/else chains for all the processing logic, and then the MCU goes back to sleep.

This has worked well for a lot of things and has a really minimal overhead.  But for one system, I'm getting to the point where there are so many control flags that I'm ready to call my own system "spaghetti".  It would be horrifying for someone new to pick up this system and implement some new functionality.

(I have a dual color LED, that must have like 8 different states and timing dependent blinking patterns depending on what state the rest of the system is at.  It's a horrifying exercise, for what should be so simple...)

I was looking at maybe doing a finite state machine, and trying to weed out so many control flags.

One conceptual problem I am seeing is the use of timers in a state machine.  Currently, I have one hardware timer and then a bunch of variable defined timers counters that increment / deincrement, a control flag variable goes to 0/1, and so we go through the if/else chain.

In my planning stage for a more strict state machine, would you just use more hardware timers and trigger the external interrupts as events to go back to the state machine?

My gut reaction (whether right or not) is using as many external interrupts as possible for the state machine is you 1)introduce all kinds of potential interrupt priority issues that bring their own set of problems, where currently the timing is very deterministic but the control logic is simply confusing and 2) you are using more current running a bunch of timers vs. just handling the timer logic as variables.

I see how you could still increment/deincrement variable timers across your state machine, but isn't that anti-ethical to the state machine pattern?

I'm pretty comfortable with the function pointers vs. switch statement debate on how you code the state machine, or if you want to use a transition table, etc.

I'm specifically wondering how folks have handled the timer management aspect of their state machines in a graceful way.


texts: How short circuit is made when connecting negative cable first when jumping start the vehicle

texts: When Jumping start, I understand that I need to connect the positive terminal first due to the safety reason. And also if I connect negative terminal first and touching the body of the vehicle with the wrench by accidentally, I might damage the battery due to making a short circuit. And could you explain how the short circuit is created?


texts:
Got a very strange error while trying to write to ATmega128. Below are the results for 3 cases (using different software but the same USBASP programmer and the same HEX file)

Case 1 : AVRDUDESS 2.3: I am able to write a program 236 bytes in size. However anything bigger than 255 bytes gives the following error

  avrdude.exe: verifying ... avrdude.exe: verification error, first
  mismatch at byte 0x0100
               0xff != 0xf1 avrdude.exe: verification error; content mismatch

  avrdude.exe done.  Thank you.

Case 2 : Extreme Burner AVR v 1.4 : Does not support Atmega128
Case 3 : AVR8 Burn-O-Mat v2 : able to program the same hex file without any issue

Can't figure out why one software would give an error while the other one works just fine when they both are using avrdude in the background


texts: Is it normal that with the same op amp but with a different voltage input, the amplifier gain is different?

texts:
So with my one of the part of my circuit below, I only wanted to see the effect on the op amp if I changed the input voltage (knowing that the inverting input is 0). My first thought was that even if I changed the input voltage, the output would changed accordingly so that the amplifier gain stays the same (since it's the same op amp).

So I first set my input voltage as 7V and found the output voltage was 8.5V.
Then I changed my input to 14V (double of the initial input) and found out that the output voltage was still 8.5 Volts. Now I am totally lost since my initial hypothesis is wrong.

Can someone guide me on where I was wrong?


texts:
I need to understand the main function of this circuit, and to interpret it.
i find something related to this circuit , in a french website (source)

(Source)


texts: Please explain why this simple circuit is latching 'on', but only when a fan is attached

texts:
My son and I made a circuit using an electronics kit.  It's supposed to work so that when the IR receiver receives a signal from a remote control, it turns on the motor.

It does that, but I noticed that if you hold the remote control button long enough for the motor to reach top speed, then the circuit latches and the motor continues  to spin even after you release the remote's button.

It only does this if the green fan is attached to the motor, otherwise the motor stops when you release the remote's button.

My first thought was something environmental, like heat from the motor (though I doubt that), light from outside - but it happens even if the IR is covered.

So is it something about the load on the motor affecting the transistor?

I'm a novice at electronics.

simulate this circuit – Schematic created using CircuitLab


texts: This PCB is to turn on and off an LED. The captive touchpad is to turn on and off the LED, and one side of this touchpad is connected to GND and the other side to Pin 2 of the IC. Pin 1 is connected to the LED, the other side of the LED is connected to VCC. Pin 3 of the IC is connected to VCC, Pin 4 is NC and Pin 5 is connected to GND. The other side of the PCB has no traces on it. I like to know how this circuit works so i can make my own version of it. Can someone explain how this PCB works and what component that is ? Thanks!


texts: Are Wire Current Ratings Different in AC than in DC?

texts: Lets say I have a 1.5 mm^2 wire (between 14 and 15 AWG) and I have to use it in two different circuits, will the current carrying capacity of the wire change? One circuit is 240V AC and the other is for a 12V DC application.


texts: Is driver necessary to drive P-FET Buck Converter using Microcontroller?

texts:
I'm building a buck converter to charge an ultracapacitor from Hydrogen Fuel Cell. I'm having some issue with the gate switching for the converter.

Currently I'm testing the buck converter with a power supply, function generator and one power resistor as load.The buck converter I built is as below,

There are two 2ohm resistors at output side to prevent short circuit current to the supercapacitor. The converter is behaving like regular buck converter below 14V. But once it passes the 14V zone, the current will increase drastically and a lot of heat can be felt from the P-FET and Charging Resistors.

Is there any mistakes in my designs? I have listed the elements I installed on the converter below. The function generator is generating 40kHz, 5Vpp,2.5V offset and 50ohm load settings

Coupling capacitor: 100V,680uF

Inductor: 100uH, Saturation Current, Saturation Current 20.6A

P-FET: ON-Semicondcutor FQPF27P06

Diode: 1.3V Vf


texts: Do capacitors need to be blown or bulged to be bad?

texts: The title says it all, I'm wondering if an electrolytic (or any other type) capacitor needs to be bulged to be bad?


texts: Audio input: stereo to mono and filtering DC

texts:
I have to get an audio input from a PCB 3.5mm jack and summing right and left channel into one (mono). Then, I have to filter any DC noise from the input.

Resistors are 1kOhm each. This, for now, work perfectly.
Then i found this circuit in another question on this stack exchange:

There are two capacitors of 10uF before the junction to filter the DC current.

Now the questions:

The circuit scheme is valid?
Capacitors are not polarized?
If I want to use a single capacitor after the junction, I have to
use a 5uF?

Thanks in advance for the answers.


texts: Connecting a half duplex and a full duplex (2 slaves) to a MCU's UART

texts:
I need to connect a half duplex part (1 wire) and another full duplex part (2 wire) to the MCU's UART (only one available), the half duplex part (1 wire) will have a baud rate of 9600bps. The MCU is an ATMega128. The slaves will be controlled by the Master (MCU) and one of them will be selected at a time. What can be done to connect the two slaves to the MCU's same UART? Can anyone suggest any wiring diagram? (Maybe using a buffer, do not have any other GPIO's available for a MUX.) I do not have any GPIO left to implement any SW UART. I cannot even have a MUX.

EDIT: Another UART is connected to a bluetooth module which is not accessed at the same time. The UART I want to Multiplex has the two mentioned slaves connected to it, so the TX on the slaves need to be multiplexed (keeping in mind that one of the slave is one wired, half duplex)


texts: Why are the advantages of JFET over MOSFET, or why are JFET still used?

texts:
I saw JFET in an electret mic circuit, and it is quite recent, so I'm wondering why.

Since we are looking for the highest gate impedance, MOSFET would seem to be a better choice.

I've also read that JFET have got a flatter response because of a higher drain resistance. I don't even understand what the drain resistance is. Is it the source drain resistance? And what does it have to do with flattness?

And more generally, what are the advantages of JFET over MOSFET?


texts:
I'm Trying to understand how the current flows and how network cards receive the electrons (packets) in a Ring network (all the servers are connected to the same cable).

My question is in the case of a broadcast one server will produce current and put it on the wire and then the electrons will flow and get captured by the first server down the line, but how do the electrons reach the second server ?

Can some provide some references to electrons flow in cables (some basic stuff) ?

Thanks


texts: Was Ethernet ever bidirectional over a single coaxial cable or single twisted-pair line?

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Comments below this answer to the question Why was SpaceWire designed with nine wires? involve the history of Ethernet.

Did the earliest forms of Ethernet allow complete bidirectional communication over a single coaxial cable or a single twisted pair (possibly/probably with a shield)?

I've looked at the Wikipedia article on Ethernet and while it appears very well written and informative, I'm a networking noob and I'm having a hard time being sure I'm understanding anything there clearly. I searched for the terms bidirectional and bi-directional without result. In this particular case, I'm turning to Electronics Stackexchange for a concise yes or no, plus perhaps a bit of history.


texts:
Is it possible to put Lipo/Li-ion batteries of different capacities in parallel?

I am aware that putting anything different in series/parallel isn't the best option, but design limitations do not allow me to do otherwise.

What other limitations should I take in account?


texts: Why do we need differential amplifier after Transimpedance amplifier?

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I am implementing the circuit published in AN3025 Transimpedance Amplifier Design as shown below.

When I am simulating this circuit, a few questions come to mind:

Q1. Why do we need a differential amplifier in stage 2?
I think  this stage is to remove the offset voltage of the first stage. Am I right? But when I am simulating the above circuit using a single power supply, I am getting offset of 29mV. So what is the need of the difference amplifier?

Q2. When I  used a dual power supply of 5V in the second stage, the offset voltage was completely removed.  However, this power supply of 5V is not recommended in the datasheet. But why is this happening?

Q3. When I have used a dual power supply of 2.5V then I got an offset of -2.47V. Why is this happening?

Q4. How do we completely remove the offset voltage?


texts: Splicing 24 awg wires - wire and tool selection

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I'm working on a raspberry pi project - a sump pit monitor that sends an emergency email if a float switch above the point where the water triggers the pump is switched (purely for monitoring, not driving the pump or anything, mainly peace of mind). I have a couple of float switches I'm using. The float switch wires are 24 awg and about 15 inches. I need them to be a few feet so I'm planning to buy some 24 awg wire and splice them to the switch wires. The wires are AWM 1007 - will any 24 awg wire do? This might be a dumb question but the bare wire is a silverish color. Is it safe to assume it's copper or could it actually be something else? Does it matter?

Anyways, for the splicing I bought a small pack of the yellow IDEAL UY IDC connectors for 5 bucks (the yellow ones here: https://www.homedepot.com/p/Ideal-IDC-Connector-Multi-Pack-UB-UR-UY-Standard-Package-4-Pack-of-25-85-960/302918233)

I didn't realize at the time how heavily it's recommended to use the dedicated crimping tool for these. The tool, at least that I saw at the store, was about 30 bucks. I would buy it but it seems very dedicated, and I may never need to use it again. I tested some 24awg wire I had laying around in the connector using just a pair of regular pliers, and got what appears to be a clean connection (using a multimeter continuity test).

If the splice failed it'd trigger the emergency email (the switch is normally closed, rising water opens it) which is the "safe" way to fail, and this itself isn't mission critical, and it only needs to carry a digital 3.3v signal - are regular pliers (and testing after making the splice) good enough for this application? Does anyone have experience with the splice failing later or intermittently?

Is there a solution for such small wire that doesn't need crimping? It appears nearly all wire nuts and other twist connectors that I can find only go down to 22.


texts: What is the purpose of the capacitor in this current transformer to arduino interfacing circuit?

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The following schematic, taken from https://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface , describes how to measure current with a current transformer and an arduino:

In the description of the schematic, in the section titled "adding a dc bias", the text states that capacitor C1 "provides a path for the alternating current to bypass the resistor."

Is the text referring to the Burden resistor?

Why is alternating current bypassing the resistor beneficial to this circuit?

The text also states that a value of 10uf is suitable for this capacitor.

Are there any other specifications of the capacitor that are important in the design of this ciruit (such as polarity)?