texts: Multi-tap transformer current handling capability

texts:
I have a transformer with a single secondary winding but with multiple taps, as shown in the image.
It is rated at 4A @ 24V (96VA).

Does this mean that at lower voltages (16V and 8V) it will be able to handle more current than 4A, considering that at any given moment only one of the taps will be used (24, 16 or 8 - but never two or more taps connected in the same time through a load to common)?

Ex: If at 24V it can handle 4A, at 16V will it be able to handle 6A?

I intend to use the transformer for a DC power supply.

Note: Please ignore the inductance values from the schematic


texts: What's the difference between a microcontroller and a microprocessor?


texts: Low Current Battery Monitor Detail Question

texts:
I'm trying to design a circuit that will be running from a battery. I'm currently working on the part that detects the voltage and came across this question (and answers) here:

It made pretty good sense and I figured I'd do a combination of the first and last answers. However, I had a question regarding the first circuit that was presented. Here's an image of the provided answer

 Basically a P Channel FET is enabled by the MCU through the BC547.

I wondered if I could re-draw the schematic using a N Channel FET in instead of the BC547. (so that I would have a lower current draw) I then wondered if I could just use the 2 of the N Channel FETs instead to hopefully reduce my number of different components.

Both of the simplified schematics are labeled below. I was wondering if anyone with more knowledge could chime in and either say to use one or the other. Or if there was something I was overlooking and I should stick to the original P Channel and BC547 design?

Also, I'm assuming in this schematic the the MCU can hold the pins low (if not I'll add a pull down resistor to the MCU output pin)

Thanks in advance!


texts: I am building something where I have a USB type B connector routed to a type A connector. Do I have to swap the D- and D+ lines or are they connected D- to D- and D+ to D+? In the attached picture, pin 3 of K1 is D+ and pin 2 is D-. Is this schematic correct for connecting Type B to Type A?


texts: LED bulb flicker @ rate of 50 Hz or more

texts:
I am currently testing a 5W LED bulb (direct operating on 230V AC) switching using a Triac BTA12-600B. I fed the signal from a microcontroller to an opto-triac coupler MOC3041. The LED bulb turns ON and OFF without any issues.
Please note: I am using the LED only for ON/OFF purpose (no dimming).

Below is the working circuit.

Now I add a snubber circuit in between just to protect my Triac in case of overvoltage. Below is the modified circuit

Now comes one big issue:

The LED bulb flickers repeatedly, think at the rate of 50Hz or more. I am unaware of the internal circuitry the LED bulb has as it is enclosed in a retrofit case.

I feel, addition of snubber circuitry is causing the flicker because the LED bulb never flicker when I used the circuit without snubber.

Any reason why the LED flickers and its possible solution ?

Thanks in advance


texts: NEPLAN Load Flow Analysis with 1-day measurement

texts:
currently I am working on a project to identify energy loses in an electrical network. I am using NEPLAN 10, and already build a small system and implemented measurements. As soon as start the calculations, I get a few values, but the graphical interface doesn't fit at all. So I am not sure whether everything is working properly or not.
Could someone help with working with NEPLAN, and have a look together?


texts: Defining a circular cutout in a pad in Altium

texts:
I'm creating the footprint for a Wurth inductor, 744043100.  The recommended land pattern is below.

They use a radius 1.8 mm circle in the middle of the component to define a void in the pad.  I'm trying to create the same shape in Altium, but am running into some trouble with it.    In the screenshot below, I've tried two methods.

Pad 2 uses a region with six vertices and an arc to define the curved region, which works but seems prone to some round-off errors.  It's not a big deal, but I can measure my radius to be ~1.76 mm at y = 0 mm.  It also requires some math to find the vertices and arc angle, and no one likes that.

Pad 1 shows what I'd like to be able to do.  My preference here would be to define a rectangular fill, define a circle of radius 1.8 mm, and use the circle as a cutout to modify the fill.  Is it possible to do this from within the PCB library editor?  Is there another way to define this shape that I've missed?

I'm using Altium 18.1.7.


texts: What is the difference between Vrms and Vm?

texts:
I am relatively new here and I am confused as to the difference between Vrms and Vm. I would be obliged if someone can explain. (This in relation to 3-phase circuits would be even better)

My shot at learning, but not many results on Google that I can understand.

Reference


texts: How to calculate a PNP transistor thermal dissipation?

texts:
I am working with a dual power circuit for using USB and a LDO at the same time with a PIC18F2550. The circuit is the same as the one in the PIC's datasheet. My question is:
How do I calculate the transistor's thermal dissipation? I will be having a 50mA current through it, and I am using the model MMBT5087.

This is the circuit.

This is from a related question.


texts:
I am doing a project to use dsPIC as controller to output PWM signal to control motors. I can use driver IC (I used L293D actually) to simply let motors to rotate, but I cannot control the voltage range to control the motor to rotate with all range of speed.

The output of dsPIC PWM pins is in the range of 0V~5V, but for motors, the input range is different.

Assume the range is -10V~10V, I want to change the 0~5V output to -10V~10V (0V->-10V, 5V->10V). Is there a good way to achieve this?


texts: BLE beacons advertising frequencies collision

texts:
I'm designing a smartphone app that gets advertising transmissions from N BLE beacons that transmit to M meters (approximately), for kind-of indoor-navigation. My goal is to maximize N and M as possible.

AFAIU the bigger N is the more noisier the air (the transmission-medium), so there is some upper bound of N that beyond it the air will be too noisy and the app won't work well because of frequencies collision

Let's say the beacons transmit 1 time per second, and M = 2 meters - what is the upper bound of N approximately? and what if M = 20 meters?


texts: How should I interpret this USB packet in a human readable way?

texts:
Using a wixel (wireless transmitter/receiver with USB capability, "this "wixel" thingy is a general-purpose microcontroller board that includes, among other things, USB, 2 UART's, and a 2.4GHz radio.") in conjunction with this wixel app to read in a transmission from a Dexcom glucose sensor/transmitter, for use in some software I'm writing. Here's the relevant pieces of C code:

void print_packet(Dexcom_packet* pPkt) {
    uartEnable();
    printf("%lu %hhu %d\n", dex_num_decoder(pPkt->raw), pPkt->battery, adcConvertToMillivolts(adcRead(0)));
    uartDisable();
}

uint32 dex_num_decoder(uint16 usShortFloat) {
    uint16 XDATA usReversed = usShortFloat;
    uint8 XDATA usExponent = 0;
    uint32 XDATA usMantissa = 0;
    bit_reverse_bytes((uint8*)&usReversed, 2);
    usExponent = ((usReversed & 0xE000) >> 13);
    usMantissa = (usReversed & 0x1FFF);
    return usMantissa << usExponent;
}

void bit_reverse_bytes(uint8* buf, uint8 nLen) {
    uint8 XDATA i = 0;
    for(; i < nLen; i++) {
        buf[i] = bit_reverse_byte(buf[i]);
    }
}

uint8 bit_reverse_byte(uint8 in) {
uint8 XDATA bRet = 0;
if(in & 0x01)
    bRet |= 0x80;
if(in & 0x02)
    bRet |= 0x40;
if(in & 0x04)
    bRet |= 0x20;
if(in & 0x08)
    bRet |= 0x10;
if(in & 0x10)
    bRet |= 0x08;
if(in & 0x20)
    bRet |= 0x04;
if(in & 0x40)
    bRet |= 0x02;
if(in & 0x80)
    bRet |= 0x01;
return bRet;
}

My problem is that the readings I get are nonsensical. I'm using Labview to write up my software, so I employ a simple VISA read (listening for a packet) for an unknown number of bytes and a termination character \n. The rest of the Wixel app shows that it's using RTS/CTS hardware flow control, so I've set that up. My problem is that I'm expecting a long decimal (%lu), an unsigned short char (%hhu), and a decimal (%d), but when I read off the individual bytes received as these data types, my values come out weird.

For example, a reading of 98 on the real glucose meter was "117888 215 0\n" in my packet. I've ruled out endianness, as reading the backwards bytes as ASCII gives super strange unicode style characters. I just fail to see how the first number is in any way related to the second one. I honestly think I may just be interpreting the data type incorrectly, although I know that printf gives purely ASCII characters. The last weird thing is that the 215 almost always shows up somewhere in the packet, be it the first number, middle number, or last number. It's quite strange and leads me to believe I might be missing something.

Any help in interpreting this data would be appreciated.


texts: How can we compare processing times of two designs implemented on different FPGAs?

texts:
How can we compare two different designs that perform same task (e.g. processing a 256x256 image) and both implemented on different FPGAs, in terms of processing time(seconds)?

For example one of them is on Virtex-5 and other one is on Virtex-7. I know that these two families have different specifications in terms of speed grade, available resources, architecture etc. So I thought it is not convenient to do this comparison (a fair way to do it would be comparing clock cycle count). But I wanted to ask it because I came upon some papers which does this sort of thing. (e.g. compares a design implemented on Virtex-5 with a design implemented on Virtex-7 and claims that his/her design/implementation is faster in terms of seconds)

Edit:  I am normally doing this comparison by mapping my design onto the same family of FPGA used by the competitor.

Edit2:

A lot of time passed since I asked this question but I still feel that I have failed to describe the situation correctly.

You can achieve better timing results if you use technologically better FPGAs. Critical term is TIMING here. Do not assume that I will set the same timing constraint for both FPGAs. This is not the case. Please consider the question like that:

For Virtex-5: timing constraint is set to 100 MHz and it is met (T. constraint 105 Mhz Fails).

For Virtex-7: timing constraint is set to 150 MHz and it is met (155 Mhz fails). So I'm trying to find out the best achievable frequency for the device. Virtex-5 and Virtex-7 are just for the example. They may not have such a performance gap.

My architecture achieves better result if I use Virtex-7.

So now imagine that someone implements a circuit that performs the same task as my design.

He/She implements the circuit for Virtex-7 and achieves a max frequency of 130 MHz.

He then compares this result (WITHOUT implementing it for Virtex-5) with my Virtex-5 result (100 MHz) and concludes that his/her architecture is better. Assume that clock cycles are equal for both circuits.

In my opinion, if such a comparison to be made; it should be done by using same family of FPGA device. Otherwise it is not a fair comparison. Purpose of this question is to find out if there are exceptions to that.


texts: How do I reuse the LO when designing a loopback receiver?

texts:
Suppose I'm designing a transmitter which has an LO and an IQ mixer. I would like to shift the LO down by 100 MHz or so, so I can mix it with the IQ mixer output so I can monitor the IQ mixer balance and LO leakage. The main issue is that the LO might be anywhere from 4 to 8 GHz. My worry is that if I use a single sideband mixer to generate the LO-100 MHz, the upper sideband (LO+100 MHz) will also mix with the IQ mixer output, and so I will never be able to tune the IQ mixer better than the SSB mixer suppresses it's upper sideband. I've determined this is the case if you assume a mixer is a perfect multiplier.

However, I understand that mixers aren't linear... if the LO+100 MHz sideband is 25 dB lower than LO-100 MHz, will it contribute at all?

Second, if I have this signal which consists of LO-100 MHz and a much smaller LO+100 Mhz, how do I knock out LO+100 MHz if LO spans an octave?

Finally, is there a good way to do what I seem to be trying to do? I just wanna get the output of the IQ mixer from the microwave range back down to the 0-1 GHz range so I can monitor it easily. I wonder if a sampling detector is a good way to go.


texts:
Package reads "2 8in 12vdc LED strips".

Plugged into a car they get hot enough to melt.
Plugged into a 12vdc 120mA transformer they work great.

What resistor do I need to bring car amperage down to 120mA?


texts: Why theoretical value and experimental value(multisim) of voltage gain in common source amp for T model are different?

texts:
gm is 200μMho and my theoretical value of voltage gain is -1/3.
My experimental value(multisim) of voltage gain is -0.43.
Why they are different?


texts: What affects IMU (Inertial Measurement Unit) accuracy?

texts:
Context

I need to analyse the performance of a system that uses inertial sensor readings as input. My knowledge of IMUs is very basic, having only read a few introductory texts.

My understanding is that IMU accuracy degrades with continuous use due to drift, which results in accumulated error.

Questions

What other operational factors (i.e. not the specific device/components, but IMUs in general) effect the accuracy of IMUs?

I have noticed in my application that the system performance degrades when the object moves, especially when the movement is fast, and then improves once the movement slows, and reaches a halt. What aspect(s) of IMUs causes this?

EDIT

To be more specific, the sensors give orientation as quaternions (rotational offset from the sensor coordinate system to a global coordinate system). The error fluctuates over time (duration of about 15 seconds), however there is not an incline in error over time. Based on this, I believe IMU drift is not an issue here.

What I am interested in understanding is why the estimate error of the object's orientation fluctuates based on the amount and speed of the object's motion.

If it helps, I am using Xsen MTx IMUs.


texts: Minimum distance from TQFP to chip cap on PCB assembly?

texts:
I want to put decoupling caps (0603) as close as possible to TQFP-48-7x7. So PCB/assembly wise how close I can put them (pad to pad, component to component)?

Does the 'court yard' need to be exactly square, or is it ok to place mentioned caps closer to TQFP in the corners where the TQFP pins leave kind of 'free space'?

For placing all small stuff I have used 30mils (0603 <-> 0805 <-> etc).

Thanks,
Tim


texts: How to set a GPIO pin HIGH in a STM32 MCU?

texts:
Just recently pick-up a ST-NUCLEO-32 to upgrade from an Atmel Atmega328p.

The board integrates the STM32L432KC

I am just playing around with the new MCU and having a harder than usual time setting Pin "PA_07" High.

Can anyone please let me know what I am doing wrong. Here's the code:

    /* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  *
&copy; Copyright (c) 2020 STMicroelectronics.
  * All rights reserved.

  *
  * This software component is licensed by ST under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
  * License. You may obtain a copy of the License at:
  *                        opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
  */
/* USER CODE END Header */

/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "stm32l432xx.h"

int main(void)
{
    RCC->AHB2ENR |= 0x01;
    GPIOA->MODER |= 0x4000;
    GPIOA->OTYPER &= ~0x80;
    GPIOA->OSPEEDR &= ~0xC000;
    GPIOA->PUPDR  &= ~0xC000;
    GPIOA->BSRR |= 0x80;

  while (1)
  {

  }

}


texts:
I have a old autoradio (cassette and not AUX input ) in my car. But i don't want change because it pretty. I just want to add bluetooth. I leave fm receiver side for the true audio / radio.

I want to know if i purchase both parts :

TDA7388 four-channel 41W audio amplifier board
and
Bluetooth home-car receiver adaptor

I connect the audio amplifier with bluetooh receiver and power amplifier with speaker and i add a switch, to switch(speakers) between true audioradio/power amplifier.

I know i must add a power convert 12V->5V for the Bluetooth module.

I want to know if this is good "cheap" solution ?

Sorry for my English, I'm French.


texts:
1- What is the purpose of D1 in this circuit?

2- Can i connect the PWM output of MCU to Vi through a diode, to protect the MCU from 12V supply of the drive circuit? (e.g. if Vi got accidentally shorted to 12V)

3- Do i need to decrease R2 value if i connect the input through a diode, to compensate for diodes voltage drop, and maintain the base-emiter current? would decreasing R2 value to 560 ohms suffice?

(MCU's output high level is 5V, and i'm using TIP122 for BJTs)


texts: For the last few days I have been trying without any luck to find a good tutorial on simple circuit simulations. I am a relatively new hobbyist and I figure if I use simulations and play around the circuit and see the output I would learn more. Can you please direct me to a simple tutorial which teaches simulation of circuits.


texts: Proff of that in RLC circuit in series where AC source works in resonant frequency the sum energy of the inductor and capacitor is zero at all time

texts:
can anyone help me please prove the statement that:
In RLC circuit in series where AC voltage source works in resonant frequency the sum energy of the inductor and capacitor is zero at all time.
I know that the impedance is pure ohm, and that there is on difference in phase shift between the current and the voltage source, but i can't figure what else..
Thanks.


texts:
I have to find the 4 current mesh in this circuit

V1= 12V
R1= 1/12Ω
R2= 1Ω
R3= 1/3Ω
I1= 6A
R4= 1/3Ω
R5= 1/2Ω
R6= 1/13Ω
I2= 6A

I tried a source transformation and got this

I3= 144V

R1-2= 1/13Ω

Then, i did another source transformation

V-1= 12V

R1-2-3= 16/39Ω

But, at this point, I was confused because the title says I should get 4 mesh currents and with this simplification, only have 3 mesh and I do not know what else to do


texts: Will using a CMOS OCXO as extrnal oscillator for the XTAL input for LPC1114FN28 work?

texts:
I am trying to make a circuit which would measure the time interval between two pulses accurately. For this I have decided to use an OCXO with CMOS output and the LPC1114FN28 microprocessor.

I plan to drive the micorprocessor using the OCXO output to the XTALIN pin and the pulses whose interval is to be measured is fed into the CT32B0_CAP0 pin, the 32 bit timer operates in "capture" mode, wherin the number of PCLK clock cycles between the rising edges of the pulses gets transferred from the TC register to the capture register.

My doubts:

(1) Will using a CMOS OCXO output connected to the XTALIN pin drive the uC? What should I do with the XTALOUT pin?

(2) If I use the internal PLL to increase the frequency, will the accuracy of the PCLK clock be degraded as compared to the OCXO output?

Any ideas?
Abhishek


texts: Freewheel diodes and shoot-through prevention required on this low-voltage H-bridge?

texts:
I have built the following h-bridge:

VMOT1 is at logic level (3.3V)
FWD and REV are driven by MCU (no PWM in the scope examples given)
Q7/Q8 are DMP1045
Q9/Q10 are BSS138
D3/D4 are 4 x 4148
the 2 voltmeters are the color-coded scope probes with common ground
M2 is one of those cheap yellow Chinese DC motors

The scope measurements are representing a switch from the motor running at full speed in one direction, switching to the opposite direction. If I have understood well, this is the most likely scenario for either shoot-through or back-EMF.

When I leave the motor disconnected, the transition looks like this:

This looks fine to me, the timing between P-MOSFET and N-MOSFET is not exactly the same, but I see no concern for shoot-through (correct me if I'm wrong).

Now with the motor connected, it starts getting interesting:

What do I see here? Is the (yellow) dip below 0V the power returned to the circuit by the braking motor or is this the back-EMF? And what are the spikes showing up just before that dip? I have seen them in all samples taken.

And more practically speaking: Do I really need those freewheeling Schottky diodes or are they just not doing anything at all in this circuit?

Another question, is there any shoot-through happening here during the ±200ns transition or can that be neglected? There is an option to control all 4 MOSFETs independently and switch the P-MOSFETS's 1us later.

-- edit --

I was asked to add a .1R resistor accross GND and measure that. I didn't have one handy, so used 1R instead.

Yellow shows the logic level at FWD, and pink the voltage accross the ' current sense resistor'. First images shows one full FWD->REV->FWD cycle:

The circuit uses a switching boost converter (TPS61322) on a dual alkaline battery so that is probably causing the ripple (?). Averiging it out, the voltage is at about -125mV, so that makes a 125mA current draw at the battery terminals. But of course the 200ms period after switching direction is more interesting:

Here's there's a brief peak to 1A at the moment of switching over then 300mA without ripple for a while and then about 80ms of 1A max! I wouldn't be surprised if that is the current limit of the switch (1.8A max, inductor used Ir is 1.6A) . So I guess I have a case of shoot-through after all?

-- edit --

I compared the behaviour with a TI DRV8835 H-bridge IC, and actually it shows a very similar output. I will also make another measurement with a lab supply instead of the boost converter. Hopefully this clears things up even more.

-- edit --

This is without the boost converter, just 3.3V from the lab supply:

And this on the DRV8835:


texts: a good way to detect disconnections on the PCB traces

texts:
I make home-made cheap PCBs (I use toner transfer, then acid etching method now, but I might use UV etching someday). I wonder what is the best (and cheap) way to control if there is no problem on connectivity of the traces?

I control the connections by a multimeter, but it takes too much time to check all the connections with it especially if I make 10 or more PCB at a time. Sometimes I see that there are very tiny gaps that disconnects the paths and too hard to see them by bare eye. Is there any spray or can I use camera (webcam) to detect the broken paths, or any smart method?


texts: Motor polarity reversing circuit using just SPDT switches

texts:
I have a 6v DC motor that controls a physical system similar to a window blind, using one SPDT toggle switch and two SPDT microswitches for control. I have seen similar setups with hoists, however I do not know if the toggle switch was SPDT or DPDT.

Ideally: A SPDT toggle switch will determine if the blind is to be up or down, reversing the polarity on the motor accordingly. One SPDT microswitch determines when the blind is fully up (And halts the motor when the toggle switch is in the up position). Another SPDT microswitch determines when the blind is fully down (and halts the motor when the toggle switch is in the down position).

Using just those three SPDT switches, is it possible to achieve the above result? I can't work out how to formulate this mathematically. Without maths, the best I have come up with needs a DPDT toggle switch, as follows:

simulate this circuit – Schematic created using CircuitLab

The next idea for a solution would be to use an H-bridge BJT circuit, perhaps with some logic or a low-end 12-series PIC microcontroller.

Any solutions would be helpful. (As a bonus, I'd be very interested in the maths which confirms if a solution with just three SPDT switches would be possible, and what the circuit would be)

Thanks


texts: Salvaging colour LCD from Brother MFC-J6710DW printer

texts:
I have salvaged a colour LCD from an old Brother MFC-J6710DW printer and I'm trying to work out its pinout, to eventually use with an Arduino.

On the back it has the following characters printed:

COM33T3M15QLX
0L 33 CX504835
A63046001
CL 1C0L CX504835

The spacing of these characters are a bit open to interpretation, but I've done my best.

I've tried Googling the printer as well as the characters printed on the back but I haven't found anything of help. How would I go about working something like this out?

If its of any help, here is a picture I took of where the LCD was connected to the main logic board of the printer:

Thanks for your help!

EDIT:
@mister-tea Here's a picture with the black housing removed. No further clues I think. Tried pumping up to 5V limited at 1A with my power supply through the +/- terminals but unfortunately nothing happened. Sounds like I should give up?


texts:
A quick question on biasing a common emitter. I am given the following circuit and asked to derive several things. I am provided with the information that the transistor is in the active region, so it can be assumed that V(base-emitter)=0.6V. I managed to do the following:

1) assuming R1 >> 1/transconductance, show that voltage gain is -R2/R1

2) determine the value of R2 such that the emitter current is 2mA; Vout=0, so that R2=7.5kΩ

3) if voltage gain is 10, find R1; R1 = 750Ω

I also have to:

4) determine the value of the ratio R4/R3 assuming that the base current is negligible comparing to the current flowing through R3 and R4.

5) Assuming that the minimum value of the current gain is β=50, determine the maximum value of R3 for which the current flowing through R3 and R4 is a factor of 10 greater than the base current.

My thinking for 4) and 5) is the following:

4) V(base) = 2.1 V (=0.6V+2mA*750Ω)

as base current is negligible, we want current through R3 and R4 approximately equal; hence the ratio R4/R3 = 2.1/(30-2.1) = 7/93 (I'm not sure if this thinking is correct)

5) This is where I struggle, I have no idea if my reasoning is correct:

β≥50; hence collector current Ic=βIb≥50Ib; we know that the collector current is approximately 2 mA, so we find that the base current is Ib≤0.04mA; we want current through R3 and R4 to be 10 times that so that the current is ≤0.4mA; I assume we can think of this as current flowing through R3 and R4 in parallel; as voltage difference across R3 and R4 in parallel is 30V, this gives a lower bound on R3 in parallel with R4, i.e. R3 || R4 ≥ 75 kΩ;

I guess from here I can use the ratio from 4) and get that R4≥81kΩ and R3≤1072kΩ.

Would that be a correct answer? Thanks in advance!


texts:
I've built a LED PWM controller according to the below schematic and the voltage regulator is getting extremely hot (I can't touch the heatsink).

I've measured input and output voltages and currents and these are:
Vin = ~24 V
Vout = ~4.85 V
Iin = 80-95 mA
Iout = 80-95 mA

If my regulator is indeed L78S05 (because the package says UL75S05, but can't find any datasheet for this) then it should handle up to 2A easily and up to 35 V on input. Also if I understand correctly, it reduces the voltage by dissipating  excess power as heat, so how hot would it get if it would be supplied by 35 V and 2A?

Unless there is something wrong with my construction and it shouldn't get so hot right now. If so, could you help me find what is wrong?


texts:
Hope that someone can help me:

I found a schematics to program microcontroller from Raspberry PI (http://mujweb.cz/tlc/rpp/) and modified it a bit (will use direct 12V and 5V power supply).

I'm trying to put it on breadboard before ordering a PCB, but found out, that GPIO4 and GPIO7 pins has ~(-1.5V) in this schematic when I add GND (no need to add 12 or 5V).

Maybe someone can see the issue from scheme?
And if there is anything else wrong, please note :)

Thanks in advance.


texts: What is the minimum supply voltage for an LM335?

texts:
The answer to this question is probably staring me in the face, but I just can't see it.  I'm attempting to interface with an LM335AZ temperature sensor (datasheet) at 3.3V.  The datasheet clearly states that the output voltage is 10mV/K, and that at 25°C and 1mV it should output between 2.92V and 3.04V.  What I do not see specified is the minimum voltage it will operate at, and the sensor I have in hand doesn't appear to work correctly at 3.3V.

With a 3.3KΩ resistor the current to the LM335 should be 1mA at 3.3V. If I directly measure the output voltage when supplying 3.3V, I get 2.46V, which correlates to −27°C; if I supply 5V I get 2.93V, or about 20°C.  Suffice it to say that I'm not performing these tests outside at the North Pole. :-)

Does the LM335AZ only work on 5V, or 5V and up?


texts: 120V between chassis grounds of two different devices

texts:
After experiencing a notable shocking type sensation after  coming into skin contact with my laptop and phone (both metal and plugged into their chargers), I decided to probe the chassis of both devices to discover a 50Hz 120V transient...

To investigate this further, I directly recorded the voltage from the grounds of the charger connectors to find the same transient. Swapping  between two different laptop and two different phone chargers, all permutations yield the a large AC signal from their grounds. That said, swapping between a 10W to a 5W usb charger did drop the difference to 60V between laptop and usb charger grounds.

I’ve even checked the sockets to ensure that its not a wiring problem, and sure enough the earth, live and neutral are all where they should be and connected properly. N.B. I’m in the UK, so 240V outlets.

This is quite baffling to me since not only are the voltages produced by the charging circuits direct current, but neither voltage exceeds 19.5V! Any explanations/diagrams to explain this would be fantastic!

Cheers!


texts: How to identify a low voltage transformer

texts:
Not 100% sure this is the correct forum for this question.  If not, I apologise.

I am trying to identify this transformer.  It comes out of a Paradigm PDR-10 subwoofer amp.  I believe it is bad as even when disconnected from the circuit board, it keeps blowing fuses.  I am trying to find a replacement but there are no other labels on the xfmr.
From the label presented, can anyone tell me how to read this label?  Is there enough information on the label to find a suitable replacement?
Thanks


texts:
I want to reduce 220VAC to 5VAC and using one 100K Ohm resistor and another 2K Ohm resistor. Two resistors are connected in series and measuring the voltage from middle of two resistors. I am happy with the result I am getting. It is giving 4.5 VAC, but the problem is 100K Ohm resistor is getting hot. I haven't used the 4.5 VAC to anything if you say the Amps are going high.

My question is: Is it normal if the 100K Ohm resistor gets hot? I might put 20mAh on 4.5 VAC.
If the answer to my question is "no" then what should I do to make it work?

Here is my schema:

Claudio Avi Chami's answer is the answer to my question, he explained it very good, since he answered to my question I am marking it as an answer, but I like Whiskeyjack's answer. He gave me better idea for what I am trying to do.


texts: NPN Transistor 2N2222 fixed bias MULTISIM

texts: I have been working on my school projects and I wanted to ask you if there is any way of editing BETA for transistor. When I click on transistor, Edit Model is not working. Anyone help me, please.. I have been trying to figure this out for hours..


texts:
I'm using Xilinx ISE 14.7 to implement my design but I have some doubts about how to read the constraint interaction report (.tsi) generated during the Post Place&Route Static Timing Analysis.

In particular I noticed that there is a section in the .tsi file called "Constraint interaction for Unconstrained path analysis" under which I have something like

"X paths removed by TS_my_derived_clock_constraint",

where X is a very big number and coincide with the number of analysed paths reported in the Static Timing report under the section Derived Constraint Report.

How should I interpret this information? Are these paths analysed or not? Is it normal that the very same number appears in these two files? What does it mean "interaction for unconstrained paths"?

The timing constraint I use is something like:

NET "CLK_P" TNM_NET = CLK_P;
TIMESPEC TS_CLK_P = PERIOD "CLK_P" 200 Mhz HIGH 50%;

This is a differential clock entering in a Xilinx clock generator, from which the derived clock constraint is obtained.

The Translate report issued some warnings but they are about mysterious "logical net 'NX' has no driver", with X are all numbers from 85 to 165 and some warnings about TNM "bus_name_reset_resync" that does not drive any flip flops. They seem ok to me.


texts:
I am trying to work out what resistor to use in a circuit.

The circuit is a series circuit. The power to the circuit is 5.5V, with a switch, which connects to a GPIO pin on the RasberryPi. I believe 3.3V is needed for the pull up resistor on the RPi.

I need to use a resistor to lower the power from 5.5V to 3.3V. I know Ohms law, but I'm struggling to use it in practice. How can I figure out the required resistor needed for this situation, and for future knowledge?

Is their a formula I can note down?


texts: How to retrieve part information from Digi-Key automatically

texts:
How to automatically retrieve, given a Digi-Key part number, information such as Manufacturer, Manufacturer Part Number, Description, etc.  Perhaps parsing the GET http respose to:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=DK_PART_NUMBER

(thanks to angryee for the correct parameters)

Where DK_PART_NUMBER is the Digikey part number.

Does anybody know if they have a web service or simply a better interface for this?

After asking this question I decided to go ahead and write something that did some basic fetching from Digikey:

dk_pn = '587-1962-1-ND'

from urllib import urlopen
from sgmllib import SGMLParser

headers = ['Digi-Key Part Number',
           'Manufacturer',
           'Manufacturer Part Number',
           'Description',
           'Lead Free Status / RoHS Status',
           'Operating Temperature',
           'Standard Package',
           'Price Break',
           'Unit Price',
           'Extended Price']

class DK_Parser(SGMLParser):
    def reset(self):

        SGMLParser.reset(self)

        self.last_td = ''
        self.inside_th = False
        self.inside_td = False
        self.grab_data = False
        self.part_info = {}
        self.hdr_index = 0
        self.row_hdrs = []

    def start_tr(self, attrs): # row
        self.first_header_in_row = True

    def start_th(self, attrs): # header cell
        if self.first_header_in_row:
            self.first_header_in_row = False
            self.row_hdrs = []
            self.hdr_index = 0
        self.inside_th = True

    def end_th(self):
        self.inside_th = False

    def start_td(self, attrs): # data cell
        self.inside_td = True

    def end_td(self):
        self.inside_td = False
        self.hdr_index = self.hdr_index+1

    def handle_data(self,text):
        text = text.strip()
        if self.inside_th:
            if text in headers:
                self.row_hdrs.append(text)
                self.last_td = ''
                self.grab_data = True
            else:
                self.grab_data = False
        elif self.inside_td and self.grab_data:
            if self.hdr_index:
                self.last_td = ''
            if self.hdr_index < len(self.row_hdrs):
                self.last_td = self.last_td + text
                self.part_info[self.row_hdrs[self.hdr_index]] = self.last_td

dk_url = 'http://search.digikey.com/scripts/DkSearch/dksus.dll'
dk_params = '?Detail&name='

sock = urlopen(dk_url + dk_params + dk_pn)

parser = DK_Parser()
parser.feed(sock.read())
sock.close()
parser.close()

for k,v in parser.part_info.items():
    print k,":",v

Only the first data line of the the [price break/unit price/extended price] table is captured.


texts: Why is the 1-wire pull-up resistor not integral?

texts:
I've read that the 1-wire pullup resistor is included so that either the master or the slave device can pull the line low in order to communicate. Makes perfect sense: if the device had a transistor output stage pulling it high, then no other device would be able to commandeer the bus.

Most hobbyists seem to use the same resistor value. I have a suspicion this is not appropriate and that cable run is a factor here.

So, why is this critical resistor, which is always the same value for a given device, not integral to the device?


texts:
My question is on lighting 128 LED's from shift registers. I had originally considered using a string of 16 74HC595's but upon further research, it appears they would not supply enough current to light my high intensity LED's, would it be more practical to just buy some TPIC6C596's (which are rated for higher current) or do some sort of NPN emitter follower's on the 595's? I would have to buy the parts either way but am curious if it would be worth the extra money to just buy the 596's or how difficult would wiring all those NPN's be? I'm not familiar with much transistor circuitry and only know the base equations and uses.
I have already coded the needed hardware SPI code to quickly light the registers from my arduino, so now it's just down to hardware selection.

Thanks!


texts: How does positive feedback generates ac waveforms in an opamp?

texts: How can an ac oscillation be obtained by using an opamp and some components and what is the working principle behind?


texts: How to modify a voltage regulator to make it very low quiescent current?

texts:
We have built a hand held RF remote controller, powered by two CR2016 batteries in order to supply 6V.

We used a microcontroller in the circuit, which runs under 3.3V. That's why, we used a voltage regulator, LM1117 for that purpose.

Problem is, after having a few empty batteries in a couple of tests, we noticed that LM1117 swallowes up the battery while waiting. LM1117's datasheet says it consumes 5mA on standby.

After a little search, we understood that we need to use "low quiescent 3.3v regulator" for that purpose, such as tps76615, LM2936, etc.

But as we live in Turkey, we can not find such parts easily, and we currently have no time for shipment. That's why, we need a workaround for that problem.

As a first resort, we will use the same circuit, except for adding a NPN transistor in series to LM1117 and trigger that transistor via MCU where MCU is powered by the same LM1117 AND another very low energy circuit.

That very low energy circuit consists of a Resistor + 3.3V Zener // Capacitor. Zener diode will assure that capacitor will have 3.3V and this energy will be sufficient to wake the MCU up after an interrupt. When MCU wakes up, it will drive the NPN transistor, which will get power to the MCU and system will feed itself.

But I can not get if there would be any consequences with that approach. Is there a working solution for that kind of problem?


texts:
I have a hard time finding a how-to.

I would like to set up a simple ESD mat and wrist wrap, but I am not sure about is the the 1 MOhm resistor should be, if at all.

Several options:

1 MOhm from ground outlet to the mat, wire from the common earthing on the mat to the wrist wrap.
1 MOhm from ground outlet to the mat, wire from another contact on the mat to the wrist wrap.
1 MOhm from ground outlet to the mat, 1 MOhm from the same mat contact to the wrist wrap.
wire from ground outlet to the mat, 1 MOhm from the same mat contact to the wrist wrap.
wire from ground outlet to the mat, wire from another mat contact to the wrist wrap.

I am not sure why the 1 MOhm wire is needed since the mat itself already has that kind of resistance (as long as the wrist wrap does not connect to ground directly, but through the mat).

Which solutions above are ok? Which is best? Should I do something else instead?


texts: wiring usb cables for powering multiple devices via a bus terminal

texts:
Hi all,

I have a created a home brew cable to power up a monitor and a raspberry pi zero, and I have blown up a capacitor on the monitor card, and I have no idea why :(

First question:
Why did the capacitor blew up?

The monitor has an LDVS to HDMI board which receives power via a usb mini-b, and the pi receives power by a micro usb. I have taken both usb cable, stripped them and soldered the red wires together, as well as the black wires together. I then used a 2 pin JST SM wire by soldering again, red with red, and black with black.

Here is a pic of the contraption

The JST connects to a 8 way bus bar. The bar is connected to a Mean Well RSP-320-5 rated for 5 Volts at 60 Amps, and the positive line has an inline fuse rated for 20 Amps.

The first time I power everything up, I had everything connected before turning the switch on, and the fuse blew up. The second time I connected the power but left the USB unconnected. First I plugged in the pi, and while the fuse didn't blow up, the pi didn't turn on. Then I unplugged the pi, and plugged the monitor, 5 seconds later the capacitor sparked, some smoke came out, and my face became painted with sadness.

I am using different cable gauge, 14 from the power supply all the way down to 22 for the JST cable, and whatever gauge the usb wires have in there (it's thinner than 22 but I am uncertain what gauge that would be)

I have confirmed the there is only continuity from the red and black cable with their corresponding usb pins.

PS: I tried the usb to jst before, with the male end directly connected to the screw terminal on the power supply, and everything worked, so I am double confused...

Second question:
How can I test this without... blowing hundreds of dollars worth of equipments up?
Is there something I can build or buy that would allow me to check my power circuitry in a safe manner?

Thanks!!!


texts:
I just need a small help to completed my project. As my output is printing 2 result but only 1 output is saving to the eeprom. How can I save multiple data into eeprom? I'm just showing the setup and loop only cause the rest is not that important.

void setup() {
  // initialize serial communications at 9600 bps:
  Serial.begin(9600);
  Serial.println("Hit 'y' and RETURN, if you want to calibrate...");
  Serial.println("Hit 's' and RETURN, if you want to collect data...");
  Serial.println("Hit 'x' and RETURN, if you want to clear the cal data in EEPROM...");
  Serial.println("If not, 'n' and RETURN");
  Serial.println(' ');
  Serial.println("\n");
  keyResponse=readkey();
  //keyResponse='n';
  if (keyResponse=='y'){
      calibration();
  }
   if (keyResponse=='s'){
      Serial.println("Collecting data...................");
  }
  else if (keyResponse=='x'){
    while (!eeprom_is_ready()); // Wait for EEPROM to be ready
    cli();
    calData.written=0;
    eeprom_write_block((const void*)&calData, (void*)0, sizeof(calData));
    Serial.println("Cal data is cleared...");
    sei();
  }
  else {
     while (!eeprom_is_ready()); // Wait for EEPROM to be ready
     cli();
     eeprom_read_block((void*)&calData, (void*)0, sizeof(calData));
     sei();
     if (calData.written==99){
       Serial.println("Using previously stored cal data from EEPROM");
       output[0]=calData.dx; output[1]=calData.dy; output[2]=calData.dz;
       output[3]=calData.dv; output[4]=calData.dd;
     }
     else {
        Serial.println("no previous cal data, using default");
     }
    data();
    exit(0);
  }
  readAcc(ValueX,ValueY,ValueZ,'x',10);
  gXA = mapAcc(ValueX, midX, sensX); //cannot let gXA at 0, will create err.
  gYA = mapAcc(ValueY, midY, sensY);
  gZA = mapAcc(ValueZ, midZ, sensZ);
  GNA = norm(gXA,gYA,gZA);
  preTime=micros();
}
void loop() {

int i=0;
  while(loopI<=2){
 // read the both analog in values:
            readAcc(ValueX,ValueY,ValueZ,'x',10);
curTime=micros();
dT=curTime-preTime;
preTime=curTime;
aT=aT+dT;
gX = mapAcc(ValueX, midX, sensX);
gY = mapAcc(ValueY, midY, sensY);
gZ = mapAcc(ValueZ, midZ, sensZ);

LPF(gX,gXP,gXA,gXins);
LPF(gY,gYP,gYA,gYins);
LPF(gZ,gZP,gZA,gZins);
gNins=norm(gXins,gYins,gZins);
cap(gNins,0.01,1);

gXinsA=(gXinsA+gXins)/2;
gYinsA=(gYinsA+gYins)/2;
gZinsA=(gZinsA+gZins)/2;
gNinsA=(gNinsA+gNins)/2;

GN = norm(gX,gY,gZ);
LPF(GN,GNP,GNA,GNins);
cap(GNins,GNlowB,GNhighB);
GNinsA=(GNinsA+GNins)/2;

Max(gNinsMax,gNins);
Max(GNinsMax,GNins);

reset_vel(gNins, gNlowB, vel);
reset_vel(GNins, GNlowB, VEL);

vel=vel+9.81e-6*gNins*dT;
VEL=VEL+9.81e-6*GNins*dT;
act_dist=act_dist+9.81e-6*vel*dT;
act_DIST=act_DIST+9.81e-6*VEL*dT;

actCnt=actCnt+1;

if (actCnt>=10){
actGN=sqrt(actGN_acc/10);
actGN_acc=0;
actgN=sqrt(actgN_acc/10);
actgN_acc=0;

dist=dist+act_dist;  act_dist=0;
DIST=DIST+act_DIST;  act_DIST=0;
actCnt=0;
}
actgN_acc=actgN_acc+(gNins*gNins);
actGN_acc=actGN_acc+(GNins*GNins);

dispCnt=dispCnt+1;
if (dispCnt>=40){
display_result(0);
loopI++;

dispCnt=0;
}
gXP=gX; gYP=gY; gZP=gZ;  GNP=GN;
  }
output[0] = gXins;
output[1] = gYins;
output[2] = gZins;
output[3] = VEL;
output[4] = DIST;
  Serial.println("Cal data written to EEPROM..."); // store to EEPROM
  calData=(calData_t){99 , 0,0,0,0,0,0,output[0],output[1],output[2],output[3],output[4]};
  while (!eeprom_is_ready()); // Wait for EEPROM to be ready
  eeprom_write_block((const void*)&calData, (void*)0, sizeof(calData));

 if(loopI>2)
 {
   exit(0);
 }
}

Updated:

  else {
     while (!eeprom_is_ready()); // Wait for EEPROM to be ready
     cli();
     eeprom_read_block((void*)&calData, (void*)(i* sizeof(calData)),sizeof(calData));
     sei();
     if (calData.written==99){
       Serial.println("Using previously stored cal data from EEPROM");
       output[0]=calData.dx; output[1]=calData.dy; output[2]=calData.dz;
       output[3]=calData.dv; output[4]=calData.dd;
     }
     else {
        Serial.println("no previous cal data, using default");
     }
    data();
    exit(0);
  }


texts:
I've noticed many motion control cards have optically-isolated inputs for limit switches? I can understand why you may do this with a signal which travels between two systems with separate power supplies, but what is the purpose when a shared power source is used?

Assume a control card with a 12v output for a NC limit switch. A voltage divider (using two resistors) lowers the voltage to an appropriate level determined by the MCU. A pull down resistor is used to tie the input pin to ground when the switch is open. In such a scenario, why would optically-isolating the input be a good idea? I can only think that a spike in the 12v output would produce an unacceptably high output after the voltage divider.


texts: Dimming LED using Transistor as a Switch or as an Amplifier?

texts:
I want to try out controlling LED strip brightness/colour (via Arduino that can't supply enough power) and I understand this can be done either with using Transistor as a Switch or as an Amplifier.

1) as a Switch, using PWM (Pulse-width modulation) to switch the transistor on/off many times per second to simulate the desired voltage. This is for some reason the preferred way according to my Googling results. However I am a bit afraid of flickering, some people are more sensitive to it than others, but I want really smooth fading. Is there some mechanism to stabilize the outputs of the switch to be less discrete? That brings me to the other option:

2) as an Amplifier, where small changes in the input voltage result in bigger absolute changes in the output voltage. My naive understanding is that this could be more "smooth" in terms of the voltage supplied to the LED and thus prevent any flickering.

What are the drawbacks of option 2?
Why is the option 1 more common?
The factors that come to my mind include price, complexity of setup, overheating and possible problems with non-linear characteristics of Amplifiers, but I am rather guessing here.


texts:
The requirements

I want to control PWM fans to maintain some HDDs in a server at about 35°C, the absolute value isn't critical, however I want the temperature to be stable regardless of the ambiant temperature (within reasonable limits of course, if the ambiant temperature is 40 °C then obviously it can't work).

I already designed a controller based on a LM35 (which will be attached to the case of one of the drives) but it was proportional only. Then I modified it to add an integral term to avoid any steady-state error (mainly due to the ambiant temperature changes).

The circuit

You can find the circuit diagram here.

U1:A is the error amplifier
U1:B is the triangle wave generator (I know it'll not generate a perfect triangle signal, it's ok for me)
U1:C is the final comparator who generate the PWM signal (not connected because it doesn't matter for now)
U1:D is the PI filter

The problems

1) I don't know how to chose the values for R9, R10 and C3 (they're just placeholder for now) because all I can find on PI(D) controllers is for software controllers (and, no, I don't want to use an arduino or any other MCU).

2) I don't know how I can control the Kp and Ki parameters independently and what their values should be for this application.

3) I'm not sure of the components arrangement around U1:D.

NB: The drives have a huge thermal inertia so I guess the loop will probably be very stable without too much tuning, but if someone can confirm it would be great. Minimizing system settling time isn't a concern at all here.

Thanks to anyone who can help :)


texts: why dc machines have double layer winding?

texts:
why do dc machines always have double layer winding?is it possible to create a single layered winding dc machine?

More generic Question: Can anyone explain the logical evolution of dc machine from the prototype (single coil) to the actual double layer-distributed winding case?

Usually in text books they use single coil to explain the principle of operation and suddenly jump to parallel paths-multiple commutator segments-double layer closed winding case .Single coil doesn't have any parallel paths and i doubt whether it is closed too.What is the logic behind the actual implementation of a dc machine and how can it be explained as progressive evolution of the simple case?
Please note I understand the reason for use of distributed winding(more no:of windings in series and hence less ripple) and to a fair extent the working of actual implementation as well.What bothers me is "can i have  a dc machine with single layer, with any no: of parallel path(can it be one?),closed or un-closed winding for achieving the same emf?".

Also i'm concerned about the conceptual understanding.I tried theoretically to extend the single coil case to 2 coils in perpendicular connected in series.But i couldn't find a suitable commutator connection which will give me the required o/p(sum of their emfs).The only possible way was to go for double layer-closed form winding(which makes it 4 coils).I was not sure of this and wanted to confirm this.


texts: Electret microphone amplifier voltage spikes

texts:
I am using this electret microphone amplifier in my circuit

I'm getting voltage spikes at the amplifier output that are randomly happening every 2-5 seconds. After shorting the microphone leads, there were no voltage spikes at the amplifier output. What could be the probable causes of an electret microphone causing voltage spikes? Is that a common problem? I'm thinking that I might need to switch to a MEMs microphone.

The amplifier output is connected to an analog input pin of an Attiny84 microcontroller as well as an input to a comparator.


texts:
I plan to create a circuit that communicate with 28 UART channels (115,200 bps for each channel).
Can you advise what could e the best architecture to create this type of circuit? Let say that those are the controller communication protocols:
USB channel, 3 SPI channels, 2 UART channels, FlexCAN, PCIe, I2C and Local bus

I thought about using MAX14830 which is a quad uart component, controlled by SPI. By using 7 components like this, I can create 28 UART channels, controlled by 3 SPI channels (using CS to choose with which uart quad to communicate with, and then control each time with each of the UART channels to use)

My question is if you have more elegant ways to do that using one of the other communication protocols I mentioned.
Thanks.


texts: How can I hook this 8x8 rgb led up to an arduino?

texts:
I've looked around for examples but I keep finding single color LEDs or in best case a two color LED but I have yet to see how to hook up a true 8x8 RGB LED matrix up to Arduino, is this even possible?

Where I'm confused is that there are more pins on the 8x8 then there is from Arduino, how can I control each individual light? I'm fine with the programming, just not with the connections.

I've attached the datasheet for those who are curious.


texts: Energy band diagram showing band bending in semiconductor when an external electric field is applied

texts:
This above Energy Band diagrams are what I found on an online forum. However I dont understand the EB diagrams drawn for the p type SC since it is different with respect to the formula and diagram that is referred in standard texbooks.

This is the formula given in textbook for Electric field from EB diagram, how can it be different for a p type SC?
I doubt if the band diagrams are drawn wrong for the p type SC


texts: Can someone help me with Nodal Analysis?

texts: I am not sure if \$ \frac{V_1}{R_2} - \frac{V_2}{R_2} = 0 \$ is correct for node V1. Can someone help me with this question?


texts: How does my phone get charged via laptop USB port at lesser current (compared to wall charger)

texts:
Today's typical smartphone chargers are rated at 5 Volt & 1+ Ampere. The laptop USB can supply 500mA 100mA.

Why is it safe to charge the phone with 1/2 the rated current?
Is it like a slow charging mode where it's the phone's responsibility to recognize a computer USB port & lower down the current demand?
Does this mean I can potentially use a 5V/0.5A wall charger with my phone without any fear of damaging it?

Edit : It seems that the answers & comments are focused on 100mA vs 500mA that the laptop USB port can supply. I'm amending that in my question & rephrasing. The real question is, even 500mA is lesser than what the wall charger supplies i.e. typically 1+ Ampere.

Edit 2 : To those who marked this as duplicate : You are confusing this question with the one that's asking whether a laptop can supply more than 500mA. It does not specifically answers the 3 points above. I'm wondering if a laptop can charge a phone, then why can't a lower current rating charger be considered safe?


texts: How to design buffer using single power supply(without using rail to rail OPAMP)?

texts: I am designing circuit which contains 4 buffers(for overcoming impedance mismatch between two circuits). These buffers needs to work somewhat linear in 0 volt to 5 volt range but the problem is I only have one 24 volt battery source for all circuitry and OPAMP requires dual power supply. How i can overcome this problem in efficient manner without using rail to rail OPAMP?


texts:
We run anywhere from 4-10 sensors from Banner Engineering (Photoelectric and RFID). They use 12V power and have a PNP output. Each sensor is 4 wires (12V, GND, NO, NC). Our goal is that we can run the M12-A Euro Style QD directly from the sensors, into some sort of PCB that sits on top of a RoboRIO. We want to use the M12 connectors because they are so reliable and a solid connection.
My thinking for the PCB is that we supply it with 12V power and ground, then that gets distributed to the 10x M12 connectors on the board. Here is the female PCB board connector I am looking at and here is the cable I am using with it.
In terms of signals, I need some way to reading the 12V signals and transmitting that the RoboRIO - I can use SPI, RS232, or I2C. I would like if I could read in the NO and NC for all the sensors, and then pick which value to use in code (I want to choose NC or NO depending on the situation and what should happen if the sensor gets disconnected).
What would be the best way to read in and transmit these signals? I was thinking about using a Teensy, but then I would need voltage dividers for all 20 inputs (which might end up being the solution).
I don't have any experience designing PCBs, but I think this will be a good way to get into it.


texts:
I'm currently "using" my TENMA 217945, which is a decent soldering iron, I guess. The main problem is that I am absolutely horrible at soldering. I'm capable of doing through-hole stuff, but tinning wires is just a trainwreck and from an expert's point of view likely looks as if it was done with a flamethrower. I have a helping hand or whatever that is called, but it doesn't work all too well. I'm doing many things wrong.

(EDIT:) I know it can’t be good for soldering, because the tip is a charred black. I have a sponge, which came with my iron, but it doesn’t get it off. As an earlier responder noted, a new iron is good, but I don’t have a job and I don’t make an allowance, etc. Should I just invest into another tip, because solder won’t stick to the tip at all. Is there anything special I should do if I acquire a new tip?

I guess the most notable thing that I need help with is tinning wires. Thinking of how I tin wires makes me cringe and invokes a feeling of spontaneous regurgitation within the back of my throat. For example, only 10 minutes ago(The reason I have come here and am asking for help) I was attempting to tin the rather flimsy wires of a micro-servo motor, without my helping hands because they are at my dad's house and I'm at my mom's house, and I couldn't even tin the first wire without giving up on myself. They say that practice is the best type of learning, but if I don't have a clue as to how to tin, then what good is practicing bad practices. By the way, I have made an attempt to learn how to solder from the internet to no avail. Ironic that I'm coming here for help then. I'm not looking for an answer such as "turn on your soldering iron", something a bit more.

I expect to be redirected to 100 different pages and/or marked as a duplicate due to the simple nature of this question.

Thanks ahead of time, in the event that I am unable to respond.

(EDIT:) Thanks for all of the help! I understand that this community is supposed to answer questions, but I have been given answers like “There’s this thing called google” and “Have you heard of the internet?” before.


texts: Safety with low voltage high current safety

texts:
For my work, I’m working on a project that uses a power supply that outputs 42A DC at 5V limit.
While I know that 5V is nothing if I were to come into contact, poor grounding can still cause flashes and burns.
So what are good safety tips when dealing with this sort of supply? Thanks!


texts:
I am designing an analog circuit for motor control for that I need to rectify AC voltage using halfwave rectifier but I don't know how to calculate the rectified voltage in the given circuit below.

In simulation when I am measuring a voltage across R1 with DC voltmeter it shows 0V. But in web example, there is a formula for measuring a voltage Vdc=Vrmsx0.45 which is equal to 103.5V

Can you help and it will be helpful if the method is given for circuits like this


texts: "Ultimate" Surge Protector with Solar Cells

texts:
I've had an idea that I was wondering if it would be possible.

I came up with this idea when thinking about local computer backups. Companies such as IoSafe make hard drives which are water & fireproof, however I'd be willing to bet that a good electrical surge would take one out.

Would it be possible to isolate a hard drive (or SSD), electricially, simply using solar cells for power and fiber optic for communications?

You'd have a light source which would power up the solar cells, which would power the HDD/SSD. You'd have a fiber optic connection for data.

In theory it would be very isolated from outside elements.

Does such a device exist? Is there a reason why not?


texts: Opening micro-controller package with vacuum pen

texts: So I recently bought an STM32H7 chip to use for my undergrad final year project. The chip comes in a package with a label saying: "Fragile, vacuum pen must be used to remove this device". Unfortunately I have found no sources online on how exactly such a case should be opened. May someone help me out with a step by step solution on how exactly I go about opening such a package.  Thanks


texts: Supply power to USB with external power supply

texts:
I have a device (pyro-electric array detector) that connects to the Pc vis a usb. The device itself has an additonal power supply as well.

Now a strange thing happens: If I connect the device to a Pc-tower, it works. But if I connect to a Laptop it does not work. On my colleagues laptop it works but only if he plugs in his laptop's power supply.

My assumption was that there must be a difference in the volatage/current supplied by the individual computers. And indeed there are small differences. 4.7V from the laptop and 5.23V from the PC. The current seems to be low 0.16mA and therewith well below the USB max spec.

What I tried next is to connect an external power supply to be able to adjust the power to the device's need.

For that I cut the USB cable, connected the D+/D- cables for data and connected the power leading to the device to the external power supply. From a control LED on the device I can see that it is happy with that. Now, however, the device is not recognized  on the PC any more (Windows device manager).

Any advice on how I can

a)power the USB device by an external power supply and

b) have it working on the PC?

Any hints are appreciated. Forgive me if what I tried is foolish. My last electronics lecture was about five years ago and I never tempered with USB before.


texts: What is a good strategy to read many button inputs while still doing USB?

texts:
I am trying to design a USB joystick with many different buttons. The board I am using right now has an ATmega32U4, USB port, and 16 I/O pins. I am using LUFA for a USB stack.

I know that I can get 8*8=64 inputs from the 16 I/O pins by creating a grid and strobing over it, but I am concerned how long this will take to complete and if it may affect the USB connection because of the delays. (I realize that strobing through 64 I/O values probably won't take that long, but I plan on putting some additional processing in that will slow things down further.)

My plan was to create a timer interrupt and use the interrupt to call the HID_Device_USBTask() and USB_USBTask() functions. Does this sound reasonable or is there a better approach I could take?


texts: MCP23017 not causing interrupts using a normally open switch on power up

texts:
I'm working on a project where I am using two 4x4 button pads. I would need to use two MCP23017 for input interrupts to support the 32 buttons. I am using a Netduino and I'm coming across an issue that I'm uncertain if its software related or hardware related.

I am using this website as a guide to understand and configure the MCP23017 and I'm following all the steps, including the diagram below:

The diagram shows the address as set, SDA and SCL have a resistor, reset is biased, a pin on the Netduino is set to handle the interrupt, and a microbutton is used to test the interrupt functionality.

I set the MCP23017 pin for the switch as input, set it to use a pull up resistor, then set the pin as an interrupt. The pin on the Netduino is set to use a pull up resistor as well and to cause interrupts when low. This works perfectly fine as long as the Netduino boots up with switch closed. If the switch is open (as it is normally open) no interrupts ever fire. I need to start the Netduino while pressing the microbutton to get the desired behavior. I'm unsure as to what is causing this. I am exhibiting the same behavior as the person commenting on the bottom of this page.

Is there either a software or hardware solution to this?


texts:
I am a noob so please excuse my lack of knowledge,

Is there a web site that can be fed with the circuit and it would route it and would give me the final bitmap of the PCB?

I'll be also glad if you guys point me out to some free software for such PCB routing.

I think there must be some kind of cheap alternative of those professional software tools that do the same but you just can't afford for small hobby activity.


texts: Can a lm317 voltage regulator be in series with a lm317 current limiter and work?

texts:
I'm building a power supply for a guitar pedal.
I'm using a voltage regulator that will set the voltage at 9V, 12V, 15V or 18V. Below is the schematic

I also need to limit the current to 250mA. So I was planning on connecting the voltage regulator in series with this current regulator circuit.

However I'm unsure if this would work. I don't necessary need to regulate the output current I simply need to limit it.
Would placing a resistor of an appropriate value to the output of the voltage regulator be enough to limit the current?


texts: Help needed with SPARTAN-3AN FPGA frequency doubler

texts:
Here I attached the routed nets for this below verilog HDL program with DCM instantiate module. while I am  implementing in XC3S50AN FPGA board using using ISE12.3 Design suite clk2x & locked outputs are not providing any output in SPARTAN FPGA  development board (https://www.pantechsolutions.net/project-kits/cpld-fpga-boards/spartan-3an) there is an output LED'S are assigned for clk0,locked,clk2x pins (p7,p8,p10 in datasheet) are output ,pins    and (p57(clk),p18(rst)) are input pins.but, i got an output only at the clk0(p7) that is 2.5 Mhz same as clk50(intenaly generated clock from 50Mhz of input clock)

module dcm_pllverilog(clk,rst,clk0,clk2x,locked);

input clk;
input rst;
output clk0;
output clk2x;
output locked;

reg clk50=0;
wire clk0;
wire clk2x;
wire locked;

reg [7:0] count=0;

clkdcm_test instance_name (
    .CLKIN_IN(clk50),
    .RST_IN(rst),
    .CLK0_OUT(clk0),
    .CLK2X_OUT(clk2x),
    .LOCKED_OUT(locked)
    );

always @(posedge clk) //---2.5 Mhz signal from 50 MHZ crystal oscillator
begin
     count<=count+1;

  if(count<=9)
     clk50<=1;
  if(count>=10)
     clk50<=0;
  if(count>=19)
     count<=0;
end
endmodule

//----------

# PlanAhead Generated physical constraints

NET "clk" LOC = P57;
NET "clk0" LOC = P7;
TIMESPEC"Ts_clk" = PERIOD "clk" 20ns high 50%;
NET "clk2x" LOC = P8;
NET "locked" LOC = P10;
NET "rst" LOC = P18;

enter image description here

enter image description here


texts: is it possible to control 8 motors with 74hc4051?

texts:
I need to control 8 motors from Arduino.

speed control only with a single pwm output

I use a single channel at time

I have 74hc4051 analog/digital mux/demux ic

if I set mosfet drive circuit with gate pull down (40kOhm) and gate resistor 100Ohm on all output channels of 74hc4051

I need to know weather there is a possibility to generate floating noise on unused channels?

according to theory since I am using mosfet gate pull down on each output of mux channels floating noise will be pulled to ground is this correct?

analog mux output connects to mosfet gate


texts: Large drift (temperature could be a culprit) in this circuit. Anyone can help?

texts:
Purpose: Amplify the differential voltage out of a bi-cell photo-diode. Amplification has to have a high gain as we are looking into nm level displacements of the IR beam centroid emitting the bi-cell

Circuit: Below is a schematic of my circuit:

TA1 and TA2 are the transimpedance amplifiers (LTC6268)
All the OPs (1-5) are LM324N
The nulling circuits ensures (\$V_A-V_B\$) is zero in initialization of the circuit.
\$V_{OS}\$ is the offset voltage that is applied during initialization and will be constant during the operation of our system.
The 100 k ohms resistors and 3 nF capacitor is to low pass filter the difference between \$V_{AN}\$ and \$V_{BN}\$
The instrumentation amplifier (INA217) with a variable resistor has gain of 1000
The output of the instrumentation amplifier is filtered and buffered to get sensOut

I need the high gain in the circuit to be able to pick up the sensOut with my 12 bit DAQ.

Problem:
I see large drifts in my circuit, no noise issues though

I appreciate any advice on how to improve my circuit. I am a novice mechatronics student and your feedback is greatly appreciated.

A picture of the voltage drift over a 24 hour data recording is below:


texts:
I am designing a board with a FT230 USB to UART IC. In battery powered applications, one of its GPIO can serve as a VBUS sensing pin.
However, the FT230X was designed for 5V applications, before the era of USB Power Delivery. In my case I'm expecting voltages of up to 20V on VBUS, but with a VIH of 2.0V on the GPIO, I don't see any voltage divider that would produce a logic high voltage on the entire 5-20V range.
So I'm looking for a small circuit that would produce a logic high whenever the VBUS is above 4.5V, as illustrated below.


texts: CPU clock cycles required to execute the following inx?

texts:
Consider the following data path of a simple non-pipelined CPU. The registers A,B, A1, A2, MDR, the bus and the ALU are 8-bit wide. SP and MAR are 16-bit registers. The MUX is of size 8×(2:1) and the DEMUX is of size 8×(1:2). Each memory operation takes 2 CPU clock cycles and uses MAR (Memory Address Register) and MDR (Memory Date Register). SP can be decremented locally.

The CPU instruction "push r" where, r= A or B has the specification
M[SP]←r
SP←SP−1
How many CPU clock cycles are required to execute the "push r" instruction?
A) 2
B) 3
C) 4
D) 5
==============================================================
Some say answer is A) some say B) and some say it's D)
I think answer is A) as SP is decremented locally; doesn't require any extra cycle. So, memory operation require 2 cycles.
This question is asked in GATE 2001 Exam,please help!


texts: Two transistor pair inverter and one transistor pair inverter

texts:
Today I made DIY inverter (the top one)
I managed to achieve ~2 volts from 5V usb, everything seemed to be ok. But I have question - is this the right way to make inverter? I also found the bottom schematic on the internet and I think it would work differently. I drew two graphs the way I imagine it works. Is it right? Does bottom schematic produce better AC current than top one? Because I think the bottom works like any wall AC socket - there is phase and "zero". Which is better? I'm thinking about making a more powerful VFD for single phase motor (a basic ventilator, that connects to wall AC socket). Which schematic should I use?


texts:
in one of my project i have 5 states , to which corresponds 3 flip flops . But 3 flip flops encode 8 states. My question is: the 3 unused states, when I create the Next State equation, are considered "Don't Care"? Cause later I have to create the K-Map using the excitation table for every input of the flip flop. So, what have I to write in the next state of the unused states?
Thanks


texts: How to amplify a 0-5V PWM Signal to 0-12V, 10A

texts:
I need a Power amplifier which amplifies a 0-5V Arduino-generated PWM Signal to a 0-12V Signal with 120W, for powering a ZVS induction heater.

Linearity is not important because i can correct the error in software.
Maybe it will be useful to convert the pwm signal to a analog signal to amplify it.

I thought about one of these Solutions: Step-up converter or a Class AB Amplifier.
I'm not sure what i should do.
What would be your solution and why?


texts: How to stop current leakage in LED matrix

texts:
I know that this issue has been discussed in this forum, but I am a beginner in electronics and I was unable to come up with a solution to my problem by reading the related threads.
I am doing a 3x5 Led matrix (cathodes are connected row-wise):

I used a raspberry Pi B+ with an MCP23017 GPIO expander, 1000 Ohm resistors and 5mm LEDs (20mA, 3.2V). I used 1000 Ohm just because this is what I had. I turn ON one LED at a time (I believe this is called multiplexing). This is my code for displaying the digit 2:

import smbus
import time

bus = smbus.SMBus(1)
bus.write_byte_data(0x20, 0x00, 0x00)#setting GPIOs of bank A as outputs
bus.write_byte_data(0x20, 0x01, 0x00)#setting GPIOs of bank B to outputs

MATRIX = [[1, 1, 1], [0, 0, 1], [1, 1, 1], [1, 0, 0], [1, 1, 1]]

for k in range(100):
   for irow, valr  in enumerate(MATRIX):
       for icol, valc in enumerate(valr):

           A = [0, 0, 0, 0, 0, 0, 0, 0] #the 8 bits to send to bank A of MCP23017
           A[7-icol] = 1 #anode of LED to light up set to HIGH

           B = [1, 1, 1, 1, 1, 1, 1, 1] #the 8 bits to send to bank B of MCP23017
           B[7-irow]=0   #cathode set to LOW

           bus.write_byte_data(DEVICE, 0x12, append(int(''.join(str(e) for e in A), 2))) #bank A

           bus.write_byte_data(DEVICE, 0x13, append(int(''.join(str(e) for e in B), 2))) #bankB

           time.sleep(0.001)

Some LEDs lit despite not being 'told so'. From what I read online, this is due to current leakage. For instance, this is a two:

Where does the problem stem from ? :
 - the code?
 - The way I drive the LEDs (should I add transistors? (and why?), should I change the value of resistors? should I add pull-up/down resistors?)

I tried alternating between one LED ON then all LEDs OFF (I set all GPIOs to '0') but that didn't solve the problem.


texts: I have searched on Google but can't find anything. Could anyone please tell me what a maintenance free battery is? Perhaps some examples of maintenance free batteries and any good sites for further research could be provided.


texts: Thermistor alternative using variable resister to identify specs and activate 18v Nicd charger?

texts:
I have a rebuilt 18V DC Powerhandle (battery)and a new charger. The charger won't activate charging likely because of defective foil wrapped component believed to be a thermistor. Can anyone tell me if a variable resister, manually adjusted, can be used to determine thermistor specs for replacement and/or activate charging? I would be grateful for your help!
enter image description here

`


texts: Manual transformer winding - dots convention

texts:
I've already seen this and this. But I can't decide how to correctly wind a SMPS transformer. This is the transformer:

I mantain the same turns direction (CCW if you look at transformer from the top).

I start winding the first half of primary. I consider this the dotted end.

Now I wind secondary in the same direction. Which is the dotted end? On the dotted end I must connect the anode of the fast rectifier diode and I don't know which one is it.

Now I wind the auxiliary. Considering the dot at start is correct?

And finally the second half of secondary. But now I'm winding from the top of the transformer towards its bottom. Is this correct?

The drawings do not reflect the actual number of turns.


texts: What Workbench Safety Improvements Have You Made?

texts: What was your worst electronics workbench accident involving equipment, voltage, soldering irons, chemicals, or whatever else, and what changes have you made to prevent that type of accident from happening again?


texts:
I have a very simple question.

I'm building a circuit that uses some integrated circuits, some of them need 5V and GND, and some like opamps need symmetrical power supply.
In summary, I will need 3 outputs for GND, + 5V and -5V to power the ICs. So I'm going to use a kind of linear source with 2 batteries to convert the 9V signal to + 5V and -5V.
I will use 2 batteries in series as follows:

My question is:

Can I use the output I have named "GND" to power the ground pins of my ICs?

Another question:

On the ground "REF GND", do I need to put some external GND reference?

Note that if I remove this "GND REF" from my simulated circuit in Proteus, I can not get + -5V at the outputs.
I am using the arduino too, if necessary, I can use the arduino GND reference, and put in "REF GND". But is this really necessary?

Last observation. I will not use the 5V pins of the Arduino, because my circuit will need a lot of power, so I have the 2 batteries to power it.

Thanks!


texts: Query regarding system monitor for Xilinx FPGA

texts:
I am stuck at a problem involving system monitor on FPGA . How do I simulate analog input for an FPGA ? The SysMon is like an ADC converting analog inputs into digital .

Can I find a sample for generating the SIM_MONITOR_FILE for the Xilinx FPGA?


texts: Options for getting 3.3v @ 220mA from small batteries

texts:
I have a system running at 3.3v requiring 70mA at most times and 220mA at peaks (roughly 20% of the time). I'd like to find a way to power this from coin cell batteries or other small portable source. Battery life needs to be about 1h but size should be as small as possible (which is why something like AA's won't work)

I see a couple ways of doing this:

Put several 4 button cell alkalines in series and use an LDO voltage regulator to get the voltage down to 3.3v
Use ~3 alkaline button cells in parallel and boost the voltage using TPS61200 (datasheet: http://www.ti.com/lit/ds/slvs577c/slvs577c.pdf). Schematic similar to this: http://www.sparkfun.com/datasheets/Prototyping/LiPower-v11.pdf
Same as the previous one but with the batteries in series. The TPS61200 will regulate down to 3.3v when the batteries are full and boost to 3.3v in the end
Same as above but with a single cell LiPo battery. I'd like to stick to easy to find batteries though. Rechargeability is not important.
Use 3 AAA batteries in series with a voltage regulator (size is a bit of a concern..)

In terms of efficiency does it matter if i put 3 alkaline batteries in series or parallel (TPS61200 can work down to 0.3v with a 0.6v startup voltage)?

So far i tried using a CR2032 lithium battery with NCP1450A (http://www.onsemi.com/pub_link/Collateral/NCP1450-D.PDF) to boost it to 3.3v but the output voltage stays around 1.4v. It may be that something else is wrong in my circuit but from what i understand the battery can't provide enough current anyway (4mA continuous, 15mA peaks) so there's no point continuing that path?


texts:
I'm making my design with Vivado HLs and Vivado and I'm doing some somewhat big transfers between DDR and my custom IP block and vice-versa.

Each transfer from DDR to custom IP is of 256x256x4=262144 bytes and it happens 4 times.

My MM2S (Memory Mapped to Stream) velocity is at 350Mbytes/s and by S2MM is at 200 Mbytes/s.

I know I can get better velocities and I guess these slow ones are related to the parameters of the Axi DMA block.

That's what I came here to ask you, to help me understand which should be the correct parameters since I still can't understand it from reading the logicore product guide.

Width of buffer length n
From what I understand this is the maximum length of the transfer in bytes like so 2^n. So in my case as 2^18=262144 shall I put 18 in here?

Memory Map Data Width
Data width in bits of the AXI MM2S Memory Map Read data bus. I have no idea here. My words have 32 bits and I defined the entrance stream of my block to have a length of 32 bits but what is this?

Stream Data Width
I guess here I should put 32 correct?

Max Burst Size

Burst partition granularity setting. This setting specifies the maximum size of the burst cycles on the AXI4-Memory Map side of MM2S. Valid values are 2, 4, 8,16, 32, 64, 128, and 256.

Again, I have no idea what to put here.

I could do a trial-and-error approach and change parameters until I find the best ones but the problem is that each re-synthesyze and re-implementation in Vivado takes a lot of time...


texts:
We've got an old Arcade machine at work that we're busy converting to being powered by a PC running an emulator. The controls have now been sorted, and audio should be a breeze.

Remaining is hooking its existing screen up to the VGA port on the PC we're going to insert into the cabinet.

Just to give some background, here is the way the Arcade machine looks like. It doesn't seem like a "standard" Arcade machine as it doesn't have any kind of branding at all. We don't know the history of the machine, but it does have a cathode tube ray setup inside.

This is how it looks like from behind the screen:

Now, we identified the output coming from the controller board above, and it has four outputs: RGBES.

Now, I know it cannot be extremely hard to convert RGB to VGA, but I'd like some pointers here. I also don't know what the "E" and the "S" stand for, and I wouldn't be surprised if they are also important.

If we could leverage existing cables available such as typical RGB to VGA adapters that would be swell, but I suspect it's not going to be that easy.


texts: How we can possibly transfer a USART signal(3.3v) over 12 meter cable without any driver?

texts:
I have two atmega328p boards working at 3.3v. First boards read a sensor value and send it to the second board through the USART. The two boards have 12 meter distance. The two boards are connected by RJ45 connector and cable. The cable lines are VCC(3.3v), GND, RX, TX. Two boards are powered from the same battery sitting near to the second board. So the first board will get power through the cable.
Important :- The installing environment will have large rpm motors.
Is it possible to transfer the USART signal without any RS232 driver over 12 meter ?


texts: Point of thin SiO2 layer for surface microstrip?

texts:
Reading some scientific journals I saw that research groups often use a silicon wafer with appropriate dielectric constant/relative permittivity and then build a microstrip (coplanar SGS or edge coupled SG) on it via lithography. While I saw that you can simply order doped silicon wafer with high resitivity (>5000 Ohm cm), I'm wondering what the point of such a thin (300-1000 nm) SiO2 surface layer is?

And if you calculate the impedance of such a waveguide on this substrate, do you still use the dielectric constant of the thick (around 400 um) silicon (around 11.9) substrate, or that of the thin SiO2? The groups operate this waveguide at low voltage, feeding in voltage with picoprobes on the lithographically structured waveguides.


texts: What is the use of the capacitors in this schematic?

texts:
I'm using an STM32L476RG microcontroller where the recommended schematic is as follows -

I was wondering what the purpose of C25 and C22 were, as SB38 and SB32 are shorted on my Nucleo development board. So, what is the purpose of these capacitors when they are shorted?

Since the picture is unclear, I have attached the link to the reference manual here. The schematic is on page 64 of the STM32L476RG reference manual.

Why have they used C25 and C22 when SB38 and SB33 are shorted in the schematic?


texts: Why Electro Mechanical Relay makes controller reset?

texts:
In my current project, I am controlling Peltier Element Temperature which is current controlled load using Arduino. I am controlling Temperature of Peltier by applying PWM to H-bridge.

In addition to this, I have to change the polarity of Peltier Element. For this functionality, I am using two Electro Mechanical Relay. Once Relay starts switching it makes the controller Reset.

What could be the possible reason for this error? And How could I solve it?


texts: Why does my 555 stop oscillating under load?

texts:
I've got a 555-timer circuit. When I examine the output-pin on an oscilloscope, I get a nice square wave.

I want to turn an LED on and off, so I've attached an LED and resistor to the output pin (see image, below). However, the LED stays on. When I examine the output pin again, I find a solid signal, rather than a square wave (see images).

If I remove the LED and resistor, and attach the timer-output to GND, I still see the square-wave (I thought perhaps creating the circuit from output -> GND was the issue). I'm not sure how to determine exactly what is happening, or why.

My questions:

Why is this occurring?
How can I modify my circuit to turn the LED on and off?
What steps could I have taken (before asking here) to further 'debug' my circuit? Using the oscilloscope showed what my issue was, but not why it was occurring.

The circuit:

My wave, before I attach the LED/resistor [sorry for the blurriness]:

When the LED is attached, this is what I get:

Here are some pictures of my breadboard:

When I insert a capacitor (1uF) over the power supply pins:


texts: How do I design the maximum current curve for a stepper motor?

texts:
I want to drive a stepper motor (0.89V/5A) with the L6470H-controller. There I have to set different values for controlling the maximum voltage each for holding, running, speeding up and slowing down the stepper motor in the registers. Now I was wondering if I should choose different settings for the current for accelerating/deccelerating the motor than for running it on a continuous speed. Is there a reason for that, or should I rather simply set all registers to the same value?
While speeding up to the desired running speed, should I increase the maximum current, or should I rather stay at the same level?


texts: How to protect the enable signal (EN) of a car battery powered device?

texts:
I am developing an electronic circuit that will be installed in a car and get its power from the car battery. The circuit will use around 600mA. The device should be turned on when the car ignition is turned on. To protect the device against voltage transients and reverse battery connection I will use this power supply reference design from TI. I'm planning to only use the smart diode controller (LM74610) and the buck converter (LM53603) part of the design, and leave the supervisory circuit and the boost controller out of the design.

My plan was to connect the car ACC wire directly to the enable pin (EN) of the buck converter, so that my device gets power when the ignition is turned on. My question is whether I also have to protect the EN pin from voltage transients and reverse battery connection?

If yes, do I need the full transient and reverse polarity section of the reference design in front of the EN pin or is there an easier way to safely detect voltage in the ACC wire?


texts: power arduino nano with usb external battery charger

texts:
I want to power my arduino nano with my phone external battery charger.
The problem is, when I connect them through a USB cable and turn on the battery charger, it works for serval seconds and then the battery charger turn off.
I was surprised because I didn't think that the battery charger is smart enough to identify the device it connected to. Any ideas how I can bypass it?


texts: Properly wire LED battery level indicator between battery and load

texts:
I'm trying to add an LED battery level indicator to a circuit between the 42-volt battery and a load.  bellow I have attached the link to info on the LED indicator. I'm just unsure of how to connect it to the load.

https://www.dhgate.com/product/round-housing-arc-line-led-digital-battery/385506247.html#cppd-1-5|null:103:r1964942355


texts: Is "switching frequency" measured for a full cycle or half cycles

texts:
Here's a sample datasheet from a FET driver:

http://www.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=ucc27211a&fileType=pdf

Section 9.2.2.5 describes calculating power dissipation.  Obviously the dynamic power dissipation goes up with switching frequency.

However, what I am unable to determine is should I use a full-period or a half-period for this calculation.

I've always assumed that "switching frequency" means "what is the frequency of switching events"

For example if the minimum time between changing states (either from low to high, or high to low) is 2us.  This means a switching event happens every 2us, so the frequency of switching events is 500kHz.  However I've seen several places where the term "switching frequency" seems to imply a full cycle, so the frequency for this would be 250kHz as it takes 4us for it to go from one "low" to the next "low" state.

Which definition is the one that TI is using in this data sheet?


texts: Hall effect current transducer schematic diagram

texts:
What is the function of the amplifier 2 in the below circuit diagram?

HCT-0016 Hall Effect Split-Core Current Transducer: https://www.magnelab.com/products/hall-effect-split-core-current-transducer-hct-0010/


texts: Need help finding the right transistor for a switching circuit

texts:
I have been doing much research to learn about transistors and to find the right resistor/transistor coupling to power a laser driver that I am building. I want to complete the circuit through the 5V/40mA output on an Arduino, as the base, to turn the laser on and off. The circuit will have between 0.2A and 1.25A current flowing through it to power the laser and that will either flow or be cut off by the transistor (the laser driver does not measure voltage, only current.) I want to use the NPN transistor as a switch so it will saturate completely.

Any help with the resistor and transistor I am looking for? I am having so much trouble reading through these data sheets. :/

Here is an image of the laser driver diagram for those who requested!


texts: Understanding a high voltage generator circuit

texts:
I found a thread in the forum about a high voltage power supply 3V to 500V DC converter and someone suggested a circuit from techlib H.V. generator for Geiger tubes:

However,when I tried to simulate it didn't work, the output is nearly 9V, as the input. In the schematic I drew, the only difference with the proposed circuit is that I used an equivalent of 2N4403 transistor and different diodes. I also tried reversing one of the winding connections but nothing changed.
Could someone explain how this circuit works and how the output is affected by the selection of the diodes? Maybe that will also help me understand what's going wrong with the simulation.

Any suggestions?


texts: VHDL 2008 Implicit Condition Operator Error? or Not?

texts:
I found the edaplayground website where it seems you can use a variety of tools (if you know the command line options) to test your code.  Moderate success so far, but when trying Cadence Xcelium 19.09 (the example counter from another thread) it is barfing on the if statement conditional saying...
xrun: 19.09-s012: (c) Copyright 1995-2020 Cadence Design Systems, Inc.
      if (Cnt_En OR not Carry_Out_a) then
                  |
xmvhdl_p: *E,OPTYMM (testbench.vhd,37|18): operator argument type mismatch 87[4.3.3.2] 93[4.3.2.2] [7.2] [10.5].
      if (Cnt_En OR not Carry_Out_a) then
                  |
xmvhdl_p: *E,IMPCOP (testbench.vhd,37|18): Indicated Expression could not be converted to expression of type BOOLEAN using Implicit Condition Operator ?? LRM2008 [9.2.9].

Cnt_En and Carry_Out_a are both std_logic, one an input and the other an output.  NOT and OR are defined for both types and should produce a compatible type (seems it actually returns a UX01 subtype of std_ulogic) which can then be converted to BOOLEAN.
Once again this is working in several tools.  Is Cadence being overly picky or is this really an error that other tools are ignoring.
Then the really important question, why do I keep finding all these issues???
Oh, then the other thing I might point out is it's possible what it's really saying is that it is NOT using VHDL-2008.  Anyone know the command line argument for the various tools to enable VHDL-2008 in Cadence Xcelium?  The Synopsys tool clearly needs VHDL2008 enabled and I can't find the command line option for that either.  Seems looking for the manuals exposes you to web sites that want to infect your computer.
The Aldec Riviera Pro tool unsurprisingly errors out in simulation rather than compile... the EPWAVE tool doesn't understand and complains there is only one "slice" of data.  ghdl won't take the VHDL-2008 command line option I found "--std=08".  Only the Mentor Questa 2020.1 tool happily compiles and runs the simulation with the expected happy results.


texts:
I need an advice.
I just got a DC motor and its controller board.

On the controller board it has 6 pin/wire: +12V, GND, PWM, ENABLE, DIRECTION, SPEED OUT.

What I want to know is how do I interpret the signal on SPEED OUT?

This signal supposed to be carrying information about the RPM speed the motor currently running right?

If so then to interpret it which one I should look, the duty cycle or the frequency of the signal?

How do I know the relation between the signal and the speed the motor currently running?

Do I need to find the relation by testing/calibrate it? (like using tool like digital tachometer?)


texts: In a shunt DC motor, how quickly after losing the field will the armature current increase to its V/R limit?

texts:
In a shunt DC motor, what are the sequence of events when the field current is lost?

From what I understand the loss of the field current, and thus the field itself, will result in a decrease in back EMF on the armature. This will allow a higher current to flow through the armature, and also cause the motor to speed up.

My question is, if the field current is lost through an open circuit and there is no field will the back EMF drop to zero? And how quickly will the armature current thus increase to the limit imposed only by the DC resistance of the wires, matter of seconds or milliseconds?

Thank you.


texts: Designing subtractor using adder in Logisim for 1-bit ALU. How to implement Multiplier in my 1-bit ALU?

texts:
How can I design subtractor using adder in Logisim for 1-bit ALU (Arithmetic Logic Unit)? And also, how can I implement Multiplier in my 1-bit ALU?
Here I tried to make 1-bit ALU which will perform AND, OR, NAND, NOR, ADDITION, SUBTRACTION, Multiplication.

Can anyone solve the problem? What's wrong with my circuit?


texts: Connecting multiple devices and speakers

texts:
I am attempting to connect several devices (Two PC sound cards, CD player, and TV audio out) to two sets of powered speakers. The devices are currently set up using a bunch of 1x3.5mm male -> 2x3.5mm female splitters. I recognize that there is a better way to do this (dedicated receiver), but is there any harm in connecting these devices with splitters? (Note that I am only using one source device to output audio at once.)

My source of worry is that while the sources are all connected to the outputs, they are also connected to all the other sources. Am I at risk of damaging the source devices?

Source devices:

Realtek PCI Sound Card
HP Chromebox
Sony Walkman
Philips TV (the headphone out)


texts: Minimum A/C Voltage to drive 12V regulator

texts: Noob here.  I have a 28V CT transformer.  I want to use it to drive a 7812 and 7912 regulators. The data sheets says min. input voltage is 14.8V.  How do I calculate what the unregulated DC voltage from a bridge rectifier would be?  Thanks.


texts: Mixing two square waves and isolating intermodulation component

texts:
I currently have two square wave signals at f1 and f2 (f1 >> f2) that serve as reference signals to two separate lock-in amplifiers that are subsequently connected in cascade to extract the component of the input signal at f1+f2 or f1-f2.

I am interested in attempting to eliminate one of the lock-in amplifiers, by somehow using the the square waves references at f1 and f2 to generate a phase stable reference at f1+f2. This could then be used as the reference for a single lock-in amplifier to directly detect at the intermodulation frequency.

Of particular importance is that the reference at f1+f2 must be phase locked to the precursor reference signals at f1 and f2. The precursor signals are generated by IR photodiodes that measure light passing through a rotating slit, and are thus subject to small drifts due to the slew rate of the motor, air currents, etc.

My problem is, then, how to generate this reference signal. As square waves, mixing the two reference signals (in a double balanced mixer) would yield all the odd harmonics, which for say f1=50~100kHz and f2=1~10kHz would be hard to filter to give just f1+f2 (particularly in a filter without some highly non-linear phase behavior).

Can anyone recommend a good starting point as to how this may be accomplished? Thank you in advance.


texts: Protecting a tethered floating device from Lightning strikes

texts:
I am building a device, current as a proof of concept, but I would like to have it in place for a long period of time (over a year) with minimal maintenance.

The device is powered by an array of solar cells, contains a microprocessor and other computational devices, and radio/microwave communications. The whole shebang is suspended underneath a weather balloon (with a few of the transceiving components and solar cells connected to the top), and that is tethered to the ground via a 200 meter length of (non-conductive) cable.

My current worry about the device is its longevity. Although in a controlled environment, the device is capable of lasting forever(ish), I am worried about environmental factors, the main being lightning strikes.

So, how can I protect the device if such an event occurs, or avoid it entirely?

EDIT

In the event anyone cares and wants to replicate what I am attempting, I went for the 600g package here on ebay.

Also if anyone knows of a better device (that could hold a greater weight without going into the 100's) that a weather balloon for suspending a device, do shout out (final weight unknown, less than 5kg)


texts: The "Miller" 1381 solar engine circuit problem

texts:
I was following the instructions on this page:
solarbotics.net/library/circuits/se_t1_mse.html

to try to build a "Miller" solar engine, using a solar panel generating ~4V to drive a small DC motor. This is the motor I used:

The schematic of the circuit is as follows, with the 2N3906 and 2.2k resistor removed, and R1 = 0 (as instructed):

I didn't have a 1381 voltage detector, and used a TC54VC3002 instead. Besides that everything was exactly the same. But after connecting the solar panel to the circuit it just won't work, no matter how I tried.

For debugging, I tried replacing the solar panel with a 9V battery and the circuit works well, the motor sucking ~150mA of current, but the 2N3904 was getting extremely hot. So I switched in a TIP120 for the 2N3904 instead. What happened was that when I switched the solar panel back for the battery, the motor actually turned!

Here's the working circuit with the TIP120 in place of 2N3904:

I am very befuddled by this and hope that someone can explain to me, what is the difference between using a 2N3904 and a TIP120 in this circumstance, such that one won't work and the other one does?