# All Questions

118,041 questions
2 views

### Is a PD controller necessary if VBUS is always >5V?

I'm trying to implement a board that will use USB Power Delivery. We want to operate with 20V 5A input. If we know the source will always be at 20V, is it necessary to put a PD controller on the board?...
12 views

### What does DC voltage reading from a DMM mean?

When a DMM is set to measure DC voltage, does it display raw voltage readings or voltages averaged over a time interval? An oscilloscope always reads fluctuations in voltage, but a DMM tends to give ...
24 views

### Missing pulse detector for low input?

I'm looking to implement a watchdog circuit. Tried the standard "missing pulse detector" schematic such as one from http://www.falstad.com/circuit/e-555missing.html - and it works well when the input ...
14 views

### High side mosfet-driver circuit configuration for current bypass

I'm designing a current bypass bms and having trouble switch mosfets between calls When i connect the high side gate drivers and simulate with Proteus the overall voltage appears at the topmost cell ...
40 views

### How can an induction motor be “self starting”

I read that all you need to start an induction motor is to apply the AC voltage, and with time the slippage decreases. How does this happen magnetically? If a rotor, connected to a moderate sized ...
26 views

### Making QI charging desk

i want to make my desk surface qi charger but i want a large surface so integrating a pd wont work. Can i dissatsemble the charger and add multiple coils to it, or i need to buy several charges and ...
34 views

### Controlling An Optical Shutter with Laptop [on hold]

I want to control the light exposure time of a light source using an optical shutter(blocks light beam when closed). My goal is to program the shutter to open for a precise time interval (say 5.25 ...
60 views

### Is using the CH340G on a commercial product a horrible idea?

I'm developing a niche product that will be produced at a fairly low volume (low hundreds). I'm using an Atmega uC, and one of the requirements is the ability to be field-flashable by the user. My ...
20 views

### Triac control circuit through load

Why is it that in every triac analog dimming circuit I find that the triac triggering circuit is fed through the load and not straight from the mains??
26 views

### Bulk header pin wire? [on hold]

Does anyone know where I can find the wire that header pins are made from, or even what its called? Or even what the type of metal would be? I need it in longer lengths, anywhere from a few inches ...
28 views

### What could be the issue with this tesla coil? [on hold]

Trying to troubleshoot this tesla coil we made several years ago. It used to work, and then it didn't. What could be wrong / broken? (To test it we're using the same 13w CFL bulb as in the video). ...
29 views

### Thin CAT6 cable - RFI problems?

I have got a short length (1m) of standard fat CAT5 shielded cable that runs inside a piece of equipment before the signal exits via a bulkhead connector to a PC. It's the old kind that is a real pain ...
24 views

### Washing machine causes noise on PC speaker [on hold]

When ever our washing machine is running, I can hear noise coming out of my PC speaker, the noise is really in sync with the way washing machine spins. I figured this out after a couple of times it ...
25 views

### Which microcontroller for homekit alarm system [on hold]

I have idea to build own PCB for alarm system which should handle following things: GSM (probably via SIM900 or Ai Thinker A6/A7) RFID (most likely external PCB) Keypad (via touch display) Homekit ...
53 views

### How come rectifier diode current waveform is not distorted?

Shockley equation is non-linear but without any linearisation effort such as in BJT small signal biasing, half wave rectifier passes almost an undistorted half sine wave. In amplifier we bring the ...
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### How to program aliexpress Xilink X-SP6-X9 FPGA? [on hold]

I am new to the world of FPGA's. I just bough a Xilink X-SP6-X9 (Spartan 6) board on aliexpress but I don't know how to program it. I got this one: https://aliexpress.com/item/32665068263.html?spm=...
14 views

### EZ430 Chronos wireless on battery vs usb power [on hold]

I have a Texas Instruments EZ430 Chronos watch, and I have an issue regarding the Chronos wireless (or RF) communication on battery power vs USB power. When I put the watch on ACC mode when on ...
64 views

### Is this symbol standardised?

Sometimes there are these two half-arrow symbols on PCBs and on enclosures. See the images, for examples. Those symbols are often placed near the screws, that are to be unscrewed upon disassembly. ...
45 views

### Constant current load circuit? (20 amp)

I'm pretty new to stack exchange and I've only just gotten my basic circuit analysis classes done in college. For my school's solar racing team, I've been tasked with designing a constant current load ...
30 views

### Understanding 3ph Transformer Specs

I am looking at a Delta-Wye with 480 on primary and 208/120 on the secondary. The transformer in question is Schneider's EX30T3HCUNLP. I came across this drawing in the spec sheet but I am not sure ...
32 views

### Itsy Bitsy M4 Locked

I am tryning to program adafruit Itsy Bitsy M4 Board using Atemel studio 7. I am trying just to program freeRTOS example through Ateml Studio. I have bootloaded the Board properly. When i am trying to ...
44 views

### Frequency Divider Analog Circuit issue

I am trying to implement a divide-by-two circuit quoted from the book "Low power CMOS circuits : technology logic design and CAD tools" by Christian Piguet Could anyone advise about the spice error "...
39 views

### Mosfet pinchoff, why the n-channel moves towards source?

Suppose we have an NMOS transistor with VGS> VT. When VDS is 0, the channel depth is uniform along the transistor. However, when we increase VDS, the channel becames deeper near the source and ...
33 views

### Phase control universal motor dimmer

I need to control the speed of a 220v universal motor using arduino and I am thinking to use an atteny85 ic with a phase control circuit (ltv814 to detect zero crosses and moc3052 to drive a triac to ...
89 views

### how can homeplug device send ethernet down mains wiring

AFAIK when you wire a patch cable out of 5e, you only need to wire two of the conductors correctly for it to function as a ethernet cablebut you won't get gigabit ethernet. However Homeplug uses ...
409 views

### How does an ARM MCU run faster than the external crystal?

So before this I only worked with simple 8 bit Atmel MCUs and I realized on my development board schematics it has only a 12Mhz crystal, yet the MCU operates at up to 100MHz. (I think the default is ...
33 views

### Making a wireless lavalier microphone with ESP8266-07

I'd like to make a lavailer microphone and receiver using two ESP8266-07 Wifi modules. I'm using a condenser microphone with it's own preamlifier using 5V. I want to compare my signal with 300kHz ...
14 views

### STM32 RTC with HAL libraries

I am working on stm32l053 (nucleo 64) and I want to track time with integrated RTC. Since I am quite new to stm32 development I am using CubeMX and HAL libraries. My problem is that the time is not ...
51 views

### 9 volt battery and a 10 watt IR LED [on hold]

I connected a 9V battery to a 10V IR led and the brightness lasts 3 seconds before "dimming" down to a soft glow. How do I maintain the initial brightness? Do I plug in a few AA or do I buy a 30 or ...
39 views

### VI component tester not working properly when capacitor is placed parallel with diode

I am trying to repair mainboards with VI component tester. (Such as this device and that device.) I check the characteristic VI curves of the components on the card and identify the defective parts ...
40 views

### Complex Boolean Algebra simplification problem [on hold]

Anyone has a solution on how to continue this simplication? \begin{align} X &= \bar R \bar S \bar T \bar u + \ldots \\ &= \bar R \bar S (\bar T\ldots)+ \ldots \end{align} Attempted but don'...
38 views

### I2C Communication Between STM32F3 and SSD1306

I am trying to write data to my 128x32 OLED display. I researched it online and found that it has the SSD1306 controller connected to the display. It uses the I2C protocol and it only has 4 pins (VCC, ...
203 views

### analysis of BJT PNP type - why they can use voltage divider?

Hi everyone, I try to understand why some books used in a voltage divider to find the Base Voltage? or maybe the right question is HOW they can use voltage divider if there is base current? what I ...
26 views

### What’s the disadvantage for solving 5 variable Kmap using overlay and reflection method? [on hold]

As far as I know solving kmap using Gray code is widely used but is there any disadvantage in it?
35 views

### Power rating of a UPS

I find it odd that manufacturers specify power rating of Uninterruptible Power Supplies (UPS) in VA instead of Watts since VA doesn't tell you how big of a load the UPS can supply. A case in point is ...
28 views

### GAN FET gate current requirement

I'm looking for advice in making sure the FET driver I've chosen is capable of driving the FETs I've chosen with turn on time as low as possible. I'm going to use the LMG1210 and EPC2020 with 12V ...
48 views

### CPU architecture

im very new to CPU architecture! I wanted to ask, what is the Data memory component in the image below, is it writing/reading to and from RAM or Cache? And also what is the sign extend used for? I ...
243 views

### Is there a down side to setting the sampling time of a SAR ADC as long as possible?

In configuring the sampling time for the internal ADC of a micro-controller (STM32F446RE) to sample the output of a current sensor connected to a PWM controlled motor, the sampling is triggered at ...
52 views

### What is the cost of converting 12V (lead acid battery) to 220V and back again to power 12V appliances?

I have a small house measuring ~ 8m x 4.5m. It is in Indonesia and power outages are expected daily. Probably the daily power outage is on average less than half-an-hour, but sometimes the outage can ...
2k views

### Placing bypass capacitors after VCC reaches the IC

I have a question about bypass capacitors and their possible placements. I am designing what I hope to be a double sided PCB, which has the VCC and the vast majority of the data lines on one side, ...
77 views

### Short Circuit Question

I know that static electricity can damage components, even if it does not destroy them or “break them” studies and tests have shown that it could decrease performance even a little if no noticeable ...
15 views

### Questions on types K Map [on hold]

What's the disadvantage of Overlay K Map vs the Reflection K Map and vice versa and what's the differences between these two
43 views

### Linear Regulation Concept Confusion

I was watching one of Jacob Baker's videos (http://cmosedu.com/videos/f10/ece5472/lec1_ece5472_video/lec1_ece5472_video.html) At minute 19:30, he explains the concept behind linear regulation: His ...
59 views

### int functions with no return statement

In a course I am taking on embedded systems, I program LPC1768s which are based on ARM using C. The main functions are always of int return type. However, there ...
16 views

### Interfacing with tft lcd(ILI9225) via SPI

As an exercise, I'm trying to make a driver for ILI9225 TFT LCD using SPI. (This one https://www.amazon.com/HiLetgo-ILI9225-176x220-Support-Arduino/dp/B00LSG5HI0) I consulted a datasheet of ILI9225 ...
356 views

### An overseas company is making a machine for me and they need to know whether I want 1,2 or 3 phase and what voltage

I'm in Quebec and the company making the machine is in China. The machine is an industrial sized T-Shirt sublimation machine that does two sided printing. So there's a large heated plate that is ...
33 views

### General open license PCB GPS antenna

Is there a basic passive GPS reference antenna design that would be considered fair-use or "free to use" that can be placed on a PCB as a strip antenna or patch antenna? I'm looking not to violate ...
30 views

### Low power 100MHz sinusoidal modulation laser driver [on hold]

I am looking for a low powered laser driver which can modulate pulses at 100MHz sinusoidal. Is this possible, something that you have come across or possible to custom design. I am looking for ...