# All Questions

118,065 questions
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### How does an ARM MCU Run faster than the external Crystal?

So before this I only worked with simple 8Bit atmel MCU's and I realized on my development's board schematics it has only a 12Mhz crystal. yet the MCU operates at up to 100mhz. (I think the default ...
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### Making lavalier microphone with Esp8266-07

I'd like to make a lavailer microphone and receiver using two Esp8266-07 Wifi modules.I'm using condenser microphone with it's own preamlifier using 5V.I want to compare my signal with 300kHz triangle ...
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### 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 ...
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### 9 volt battery and a 10 watt IR LED

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 ...
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### VI component tester not working good 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 ...
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### Complex Boolean Algebra simplification problem

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}
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### 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, ...
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### 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 ...
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### What’s the disadvantage for solving 5 variable Kmap using overlay and reflection method?

As far as I know solving kmap using Gray code is widely used but is there any disadvantage in it?
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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, ...
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### 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 ...
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### Questions on types K Map

What's the disadvantage of Overlay K Map vs the Reflection K Map and vice versa and what's the differences between these two
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### Which power supply choose for lineal actuators?

I have two actuators each of them with the following characteristics: 16 inch, 12v, load 750 N, travel speed 10mm / s, duty cycle 25% BUT Current Draw is not specified, and I have no access to the ...
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### How do you properly install backup power delivery? [migrated]

I have a backup power bank made of an inverter and car batteries. It charges when the grid power is on and turns on when the grid power turns off. However, my "electrician" repurposed the grounding ...
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### VF Parameter in a Transmission Line

For a lossless line, you have $Z_0=\sqrt{\frac{L}{C}}$ and $VF=\frac{1}{c\sqrt{LC}}$. For a line with R, L, G and C parameters, we have $Z_0=\sqrt{\frac{R+j\omega L}{G+j\omega C}}$. But how ...
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### Relationship of Slip and Angle Between Rotor and Stator Flux for Induction Motor

I know how slip and flux angle individually affect torque of induction motors but I can't understand the relationship between slip and flux angle in terms of torque. Do they both have different effect ...
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### X Ray Transformer with Full Wave Rectifier Design

I current am in possession of a center tapped X-ray transformer that can supply 80 kV and 10 mA. However, I need this transformer to supply approximately 0 to -37 kV DC at around 8 mA. In order to ...
283 views

### Is this resistor leaking? If so, is it a concern?

I found this resistor on the control board of an old Whirpool washing machine: Is that fluid leaking from the resistor? (Why would that happen?) Could it be something like stray epoxy or a chemical ...
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### USART6 STM32F746NG isn't working

I'm having trouble configuring the USART6 in my STM32F746NG. I am setting up the USART6 to enable UART comunication, using the code below to initiate it and also create an echo function. ...
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### What are the differences between triacs?

I need to replace a broken BT134-600E triac. I found out it's 600V 4A sensitive gate triac. Which of the following triacs can be used to replace the original one and why? MAC97A6 MAC97A8 BTA16-600B ...
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### Turn on led-strip parts using arduino [on hold]

I am software developer and I am starting my electronics adventure, so I have a very basic knowledge. As a first project I am thinking about arduino and led-strip. I would like to split led-strip to ...
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### Why does the current in MOSFET have a quadratic function (explain logically without using the integration method)?

The current equation relating Vds ,Vgs and Vt is already known to us ,but if there is any way we can find out how it varies quadratically without using the formulae?
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### What are laser diode drivers used for

When do you need a laser diode driver to power and pulse a laser diode? Is it related to the power it needs or the speed of the pulse? I am looking to use multiple laser diodes which have an output ...
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### Fringe field effect: calibrating vs guard electrode

Which method is more effective at limiting errors associated with the fringe field effect when performing a liquid conductivity measurement, using a guard electrode or using a reference liquid to ...
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### stm32F401re ethernet shield unable to associate IP address

I bought STM32 F401RE and Ethernet shield HR911105A with MCU W5100. I'm not able to configure simple connectivity with it. I have setup all SPI wires and simple code for setting up IP, subnet, and ...
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### USB LPT Converter by FT232R

I am really green and even greener in these topics, but i am trying to create a project which will be converting lpt signal to usb signal via FT232RL. I was searching a lot in internet and i have some ...
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### Does the 969973-3 SMD receptacle need mounting holes?

I am designing a board that uses a 969973-3 wire-to-board receptacle. In its drawing there are specified six 1.2 mm (mounting?) holes. Does anybody know what are they used for? I've seen pictures ...
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### Kirchhoff Voltage Law in a two port network

In a tutorial about h parameters of a two port network, I find the below snippet in the image unable to grasp. According to KVL, the total voltage in a loop is the algebraic sum of the individual ...
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### What are these soldered/un-soldered dotted-shapes? on the traces which don't have soldermask?

Please look at this image(see the soldered/un-soldered dotted-shapes which are identified by arrows). This circuit belongs to a laptop adaptor. What are these soldered/un-soldered dotted-shapes? As ...
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### Why is recombination rate in an intrinsic semiconductor proportional to product of number of mobile electrons and number of holes?

I know that when an electron falls into a hole the number of mobile carriers reduces to zero from two. And when an electron jumps into conduction band the number of mobile carriers increases to two ...
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### How to recognize an OTG USB port on an embedded device?

Sorry for the noob question, I'm trying to flash a new firmware on a tv box with rk3066. The datasheet says that the chip has OTG capability but there are 3 usb ports on the board and I can't tell ...
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### Inferior limit of output voltage in op-amp low-pass inverting amplifier circuit

I'm simulating the low-pass inverting amplifier circuit using LTSpice: I put a sine of amplitude 4 as input to see the behaviour of the op-amp in the non-linear zone. I was taught that the output ...
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### Simple fuzz pedal using breadboard

Complete newbie here. I've been trying to reproduce a simple fuzz pedal using breadboard. Here is the scheme: And here is the current state of my breadboard: The only sound I hear is white noise ...
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### Circuit Diagram with only NAND Gates

I need confirmation that the following circuit diagrams are correct for their Boolean expressions. I've been told that each logic circuit must have a MAXIMUM of 4 NAND gates, however, I cannot manage ...
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### Why are these traces shaped in such way?

Please look at this image(see the PCB traces within the circles). This circuit belongs to a laptop adaptor. What are those parallel soldered-traces on the PCB traces? Why aren't they soldered to ...
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### What will be the real voltage along the line with a voltage source and a capacitor?

Take the following circuit: If I do a simulation of this circuit I get this graph: The strange thing is that in the simulator it gives the same voltage sine wave in the circuit, near the voltage ...
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### Surge arrester placement in substation

Is it enough to place surge arrester on the terminals of the transformer in a substation, or every power line entering the substation should have its own?