Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [variable]

120 questions
23
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7 answers

Is there such a thing as rubber band resistor?

I'm doing a project with some tight requirements, in which I need to measure the distance between two points, which might not be in direct view of each other, and on parts that are too small to mount anything on them. An elegant solution would be to…
Drath Vedro
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4 answers

Why is home voltage value higher during the night?

I have been monitoring the voltage in my own home (Mexico 120V 60Hz). I have been graphing the values every minute and I'm starting to notice that during the morning voltage gets up to 127, and during the day (4pm) it can go as low as 118V — why…
GoatZero
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2 answers

What is 'unsigned char near'?

I read a datasheet and I found variable defined as unsigned char near Sample_X. What is this, and how does this differ from unsigned char Sample_X?
oppo
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11
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3 answers

Variable declaration with @ in C

I am reading some C code and came across this declaration in the program: unsigned char serv_ctr @0x0002; Can someone point me to documentation, or explain what the "@0x0002" is for in the Mplab XC8 v1.35 C compiler?
be-ee
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9
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4 answers

Voltage Regulated by Resistor in Generator Circuit

So I am tinkering with making a circuit that will allow a motor to generate power to charge a battery. I have this, what I presumed to be an, AC induction motor I salvaged from an old Christmas decoration. After removing the motor from its casing,…
Ninjas Kill
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7
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5 answers

where are constant variables stored in microcontroller?

As per the memory layout of C program ,constant variables are stored in the Initialized data segment of the RAM. But as per some of the Microcontroller memory layout ,const variables are stored in FLASH Memory. I have also seen that the size of BIN…
Arun Joe Cheriyan
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6
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3 answers

Design of a switchable dual voltage power supply

My project would benefit from power supply with two modes selected by a switch. The 'normal' mode is full voltage (±13.5V) at full current (~5A), the 'high' mode is double voltage (±27V) at half current (~1.8A, see note 2). I came up with pretty…
Eugene K.
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5
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2 answers

How to save variables inside microcontrollers memory

I am designing an application which include GSM SIM900 with PIC18F2520. The application includes basic calling and sms services. A user will press a button a call will be made to a defined number. This number can be changed via sms. So whenever the…
S Andrew
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4
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3 answers

Can a buck converter provide a lower voltage based on a target differential - instead of an absolute target?

I have an application where I need to provide a lower voltage from a starting voltage. In other words - I need a buck converter. My question is - if I have a known required differential but a potentially variable input voltage how close to my target…
Daniel Miller
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4
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3 answers

Is this a variable resistor?

I acquired a lot of vintage electronic components at an estate sale. The sale included a dozen of what may be variable resistors. These components are all the same size and have the same plastic mounts. The code on the bottom varies but the last…
Roger
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4
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2 answers

Variable field magnet motor?

See the video in the following link: https://www.youtube.com/watch?v=olnXy-J48SY "Variable field magnet motor" How does this work and is it actually efficient?
FatalSleep
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4
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High voltage variable capacitor design

I’m building a homemade small magnetic transmitting loop antenna that I want to ultimately operate at up to 1500 watts over the HF ham radio bands. One of the challenges with these antennas is the high voltages present at the variable tuning…
rbraddy
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4
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Why does Modelsim say that VHDL shared variables must be protected?

So I created a shared variable in a purely non-synthesizeable code. When compiling ModelSim generates a warning: (vcom-1236) Shared variables must be of a protected type. Why is it a warning and not an error if the shared variable must be…
quantum231
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State Space Model for Variable Mutual Inductance

This is a hell of a request, but today I have recently introduced myself to the concept of the 'State Space' model. I've understood, to a basic level, how state space models work and I am convinced that state space is the correct method to progress…
Vhaanzeit
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Confusion with variable update in microcontroller programming

I use an STM32 microcontroller board and to summarize the question, in the following code inside the if clause the variable called current_val does not take the value it is assigned some lines before: int main(void) { //initialization code while…
user1245
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