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1500 questions
25
votes
3 answers
Difference between Line and Neutral in AC
I want to find out what is the difference between the AC (220 VAC) lines, (phase and Neutral).
As I know that the Alternating Current (AC) has no polarity, so why do we have a "phase" line and a "Neutral" line ?!
Why one of them (the phase line)…
mina_g
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25
votes
3 answers
Why does inverter synchronization with the grid take 5 minutes?
We had some solar panels & an inverter installed recently. Every time the inverter is turned on (after maintenance or with the first light of the day) it has to synchronize its generation phase with the grid, and it is easy to understand.
But why…
dvdmn
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25
votes
17 answers
What is a sine wave?
This came up when a student asked me. A simple question one might think. Except... how to define one without tautology? That is, without using the word "sine" (or cosine for that matter). Wikipedia does not help, although the moving disc might be of…
Dirk Bruere
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25
votes
4 answers
Why use 2.048V and 4.096 as a reference?
On many voltage reference ICs (As an example a MAX610x) there seems to be various different reference voltages available (1.25, 1.8, 2.5, 3.3 etc).
What strikes me as odd are the 2.048V and 4.096V references. Why do we use references at those…
MCG
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25
votes
6 answers
Have I placed too much on this PCB layout?
I am doing my first PCB layout (using Altium) and have finally gotten past the auto-router stage. The result is a mess and there are some missing nets and design rule violations. Have I packed too much on this board or do I just need to re-think my…
user8908459
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25
votes
11 answers
VHDL interview question - detecting if a number can be divided by 5 without remainder
I saw a nice interview question for VHDL - build a system that receives a number and detects if it can be divided by 5 without remainder. I tried to solve that with a state machine (I suppose they don't want you to use mod or rem) and while I did…
nettek
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25
votes
4 answers
Why aren't solenoid/electromagnet windings insulated?
This has been bugging me for a long time. Take this video for example.
I have always thought that electricity will take the shortest path. When the electromagnet's windings are uninsulated, it seems that the electricity would flow straight through…
Joel
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25
votes
4 answers
Short Distance Board to Board Communication
My MCU runs a SPI bus with about 4 devices. I'd like to extend this bus to be off board as well i.e. have some PCBs connect to the "main" board and extend the functionality. The "pad to pad" distance would be:
trace length of main board + Cable…
Saad
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25
votes
3 answers
How is 255 Tbit/s processed in optical fiber communication?
I have never understood how the new record breaking data transfer speeds are achieved in terms of converting from/to electrical and optical signals.
Suppose we have 255 Tbits of data and we want to transfer it in one second. (This is a real world…
stevie
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25
votes
9 answers
What makes a good soldering station
I am a hobbyist looking to buy a soldering station. The market for soldering equipment ranges from $10 to $1000.
This begs the question:
* What is the reason behind these huge price differences?
* What attributes should I look for in a good…
Lefteris E
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25
votes
1 answer
What is this transformer-like component, and why is it not really connected?
Recently, a power surge took out a few components in my PC's ATX power supply. While repairing (I hope), one component in the power drew my attention. I'm an electronics engineer, but I'm confused about it's purpose:
At first sight, it looks like a…
jcoppens
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25
votes
4 answers
How can I quickly and safely discharge a charged capacitor (small and low voltage; <= 42V)?
I am learning how to use capacitors (ceramic and electrolytic from 1pf - 1000uf) and am trying out various experiments using a breadboard. I am constantly adding/removing things to my layout to see what happens... but waiting for a capacitor to…
glenneroo
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25
votes
7 answers
Why do we need resistors in led
I've researched and it says that resistors limit the current flowing through the LED.
But this statement confuses me because we know that in a series circuit, the current is constant at every point, so how come a resistor can limit the current…
vvavepacket
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25
votes
3 answers
How are LEDs considered efficient?
I've always found circuits containing LEDs hard to understand, please bear with me. I know most people find it easy, but I'm confused by them so some of my assumptions might not be correct, please correct me if that's the case.
So onto the question:…
kumowoon1025
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25
votes
5 answers
Why are relays still used in electric ovens?
I bought a new electric fan oven recently. It has a digital thermostat and control system. Yet much to my surprise, I can hear a relay clicking on and off inside it to control the power to its heating element. The oven is rated at 4kW (230V).
I…
nigel222
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