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1500 questions
37
votes
10 answers
If Infrared not visible, why the red LEDs?
If infrared light is not visible to the human eye, why do most tv remote controls and security cameras appear to have a visible red colored LED lit when the infrared light is being emitted?
Is that visible red light present as a convenience…
dtmland
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37
votes
9 answers
Fast and memory efficient moving average calculation
I'm looking for a time and memory efficient solution to calculate a moving average in C. I need to avoid dividing because I'm on a PIC 16 which has no dedicated division unit.
At the moment, I just store all values in a ring buffer and simply store…
sensslen
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37
votes
3 answers
What does 232 signify in the RS232 standard?
"RS" in communication standards RS232 and RS485 stands for "Recommended Standard". But what information does "232" or "422" or "485" convey in the name? What naming convention is used for numbers succeeding the letters "RS" when naming the RS…
Sonam
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37
votes
11 answers
I'd like to learn how to make my own USB gadgets
I've been writing Linux character device drivers for other people's stuff for some time. I'd like to find a new hobby and the thought of making my own USB gizmos seems really neat.
I would be thrilled to be able to control some LEDs, servos, and…
Tim Post
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37
votes
2 answers
"Tristate a pin"
What does it mean to "tristate a pin" on a CMOS microcontroller?
J. Polfer
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37
votes
2 answers
How does a laser printer control the laser to produce such high resolutions?
I opened up a broken laser printer yesterday to find one of the important sections (this is an example photo from Google Images), trying to learn from the design of the laser+polygon mirror motor within:
I was able to find the pinout of the driver…
sasha
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37
votes
3 answers
What does "no clean" solder actually mean?
I bought some solder that says it doesn't require cleaning. The description specifically says "Eliminates the need and expense of cleaning". But there's still a lot of some substance left on my board that I can't easily clean off. What is this…
Stephen Collings
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37
votes
7 answers
Is circuit design based on min/max values good practice?
Time and again I am arguing with a colleague of mine about the question above. When I design a circuit for mass production (> 10k/a) I want to make it robust against every possible variation of component parameters that I know about. This means for…
christoph
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37
votes
1 answer
Why does my AVR reset when I call wdt_disable() to try to turn the watchdog timer off?
I am having a problem where executing a disable watchdog sequence on an AVR ATtiny84A is actually resetting the chip even though the timer should have plenty of time left on it. This happens inconsistently and when running the same code on many…
bigjosh
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37
votes
7 answers
Why does the USA use 110V and UK use 230-240V?
Why does the USA use 110V and UK use 230-240V? What are the advantages? Explain me with calculation. Why do they use different frequencies like 50Hz, 60Hz? What is the reason?
user43153
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37
votes
5 answers
What's the difference between a potentiometer and a rheostat?
I've seen that a number of schematics will connect the center (common) pin of a potentiometer to one or the other leg, and it then functions more like a rheostat. Is that how a rheostat is wired internally? What's the difference between a…
JYelton
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37
votes
9 answers
Organizing electronic parts?
I've got one of these cabinets, which I intend to use for storing electronic components:
It has 24 drawers (each 175 x 69 x 37mm).
Every drawer can be subdivided into up to six compartments by installing dividers.
Can you suggest a good system for…
NPE
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36
votes
7 answers
When people talk about a device "drawing" current, what do they mean? Why do devices under load "draw" more current?
In my (extremely rudimentary) understanding, the amount of current flowing in a circuit is determined by a) its resistance, and b) the voltage of the power source (voltage from beginning to end), which forces the charge to flow through.
Why then, do…
Chris Cooper
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36
votes
6 answers
Do electrolytic capacitors have a limited shelf life?
Do electrolytic capacitors have a limited shelf life? I would like to know for both aluminium and tantalum.
stevenvh
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36
votes
2 answers
What is Manhattan routing?
In an answer by The Photon he mentions 'Manhattan routing' in regards to PCB design. I haven't found a lot of relevant information about this term on the internet; therefore the question: What is Manhattan routing?
m.Alin
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