Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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1500 questions
52
votes
9 answers

Using volatile in embedded C development

I have been reading some articles and Stack Exchange answers about using the volatile keyword to prevent the compiler from applying any optimizations on objects that can change in ways that cannot be determined by the compiler. If I am reading from…
Pryda
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52
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3 answers

How to drive a Peltier element?

Maybe the underlying question is what the Voltage-Current curve looks like. Can I drive it from a voltage source (like you drive a heater) or from a current source (like you drive an LED)? Or even different than those two options? ADDITIONAL1: Say…
jippie
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52
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9 answers

Why are copper cables round?

Why are cables only made of round shapes? What is the advantage of it? Why aren't there triangular or quadrilateral or pentagon shapes of cables?
Keno
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52
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11 answers

Why three-phase power? Why not a higher number of phases?

Is there a reason, beyond historical reasons, that three phases has become the dominant number of phases? I am aware of the advantages against one phase and two phase, namely the reduced amount of conductor needed, and that motors can provide torque…
Hugoagogo
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52
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2 answers

Why do some diodes have a glass package?

Put simply, why do some diodes such as most Zeners and Schottky diodes have a glass package as opposed to the more traditional plastic package? Is it ease of manufacturing, thermal properties, or some other electrical phenomenon?
Hugoagogo
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51
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4 answers

How to make traces on an universal PCB?

I hope this question won't be closed as too subjective. I'd like to know best practice - how to make traces on universal PCB's with individual holes without traces (like the following image). My idea is to bend the ends of discrete components and…
Al Kepp
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51
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8 answers

Why is digital serial transmission used everywhere? i.e. SATA, PCIe, USB

While looking at SATA, PCIe, USB, SD UHS-II it struck me that they are all the same: digital serial bitstream, transmitted using differential pairs (usually 8b/10b coded), with some differences in link/protocol layers. Why so? Why did this become…
artemonster
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51
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2 answers

Competing PCB Crystal layout recommendations

This is related to this question: How's my crystal oscillator layout? I'm trying to layout a 12MHz crystal for a micro controller. I've been reading through several recommendations specifically for crystals as well as for high frequency design. For…
helloworld922
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51
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5 answers

Why do you need 2 resistors when hooking up a transistor as a switch

What is the point of R2 in the following diagram: I get that R1 controls the current to the Base, but what does R2 do?
Tyler DeWitt
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51
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17 answers

Complete alternatives to the Arduino IDE?

I'm not that big of a fan of the official Arduino IDE (in terms of visuals), so I've started looking for nicer alternatives. However, most of the projects I've found are in alpha/beta and are generally incomplete. I'm 100% new to circuit board…
n0pe
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51
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8 answers

Can a 12V battery give you a shock or not?

I am reading a book called "Make: Electronics" and, on page 9, it says: "Anyone who has dropped an adjustable wrench across the bare terminals of a car battery will tell you that short circuits can be dramatic at a "mere" 12 volts, if the battery is…
Bitcoin Cash - ADA enthusiast
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51
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6 answers

Does pulsing an LED at higher current yield greater apparent brightness?

This question implies two assumptions: The frequency of a switched LED driver is high enough that average power, not instantaneous power, should be used to determine maximum drive current. The limiting factor which determines maximum current at…
Kevin Vermeer
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51
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3 answers

What's the reason to make power supplies external?

Many years ago most electronic devices had internal power supplies only - there was a mains voltage cable running into the unit where mains AC would be converted and distributed for consumption. That was typical for shavers, TV sets, monitors,…
sharptooth
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51
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9 answers

Is a current-limiting resistor required for LEDs if the forward voltage and supply voltage are equal?

For blue LEDs with a forward voltage of 3.3 V and supply voltage of 3.3 V, is a series resistor still needed to limit current? Ohm's Law in this case says 0 Ω, but is this correct in practice? Perhaps just a small value like 1 or 10 Ω just to be…
Craig
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50
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11 answers

How do I improve a simple home-made capacitor?

I was explaining to my son that a capacitor is simply 2 sheets of foil separated by a dielectric and rolled up and he said, "can we make one then?" I'm giving it a go. I used household aluminum foil and some parchment paper. I cut the foil into…
nuggethead
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