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1500 questions
23
votes
2 answers
Why would you short two pins of a potentiometer?
I've found a potentiometer which controls the heat of a cook top. One of the outer pins and the centre pin were shorted with a soldered jumper.
Why would someone do that? What does this achieve?
user1937747
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23
votes
5 answers
Cheapest ARM with an MMU
What is the cheapest ARM processor with an MMU so I don't have to use uCLinux?
Bonus for non-bga and integrated RAM/Flash
stbtra
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23
votes
8 answers
Why do USB connectors only fit one way?
Why do USB plugs only fit one way into USB ports?
Forgive my ignorance, but there are several types of plugs that are "omnidirectional" and do not have to be oriented a certain way to fit into the corresponding plug (pursuant to shape). In the case…
joelpt
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23
votes
2 answers
What happens when a device draws more current than the power supply can provide?
I am more of a software programmer, but I have a basic question on electronics.
What happens when a device draws more current than the power supply can provide?
And under what circumstance can it happen - bad board design or not determining the…
user7441
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23
votes
4 answers
Differences between thermistors and thermocouples
As I understand it, both thermistors and thermocouples are temperature sensors. So what are the advantages/disadvantages of using one over the other to measure the temperature?
What are the specific applications for either of the sensors?
m.Alin
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23
votes
2 answers
Why would you stack a resistor and capacitor on top of each other?
I've inherited an charge amplifier/shaping circuit from my predecessor. When he wanted to make a low-pass filter with current-to-voltage conversion, he had a standard circuit like:
simulate this circuit – Schematic created using CircuitLab
He…
Seth
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23
votes
7 answers
Why are batteries measured in ampere-hours but electricity usage measured in kilowatt-hours?
I was reading about energy usage in batteries and don't quite understand why it is measured in different units than home electrical usage. An ampere-hour does not include a measure of volts. But my understanding though is that a battery has a…
Alexis K
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23
votes
2 answers
Why are there 3.15A fuses?
Why are there 3.15A fuses?
Did someone decide that \$\pi\$A was a good rating?
Or is it \$\sqrt{10}\$A they're aiming for?
Is it even possible to make fuses with better than +/-5% tolerance?
Jasen Слава Україні
- 33,738
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23
votes
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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23
votes
8 answers
Suggestions for small and handy connector for in-circuit programming?
I have many PCBs that use an AVR in SMD packaging, and since I frequently change the firmware in prototype boards, I'm trying to come with the best solution to program the AVR quickly and easily.
The first approach was to have a standard header (2x5…
fceconel
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23
votes
3 answers
How to chose via diameter and drill size based on trace width
I am designing a two layer board, the problem is I do not know how to select via diameter and drill size, as well as outer and inner diameters.
In my circuit I use 056, 012 and 006 mil traces:
I have asked the manufacturer, they said they can…
Dumbo
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23
votes
1 answer
SPI bus termination and pull-up resistors
My microcontroller (ATMEL series) needs to communicate to a slave device using SPI protocol. I am designing the hardware. The maximum SPI bus speed is 1 MHz. The distance between the master and slave is less than 50mm.
Q1) Do I need to add…
Bharav
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23
votes
5 answers
How can a capacitive touch screen be triggered without human contact?
I want to robotically touch an iPhone screen without any human intervention.
I've done some experiments but have not found a reliable solution. It seems even styluses that work through gloves still rely on the capacitive characteristics of the…
Tom R
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23
votes
3 answers
JTAG debugging AVR
Can anyone advise what hardware and software is required for debugging AVR in circuits?
JohnC
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23
votes
4 answers
What is the objective of a base-emitter resistor?
What is the purpose of the resistor \$R_2\$? If I remove \$R_2\$, the circuit will perform the same result, won't it?
simulate this circuit – Schematic created using CircuitLab
ferdepe
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