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1500 questions
29
votes
3 answers
Odd PCB Layout for Voltage Regulator
I am reverse-engineering a board which has a Xilinx Spartan 3E FPGA, with VCCAUX powered by a 2.5 volt regulator. Below is the PCB layout for the regulator part of the circuit, and something seems very fishy to me.
My apologies for the horrible…
DerStrom8
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29
votes
13 answers
How can I wire a 9-position switch so that each position turns on one more LED than the one before?
I have a 9-way switch like this guy:
And I'm trying to figure out how I can turn on one LED with position 1, 2 with position 2, all the way up to all 9 in position 9.
Obviously I can repeat all the wiring for the LEDs at each position, but that…
Isaac Lubow
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29
votes
3 answers
FCC and CE Testing / Failure Resolution
I'm seriously thinking about (practically committed to) taking one of my products through FCC and EC testing and it's my first time doing so. It's Arduino based electronics running off a 16MHz crystal with an Ethernet Controller running off a 25MHz…
vicatcu
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29
votes
5 answers
Why does a single AND gate need 60 transistors?
Looking at the datasheet for the MC74VHC1G08, under the features section, it states Chip Complexity: FETs = 62.
Why does this IC need 62 transistors, while an AND gate can be made with only 6 transistors?
What are the other 56 transistors being…
eeze
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29
votes
5 answers
I've become an electrical conductor for my headphones... but how?
So I have a pair of Bose noise-cancellation headphones that I plug into my keyboard every night to charge them (via my keyboard's USB port). My keyboard happens to be a metallic Apple keyboard. You will see why this may be important to note…
GDP2
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29
votes
3 answers
Are audio cassettes FM or AM?
I know that cassettes store an analog signal, but is the signal Amplitude-Modulated (AM) or Frequency Modulated (FM)?
Ian Rehwinkel
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29
votes
8 answers
Where exactly does the power company cut my power when I fail to pay my electric bill?
I only have a somewhat vague understanding how the electrical grid works. I know the basics of energy production, and that the electricity comes to our homes using power lines resting upon those big supports we see everywhere. I would imagine the…
S. Rotos
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29
votes
9 answers
Why not implement 1Gbps, when all I need is 20Mbps?
Background
I am working with a client on a large project which requires a custom networking chip to be designed to solve the data transfer requirements within the project. The network is intended to send small packets a few inches from one PCB to…
Rocketmagnet
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29
votes
7 answers
What's the purpose of these two diodes in this circuit?
What's to point of using these two diodes? Can't you just replace them with a resistor?
Michael Koeppen
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29
votes
5 answers
Standard wire colors
I am fairly new to "electrical" engineering as a hobby/ past time. I have always loved electricity and have made simple circuits since I was a little baby.
I am now working on one of my first arduino projects and I started thinking about what…
Sponge Bob
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29
votes
6 answers
Does this photodiode circuit work?
Oli used this circuit
in an answer, and it pops up a lot on Google images too. But does it work? If it does a theoretical explanation will be welcome.
stevenvh
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29
votes
6 answers
How can the contact points of jumper cables handle the hundreds of amps required to start a car?
When jumpstarting a car, you connect those big alligator clamps to the terminals of the batteries. The cables themselves can handle the current just fine, but the contact points between the alligator clamps and the battery is extremely small. I'd…
Daffy
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29
votes
2 answers
What are the RAM-only microcontrollers intended for?
While looking for some detailing on part number construction for Texas Instruments's MSP430 series, I came across this wiki page: TI MSP430
There is a statement,
"L" as in the MSP430L09x series, which indicates a RAM-only part; it must remain…
WedaPashi
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29
votes
5 answers
How to create measurement points on a PCB for diagnostics?
What is the best way to implement a point on a PCB, where a voltage (e. g. output of a regulator) could be measured with multimeter for the purpose of verification of the assembly or diagnostics in case of malfunction (preferably in Eagle)?
Andrey Pro
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29
votes
3 answers
Why are resistors tolerances relative instead of absolute?
Every resistor has a tolerance, this provides the user with an idea of the accuracy of the product. This tolerance is represented by a percentage. This means: a big value resistor will be less accurate than a small resistor with the same…
M.Ferru
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