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1500 questions
22
votes
4 answers
Why does a mouse need a crystal?
I was looking at this schematic for an old (pre USB) mouse:
when I noticed it had a crystal on it (Y1). I was curious why a mouse would need a timer? Wouldn't it be able to use the clock from the computer? Also if it has its own crystal couldn't…
Tyler Hilbert
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22
votes
2 answers
Why are many IR receivers in metal cages?
I'm guessing it's a Faraday cage around the receiver, but don't know why they might need one. Is there some sort of common interference around 38kHz (their operating frequency)?
It's the only component I think I've used that gets this special…
R Zach
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22
votes
4 answers
Energy in capacitors - loss?
The energy stored in a capacitor is
$$ U= \dfrac{1}{2} CV^2 $$
So when I have a 1F supercap charged to 1V the energy is 0.5 J. When I connect a second supercap, also 1F in parallel the charge will distribute and the voltage will halve. Then
$$ U…
Federico Russo
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22
votes
7 answers
Staying in Phase On The Grid
I have been an EE for over forty years and never did find out the right answer to this one....
How do power-stations and transformer switching stations ensure that the power they are feeding into the grid is in-phase with the existing power on the…
Trevor_G
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22
votes
8 answers
Pre-programming surface mount ICs
I'm trying to set up a PCB with an atmega168 and no programming header. I intend to use a serial bootloader (there is a ft232 on the board) to reprogram but I am wondering about the best way to program the bootloader on. Has anyone else tried this…
jeremy
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22
votes
2 answers
Difference between a rectifier diode and signal diode
Can somebody please explain to me the differences between a signal diode and rectifier diode in terms of their electrical characteristics and their Lissajous patterns? I know that Shockley's equation is used as the mathematical model for the general…
D Brown
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22
votes
5 answers
Effect of bootstrapping in amplifier circuit
I am trying to understand this "bootstrap bias" amplifier circuit. The picture below is adapted from the book "Transistor Techniques" by G. J. Ritchie:
This circuit is a variation of the "voltage divider bias", with the addition of the…
favq
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22
votes
11 answers
When is it okay to exceed the absolute maximum rating on a part?
I've always thought that the absolute maximum ratings on a part are the limits that thou shalt not violate. Period. End of story.
However, another engineer is making the case that it's okay to exceed the absolute max rating for the input voltage…
CHendrix
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22
votes
5 answers
Why do people use AT commands in serial communication?
I need to know why people in embedded systems use AT commands?
When I have asked people say that it is a standard.
So my question is: What does "AT" means? Why do people keep saying it's a standard?
xsari3x
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22
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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22
votes
3 answers
Dual-SIM phone, do they use 2 GSM modules ? Anyone has high level schematic?
As an slight extension of my project, I am trying to see if I can improve connectivity resilence by using a dual-SIM approach. Dual-SIM phones (or Tri-SIM, quad-SIM phones) are quite popular in many developing countries, and AFAIK, most are based on…
bdutta74
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22
votes
7 answers
Identify processor type from raw binary code?
Not really related to chips, but hopefully I'll get some directions to follow from here.
I got a chunk of code, but I don't know what processor it intended for.
Are there tools available that can help me identify the code type?
What statistic…
mentalist
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22
votes
8 answers
Why don't we have more registers in microprocessors?
Registers are theoretically not required; all microprocessors would still work without registers. But this seemingly trivial addition has helped make microprocessors more efficient.
Why can't we have more registers to further extract benefit from…
Darshan Chaudhary
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22
votes
3 answers
Why does an inductor behave as a capacitor at high frequencies?
In truth, I've only been told this anecdotally by an instructor, but can someone explain the physics at play?
I have been told that if an inductor is driven at a high enough frequency, it will begin to behave as an capacitor, but I cannot figure out…
Michael
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22
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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