Most Popular
1500 questions
30
votes
3 answers
Why do batteries recover after a load is removed?
I carry a small 2-AA flashlight, and a few times, I have accidentally left it on in my holder. Each time it dies completely, so that no light is emitted, but if I turn it back off and wait for a few minutes, the light works weakly again. The…
Daniel
- 403
- 4
- 8
30
votes
6 answers
What is noise gain, really? And how is it determined in the general case?
UPDATE: This question triggered what might fairly be called a research obsession for me. I've gotten pretty close to the bottom of it I think, I've posted my findings as an answer below.
There was a similar question here but it did not ask for nor…
scanny
- 7,122
- 6
- 48
- 88
30
votes
4 answers
Which chemicals can be used to clean electronics?
I have access to these
isopropyl alcohol
ethyl alcohol
vodka
rum
acetone
And would like to know which ones should be used to clean electronics, and (out of curiosity) why some are worse choices than others?
Brian Harris
- 409
- 1
- 4
- 3
30
votes
6 answers
How do electricians know where the line is down?
I had a power outage and I thought about the utility poles near the street. How do electricians know which power line is down considering that there are many miles of them? For example, if there's a car that crashed into the pole and brought the…
netrox
- 403
- 1
- 4
- 4
30
votes
3 answers
Why is there always a capacitor on input and output of a voltage regulator?
Looking at the datasheet I can see that the voltage regulators are not just a zenner diode inside, they are complex devices. I have noticed that there is always a capacitor at the input and another one at the output. An example is the uA7800 series…
quantum231
- 11,843
- 26
- 106
- 216
30
votes
5 answers
Lowest voltage drop diode possible
I am harvesting energy from an NFC device using a tuned antenna on my PCB. Through this method, I am able to generate about 3.05V. I would like to charge a super capacitor using the power harvested from the NFC device. To do this I have used the…
Anthony Phan
- 911
- 1
- 12
- 22
30
votes
7 answers
Is transistor the only electronic component on a CPU?
I have been reading about CPUs recently and came to know that all logical blocks and memory on CPU can be made out of transistors. So is it the only electronic component on CPU?
Edit (Made after first two answers):
But the making of CPU only talks…
Darth Pingu
- 471
- 1
- 4
- 7
30
votes
7 answers
Least expensive way to boost DC voltage
What would be the least expensive way to boost a DC voltage?
The aim is to convert 1.2 V/1.5 V (from an AA/AAA cell) to 3.3 V to power a small 8-bit microprocessor, like Atmel ATtiny45 or ATtiny2313, and also (if possible) 6 V to power a…
bdutta74
- 3,534
- 12
- 47
- 67
30
votes
6 answers
Why does a relay have a minimum applicable load?
I am trying to find relays for my application and I read a data sheet which looks fine but specifies
Minimum applicable load: 10mV 10µA
In my circuit, it is expected that the relay closes but no voltage and current is applied. You can think of it…
Thomas Weller
- 1,049
- 1
- 12
- 25
30
votes
4 answers
Why is it good to slow down digital lines with resistors?
I've heard that sometimes it is recommended to "slow down" a digital line by putting a resistor on it, let's say a 100 ohm resistor between the output of one chip and the input of another chip (assume standard CMOS logic; assume the signalling rate…
Alex I
- 3,431
- 3
- 36
- 62
30
votes
2 answers
ERC error "ErrType(3): Pin connected to some others pins but no pin to drive it"
The following simple circuit gives the following error message
when running ERC check:
ErrType(3): Pin connected to some others pins but no pin to drive it
@ (2.5000 ",4.0000 "): Cmp #PWR01, Pin 1 (power_in) not driven (Net 5)
The CONN_2…
hlovdal
- 1,009
- 1
- 14
- 22
30
votes
2 answers
Do op amps need one bypass capacitor or two?
As with other ICs, it's standard practice to place bypass capacitors near the supply voltage pins of op amps. But I've seen conflicting opinions on how to properly bypass an op amp (here, for example). Some people suggest putting a single capacitor…
Adam Haun
- 21,959
- 4
- 51
- 91
30
votes
6 answers
Serial protocol delimiting/synchronization techniques
As asynchronous serial communication is widely spread among electronic devices even nowadays, I believe many of us have encountered such a question from time to time. Consider an electronic device D and a computer PC connected with serial line…
Eugene Sh.
- 10,041
- 2
- 27
- 41
30
votes
2 answers
Why are the contacts for the Data lines in USB A and B plugs shorter than the contacts for Ground and Power?
I was reading up on USB connectors on Wikipedia and I've noticed that the contacts for the data lines (D+ and D-) are shorter in both the Type A and Type B plug.
What could be the reasoning behind this design?
Wilhelm Schuster
- 313
- 3
- 5
30
votes
3 answers
Should I worry about the risk of tombstoning?
A colleague has (apparently unsuccessfully :-)) tried to convince me of the risk of tombstoning
in the following situation:
He claims pad 1 for R55 and R59 will lose heat faster during soldering because they have two traces leaving, while pad…
stevenvh
- 145,832
- 21
- 457
- 668