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1500 questions
25
votes
1 answer
PCB layout questions for MCU breakout board
I'm attempting to route a board that is, essentially, a breakout for the LPC23xx/LPC17xx MCU. I've never routed anything approaching this complexity before, and I have a few areas of concern. I know that a four-layer PCB would be optimal, but I'm a…
Mark
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25
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5 answers
How do electronic devices keep track of time without power?
There's laptops, PCs, microcontrollers and a lot of other things that can be plugged out and plugged in without a battery. But how does the system clock still keep track of time without anything to power it?
Loogai
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25
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4 answers
How can a high-voltage transistor be in such small packaging?
For example:
STN0214 - Very high voltage NPN power transistor
It is said to accept more than 1 kV between its collector and emitter. It comes in a SOT-223 package (3 pins plus a tab). With a dielectric strength of 1 kV/mm for humid air, cannot an…
julienfr112
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25
votes
1 answer
Is my MOSFET-based bidirectional level shifter insane?
In a moment of cheapness, I decided not to order a 5v to 3.3v level shifter from Sparkfun, but instead to put it together myself. The original schematic used a BSS138 MOSFET, but since I enjoy surface-mount soldering about as much as root canal…
Jon Bright
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25
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6 answers
How to Transition from "Basic" Microcontrollers to ARM Cortex?
I have many years of experience with 8-bit cores from various manufacturers - namely 8051, PIC, and AVR - and I now have a Cortex M0 to figure out. Specifically this one, but I hope we can be more general than that.
It's turning out to be a bit…
AaronD
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25
votes
3 answers
How to drive a MOSFET with an optocoupler?
What's the proper schematic for driving this IRL520NPbF MOSFET from a microcontroller pin through this CNY17F or this SFH6206 optocoupler?
The MOSFET will drive a motor @ 24V, 6A.
m.Alin
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25
votes
5 answers
Why are consumers located near high-voltage lines typically not connected to those lines but instead are connected through a lower high-voltage line?
A typical grid uses 110..500 kilovolts lines to deliver electricity to substations which lower that to 6..20 kilovolts and then lines with that lower voltage get to consumers where yet other substations are located which finally lower those 6-20…
sharptooth
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25
votes
2 answers
Single supply op-amp audio amplifier
I am trying to create an op-amp amplifier that would work from single 5V supply, and would be able to amplify -100mV to +100mV audio signal to around a 1V peak-peak or so. I've came across this circuit from this article, that could seem to work, but…
Golaž
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25
votes
11 answers
Why is sine wave preferred over other waveforms?
Why did scientists chose to go with sine wave to represent alternating current and not other waveforms like triangle and square?
What advantage does sine offers above other waveforms in representing current and voltage?
Rookie91
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25
votes
8 answers
Why are some AC outlets and plugs polarized?
This will show my naivety when it comes to alternating current... but why are some plugs and sockets on AC outlets polarized (one prong is taller than the other)?
(See this question on DIY.) (Or this one.)
My thought is that if the current is…
JYelton
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25
votes
8 answers
How do you attack a new board?
You get your PCB back from the manufacturer. It is a new design, you have of course bread-boarded all the major parts, but you know there are going to be problems. There are just too many things that can cause problems, e.g.:
Errors in the…
morten
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25
votes
6 answers
Why is three-phase offset by 120 degrees?
For three phase electricity the wave is offset by 120 degrees(2\$\pi/3\$ Rad). Why aren't the phases closer together? Is it because it will affect the frequency of the phases? How was this 120 degrees chosen?
Dean
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25
votes
2 answers
6 Band Resistors, which way should the bands be read
I've just bought a bag of random resistors from Maplin, and can't work out which way round the six band ones should be read.
For instance I have one which is either:
Violet Orange Red Brown Brown Red
or
Red Brown Brown Red Orange Violet
The red…
Amos
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25
votes
8 answers
What happens to excess energy fed into the power grid?
The closest question to this is Linear useage of excess power generation.
I'm no engineer so I may not be able to phrase this correctly and would appreciate an answer which assumes minimal background knowledge (I have only a basic understanding of…
cluelesscoder
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25
votes
4 answers
Long-Life Electronics
i was wondering for a project of mine if i can order components
that are made for a long time of usage. would Mil-spec components fit under this
category?
What i basically want are parts that are good for a very long time, and have a very high…
DownCount
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