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1500 questions
28
votes
4 answers
How to choose an ARM Cortex M3 microcontroller?
Based on my rough requirements of being in the 36 to 72 MHz range, having 16kb+ SRAM, 128kb+ flash, being programmable in C, I have decided that for my application I want to use an ARM Cortex M3 MCU.
The question is, what criteria do people use to…
JDS
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28
votes
7 answers
NEMA 5-15P blade holes
Why do most NEMA 5-15P (North America 125V 15A) line and neutral blades have holes in them? I've been wondering this for quite some time and haven't yet found a satisfactory answer.
Adam Lawrence
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28
votes
4 answers
Best licenses for Open Hardware
Can anyone give me a rundown of the various licenses that are well-suited to open hardware? I've designed a few circuit boards and would like to make them available for others to use, so I need to choose a license for them.
Things I'm concerned…
edebill
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28
votes
7 answers
Why do PBX systems use -48 V?
It seems common that PBX and other telephone hardware use a positive-ground power supply, where the "hot" line is at -48v. What's the reason for that?
Carl Raymond
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28
votes
7 answers
One large microcontroller, or lots of small microcontrollers?
I'm used to doing basic and straightforward things with microcontrollers, relatively speaking. Things such as driving LEDs, running motors, basic routines, GUIs on character LCDs, and so on, but always just one key task with at most a few little…
BB ON
- 2,304
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27
votes
6 answers
How does an LM7805 voltage regulator work?
How do most voltage regulator ICs work? Are they the same as hooking up a variable resistor and a voltmeter and turning the knob until you get the desired voltage?
joeforker
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27
votes
3 answers
Difference between blocking and nonblocking assignment Verilog
I was reading this page http://www.asic-world.com/verilog/verilog_one_day3.html when I came across the following:
We normally have to reset flip-flops, thus every time the clock makes the transition from 0 to 1 (posedge), we check if reset is…
Void Star
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27
votes
7 answers
Can Peltier devices be cascaded?
Can Peltier devices be cascaded to create a bigger temperature difference? Like mounting one on top of anther one to increase the maximum difference from 60 degrees C to 120 degrees.
pebbles
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27
votes
5 answers
What is the difference between 1N4001 and 1N4007 other than their maximum reverse voltage?
I compared 1N400x diodes here. As far as I see, all of their properties are same other than their maximum reverse voltages.
Their
maximum current
recovery time
reverse leakage current
capacitance
are the same.
It looks like 1N4007 is the super…
hkBattousai
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27
votes
3 answers
What's really the difference between the Cortex-M series and the Cortex-R series?
It's interesting! I searched for find a clear article, but I couldn't find a clear article for this. Also I found this link: ARM Cortex-R and this link: Cortex-R Series but they are not exactly clear. in the wiki page wrote:
The cores are intended…
Roh
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27
votes
5 answers
Differentiation between passive and active components
While I (most of the time) know from experience what components are generally considered active or passive, I have yet to come across a satisfying definition.
Why do we divide electrical components into those two main categories at all?
Some…
Rev
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27
votes
5 answers
Mosfet usage and P- vs N-channel
I'm trying to use an Arduino to enable/disable a 12V solenoid. I used an H-bridge and got that working fine. Then, I decided to simplify things and get a single mosfet instead of a multi-channel H-bridge and have gotten myself very confused. I'm…
kolosy
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27
votes
6 answers
Why do we connect a resistor before a Zener diode?
Why do we need a resistor in a Zener diode circuit, like in the diagram below?
I understand it is to limit the current but how so, and why do we need it for a Zener diode?
Does selecting different values of resistors affect the circuit performance?…
Sherby
- 2,356
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27
votes
3 answers
Does leaving a cell phone on charge all the time weaken the battery, and why?
If I leave my cell phone with the charger plugged in all the time, would this weaken the batter, and why? I've heard that you should only charge the cell phone when you receive a 'battery low' message and leave it off the charger at other times?
The…
Click Upvote
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27
votes
4 answers
Guidelines for determining shock hazard of capacitors
I'm looking for guidelines on how to identify capacitors which have the potential to cause pain, injury or death due to electrical shock if not handled correctly.
I recently purchased a "getting started with electronics" kit from Radio Shack. It…
user2245766
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