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1500 questions
24
votes
4 answers
Do ‘wiperless’ potentiometers exist?
Potentiometers are renowned for wearing out (at least in my experience); the little wiper eventually just wears its contact and nolonger has a firm electrical connection. For an audio device, this can manifest as a crackle when changing volume. The…
James Haigh
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24
votes
9 answers
fastest way of doing on/off-modulation of a LED?
I need to modulate a LED quickly (multi-megahertz range) on/off. It's a high-power LED. I have had some trouble locating any well-known methods to do this. Simply switching the voltage with a FET turns on the LED quickly but the fall-time will…
Bjorn Wesen
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24
votes
1 answer
What's input bias current in opamps?
Is it the current you have to drive in the input to get a specific, defined voltage at the output? And don't the currents cancel each other when applied to both inputs?
Federico Russo
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24
votes
4 answers
Gate capacitance vs. Gate charge in n-ch FETs, and how to calculate power dissipation during charging/discharging of the gate
I am using a MOSFET driver (TC4427A), which can charge a 1nF gate capacitance in about 30ns.
The dual N-ch MOSFET I am using (Si4946EY) has a gate charge of 30nC (max) per fet. I am only considering one for now as both on the die are identical. I…
Thomas O
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24
votes
4 answers
Do components have an un-used lifespan?
Lets say for example, that I had a box full of transistors, resistors, capacitors, diodes, leds, this and that, and left it in a cool, average environment for lets say... 50 years.
Do these components have a lifespan while been unused? Do the…
user62118
24
votes
7 answers
For embedded code, why should I use "uint_t" types instead of "unsigned int"?
I am writing an application in c for an STM32F105, using gcc.
In the past (with simpler projects), I have always defined variables as char, int, unsigned int, and so on.
I see that it is common to use the types defined in stdint.h, such as int8_t,…
bitsmack
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24
votes
5 answers
Explain what is a transistor in plain English!
Can someone care to explain - in plain English - what a transistor is and how it works. I know computers are full of these but don't know much about them.
P.S. I know about this site from another one in the family of StackExchange (I have no…
curiousJoe
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24
votes
4 answers
How do you determine how much flash/RAM you need for a microcontroller?
Let's say you are starting an embedded project with some known functionality. When you select a microcontroller how do you select how much RAM you need?
Do you use a developer board and code your project first and then see how much memory you have…
efox29
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24
votes
5 answers
Which soldering iron tip should I use?
This is a pretty open-ended question intentionally. :-)
All of the soldering I've done to this point has been with through-hole components. I hope to move up to some smaller surface-mount parts at some point in the future. I've got a Weller WES51…
blalor
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24
votes
4 answers
Preferences: Male or Female connector on board
On a prototyping board for use by students, should one place male (pin) headers or female headers on the PCB, considering that most of the pins will be unused most of the time.
I'm inclined to place the female headers on the PCB and have male pins…
Arne
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24
votes
9 answers
Why are electrons not pushed out from the conductor at an open circuit under the influence of a power source?
Frequently, electric current is compared with water flow. For example, if I make a hole in a water tank, water will flow till the tank pressure and the atmospheric not become equal or the tank becomes empty. Why does this not happen with…
user3131972
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24
votes
6 answers
What are the highest DC and AC voltages or currents that can be considered as safe?
By safe I mean safe for us when we touch a wire that is not insulated. I have heard that human body resistance is normally 50k Ohm when dry and 20K Ohm when wet. Therefore, these voltages or currents should be safe for a person who is wet. It should…
Amit Hasan
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24
votes
5 answers
How termination resistors work; what happens if I use lower values?
I am going to try to interface low-speed 8bit DDR2 chip to FPGA, and I've got some questions crucial to make it work :-)
Is that correct that the idea of termination resistor is to sink most of the signal to GND, so that only small part of it…
BarsMonster
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24
votes
3 answers
Anti-static vs. conductive vs. dissipative foam?
UPDATE: I have included some basic answers inline that I received after talking in depth with an application engineer at a foam company. I think it would still really help for someone to help flush out the theory behind these answers.
I am having…
user39075
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24
votes
2 answers
Firmware protection on AVR and PIC controllers
Can someone extract the HEX file that I burn in a microcontroller I provide them?
If that is possible, how can someone ensure that their code is secured in embedded systems? In the case of PIC and AVR microcontrollers, how can one protect their…
Rookie91
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