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1500 questions
27
votes
3 answers
Are there resources for learning to write drivers?
I have a decent amount of experience designing hardware and embedded systems in general, but I have never written a driver for an operating system.
I would like to know if there are any good guides, preferably online, although good books would…
Kortuk
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27
votes
4 answers
Do electrons actually flow when a voltage is applied?
It's said in books that a circuit is a closed path and thus that electrons come back to the source. If that's the case, what would happen when there were an earth fault in a circuit? How would the electrons return to their source?
Do the electrons…
Ranjit
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27
votes
4 answers
Why is crystal frequency often multiplied inside a microcontroller?
I noticed often times the external crystals frequency is multiplied to arrive at a microcontroller's clock speed. Why is this done?
Take, for example, the TI CC2650. In its default configuration, it uses a 24 MHz crystal to arrive at a 48 MHz clock…
Questy
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27
votes
10 answers
How can you achieve decent clock accuracy in microcontrollers (e.g., max 1 second drift in a year)? How do digital watch manufacturers accomplish it?
I am learning with microcontrollers (mostly PIC16/18 and AVR) for some time, making various experimental projects. One of things that I found surprisingly challenging is maintaining decent clock accuracy.
Most of my projects have internal clocks at…
Petr
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27
votes
3 answers
What does "no fit" mean in electronics?
I have found at some places, especially:
Raspberry Pi Forums
eLinux RPi Hardware page
the following wording:
S2: DSI interface. 15-pin surface mounted flat flex connector
(possibly no-fit) S5: MIPI CSI-2 interface. 15-pin surface mounted
flat…
dash17291
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27
votes
3 answers
Why use two transistors driving LEDs when one would work?
Recently received a small PCB from China with a simple LED driving setup (12v input).
I spent some time probing it out and reverse engineered this schematic;
I'm trying to understand why they designed it so that this uses 2 transistors (granted my…
VindolandaHand
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27
votes
5 answers
How to use a capacitive touch screen without a human hand
I'm a programmer, and I usually hang out over on stack overflow, but I have a electricity question.
I'm trying to interact with an APP on my phone by indirectly touching the the screen. Modern touchscreens, as I'm sure everyone here knows are…
Jeff Ryan
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27
votes
3 answers
Do antistatic bags have conductive interior, exterior or both?
From Wikipedia:
To create the anti-static effect, the black or silver bags are slightly conductive
and
A device should not be powered while in an antistatic bag, because the conductivity of the bag could cause damaging short-circuits between…
Jader Dias
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27
votes
2 answers
What do the line-and-circle symbols mean on these electric meters?
I was looking at an electrical installation and came across unfamiliar symbols on the front of a pair of meters.
These are from three-phase 240v meters running on a timed system. One each for peak/off-peak usage.
On the first image, I recognise part…
Ben
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27
votes
7 answers
Why are two 555 timers in separate sub-circuits cross-talking? (Poltergeist in the Breadboard)
As an introduction to electronics, I am following Charles Platt's Make: Electronics (2nd edition).
Every circuit worked as expected, until Experiment 17: Set Your Tone.
In circuit on figure 4-37 (page 163), two 555 timers are used in astable mode…
Ad N
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27
votes
6 answers
Why would an AND gate need six transistors?
I'm taking a digital design course, and I've been told that a NAND gate needs four transistors to implement and an AND gate needs six (four for a NAND gate and two for an inverter). That makes sense until one of my classmates told me he could…
Dev-XYS
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27
votes
4 answers
Considerations in a bench/lab power supply?
I'm looking at adding a low-cost variable power supply to my electronics hobby bench. After years of cobbling together LM317's and LM7805's, it's about time...
Considerations:
I've found a few options which I am unsure about.
Dave at EEVBlog states…
JYelton
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27
votes
4 answers
What is the purpose of this disk over a Samtec connector?
With beautification in mind I decided to attach 3D-STEP models to elements on my PCB.
One of them is a connector from Samtec. They do provide a STEP models for a download, but it was immediately suspicious to me, that the preview had this weird disc…
PF4Public
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27
votes
17 answers
Most affordable FPGA dev kit for learning VHDL and FPGA theory?
I'm looking for something that I can play around with but not spend too much on. I'm not eligible for an academic discount so take that into account when making suggestions.
Matthew Miano
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27
votes
4 answers
How do I calculate how fast a capacitor will discharge?
Say I have a 1F capacitor that is charged up to 5V. Then say I connect the cap to a circuit that draws 10 mA of current when operating between 3 and 5 V. What equation would I use to calculate the voltage across the capacitor, with respect to time,…
PICyourBrain
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