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1500 questions
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7 answers

Why is the unit for capacitance so large?

Most capacitors are in the µF, nF and pF range. I know there are some special ones that go that high, but at the time faraday was around, and the unit was named after him, they didn't have such a thing. Why is the unit so large if we rarely use caps…
skyler
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Wouldn't charging a lithium battery to 80% only defeat the purpose of putting the battery into longer use in the first place?

I see most smart devices (laptops/tablets/phones) now have the option to optimize your battery by charging it to 80% only. But wouldn't this reduce your capacity i.e. your brand new battery now only has 80% of its rated capacity, which means more…
GuitlyofNtAsking
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Is paralleling diodes a bad idea?

I'm trying to repair an 800W power supply (see my previous question on this.) One thing that gets me is that the design has two schottky diode packages (in TO-220) in parallel. I was always told this was A Bad Idea, but since they are thermally…
Thomas O
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5 answers

Are decoupling capacitors needed with battery power?

Currently I run all my gadgets from batteries and don't use decoupling capacitors. Are they generally needed/useful when drawing energy from a battery?
Mr. Hedgehog
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7 answers

What do I need for a basic RF circuit?

I'm looking for any resource that can help me build a very very basic RC circuit. I'm talking as simple as using RF to turn on/off an LED. The purpose of this circuit is for research and education. If anyone knows where I can get parts for simple RF…
Digital Brent
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Why wiggle nearby tracks on a PCB?

I've been reading an article (TheMagPi eMagazine) relating to the Raspberry Pi; "An ARM GNU/Linux box for $25." In the article, page 17 at the bottom it shows an area on the Pi where a track zigzags next to a straight one with the explanation…
George Duckett
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8 answers

Am I insane to question that only with a closed path can electrons move?

First of all let me just state that I do not feel confident enough to tell anyone anything about how electric circuits work or anything about the physics behind them because I simply do not know or understand it all. But I have many times read that…
µDavid
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How do GPS satellites refresh their clocks

How do GPS satellites keep their on board clocks accurate? I assume that they need to get update from a base station. But how do you make sure that after the update all the satellites are synchronized, i.e. there isn't any phase shift. You have…
user110971
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Why do CPUs need so much current?

I know that a simple CPU (like Intel or AMD) can consume 45-140 W and that many CPUs operate at 1.2 V, 1.25 V, etc. So, assuming a CPU operating at 1.25 V and having TDP of 80 W... it uses 64 Amps (a lot of amps). Why does a CPU need more than 1 A…
Leonardo Bosquett
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How to connect multiple i2c-interface devices into a single pin A4 (SDA) and A5 (SCL) on Arduino?

I want to add a real time clock module into my little project. I want to display both time and date on my existing i2c 2x16 LCD module. Both i2c-interface real time clock module and 2x16 LCD module use the same pin A4 (SDA) and A5 (SCL) on Arduino…
banksia
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3 answers

What is the purpose of a buffer gate?

As I understand a buffer gate is the opposite of a NOT gate and does not change the input: However I sometimes see buffer gate ICs used in circuits and to an inexperienced eye they seem to do nothing at all. For example recently I've seen a…
I have no idea what I'm doing
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5 answers

Does PCIe hotplug actually work in practice?

I've got into a discussion in the comments of https://security.stackexchange.com/questions/109199/is-physical-security-less-important-now-for-securing-a-server?noredirect=1#comment194327_109199 The question is simple. Has anyone experience of…
pjc50
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Is current source also a voltage source?

I'm confused between current and voltage sources; I get the text book definition but I am not able to understand real world difference. To me both current and voltage sources seem as the same. I understand that ideal sources doesn't exist. What is…
user3551094
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11 answers

What is the smallest and simplest seed for a random number generator?

A small microcontroller (8-bit Atmel) controls a number of lights in order to present a light show with many fancy randomized light sequences. A suitable pseudo-RNG does its job nicely, but I'm looking for a good seed for it. A seed will be…
vsz
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New eagle library: reuse standard package & symbol

I need to make few components in Eagle, which are all in standard packages, and I can see them in ref-packages.lbr. The problem is that when I am creating my library I don't see how I can reuse package/symbol from another library, so that I only…
BarsMonster
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