Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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1500 questions
114
votes
8 answers

Best One-Off DIY PCB Creation Technique

I have finally built up a lab to design electronics in. I have quite a few designs I would like to test. I have tried the printer toner/iron technique a few times but have found that I cannot create small pitch sizes as they tear off while removing…
ThaKidd KG5ORD
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113
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6 answers

Are tantalum capacitors safe for use in new designs?

I've heard it suggested that "solid tantalum" capacitors are dangerous and may cause fire, may fail short circuit and are fatally sensitive to even very short over voltage spikes. Are tantalum capacitors reliable? Are they safe for use in general…
Russell McMahon
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111
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9 answers

Why does a resistor need to be on the anode of an LED?

Please be kind, I am an electronics nub. This is in reference to getting an LED to emit photons. From what I read (Getting Started in Electronics - Forrest Mims III and Make: Electronics) electrons flow from the more negative side to the more…
Spechal
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111
votes
11 answers

What is negative voltage?

Just a general electronics question: What is negative voltage, like -5 Volt? From my basic knowledge, power is generated by electrons wandering from the minus to the plus side of the power source (assuming DC power here). Is negative voltage when…
Michael Stum
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110
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6 answers

My linear voltage regulator is overheating very fast

I'm using a 5 V / 2 A voltage regulator (L78S05) without a heatsink. I'm testing the circuit with a microcontroller (PIC18FXXXX), a few LEDs and a 1 mA piezzo buzzer. The input voltage is aprox. 24 VDC. After running for a minute, the voltage…
m.Alin
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108
votes
4 answers

How do I calculate the required value for a pull-up resistor?

There are many tutorials that use a pull-up or pull-down resistor in conjunction with a switch to avoid a floating ground, e.g. http://www.arduino.cc/en/Tutorial/button Many of these projects use a 10K resistor, merely remarking that it is a good…
Mark Harrison
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108
votes
5 answers

Can microcontrollers be run at arbitrarily low clock frequencies?

The datasheet for the ATTiny13A, for instance, lists Min frequency of 0 MHz. Does this mean the clock can be run at any arbitrarily low frequency with no ill effects? I'm assuming it draws lower current at lower clock speeds? Does 0 MHz mean you…
endolith
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108
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5 answers

Why are there 3 pins on some batteries?

Lots of new batteries (for mobile devices, MP3 players, etc) have connectors with 3 pins. I would like to know what is the purpose of this and how should I use these three pins? They are usually marked as (+) plus, (-) minus, and T.
adopilot
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107
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6 answers

Ceramic caps vs electrolytic. What are the tangible differences in use?

A quick google around and all I seem to be able to find are people talking about the physics & the chemistry of the capacitors but not how this affects choosing which to use. Avoiding talking about the difference in their make-up, and the larger…
James T
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106
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11 answers

VHDL vs. Verilog

VHDL and Verilog are some of the HDLs used today. What are the advantages and disadvantages of using Verilog or VHDL over the other?
stevenvh
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105
votes
13 answers

Measuring feline capacitance

When I pet my cat, and then touch her on the nose, I get a little shock. Sometimes, when she walks up to something, her nose sparks and she jumps back and puffs out. I was wondering how I might go about measuring the capacitance of my cat. So how…
timthelion
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101
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5 answers

What is the difference between Flash memory and EEPROM?

Flash memory storage and EEPROM both use floating gate transistors for storage of data. What differs between the two and why is Flash so much faster?
skyler
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101
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10 answers

Why does a Tesla car use an AC motor instead of a DC one?

I was just watching a mega factory video and wondered why they use an AC motor which requires a power inverter instead of DC which may be powered directly from their DC battery? Introducing an inverter means more cost (weight, controller, etc). Are…
wizzup
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101
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29 answers

What's the best way to store and categorise resistors/capacitors/ICs/etc?

I did a big cleanup of my collection of parts today and I now have a big pile of parts on my desk (the majority of which is resistors). My previous method of finding the resistor value I wanted was to look through my little box and read the colour…
jeremy
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97
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4 answers

What kind of components are black blobs on a PCB?

In low-cost mass-produced items I often run into black blobs of what looks like resin applied directly on top of something on the PCB. What are these things exactly? I suspect this is some kind of custom IC that is layed out directly on the PCB to…
drxzcl
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