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1500 questions
57
votes
3 answers
Which products should have FCC certification and about how much does that cost?
I'm aware that nobody actually does this at the hobbyist level, that successful commercial products have been launched without certification, and it's probably something I can't afford if I have to ask. However, I've always wondered about the…
joeforker
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57
votes
7 answers
How can I get my atmega328 to run for a year on batteries?
Scenario
I have created a nice electronic door lock for my dorm room. It is currently an Arduino Diecimila with a servo [un]locking the door. It has a numerical keypad with 3x4 buttons and 5 LED's (2 serie pairs and one single LED). It also…
Pangolin
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57
votes
1 answer
What does this symbol mean on my Samsung travel adapter?
The charger was bought in Austria two years ago, and I know about all symbols/labels except this one. Google reverse image search did not help.
Hallo1234 Hallo12235
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57
votes
5 answers
Are LEDs better than we think?
Conventional wisdom about LEDs says their maximum reverse voltage \$V_{R(max)}\$ is quite limited, usually in the 5V-8V range.
So, for experimentation purposes, I wanted to bring an LED into controlled breakdown, using my current-limited power…
LorenzoDonati4Ukraine-OnStrike
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57
votes
6 answers
What gauge of single strand wire works well with breadboards?
I bought some single strand wires hoping to prototype on the breadboards. Unfortunately it was too small to properly fit into the breadboard holes.
So my question is which gauge fits well on those small holes of breadboard?
0xakhil
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57
votes
3 answers
What does 3V3 or 1V8 mean?
While reading a datasheet for an IC I came across the pin voltages being presented as 3V3 or 1V8. What does this representation stand for?
Ankit
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57
votes
8 answers
Why weights on cables between utility poles?
Yesterday I saw what look like weights hanging from a cable between utility poles. This was in northeast Arizona on Route 60 between Show Low and Springerville. Here is a picture of a whole span:
The white blobs are the weights. Here is a…
Olin Lathrop
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57
votes
1 answer
What is this object found on transmission lines?
What are the components, circled in red in the figure, on this transmission line ?
Electrical Engineer
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57
votes
5 answers
Stripboard/veroboard/matrix board design software
I'm prototyping a simple layout for a small project on matrix board, but figured there must be a better way than drawing it all out on paper. Are there any aimed at matrix board?
I've found the following software for stripboard, but nothing…
Mat
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57
votes
5 answers
When to use pull-down vs. pull-up resistors
After learning and experimenting with microcontrollers, I've understood the concept of pull-up- and pull-down resistors. I now understand when and how to use them, and how they work. I've mainly used pull-ups because I was taught to, but it has…
osvein
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57
votes
3 answers
Lightning bolt vs. batteries: a coulomb in everyday terms
I am trying to decide if the information on the wikipedia page
http://en.wikipedia.org/wiki/Coulomb#In_everyday_terms
is reasonable. In particular the statements that a lightning bolt has about 15 coulomb, where a battery has 5000. My first…
kasterma
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56
votes
3 answers
What is the purpose of tiny "bumps" on LED legs?
A lot (if not most) LEDs have some kind of small thickenings on their legs. Sometimes they are almost as wide as the leg itself and barely visible, sometimes they are twice as wide and instantly noticeable.
When present they seem to be the same on…
HYBRID BEING
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56
votes
3 answers
How do lasers measure short distances (<1cm) when electronics are too slow for time-of-flight to work?
I was wondering how LIDAR sensors are able to measure distances less than 2mm. I don't see how they can possibly do that.
The speed of light is 300,000,000 m/s, so the round-trip time should be within 14ps which is far beyond the capabilities of…
Ron Vaisman
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56
votes
7 answers
Does a dangling wire really electrocute me if I'm standing in water?
We've all seen this scenario in movies; somebody has to cross a room half filled with water and there is a dangling electric wire that shoots sparks everywhere. The poor person has to cross the room but cannot do so because if the wire hits the…
S. Rotos
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56
votes
3 answers
Fan speed switch: why OFF :: HIGH :: MED :: LOW?
Many AC fans, including inexpensive floor models, have a rotary speed control which rotates from OFF to HIGH to MED to LOW. Since the switch does not rotate 360°, you have to rotate it backwards to shut it off. This has always slightly annoyed me,…
RichF
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