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1500 questions
58
votes
6 answers
When would I use a voltage regulator vs a voltage divider?
When would you use a voltage regulator vs a resistor voltage divider? Are there any uses for which a resistor divider is particularly bad?
Pete
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57
votes
5 answers
How can PCB trace have 50 ohm impedance regardless of length and signal frequency?
Hmm, this seems to be just another question on line impedances.
I understand that when we say "transmission line" effects we talk about things like cross talk, reflections and ringing (I guess that is just about it). These effects are not present at…
quantum231
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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
6 answers
Does my Arduino-based device need FCC certification?
I've built a small consumer device that contains an Arduino Nano. It's coupled to a custom daughter board that allows it to pulse a 12V electromagnet at about 1 hertz as well as inteface to some sensors. It does not intentionally produce any RF…
Cerin
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57
votes
4 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
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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57
votes
6 answers
Maximum I2C Bus Length?
What is the maximum length of cable that could be used to connect two I2C devices (I2C master-> I2C slave)?
Yes, I know that I2C is really designed for intra-board communication. I have been tasked with a "design goal" of using a common I2C bus for…
Nate
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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
5 answers
Programming microcontrollers: JTAG, SPI, USB oh my!?
I've noticed, with regards to microcontrollers, there are several way to program them. I am sorta familiar with USB as my Arduino's can be programmed via USB.
What is a JTAG or SPI interface?
Ultimately I know that these interfaces provide a means…
jdiaz
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