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1500 questions
38
votes
3 answers
Can people act like antennas?
I was watching my oscilloscope as I was holding a very short wire attached to the probe. It was showing about 0 voltage (small spikes) until I touched the metal. When I touched the metal, the scope immediately showed a 60.0Hz (peroid of 16.66ms),…
dpdt
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38
votes
12 answers
Soldering Iron Maintenance
How often should I tin my soldering iron? It doesn't seem to pick up the solder quickly any more; I have to hold it there for 10 seconds before it melts.
Jules
38
votes
5 answers
Why don't we use neutral wire for to ground devices and earth wire for closing the circuit?
I know that the neutral point of a distribution transformer is connected to the grounding (earthing) wire, so I think they are the same.
Can I use the neutral wire for protecting metal-cased electric devices by connecting it to the case (cover)?
Can…
Michael George
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38
votes
7 answers
What is the advantage of a "straw hat" (inverted cone) LED?
LEDs with a concave cone-shaped lens are sometimes called "straw hat" LEDs. What is the advantage compared to the more common hemispherical lens?
joeforker
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38
votes
12 answers
Correcting for non-linear brightness in LEDs when using PWM
When driving an LED with PWM, the brightness (as I perceive it) does not scale linearly with duty cycle.
The brightness is slow to ramp up, then increases exponentially with duty cycle.
Can anyone suggest a rule of thumb to use as a correction…
Toby Jaffey
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38
votes
8 answers
Why do Microcontrollers need a Clock
Why do instructions need to be processed at set time intervals (i.e. with the use of a clock)? Can't they be executed sequentially - immediately after the previous instruction has completed?
An analogy for the necessity of clocks in microcontrollers…
M-R
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38
votes
1 answer
KiCAD - Moving and rotating components with wires connected
I'm a major major noob to KiCAD and having done a couple of tuts in Eagle, I do like the separation of footprints from the schema.
But one thing that took me by surprise is that the wire connections don't stay connected or become weird angled if I…
Plasty Grove
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38
votes
6 answers
Why does there seem to be a missing component in many PCBs?
I've seen some PCBs were some components have been sketched, but they don't seem to be mounted on the board. See, this image (of a PlayStation 2) where the transformer has been drawn:
Why is this done on some circuits?
jinawee
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38
votes
7 answers
Using a bottle of water as a resistor
Today, while drinking some water from a \$500mL\$ bottle, I started reading the info about the water and found out that the conductivity (\$\sigma\$) at \$25°\$C is \$147.9\mu S/cm\$. So it came to my attention that maybe I could calculate the…
Thiago
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38
votes
3 answers
How does USB Type C handle reverse polarity / signal duplication
The new USB Type C connector doesn't have a physical reverse polarity protection any more. You can plug it in any way you want on both ends, there is also no A and B end any more, it's all the same.
So how does this new USB type handle that the…
timonsku
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38
votes
8 answers
In what situation should I keep the brown-out detection feature OFF on a microcontroller?
When the power supply on a microcontroller falls under a certain threshold, a brown-out conditions occurs and RAM may get corrupted. Provided that every power down sequence of the circuit can mean a potential brown-out condition, I always enable…
m.Alin
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38
votes
12 answers
Why do we need so many transistors?
Transistors serve multiple purposes in an electrical circuit, i.e switches, to amplify electronic signals, allowing you to control current etc...
However, I recently read about Moore's law, among other random internet articles, that modern…
Kenneth .J
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38
votes
4 answers
Make a custom plastic case
I have worked on many electronic DIY projects like MIDIbox (http://www.ucapps.de/), it always was fun and working but at the end, the problem was that I ended with a cool gear, but in a poor casing, for example : wood very roughly cut (by…
Basj
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37
votes
5 answers
37
votes
4 answers
I2C 3.3 to 5.0 V conversion
I'm trying to interface a 3.3V I2C device to a 5V Arduino.
I don't have any problem with SCL line.
I can use a simple voltage divider but I have an issue with the SDA line as this is bi-directional.
I'm not at all sure how to handle this. I have…
JohnC
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