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1500 questions
21
votes
3 answers
Do magnetics connectors exist?
Conventional connectors, where the plug and socket have metal parts which touch, suffer from the following problems:
Limited mating cycles or expensive plating.
Impedance mismatch (relevant for high speed signals only).
Lack of isolation.
Here's…
Rocketmagnet
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21
votes
3 answers
What is "drive voltage" for a MOSFET?
In the attributes of a MOSFET, Digi-Key lists several different voltages. I think I understand what most of them are, but there's one I don't understand: "drive voltage."
Let's take this P-channel MOSFET as an example:
So, there's "Drain to Source…
user31708
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21
votes
5 answers
Why is a current signal preferred to a voltage signal for long analog transmission?
Some sensors act like current sources, and I have seen it several times, especially for very long wires even at outdoors like wind vanes. 4-20 mA current loops are used instead of 0-10 V voltage for instance.
What can be the physical explanation for…
cm64
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21
votes
2 answers
Why is Zener avalanche noise saw tooth shaped?
I have the following schematic of a Zener based noise source:-
simulate this circuit – Schematic created using CircuitLab
When built, an oscilloscope reveals a saw tooth noise signal at the "Noise" node, like:
The time base is 1us/div. Can anyone…
Paul Uszak
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21
votes
3 answers
What is the difference between SOT 23 and SOT 23-3 package types?
I am faced with two types of packaging:
SOT 23
SOT 23-3
Is there some difference between them?
Based an article in Wikipedia it seems like there are no differences.
KMM
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21
votes
1 answer
Difference between drill layer, hole layer, and milling layer in Eagle
What is the difference between the drill layer (44), the hole layer (45), and the milling layer (46) in Eagle PCB?
Alexis K
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21
votes
17 answers
How to 'fix' this in an enclosure without glueing?
I have an enclosure, and want to fix/put a STM32 inside, a relay and probably later a small circuit board.
However, the STM (STM32F103C8T6) and the relay do not have holes to fix them... and I do not want to glue them because maybe later I want to…
Michel Keijzers
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21
votes
1 answer
TO-92 not getting hot enough
I am controlling a DC fan by an AVR MCU and I am curious about the thermal characteristics of a 2N3904 NPN transistor over which the fan is connected.
Reading the transistor's datasheet, I find the following values:
$$
R_{\theta J-A} = 200\text{…
Nikola Malešević
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21
votes
2 answers
What might be the cause of high pitch sound coming from a switching regulator circuit?
We designed a switching regulator circuit using a 1.5MHz, internal-switch, switching regulator (semtech.com/images/datasheet/sc185.pdf). Vin is 5V, Vout is 3V3. We have an input capacitor (47uf), an output capacitor (47uf) and an inductor (1uH). The…
SomethingBetter
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21
votes
8 answers
How to deal with long chip lead times in small company
I am the chief engineer at a small company. Our product popularity is growing rapidly, and now we are learning about painful lead times for microcontrollers. The owner is demanding product overhauls to avoid distributor lead times. My question…
Zachary Scott Dickerson
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21
votes
10 answers
Why do I need a ground when simulating a circuit? I thought voltage was relative between two nodes!
Electronics is very new to me.
I took the most basic circuit I could think of: A voltage source of 1V and resistor of 1 Ohm
As far a I understand I should get a current of (I = V/R) 1 Ampere. But the simulation does not give a solution and said I…
user135172
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21
votes
4 answers
How to tell polarity expected of a DC barrel jack?
I'm sure this information is somewhere around the internet, but I can't find it.
I have a device that takes a DC barrel jack. I don't know the polarity it expects though. There is a marking though. It looks like this:
___
--- 12VDC
I'm 99% sure…
Earlz
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21
votes
3 answers
Difference between maximum amps for chassis wiring and power transmission
I am putting together a test system that'll be carrying over 50Amps.
I need to rate the wires that will be powering the device under test and also querying voltages and signals on the device.
Looking at the AWG table hosted by powerstream there…
SeanJ
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21
votes
6 answers
Why does this comparator not output a square wave?
I have a 4.43MHz sinusoidal output from an IC that I want to convert to a TTL square wave to use as a clock. The signal has a DC offset of around 2.5V and has an amplitude of about 0.5V peak to peak.
I attempted to convert this to a 0-5V square wave…
Batperson
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21
votes
6 answers
How to combat noise from my circuit polluting my 12V rail?
I made a controller for 12V DC fan. It is basically a buck DC-DC converter controlled by voltage. It regulates voltage for fan from 3V (lowest speed, fan draws 60mA @ 3V) to 12V (full speed, fan draws 240mA @ 12V). This controller works well, it…
Chupacabras
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