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1500 questions
54
votes
16 answers
Why use PLC instead of microcontroller?
Why does everyone use PLCs in industrial environments, instead of a microcontroller based solution?
For a longer task, the PLC program is as complicated as a microcontroller program.
A microcontroller based solution may be more customisable, and of…
Saneesh A T
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54
votes
3 answers
How to go from a development board to a production board?
Ok, I am a software guy and new to electronics. My product needs a small computer and currently I have developed everything on development boards like raspberry pi and such. As the development board does not have all the hardware that I need, I have…
iCode
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54
votes
13 answers
What kind of components in a computer power supply can explode loudly?
Today I heard a loud bang that tripped the circuit breaker in my server room. It must have been really loud because I could hear it 2 rooms away through 2 heavy doors and it was like a firecracker going off right next to me.
Long story short, it…
user81993
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53
votes
7 answers
How do you simulate voltage noise with LTSpice?
Is there a way to setup a voltage supply with voltage jitter/noise? I want to experiment with filtering out noise on various voltages etc. but not sure how to configure LTSpice to create a noisy voltage supply.
josef.van.niekerk
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53
votes
6 answers
Standard PCB trace widths?
Is there a standard for the sizes of PCB traces?
That is are some 25 mil and others 10 mil or is can you choose your own?
I plan to run 400mA through some thicker traces, but less than 30mA for all other traces. About what size would I need?
Thomas O
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53
votes
5 answers
Why does music synthesizer built from chain of astable multivibrator circuits get "out-of-tune" after a few hours?
I built a prototype keyboard/sound synthesizer using a chain of 13 astable multivibrator circuits whose outputs are connected to an audio amplifier chip (LM386) and speaker, all powered off a 9V DC battery.
Each individual circuit gets tuned to one…
Assad Ebrahim
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53
votes
5 answers
Is a CAN enabled microcontroller sufficient to drive a CAN bus?
There are a number of CAN modules built into microcontrollers these days. The PIC18F2480 is an example of that. Is that microcontroller (with built-in CAN) capable of driving a CAN bus on its own or is an external CAN transceiver/controller…
efox29
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53
votes
6 answers
Why do transformers use so many turns?
Transformers have hundreds of turns on both the secondary and primary winding, and as a result use very thin copper wires for each. But, why do they not just use fewer turns on each winding and get the same voltage ratio?
More importantly, why not…
user3503966
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53
votes
9 answers
How safe is 48V DC?
In many Power over Ethernet (POE) setups the transmission voltage is 48V or slightly more. While higher voltage has obvious efficiency advantages, how safe it is? Is there any risk of electrocution when accidentally exposed, in particular to…
Petr
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53
votes
2 answers
Why are USB devices slower than 480 MBit/s
Motivation
With a signaling rate of 480 MBit/s USB 2.0 devices should be able to transmit data with up to 60 MB/s. However today's devices seem to be limited to 30-42 MB/s while reading [Wiki:USB]. That is a 30 percent overhead.
USB 2.0 has been a…
Chris
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53
votes
11 answers
Can a radio transmitter somehow detect the number of receivers in its area?
During conversation, a colleague proposed that over-the-air television and radio broadcasters can determine the number of viewers or listeners based on the "load" on their signal. This seems to me like total bupkis, but he's piqued my curiosity and…
ghaberek
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53
votes
2 answers
What's the third wire on a piezo buzzer?
Most piezos I've seen have just two connections, but this type has three.
What's the third wire for?
Federico Russo
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52
votes
4 answers
What are the little bits of metal that come out of light bulb filaments and why do they stick to only one terminal?
Recently I changed the headlights in my car and took a few micrographs of the filaments. A couple composite photos of old bulbs:
For reference, here's a new bulb filament:
On the left wire in the images of the old bulbs, there are many metal…
rsaxvc
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52
votes
6 answers
Does turning a lighbulb on and off repeatedly use more energy than just leaving it on for hours?
Let's say I have a 60W bulb in a lamp in my bedroom. If I kept the lamp on for 2 hours straight but the next day, I switched it on and off 10 times in intervals of 5 minutes. Which scenario would use more energy?
Christopher Chipps
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52
votes
7 answers
The best stack-up possible with a four-layer PCB?
I'm designing a 4 layer PCB and I know that the standard stack-up is
Signals
GND
VCC
Signals
(GND and VCC can be switched depending on the layer with more signals)
The problem is, I don't really want to connect all ground pins through vias, there…
mux
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