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1500 questions
26
votes
2 answers
'bridges' on a PCB copper layer
I've come across a design where each pad was connected using 4 'bridges' to the GND copper layar. What stands behind these 'bridges'? Why not make a full copper layer with only solder-mask defining the pads?
Gilad
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26
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3 answers
AC to DC without transformer. How does this thing work?
I disassembled a Chinese-made flashlight and found they use just capacitors to bring down the voltage instead of a transformer. They are using it to charge small lead-acid battery.
My question is how a capacitor alone can be used to bring 220 V down…
Ryu_hayabusa
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26
votes
3 answers
What are Atmel Fuses?
What are Fuses in Atmel microprocessors and when I should or need to change the default settings?
tuupola
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26
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4 answers
Which of these marks signifies Pin 1 on the STM32F (LQFP64)?
I'm using the STM32F105, in a LQFP64 package. It has two circular markings, on opposing corners of the IC. This picture is for a different ST ARM, but the markings and silkscreen are similar:
The larger mark in the upper-right of the picture has a…
bitsmack
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26
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4 answers
What's the maximum CAN bus frame (message) rate at 125 kbit/s?
My CAN bus is running at 125 kbit/s and is using extended frame format exclusively. I would like to know what's the maximum rate of CAN frame I can send out. Suppose the data length is always eight bytes.
According to this Wikipedia page, each frame…
Penghe Geng
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26
votes
5 answers
How much current can Solderless Breadboards handle?
I'm working on a project with a few stepper motors. I want to breadboard them so I know the circuit works well before creating a physical PCB.
Each of the three motors is rated 2A, but I'll be prototyping with 1A (controled with driver chip) at 12V.…
Anonymous Penguin
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26
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15 answers
Controlling 500 LEDs with PWM
I'm considering taking on a project that would involve individually addressing 500 LEDs, optimally with PWM support for each.
I'm planning on using an Arduino since I already have one, but I'm open to suggestions if anyone thinks a different…
littlebirdceo
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26
votes
5 answers
Board Design for High Impact Environments
I'm looking to design a PCB that can reliably survive constant impact. The board will be rigidly mounted to an enclosure that will protect the board from actually hitting anything. The nature of the impact would be similar to a bowling ball, or a…
W5VO
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25
votes
9 answers
LED and lamp in series - why does the bulb not light?
My 6 year old son has just started experimenting with a Snap Circuits style kit and already we have a very basic question.
If we arrange an LED and lamp in parallel powered by batteries then both LED and lamp light up brightly.
However, if we…
Mark McLaren
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25
votes
7 answers
Correct use of Flyback or Snubber diode across Motor or Transistor?
From seeing a few schematics where the flyback or snubber diode has been placed across the transistor C-E terminals (Right Configuration), instead of what I typically seen as the the flyback being placed across the coil terminals (Left…
Passerby
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25
votes
3 answers
How much of a GPU's electrical usage is probably turned into a increase in air temperature?
I am trying to find a good rough guesstimate of how much of the maximum wattage usage of a graphics card is turned into hot air.
Say a graphics card is rated at using X watts at maximum usage. How much of that is released as heat into the air via…
KDecker
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25
votes
4 answers
Sizing a trace on a PCB to carry 2.5 amps
I need a trace on my PCB to carry up to 2.5 amps (average) current, with 5-6 amp spikes (it's going to a switch mode power supply.) How wide should the traces be? I've got a trade off between reliability and size, as the product is space…
Thomas O
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25
votes
5 answers
Is there a difference between using a built in SPI module and bit-banging?
Is there a difference between the two, or is it just a matter of abstraction? My intuition says there's no difference but I'd love to be wrong.
Skaevola
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25
votes
4 answers
Why do fabs bother to print circuitry right up to the edges of a wafer when they know that the partial dies will be discarded later?
Around the edge of a wafer (see image below) you will observe that there are many partial dies. It seems wasteful to use the lithography machine to print these partial dies because they will be discarded later. Surely the stepper motors that move…
phil1008
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25
votes
3 answers
AVR - How to program an AVR chip in Linux
I recently got an AVRISP MkII AVR programmer, and I have an ATtiny85 and an ATmega328. I was wondering how I could program these chips with the programmer, but when I try getting Atmel Studio 6 it is only for Windows. Is there a way I could use in…
user151324
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