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1500 questions
45
votes
8 answers
How to resolve I2C address clashes?
I want to connect multiple I2C slave devices to a micro controller all on the same set of pins but the I2C devices all share the same address. The addresses are fixed in the hardware.
Is there any way to connect multiple devices with the same…
Simon P Stevens
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45
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9 answers
Why use capacitors?
Why do you need to store the voltage for some time in a capacitor? I've always assumed circuits to work when you power it on and stop when you power it off.
Why can't the whole circuit be drawn capacitor free? If it's meant for storage why not just…
user1424
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45
votes
4 answers
What are the advantages of this gold finger shape?
Some PCBs, like the PCI card specification have gold fingers which start very narrow near the bottom edge, and gain their usual width much higher, where the actual contact is expected to be made.
What is the advantage of having the narrow part?
Why…
akwky
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45
votes
5 answers
How can I use a 12 V input on a digital Arduino pin?
I am creating a controller for a 12 V system using an Arduino Uno microcrontroller. For the outputs I am using a relay shield to switch the 12 V components. I have a 12 V toggle switch that turns on some 12 V components in the system and I want to…
D.W.
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45
votes
8 answers
Why is 50 Ω often chosen as the input impedance of antennas, whereas the free space impedance is 377 Ω?
In order to efficiently deliver power to a different part of a circuit without reflection, the impedances of all circuit elements need to be matched. Free space can be regarded as a further element, since a transmitting antenna eventually should…
DK2AX
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45
votes
3 answers
Minimum operating temperature - Outer Space?
I've been looking at some microcontrollers and I've seen they've got some "weird" minimum operating temperatures, like -25 degrees or -10 degrees etc. But I can't really understand why there is a minimum, a maximum I do understand because everything…
Harry Svensson
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45
votes
5 answers
How can cache be that fast?
Here is a screenshot of a cache benchmark:
In the benchmark the L1 cache read speed is about 186 GB/s, with the latency being about 3-4 clock cycles. How is such a speed even achieved?
Consider the memory here: the theoretical maximum speed is
665…
Knight
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45
votes
6 answers
Why does hardware division take much longer than multiplication?
Why does hardware division take so much longer than multiplication on a microcontroller? E.g., on a dsPIC, a division takes 19 cycles, while multiplication takes only one clock cycle.
I went through some tutorials, including Division algorithm and…
Marko Gulin
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45
votes
6 answers
What is electrical insulation tape officially for?
Seemingly obvious question, but. There are electrical supply companies that sell insulation tape in boxes of 12 or 24 units. Seems that there's quite a demand for the stuff.
No commercial product I've ever seen uses insulation tape. They use…
Paul Uszak
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45
votes
11 answers
What would happen if I connect two different DC voltage sources in parallel?
I have a computer power supply that I'm hacking together as a bench supply. For this particular model to power on, I need a minimum load across both +5V and +12V.
"Easy," I thought, "I'll just connect both +5 and +12 to my power resistor!" And it…
rascher
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45
votes
5 answers
Why do ICs have NC (No Connection or No Function) pins?
In case they have no use to the end users and have no function, why are they given as pins instead of being just closed? Some ICs have even 4-5 NC continuously (in accordance to their pin number).
Ajith Natarajan
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45
votes
3 answers
Basic transistor questions
I've created the circuit shown. I'm using a 9V battery (actually throwing out 9.53V) and 5V coming from an Arduino to test with both 9 and 5 volts. The transistor is a BC 548B (datasheet I'm using is here).
simulate this circuit – Schematic created…
hojkoff
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45
votes
8 answers
Why isn't there a potential difference across a disconnected diode?
I know this question sounds silly, as if there was a potential difference a current would be created when the terminals are connected together and this would mean energy has come from somewhere.
The reason I ask this though is that from my…
Blue7
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44
votes
1 answer
Step up 3.3V to 5V for digital I/O
I normally use an Arduino for my projects because it has 5V inputs and outputs and has 5V Vin so that makes life very easy when interfacing with 5V components. For this project I want to use a Raspberry Pi because I want to hook it up to a display.…
Huckle
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44
votes
2 answers
Sharp corners in PCB traces
Why does a typical PCB always has rounded tracks? What harm can a sharp edged PCB track can cause? Please explain!
Vinit Shandilya
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