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1500 questions
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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53
votes
6 answers
Easy way to figure out a LED's Vf in order to pick an appropriate resistor
I was wondering what the easiest way to figure out a LED's forward voltage is, using measurement tools. I know we can assume red LEDs to be around 1.8V - 2.2V, and that we have similar information for other LED colors, but I was wondering if…
diegoreymendez
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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
4 answers
How to make traces on an universal PCB?
I hope this question won't be closed as too subjective. I'd like to know best practice - how to make traces on universal PCB's with individual holes without traces (like the following image). My idea is to bend the ends of discrete components and…
Al Kepp
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52
votes
9 answers
Using volatile in embedded C development
I have been reading some articles and Stack Exchange answers about using the volatile keyword to prevent the compiler from applying any optimizations on objects that can change in ways that cannot be determined by the compiler.
If I am reading from…
Pryda
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52
votes
2 answers
Competing PCB Crystal layout recommendations
This is related to this question: How's my crystal oscillator layout?
I'm trying to layout a 12MHz crystal for a micro controller. I've been reading through several recommendations specifically for crystals as well as for high frequency design.
For…
helloworld922
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52
votes
5 answers
Why do you need 2 resistors when hooking up a transistor as a switch
What is the point of R2 in the following diagram:
I get that R1 controls the current to the Base, but what does R2 do?
Tyler DeWitt
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52
votes
8 answers
Can a 12V battery give you a shock or not?
I am reading a book called "Make: Electronics" and, on page 9, it says:
"Anyone who has dropped an adjustable wrench across the bare terminals of a car battery will tell you that short circuits can be dramatic at a "mere" 12 volts, if the battery is…
Bitcoin Cash - ADA enthusiast
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52
votes
2 answers
Why do some diodes have a glass package?
Put simply, why do some diodes such as most Zeners and Schottky diodes have a glass package as opposed to the more traditional plastic package?
Is it ease of manufacturing, thermal properties, or some other electrical phenomenon?
Hugoagogo
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51
votes
8 answers
Why is digital serial transmission used everywhere? i.e. SATA, PCIe, USB
While looking at SATA, PCIe, USB, SD UHS-II it struck me that they are all the same: digital serial bitstream, transmitted using differential pairs (usually 8b/10b coded), with some differences in link/protocol layers.
Why so? Why did this become…
artemonster
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51
votes
7 answers
How do I measure a negative voltage with a ADC?
I am working with a PIC micro-controller with inbuilt 10bit ADC and want to measure a voltage in the range of -1 to -3Volts.
I thought of using an op-amp in the inverting mode to make voltage positive and then feed it to the adc of the…
Kevin Boyd
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51
votes
18 answers
Complete alternatives to the Arduino IDE?
I'm not that big of a fan of the official Arduino IDE (in terms of visuals), so I've started looking for nicer alternatives. However, most of the projects I've found are in alpha/beta and are generally incomplete.
I'm 100% new to circuit board…
nopcorn
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51
votes
6 answers
Does pulsing an LED at higher current yield greater apparent brightness?
This question implies two assumptions:
The frequency of a switched LED driver is high enough that average power, not instantaneous power, should be used to determine maximum drive current.
The limiting factor which determines maximum current at…
Kevin Vermeer
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51
votes
3 answers
What's the reason to make power supplies external?
Many years ago most electronic devices had internal power supplies only - there was a mains voltage cable running into the unit where mains AC would be converted and distributed for consumption. That was typical for shavers, TV sets, monitors,…
sharptooth
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