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31
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1 answer
What effect does selecting the wrong load capacitance for a crystal have?
I've seen questions such as this one and this one that talk about selecting capacitors that, in series, match up as closely as possible to the load capacitance of the crystal.
What effect does selecting the wrong capacitance have? Does it skew the…
Polynomial
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31
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2 answers
Capacitor Sizes for 7805 Regulator
It says in the datasheet these values in this picture:
But I've also seen it with these values:
So what values should i use or doesn't it matter? And its for when its first starting.
Dean
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31
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6 answers
Is it really a bad idea to leave an MCU input pin floating?
I've heard that leaving a pin floating on an MCU when configured as an input (vs. the default output) is bad for the pin, and can eventually cause it to fail prematurely. Is this true? N.B. in my instance the pin is floating somewhere between 0.3V…
Thomas O
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31
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3 answers
What does this symbol on a voltmeter looking like an upside down U with a small line under it represent?
I decided to start a new question because I have no idea what word describes it at best, let alone to do a research (aka googling) which can be a bit inconclusive.
At first glance, it looks like it convincingly represents an LED, albeit not with…
Yudhi G.
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31
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2 answers
Why can't USB-C receivers be as small as their USB-A counterparts?
We're all familiar with the USB-A 2.4 GHz receivers from companies like Logitech that are absurdly small and barely protrude from the port. But when looking at available USB-C equivalents, they are quite a lot larger even after accounting for the…
Adam
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31
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6 answers
How precise is the frequency of the AC electricity network?
If I make a digital clock which first detects the AC frequency roughly (whether it is 50, 60, 100Hz, etc), then uses it as its clock pulse source, how precise would it be? Would it work world wide precisely?
For instance, in USA, what is the mean…
hkBattousai
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31
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4 answers
Why are most COB LEDs physically yellow?
Many "LEDs" found on devices nowadays appear to be yellow where the light comes from (when the device is off). Why yellow?
I put LEDs in quotes because COB leds can consist of many individual LEDs in an array/grid. In my example photo below, you can…
Bort
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31
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4 answers
How were four wires replaced with two wires in early telephones?
In this video, when A wanted to talk to B, a microphone was connected to a distant speaker using two wires (A → B).
When B talked to A, a copy of above was used in the other direction (B → A) using two more wires.
This required four wires:
But then…
across
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3 answers
Can you make a CPU out of electronic components drawn by hand on paper?
I explored a lot of literature about paper-based electronics recently, and one particular paper caught my interest: “Handwritten Oxide Electronics on Paper” (DOI: 10.1002/admt.201700009) by Elvira Fortunato et al.
It explains a method to make…
Zoé Martin
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31
votes
2 answers
What exactly are the differences between a USB host and device
Came across some doubts:
What exactly are the differences between a USB host and device? Is it just that who powers the bus?
When two devices connect how the device say "hey I will be the host and you be the device?"
Can one device acts as a host…
Kozlov
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31
votes
5 answers
Stealing energy from radio towers or power lines
From this answer: How much energy can be harvested from nearby radio towers or power lines? What circuits would you use? How much would you have to absorb for it to be noticeable by the producers or by other consumers?
I see a lot of stories,…
endolith
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31
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9 answers
What is the process of going from machine code to electrically controlling individual transistors?
For someone who writes software but doesn't have a computer engineering background, the dozens of abstraction layers have always bewildered me.
I know all source code in their most fundamental level is broken down into 1s and 0s. I also know all…
master_of_privates
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31
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5 answers
What does the multimeter dial do internally?
Everyone who has ever handled a multimeter is familiar with these dials. The position of the dial indicates the maximum range of the quantity that can be measured.
But why are we required to adjust the maximum range ourselves? What happens…
S. Rotos
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31
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11 answers
What is the most amazing PCB artwork you've ever seen?
Have you ever looked at a PCB and burst out laughing?
Have you ever looked at a PCB and said "Wow, that is amazing"?
Have you ever seen a PCB that artistically expressed criticism of society's treatment of the poor?
I'm focusing here on the PCB…
davidcary
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31
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3 answers
Why are lightbulbs considered resistive load?
A lightbulb (a plain old incandescent lamp) is typically brought up as an example of resistive load.
Yet the filament is actually made of several feet of very thin wire cleverly coiled to form a filament which is about one inch long. Clearly…
sharptooth
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