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1500 questions
26
votes
6 answers
Using the ATMega328 with the internal oscillator?
I have a project that I think would be best suited for an ATMega328P. However, in every simple project I've seen, people always hook up a 16MHz external oscillator. From what I can see, it should have an 8MHz internal oscillator. My project doesn't…
Earlz
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26
votes
3 answers
Pull up resistors on UART
I was going through an app-note AN2606 where I came across this connection diagram:
As per my knowledge, UART is push-pull type and Tx provides the pull-up required and hence we don't need to use any external pull ups. Am I missing something here?
Whiskeyjack
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26
votes
8 answers
Is it worth it learning how to use 7400 series "jelly bean" logic IC's or are they completely obsolete?
My road map for learning electronics included the 7400 series logic chips. I started in on electronics by following the labs in the "Art of Electronics" lab manual which includes labs with these chips. I ended up building several custom Microchip…
Dave.Mech.Eng
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26
votes
6 answers
PCB 90 degree angles
Not a dup of which barely attends to the technical reasons for or against using 90 degree routes.
As a hobbyist who's enrolling in an EE program in the fall, should I just get in the habit of avoiding right angles in PCB layout? Is this always a…
inbinder
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26
votes
3 answers
How does a microcontroller boot and startup, step by step?
When C code is written, compiled and uploaded to a microcontroller, the microcontroller starts running. But if we take this uploading and startup process step by step in slow motion, I have some confusions about what is actually happening inside the…
user16307
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26
votes
3 answers
Why is the Nyquist data rate lower than the Shannon data rate?
In the book Computer Networks, the author talks about the maximum data rate of a channel. He presents the Nyquist formula :
C = 2H log\$_2\$ V (bits/sec)
And gives an example for a telephone line :
a noiseless 3-kHz channel cannot transmit binary…
subb
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26
votes
3 answers
ICs ("chips") are typically packaged in what material?
ICs are typically packaged (encapsulated) in a black "plastic". What is this packaging material made of?
(source)
Sparkler
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26
votes
4 answers
Does (and when how) the lifetime of a LED depend on the PWM frequency
Let's assume two options for driving a standard LED at its rated current.
PWM set to 50% duty cycle at 10 kHz
PWM set to 50% duty cycle at 50 kHz
Technically both LEDs would produce the same amount of light and the 'blinking' won't be visible to…
Gilad
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26
votes
15 answers
Beginner's logic analyzer?
Can anyone recommend a low cost or DIY buildable logic analyzer?
Mostly, it would be for debugging serial protocols (SPI, I2C, RS232) at low voltages.
Toby Jaffey
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26
votes
6 answers
Why doesn't my 5050 led strip draw as much power as I expect?
I've been playing with a 5m long RGB LED strip, with 300x surface mount 5050 RGB LEDs, but can't understand why the strip isn't as bright or drawing as much power as I was expecting.
I've had a look at Arduino and 5A 12Volt driver, which appears to…
Mark Booth
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26
votes
3 answers
Why does the LM1117 data sheet specifically specify tantalum capacitors?
I'm planning on using an LM1117 to regulate 5 V to 3.3 V. Looking at (any of the several) data sheets for the LM1117, they recommend 10 µF tantalum capacitors between input and ground and between output and ground.
I understand the need for the…
Jon Bright
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26
votes
6 answers
Can the noise of any switching PSU be attenuated if I put linear regulator before the output?
A friend told me that noise of any switching PSU can be attenuated if I put linear regulator before output. Is that true?
For example, if I want to power a +-12 V op-amp for an amplifier, I can use a switching-mode power supply (SMPS), say, with a…
sekharan
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26
votes
4 answers
True GPS Location - At the Antenna or Receiver Chip?
Suppose I have a GPS unit attached to an antenna through a 50 meter coax cable.
How would the location as calculated by the GPS unit be affected by the cable length? As a bonus question, how would the time accuracy of the GPS be affected by the…
David Gardner
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26
votes
6 answers
New to PCB design - why doesn't auto placing components exist?
The circuit design software I have seen has the ability to automatically route traces etc. on a PCB.
But why doesn't this software have the ability to automatically place components on a PCB say to minimise total board size?
Is this just too…
Adam
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26
votes
3 answers
Why are silicon wafers used in semiconductor production round?
Wafers used for making semiconductors are round -- but this wastes quite a few chips around the periphery of the wafer in the fabrication process. Wouldn't it make sense to make the wafer as a square or rectangle instead?
Is there some aspect of the…
Billy ONeal
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