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Example power supply for AVR

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Mike odom

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View attachment example1.PDF


View attachment example2.PDF

Example1.JPG Example2.JPG
 
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AREF should be disconected from +5V.
The 100nF Capacitator at AREF should be leave conected.
An additional 100nF Capacitator must be conected then to the AVCC Pin, because the connetion to AREF ( and the capacitator ) is removed.
So You have the choice between different A/D Reference Sources, including the internal one.

Why built in so much Zener Diodes to stabilize the Voltage.
You could also use Voltage Regulators.
TRACO Power has some switching regulators in it's Portfolio.
Look at this https://www.reichelt.de/Wandler-Mod...8AAAIAAHLqxvAfa5749f8d02859f725ae89da4945ade5
That'a an example for an 5V Output Switching Regulator. It's pin compatible with an 7805 type.
 
It only has one zener on the 12V line. It doesn't need a highly regulated 12V line.
It uses TVS (transient voltage suppressors) to clamp voltage spikes.
The 7805 is reliable, cheap, and all that is needed for this design. Why would I spend $11.85 for a 5V regulator when a $0.25 LM7805 part will do? Half the art of engineering is not just getting things to work, but to do the best job for the cheapest cost.

The choice for this design was AVCC from the external design. That's why it's called an example... it's a design I used and he was asking about the protection I use to keep the micro from shutting down when you don't want it to.

Quote: "Anyone can build a bridge. But it takes an engineer to build a bridge that just doesn't fall down."
 
The 7805 is reliable, cheap, and all that is needed for this design. Why would I spend $11.85 for a 5V regulator when a $0.25 LM7805 part will do?
That's absolutely right.
I've thought, you would stabilize the 12V Voltage via Zener Diodes.
That is very ineffective, so I would suggest You to use a Switching Power Supply.
 
you don't really need them unless you're in a noisy environment. I did this design to run off the same power supply as a 1/2 horse power motor, and you could hold the unshielded board right up beside the motor while it was running without it resetting. They are also a good idea if you're building a commercial product and have to pass FCC testing, or what's equivalent to our FCC in your country. They keep the microcomputer switching noise off the power supply line and vice versa. They filter out the 3.6MHz crystal frequency.
 
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That's absolutely right.
I've thought, you would stabilize the 12V Voltage via Zener Diodes.
That is very ineffective, so I would suggest You to use a Switching Power Supply.

It's very effective. Like I said, a well regulated 12V supply is not needed. Just something in the area of 12V, which feeds 4 switching power supplies that I control via the micros. Which I built, like I said, why would I buy a $10 supply (x4) when I can build it for $3.00... and part of the design dictated that it couldn't be an off the shelf design, has to output responding only to a limited input frequency from the micros, so I drive them directly and not using an interrupt routine.

If the design calls for a well regulated 12V supply, then I use one. If it needs a lot of current, then I use a switcher. The idea is to go only as far as needed. True, I only have a couple of hundred in the field (not like my waffle cooker that has 20,000), but so far there's only been one reported failure in 8 years, and that was due to a wiring error at installation, not a hard board failure, and they operate out doors (shack sitting beside a railroad) from Bath, Maine to Detroit, Michigan.
 
you don't really need them unless you're in a noisy environment. I did this design to run off the same power supply as a 1/2 horse power motor, and you could hold the unshielded board right up beside the motor while it was running without it resetting. They are also a good idea if you're building a commercial product and have to pass FCC testing, or what's equivalent to our FCC in your country. They keep the microcomputer switching noise off the power supply line and vice versa. They filter out the 3.6MHz crystal frequency.

lol :)..it not going for any FCC that for sure...

For home use i guess i dont need it. Can blender or vacuum cleaner in my house create motor like noise in the main AC and cause my Uc to hang.

My power supply design is very straight forward
its 220VAC to 12VAC transformer to full wave rectifier bridge to 2200uf and .1uf cap to LM7805 input pin. Output pin of LM7805 also has a 0.1uf.
 
lol :)..it not going for any FCC that for sure...

For home use i guess i dont need it. Can blender or vacuum cleaner in my house create motor like noise in the main AC and cause my Uc to hang.

My power supply design is very straight forward
its 220VAC to 12VAC transformer to full wave rectifier bridge to 2200uf and .1uf cap to LM7805 input pin. Output pin of LM7805 also has a 0.1uf.

anything is possible, but probably not unless you are running this in the kitchen along side them and off the same circuit.

I would also suggest a 10uF on the output of the 7805. There should be a .1uF on the input and output of the 7805, as close as possible to the device.
 
anything is possible, but probably not unless you are running this in the kitchen along side them and off the same circuit.

I would also suggest a 10uF on the output of the 7805. There should be a .1uF on the input and output of the 7805, as close as possible to the device.

no its far away from the kitchen. i will put a10uf in the output. I actually solder the cap's directly in the 7805 legs :D saves space and time
 
yes, those are capacitors... unfortunately, capacitors aren't stamped like resistors. The only way to tell what they are would be to pull them and measure with a capacitance meter.

and you still wouldn't know the voltage or chemistry (ceramic material type)... the voltage you can guess by the circuit they're used in, and the chemistry, just pick the best one.. X7R
 
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