AVR Microcontroller with DC 12V 10A input source

Thread Starter

mukund_bm

Joined Aug 24, 2014
18
Dear Friends,

I am using Atmega328P, input source of 12V10A with 7805 Voltage Regulator, when I connect the input source the regulator Capacitor got burnt.

Kindly advice, if we need to add 7812 voltage regulator before 7805?

Below Schematic

1622812283499.png
 

Irving

Joined Jan 30, 2016
1,540
No reason to, 47uF should be fine as long as its a good brand and not a cheap fake, or a very old dried out one, or wired in back-to-front. Suggest a 16 or 25v rated version, 1000v seems a little excessive.

When you say 'burnt' what exactly happened to it?
 

BobTPH

Joined Jun 5, 2013
3,316
Where did you get a 47uF 1000V capacitor? The two listed on Mouser.com are $60 each. Somehow I doubt that that is what you have. So I also doubt that it is 47uF. What is it really?

Bob
 

Thread Starter

mukund_bm

Joined Aug 24, 2014
18
Thank you very much Mr. Irving for immediate support.

It was blunder mistake done while connecting the input source. I have corrected now and it is working fine. As you have suggested capacitor 1000v is not required, I have changed to 47uF 25v.

Bhimsen
 

BobaMosfet

Joined Jul 1, 2009
1,776
Dear Friends,

I am using Atmega328P, input source of 12V10A with 7805 Voltage Regulator, when I connect the input source the regulator Capacitor got burnt.

Kindly advice, if we need to add 7812 voltage regulator before 7805?

Below Schematic

View attachment 240453
You misconnected something- which is why you should also have a fuse and/or diode on the input power. Secondly, your LM7805 will run a bit hot because you are forcing it to drop ~7V... it has to dissipate that energy. You could use a zener/transistor circuit ahead of the LM7805 to drop the voltage, or use an LM7808 to approximately halve the 7V problem, which will let the LM7805 run cooler.

Remember Thermal Junction Temperatures- you run high voltage, you lose the ability to pass current. The lower your voltage, the more current you can pass through a given junction.

Using your numbers- 12V in, and 5V out, without a heatsink, the max current you can get out of an LM7805 while keeping it at 38.8C is 318mA:

1622817904145.png

If you make the input 8V into the LM7805 it becomes:

1622817971315.png

And if you add a TO-220-3 heatsink (assuming you're using a TO-220 package LM7805):

1622818034193.png
 
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