ATmega168 overheated?

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limseckhoung
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Posted by limseckhoung: Wed. Sep 9, 2009 - 12:08 PM
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Hi,

I'm new to all these.

I used LM7805 as the power supply, connected to a 9v battery

Atmega168-Pin 7,Vcc and pin20, Avcc connected to positive, Pin8, Gnd and pin22, Agnd connected to negative.
Pin1, reset connect high.

Atmega168 is connected to STK parallel port dongle programmer.

I turn on the power for the 1st time, and used the mutlimeter to check the power rail and only found 2.4v. I got smells of something burning, the Atmega168 was very hot, but no smoke seen.

So, the is the Atmega168 overheated and damaged?

thank you.

Tags:

AVR Microcontrollers, megaAVR and tinyAVR, ATmega16, ATmega168
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Gold Markclawson
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Posted by clawson: Wed. Sep 9, 2009 - 12:27 PM
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Quote:

So, the is the Atmega168 overheated and damaged?

Sure sounds like it. It might recover but I'd never trust a chip that's got hot/smelly. Bin it then start again - socket the chip and before fitting it test the voltage on each pin (the regulator may need a load to start)

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meslomp
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Posted by meslomp: Wed. Sep 9, 2009 - 12:28 PM
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it might be......

you might be lucky and only have reduced it's lifetime with a enourmous amount. But it might also be that you ried the chip.

I'm more wandering why this happened in the first place.

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Jepael
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Posted by Jepael: Wed. Sep 9, 2009 - 12:30 PM
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nobody knows. it may or may not work anymore, and even if it seems to work, it may only work partially.

what is more important is that do you know what you did to it? was the power backwards? or did you try to feed 9V to it by some accident?

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leon_heller
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Posted by leon_heller: Wed. Sep 9, 2009 - 12:48 PM
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Did you check that the regulator output was correct before you added the chip?

Leon

Leon Heller G1HSM

Last Edited: Wed. Sep 9, 2009 - 12:57 PM
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Gold Markclawson
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Posted by clawson: Wed. Sep 9, 2009 - 12:53 PM
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The 2.4V sounds more like a 0V vs 5V "battle"

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limseckhoung
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Posted by limseckhoung: Wed. Sep 9, 2009 - 01:12 PM
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I've definitely checked the 5v before using it.
If I connected 9v to the power rail, then would the 2.4v appear?
However, I'm still figuring what I did to it.

Hmm... I guess it's safer to get a new one $$ and be more careful the next time.

thanks.

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Gold Markclawson
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Posted by clawson: Wed. Sep 9, 2009 - 01:22 PM
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Yes but as others have said do not simply plug in a replacement without first working out why it was damaged or you could work your way through a tube full of the things melting each one in turn.

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limseckhoung
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Posted by limseckhoung: Wed. Sep 9, 2009 - 02:47 PM
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ok thanks for advise!!

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Bronze Markjs
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Posted by js: Wed. Sep 9, 2009 - 10:47 PM
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Quote:
reset connect high.
I hope NOT directly to VCC but pulled high by, say, a 10K resistor?

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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DocJC
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Posted by DocJC: Wed. Sep 9, 2009 - 11:16 PM
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Quote:
If I connected 9v to the power rail, then would the 2.4v appear?

Do NOT do this. You will get another hot and dead chip.

JC

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limseckhoung
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Posted by limseckhoung: Thu. Sep 10, 2009 - 12:02 AM
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js wrote:
Quote:
reset connect high.
I hope NOT directly to VCC but pulled high by, say, a 10K resistor?

yes, pulled high by a 10k resistor.

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meslomp
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Posted by meslomp: Thu. Sep 10, 2009 - 06:23 AM
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If the supply was OK before connecting the AVR then perhaps the problem is the connections of the avr.

check that you have connected the power supply correctly.
if you are 100% sure then first add a new chip without the programmer. immidiately start to feel if it gets hot and if it dies then remove the supply. Most chips can handle a power supply error for a very short time.

if it does not get hot then you can add the programmer to the setup and check that the chip still does not overheat. and also before attaching make sure that the connections are correct.

regards

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