Re: [avr-chat] Strange Timer Damage on ATMega16?

[Blake Leverett]

I would guess that the inductance of the motor parts has caused a voltage 
transient on your timer port pins.  I would have to see the schematic to 
guess how that is happening.  Feel free to send it to me to look at.

I would be very suspicious of having a burnt-out microcontroller in a motor 
drive circuit.  If it happens in the lab, it will surely happen in the field.

Blake


On Wednesday 16 January 2008, Shashank Chintalagiri wrote:
> Hi
> I've got some strange problem with the timers on an atmega16L. I'm
> using timer1 to produce two pwm signals that go on to some other
> circuitry that in general should not be drawing much current, and
> certainly not more than say 10 mA. The pwms seem to be working fine as
> long as the attached circuitry  (in specific, a motor driver) is
> powered down and I see the variation in  voltage with pulse width as
> expected. However, once the rest is turned on, the pwm outputs both
> jump to 5v. I _think_ it used to work for sometime earlier before
> going to 5 volts, but I cant say that for certain. Now the correlation
> between the turning on of the switch and the change in the output of
> the pwm pins is impossible to ignore.
>
> Also, replacing the atmega with another one, it seems to work just
> fine. I'll do some more testing to see if this one also starts
> behaving this way after some use, but as of now it seems to be more
> stable than the other one. The new atmega happens to be an atmega16
> (as opposed to the 16L used initially). I dont see how that would make
> a difference in this case, though. Both are using the internal
> oscialltor.
>
> Any ideas on what may have happened? Does anyone know of an atmega
> getting damaged/behaving in this way? Most importantly, should i worry
> about the same thing happening to next one also and make some changes
> to the rest of the circuitry.
>
> Thanks
> Shashank