RE: [avr-chat] battery-operated AVRs

[larry barello]

Do you have the brownout reset enabled?  What voltage?  If the supply is
below the BOD the processor will never come out of reset.

-----Original Message-----


Hi Bob,

I may not have time to draw and post a diagram before heading to the 
airport for my meeting tomorrow, but verbally here it is:

AVR:GND to ground end of 3 AAA's in series
AVR:Vcc to +4.5 end of 3 AAA's
1uF bypass capacitor

PA0-PA7 to input pins on 7-segment display
each (of 2) 7-seg ground pins through 100 Ohm resistor to ground
(Yes, it's common cathode.)

That's it.

I have not got this working yet, but the circuit still works correctly 
when powered by the STK500, so I am now wondering whether the problem is 
the need for an external clock, as Michai suggests.

However, I have switched to an alternate strategy, and I am now stringing 
9 AA batteries together to power the STK500. This is working, so far. Any 
guesses how long these batteries can power this setup? I only need about 
an hour...

-Marge

On Tue, 11 Mar 2008, Robert L Cochran wrote:

> Can you post a circuit diagram? Have you worked out a power budget for
> the circuit? I'm following the discussion with great interest.
>
> Thanks
>
> Bob Cochran
>
>
>
> Marge Coahran wrote:
>> Does anyone have experience running AVRs on batter power? I want to
>> give a brief demo at a venue without AC. I was hoping that 3 AAA
>> batteries would work, since that gives 4.5V and the datasheet says the
>> AVR I am using (Atmega8515L) can accept 2.7-5.5V power supply.
>> However, this does not work. Perhaps AAA does not produce enough
>> current? Does anyone know if using larger batteries (AA, C, etc) would
>> work, and if so what batteries I need?
>>
>> Marge
>>
>>
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>>
>


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