AVR-Chat

I think you need to disconnect the voltage divider using an fet. The voltage divider will draw more juice than the avr in sleep mode! I assume you read the datasheet about the half dozen or so best ways to cut down on power consumption? (turn off a/d, turn off pullups, which sleep mode to use, etc)

-----Original Message-----
From: Richard Cooke <rcooke@digitalwavelength.com>
To: AVR-Chat@yahoogroups.com
Sent: Mon, 18 Jun 2007 12:30 pm
Subject: [AVR-Chat] Using the ADC to measure the battery supply?



Hi Folks,

I'm using the ATmega48V in a project and I need to monitor the battery
level (2 AAA cells) every so often and when low give an indication to
the user that it's time to change them.

I'm trying to minimize current consumption and I'm using the internal
1.1V reference so I'm using a voltage divider 1M + 3M to bring the
signal down to below the 1.1V reference.  I don't care how long the
conversion takes as I'm only making the measurement every 10 minutes
or so.

Do I need to use a buffer between the divider and the input to the
ADC?  If I do, what small, cheap and low power chip would you recommend?

Thanks,

Richard Cooke



 
Yahoo! Groups Links





________________________________________________________________________
AOL now offers free email to everyone.  Find out more about what's free from AOL at AOL.com.


[Non-text portions of this message have been removed]