AVR-Chat

I can't recall the circuit for the Butterfly, but if I was you I would put a
5.1V zener diode across the input to the AVR ADC input just in case your
input goes above 30V or you resistor fails for some unknown reason. This was
you will protect the AVR from damage. I find this good practice when there
is a risk of the input voltage ever going above the max of an input pin.

 

Dave.

 

 

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Graham Davies
Sent: 12 August 2009 22:29
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] Re: Butterfly mod

 

  

--- In AVR-Chat@yahoogroups.com <mailto:AVR-Chat%40yahoogroups.com> ,
"u4ia2000" <u4ia2000@...> wrote:
>
> The Butterfly will read 0 to 5v.
> My question is can I get to to
> read 0 to 30v simply or would
> take a lot of hardware?

It would take two resistors. Just make up a voltage divider. Begin by
looking up the schematic of the AVR Butterfly to see what the input
resistance of the analog input is. Take that into account when you calculate
the resistors of your voltage divider. Use 1% tolerance resistors if you
need that accuracy.

Graham.



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