Digital logic and voltage requirements

Archiver

I have a situation in which I'd like to know if a battery is going
dead soon. The battery is a 12V.

What I thought of doing was running a voltage divider in parallel
with the stamp curcuit it is supplying, to output a 5V signal, which
runs to the stamp. When the 12V supply starts to go, the voltage it
can supply will diminish slightly, forcing the divided output below
the 5V "logic" level. What I'm wondering though is how sensitive is a
stamp to the voltage level? If the voltage is at 4.9V will it read
as false?

I was also thinking about running the voltage through an ADC to guage
it, but I'd prefer the simplier method, if possible.

Thanks!

Archiver

>I have a situation in which I'd like to know if a battery is going
>dead soon. The battery is a 12V.
>
>What I thought of doing was running a voltage divider in parallel
>with the stamp curcuit it is supplying, to output a 5V signal, which
>runs to the stamp. When the 12V supply starts to go, the voltage it
>can supply will diminish slightly, forcing the divided output below
>the 5V "logic" level. What I'm wondering though is how sensitive is a
>stamp to the voltage level? If the voltage is at 4.9V will it read
>as false?
>
>I was also thinking about running the voltage through an ADC to guage
>it, but I'd prefer the simplier method, if possible.
>
>Thanks!

The voltage logic threshold for the stamp is near 1.4 volts. That is
what you would need for the voltage divider.

An alternative that I like to use is RCtime. Here are details:
http://www.emesys.com/BS2rct.htm#B_voltage

-- regards
Tracy Allen
electronically monitored ecosystems
http://www.emesystems.com
mailto:tracy@e...