volt. monitor

Archiver

I wish to monitor the stamp battery(9v.) to determine when it is no longer
of use to the stamp and I have some questions:

1. what is the voltage that the stamp will no longer function at: 5v, 4.5v,
4v?

2. Am considering a voltage monitoring led from lumex(@ Digikey); it says
it will monitor breakdown voltage from 7.5v to 3.5 v but resistors must be
used with this 3 lead led to determine your detection voltage. I believe I
understand the resistor calc.'s for a voltage divider to set the detection
voltage but am not sure how to insert it in between the 9v and stamp(along
with which voltage to use as detection voltage--see 1. above)?

Another thot was to use Zener diodes and reg. led to detect voltage drop.
Requesting help on this circuit also.

Thanks in advance,

John Bell



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Archiver

I am using the stamp itself to monitor the 9 volt battery using a simple
voltage divider. I ultimately plan on using the RC Time command to detect
various states of charge of the battery. Does anyone have any thoughts on
this. In the "nuts and Volts of Basic stamps" book, there was an article on
doing this but it used a homemade optoisolator. Seemed a little clunky and it
seems the same results should be obtainable with just a simple RC network
tied to the battery. Does anyone have any experience with this technique??

Archiver

This seems to come up a lot. Tracy Allan has already done the work for us,
and generously posted how to get it done, along with a few other hints and
tricks......

See http://www.emesystems.com/BS2rct.htm#B_voltage


At 01:02 AM 4/29/02 -0400, you wrote:
>I am using the stamp itself to monitor the 9 volt battery using a simple
>voltage divider. I ultimately plan on using the RC Time command to detect
>various states of charge of the battery. Does anyone have any thoughts on
>this. In the "nuts and Volts of Basic stamps" book, there was an article on
>doing this but it used a homemade optoisolator. Seemed a little clunky and it
>seems the same results should be obtainable with just a simple RC network
>tied to the battery. Does anyone have any experience with this technique??
>
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