>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 11 August 2005 21:17
>To: Microcontroller discussion list - Public.
>Subject: Re: [EE] Signalling low battery voltage
>
>
>Easy :
>1 op-amp (or comparator), a few resistors, a NPN if the IC
>is weak, and a diode (whatever kind) + LED. The diode serves 
>as a 0.6V (or whatever, it could be a zener) reference. You 
>have a divider network formed by 2 resistors arranged so that 
>the voltage is 0.6V when discharge point is reached. Connect a 
>LED+resistor on the output. I made one mounted on a LM741 
>body: http://rsc-mirror3.netfirms.com/1/elec/batmon.htm
>The LED is hidden behind the potentiometer.

Very cheap, but the tempco of a silicon junction could mean your discharge indication voltage varying significantly with temperature.  A proper voltage reference would be much better.

Regards

Mike


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