[chbot] Circuit help please, low voltage cutout

Chris Hellyar chchrobotics@lists.linuxnut.co.nz
Mon, 23 Apr 2007 09:14:00 +1200

Forgot to mention...

For a 'bot' application, you might find you need a 1uf cap on the '+'
input of the opamp as well, as this circuit stands a transient drop in
battery voltage from a motor stall or similar would turn the power off,
even though the cell is not flat.

Cheers, Me...

On Mon, 2007-04-23 at 00:53 +1200, Carl Ranson wrote:
> Ive been looking at this circuit for my bot's battery protector circuit:
> http://www.siliconchip.com.au/cms/A_104378/article.html
> There  are a couple of things I don't understand about it:
> a. Whats the point of ZD1? How does its value effect the cutout voltage 
> which I thought was determined by the voltage divider involving VR1?
> b. Can Q2 be replaced by a normal transistor and a relay? is the choice 
> of a mosfet because it will use less power than a relay?
> I know it was mooted that i could do it by using a voltage divider to 
> one of the pics ADC pins etc, but i want it to cover all of the 
> circuitry on the bot (even if the controller is disconnected).
> I will probably still monitor the voltage into the controller to 
> determine bot behavior but thats a ways off yet.
> Thanks all,
> CR
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