Simplest I have seen is a zener biased pnp as a low voltage drop out switch and a dpdt relay. I'll try to find this, no promises though. You could even use an MC34064 low voltage detect, suitably biased. On 6 Nov 2016 08:17, "Chris McSweeny" wrote: > A request from a friend - he's after a really simple cutoff circuit to > disconnect an external battery when it drops below a certain voltage. > > The best I can come up with is an op-amp with the negative input biased > with a zener diode and resistor (and a voltage divider on the positive > input) to create a schmitt trigger, with the output driving a FET, a tota= l > of 6 components (excluding any caps, but my feeling is we could get away > without those if necessary). Is there any simpler way to do it, or if not > is my circuit likely to be reliable? > > About 100 of these circuits needed, so we're into proper small batch > fabrication rather than hobbyist scale, and it is for a commercial > operation my friend runs (I'm hoping there is some budget for this, and i= t > might even lead to other opportunities). > > Thanks, > > Chris > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .