You could get around the hysteresis issue by implementing a PTC switch. Push To Connect. Press switch to connect load. Once battery falls below cut-off, the NO switch prevents reconnection. On 6 Nov 2016 09:39, "Chris McSweeny" wrote: > Thanks - looking at the datasheet for that MC34064 it does strike me that > my suggested circuit has an issue with lack of hysteresis which could > result in oscillation. I suspect the zener biased PNP you're suggesting > would also suffer from that (because the battery voltage would recover > following cutoff). > > Chris > > On Sat, Nov 5, 2016 at 9:53 PM, Antonio Benci > wrote: > > > 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 t= o > > > 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 bias= ed > > > with a zener diode and resistor (and a voltage divider on the positiv= e > > > input) to create a schmitt trigger, with the output driving a FET, a > > total > > > 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, a= nd > > it > > > 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 > > > > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > 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 .