PIC10F320 *2.3 to 5.5V operation. *Low Power Sleep Mode *Fixed Voltage Reference (FVR) with 1.024V, 2.048V and 4.096V Output Levels *A/D Converter: 8-bit resolution with 3 channels Part Count: 3-ish. PIC, P-Channel FET, decoupling cap. The PIC10F320 only costs $0.42 USD at a quantity of 100 from digikey (SOT23-6 package). Sounds quite reasonable to me since the PIC can be powered directly from the battery with no voltage regulation. I hate to bring this up, but... At least in the US, the use of a Micro means typically that the product should be FCC tested before sale (unless this falls into an exempt category [1]?). Undoubtedly your battery cutoff device would pass, but even minimal testing is expensive. Going without any testing would entail certain risks which, hopefully, you are quite aware of. Because of the regulations it may be advisable for you to stick to analog components. [1] FCC Part 15, Section 15.103 On Sun, Nov 6, 2016 at 1:31 PM, Steve Smith wrote: > 10F and a p fet 3 parts ! and I am pretty sure that one of the 10F's has = a > 1.2v bandgap reference worse case add two resistors > > S > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf > Of > Chris McSweeny > Sent: 06 November 2016 18:07 > To: Microcontroller discussion list - Public. > Subject: Re: [EE] Really simple cutoff circuit > > http://www.batterysupports.com/queclink-gps-tracker- > gl200-gl300-gl300w-3400m > ah-external-battery-p-481.html > - so I was wrong about 4.5v cutoff. That does look like it already has a > circuit which should do this, but apparently it doesn't, so we're looking > at > 3v cutoff (and 4.2v max). Current draw as I suggested before - a 1700mAh > battery will do 24hrs, so ~70mA. > > Thanks, > > Chris > > On 6 Nov 2016 15:19, "Chris McSweeny" wrote: > > > On Sun, Nov 6, 2016 at 12:50 PM, IVP wrote: > > > >> How about a PIC10F with ADC ? Economy vs discretes might not be too > >> bad in quantity (10F320 ~ NZ$0.70 @ 100) > >> > > > > Hmm - I don't think the price of that would be a problem - > > realistically the cost of components is likely to be dwarfed by the > > build costs whichever way we go. It would certainly be straightforward > > to avoid the oscillation problem which I think would be an issue with > > most or all of the other proposed circuits. Not really sure why I > > didn't think of that when posting to a PIC list (though I suspect I'd > > probably go with an AVR as I have more recent experience of those, so > > the dev would be a lot quicker). Not that it would reduce the part > > count much - it would still need a potential divider on the input, > > something to drop the input voltage within range and an output FET. > > > > In answer to some of the queries, current requirement is low - I'd > > assume less than 100mA because it's for something which would last > > many hours with a fairly small battery. I'm not sure of the battery > > chemistry and hence max voltage or quiescent current requirements > > (though I'm expecting quiescent current not to be a big problem) - the > > only spec I've been given is a 4.5V cutoff. Will get some more details = in > order to spec this better. > > > > Some more details - it's for an external battery for a tracking > > device, to be used in an event which lasts up to 7 days - though the > > battery will get switched over during that, so I'm not sure of the > > expected duration. Needs to be small, light and simple - I don't think > > pressing a button to enable it is likely to be a good idea, it needs > > to be fully automatic when plugged in. > > > > Thanks for all the info so far - it seems I wasn't too far off with my > > initial thoughts, though it's good to get better suggestions. > > > > Chris > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change > your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t > > -- > 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 Jason White --=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 .