On Sun, Nov 14, 2010 at 04:11:32PM -0500, Jim Lynch wrote: > > To keep this on point I recall hearing a talk about modern electronics > aboard boats. One of the devices discussed is a bilge pump that > periodically turns on and if the pump senses it isn't pumping water, it > turns off. I'm sure it's measuring the current draw to determine if > water is flowing.
They're made by Rule and are referred to as "Fully-Automatic" bilge pumps. For some reason, they're very hard to find, even on the Net. Here's an example from a UK shop: http://x.co/KGdb This one is listed as cycling every 20 seconds; in other places, they're shown as cycling every 2.5 minutes for a couple of seconds. It may be worth calling Rule to get the full story. > My bilge is designed such that switches are quite > impractical and I'd sure like to find on of those beasts. Before > someone suggests an integrated switch/pump, I've had bad luck with those > in the past. > > I've googled but I can't seem to find the right combo of search terms. > > I'm working on designing one of my own based on a microprocessor, a RTC > and some other parts but I wouldn't mind having a commercial one foe > backup. Can't see where you'd need a microprocessor; a timer chip, an op-amp comparator, and a driver transistor should do it - maybe $10 worth of components all together. Feed one side of the comparator from a shunt, and drive the other input from a voltage divider driven by the timer on one end and positive feedback from the output of the comparator on the other. Set the divider so that when the pump is dry, there's not enough drive to kick the comparator on - but when the pump is loaded, the voltage from the shunt is enough to keep the comparator on. As they say, this is untested but should work. :) -- OKOPNIK CONSULTING Custom Computing Solutions For Your Business Expert-led Training | Dynamic, vital websites | Custom programming 443-250-7895 http://okopnik.com http://twitter.com/okopnik _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://liveaboardonline.com/mailman/listinfo/liveaboard To subscribe send an email to [email protected] To unsubscribe send an email to [email protected] The archives are at http://www.liveaboardonline.com/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
