What you really want is a mechanical latch that holds your bin in position with NO power. Then a pulse to the electromagnet moves a pin that frees the latch, even when under heavy load (a matter of design). R Mike Hord wrote: > On Wed, 29 Sep 2004 09:49:38 +0100, Alan B. Pearce wrote: > >>>The big question now is, can I make an electromagnet capable of >>>pushing the magnet away and still run the thing on batteries? >> >>How are you going to charge the battery? This starts to look like a device >>with a cable coming out, to go to a single central battery that powers all >>units. They do not all need to let go simultaneously, to lower the battery >>current demand, if you can use (say) a six conductor cable (I am thinking >>something rugged like used for trailer connections on cars) which will carry >>the power and enough communications between devices for a sequencing signal. >>Now one battery, an SLA or similar in the office can be on float charge, >>removing maintenance of that from the hassles the worker has to deal with. > > > The original hope was to do this on three or four D-cell alkalines, > and I may yet > realize that hope. It may require a step-up charger into a cap, to get many > small sips of juice from the battery to end up with a high enough burst into the > EM coil to release the magnet for the critical instant. > > Or I may end up doing something completely different. Some initial experiments > with a solenoid yesterday showed that even up to 12V, the solenoid did not > really want to repel even a small magnet, much less one capable of doing what > I need it to do. All in all, it's been a fairly educational process. > I will certainly > try to remember to post a result and let you all know which method proved > most effective. > > Mike H. > _______________________________________________ > http://www.piclist.com > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > _______________________________________________ http://www.piclist.com View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist