Yes, an even better idea! I had not thought of that for this application, but it sounds good. In the products I've done, I don't know how someone could stuff more AA cells in there than I had designed for, but SOMEONE could overvoltage it! Harold Harold Hallikainen harold@hallikainen.com Hallikainen & Friends, Inc. See the FCC Rules at http://hallikainen.com/FccRules and comments filed in LPFM proceeding at http://hallikainen.com/lpfm On Mon, 8 Nov 1999 08:14:03 -0800 Nick Taylor writes: >Harold's suggestion is good, but it can be improved by using an >appropriate valued zener for the diode ... also gives overvoltage >protection. It's saved my breadboard circuits from frying more >than once. > - Nick - > >Harold Hallikainen wrote: >> >> How about a series PTC then a shunt diode. The diode will >conduct if >> the batteries are put in backwards, opening the PTC. >> >> Harold >> >> On Mon, 8 Nov 1999 05:26:07 -0800 mazzoni michele > >> writes: >> >Hello List, >> > >> >I have realized an alarm for my bycicle using a 12C508. It is >powered >> >by two AA >> >size alkaline battery. >> > >> >I would like to know if there is a simple (and economic!!) solution >> >which >> >I can use to protect my circuit against polarity inversion during >> >battery change. >> >(I know it's a remote possibility, but it exists) >> > >> >I thought to use a serie diode, but the voltage drop bring the PIC >> >power voltage >> >near the power supply limit of the MCU. >> > >> >Thanks. >> > >> > >> >Best regards, >> >Michele >> > >> >_______________________________________________________ >> >Are you a Techie? Get Your Free Tech Email Address Now! >> >Many to choose from! Visit http://www.TechEmail.com >> >> ___________________________________________________________________ >> Get the Internet just the way you want it. >> Free software, free e-mail, and free Internet access for a month! >> Try Juno Web: http://dl.www.juno.com/dynoget/tagj. ___________________________________________________________________ Get the Internet just the way you want it. Free software, free e-mail, and free Internet access for a month! Try Juno Web: http://dl.www.juno.com/dynoget/tagj.