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jcferguson
01-21-2007, 06:15 AM
I have a stamp circuit that needs reverse voltage protection (it's a slot car arrangement that could be put on backwards pretty easily). Right now I have an in-line diode, but the voltage drop is too great for my purposes.

I found these two solutions and wonder if anyone has any thoughts on which would be better? If I use a fet, how do I choose which one?

Thanks,

Carlos Ferguson

http://www.elecdesign.com/Articles/ArticleID/9945/9945.html

http://www.chris.org/Modifications/reverse-polarity-protection.html

PJ Allen
01-21-2007, 08:00 AM
jcferguson said...
If I use a fet, how do I choose which one?

The www.elecdesign.com (http://www.elecdesign.com) article states that an IRF7342 was used in one and·an IRF7341 was used in the other circuit.

The http://www.chris.org article uses a relay (and they suck current.)

Update --

http://catalog.digikey.com/scripts/partsearch.dll?lang=en&site=US&keywords=IRF7342

http://www.jameco.com/webapp/wcs/stores/servlet/CatalogSearchResultView?langId=-1&storeId=10001&catalogId=10001&searchType=m&searchValue=irf7342&categoryId=51035

Post Edited (PJ Allen) : 1/21/2007 2:41:03 AM GMT

jcferguson
01-22-2007, 12:22 PM
thanks PJ,

I guess my question is which method makes more sense for this application - I probably have about 2 amps max at 12v drawn by my circuits, I tried out the relay method, it works fine... I want this to work for a good long time though, do I need to worry about the relay wearing out, and would a fet be better in this respect, or do I have to start worrying about heat with the fet?


thanks,

Carlos