I don't agree with the statement that your product has failed. Just the contrary. The user has preserved his/her investment in that product. The failure is in the user not following instructions in installing the batteries. If they would have been paying attention, they wouldn't have put the batteries in backwards, and they would not have had the inconvienence of a blown fuse. But they only lost a fuse and a little time, not the whole unit. As far as not being servicable by the user, how much education and coordination does it take to change a fuse. It would have taken less time to pay attention to the battery installation instructions in the first place, thereby saving time and trouble. The end choice is up to the designer. I only offered a suggestion. One that has been used and proven by me. It is there for you to consider. Whether you use it in your end product is totally up to you. Whatever failsafe method is chosen, as long as it provides the degree of safety necessary, and at a cost that is agreeable by everyone involved, is the right choice for that product. I guess I'm done now. Thanks for letting me sound off on what I think regarding this issue. Good Luck, Jim -----Original Message----- From: Paul B. Webster VK2BZC To: PICLIST@MITVMA.MIT.EDU Date: Monday, May 31, 1999 5:25 PM Subject: Re: Reverse Polarity Protection for 3V PIC Circuit. >Jim Paul wrote: > >> You could add a diode across the batteries with a fuse so that is the >> batteries are inserted the wrong way, the fuse blows cutting off the >> power source. > > But then your appliance has "failed". Not good publicity. OK, if it >is used under supervision and can be repaired and put back into service. >Better to use a resistor (only need a few ohms) and diode. > > Reverse-inserted batteries promptly go flat. "Darn batteries!" >Properly inserted ones last for "ages". Appliance always works if >good batteries inserted correctly. This is the "teaching" approach. >-- > Cheers, > Paul B.