How does reverse polarity protection work?

[cleetus03]

Was wondering if someone could explain this concept (reverse polarity protection) to me in layman terms?

For example, I read that if you put the batteries in backwards in a minimag led, the moment you twist it on.......poof?


I am assuming flashlights without reverse polarity protection are the minority?.....Is this correct?

Appreciate all the help and info yall can give me!

 

[Marduke]

Most reverse polarity protection is a physical ring which allows a positive nipple to contact the board, but won't allow the negative end to touch.

Most lights have no protection. Don't assume it does unless it explicitly states so.

 

[kramer5150]

As marduke says... usually a ring or raised bumps around the + contact. They prevent electrical contact when the cell is installed backwards. Some DC-DC boards have diodes in line with the +ive input to protect the circuit, they present a Vdrop to the circuit though so a physical type of prevention is better. I always bypass the diodes on my boards to keep the 7135 chips running in regulation for a longer time.

 

[cleetus03]

appreciate the reply's and apologize for putting the thread on the wrong subforum...

 

[BackBlast]

You can also use FETs to provide reverse polarity protection with a minimal drop compared to, say, a straight in-line diode.