Reverse polarity protection

[videoman]

I am using a DX driver (26110) that is not polarity protected from the input DC source. I would like to have a way to protect the circuitry so that in the event that the input is reversed, the driver would not go up in smoke. Can a simple diode or rectifier be placed in line with the driver in + lead so that the current will only flow in the proper direction ? If so, are there any values of the diode that I should get? The input DV voltage to the driver is between 7.2 to 16V DC. It is a 1200 ma driver ( Buck type)

 

[qwertyydude]

You could put a diode in line but it would drop voltage so you'd lose efficiency. The way most people accomplish reverse protection without dropping voltage is to put an inline FET. You can read more about it here and see an electronic diagram too.

http://electronicdesign.com/article/power/fet-supplies-low-voltage-reverse-polarity-protecti.aspx

 

[VegasF6]

Try a 1n5820, 1n5821 or 1n5822. 3A Schottky. Or a 1n5401 silicone diode. Also 3A but will have a higher voltage drop. Or 02. Or 03. Whatever you can find I suppose.

Are you limited on space?

 

[uk_caver]

Just in case anyone reads the article linked to by qwertyydude a bit too quickly, I'd emphasise that for reverse polarity protection, the FET is connected the 'wrong' way round, so if using an N-channel FET for low-side connection, the gate goes to input/circuit positive, the drain to input negative, and the source to circuit negative.

 

[Lighthouse one]

You might also look for a very thin nylon washer at a good hardware store. I found one that has a center hole just the size of the positive nose of a battery. At 1/16" thin it prevents the negative end of a battery from making contact. I use one for my Nitecore EX10.

 

[Notsure Fire]

You might also look for a very thin nylon washer at a good hardware store. I found one that has a center hole just the size of the positive nose of a battery. At 1/16" thin it prevents the negative end of a battery from making contact. I use one for my Nitecore EX10.

That's pretty ingenious. I'd never thought of that.

 

[VegasF6]

Yah, that is a pretty good tip. Long ago I bought the "Tonch" from DX (anyone remember that?) it had a similar setup.

Dunno what videomans application is though. At first I thought automotive, but perhaps being videoman it is an external camera light with a separate battery pack. Or who knows.

 

[videoman]

Thanks for all the responses. I need the protection for a video light. I just want to be sure that if I lend the light to fellow videographers that they will not damage the driver if their battery set up is in the reverse polarity.The light has a DC in plug that has the center tip as positive. There are no standards as to the polarity of 5.5 X 2.1 mm round DC power in plugs as some portable radios and DC powered gadgets seem to have the sleeve as positive and the center pin as negative. A wedding is no time for video lights to fail due to reverse polarity mishaps.

 

[alpg88]

That's pretty ingenious. I'd never thought of that.

+1 on that,