Teardrops n Tiny Travel Trailers

by **madjack** » Thu Sep 07, 2006 4:37 pm

I was asked a question that I am not sure of the correct answer...If you have a light/fan combination that runs offa 9VDC, what kinda resistor would you need to put in line (parallel) to run it off of 12VDC power...anybody got a good guess for me or should I get a potentiometer and use it to vary the voltage.....
madjack

by **SteveH** » Thu Sep 07, 2006 4:45 pm

Jack,

I would do it with two resistors...one in the lead to the light, and the other in the lead to the fan. You first need to know the current draw or each to figure the size of the resistor. Basically, you need to drop 3 volts at the current the fan/light is drawing at 9 volts.

by **PaulC** » Thu Sep 07, 2006 4:58 pm

Why not just go and buy a 12v fan instead of all the mucking around? :roll:

Cheers
Paul :thumbsup:

by **madjack** » Thu Sep 07, 2006 6:13 pm

Paul, that was my suggestion, but the person who asked me the question had found a fan/light combo that ran off of 9vdc and they wanted to use it for both instead of 1 of each...
madjack

by **sdtripper2** » Thu Sep 07, 2006 6:26 pm

MadOne:

How much current are you pulling with this fan/light?
If it is a small draw maybe this adapter would work for you?
9DC volt only adaptor
http://tinyurl.com/rzchh
Multiple volt
http://tinyurl.com/mgh22

by **madjack** » Thu Sep 07, 2006 6:32 pm

SteveT, that was my second suggestion BUT said questioner is a truly a tight b@[email protected] think the Radio Shack adpts are gonna be the way to go..
madjack

by **madjack** » Thu Sep 07, 2006 6:34 pm

SteveH, could you put a pot in line and use it to vary the voltage.............................

by **sdtripper2** » Thu Sep 07, 2006 6:42 pm

MadOne:

Here is a schematic for those that are not circuit challenged.

http://tinyurl.com/op5mf

Here are some Kits that will give you the 9 volt output.
http://tinyurl.com/ozbx6

by **sdtripper2** » Thu Sep 07, 2006 6:48 pm

MadOne:

This is the model I have

GE AV93600 Universal DC Battery Eliminator

Permits the Use of Equipment such as Radios, Portable CD Players, Small B&W TVs, etc.1200mA for Equipment Requiring 3-12 volts

http://tinyurl.com/qzehg

by **madjack** » Thu Sep 07, 2006 6:59 pm

Thanks for the replies gizes but as Emily LeTella sez..."never mind" after calling back to my buddy and informing him of options, they cost more than the fan/light combo did so he is gonna go with a 12v fan and a 12v light....which is what I told him to do in the first place...sighhhhhhh...that damn horse to water syndrome :lol:

madjack

by **GHOSTSSX** » Thu Sep 07, 2006 10:35 pm

MJ

Get a pic of that 9v fan/light. I wanna see it!!! Do you know what it was intended for??

CHUCK

by **bdosborn** » Thu Sep 07, 2006 10:43 pm

MJ,

You can use a voltage divider to do it.
http://www.doctronics.co.uk/voltage.htm

Just make sure your resistors are rated to handle the wattage of the fan/light combo. A voltage divider isn't an efficient way to drop voltage but its easy and cheap.
Bruce

by **madjack** » Thu Sep 07, 2006 10:46 pm

GHOSTSSX wrote:MJ

Get a pic of that 9v fan/light. I wanna see it!!! Do you know what it was intended for??

CHUCK

Chuck, all I know is that it was a Wal Mart cheapy from the camping section...after I informed my buddy what was going to be entailed in doing what he wanted, he decided to go a different direction...
madjack

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