Powering FM Modulator

**MoniraInc** · 08-14-2004, 06:51 PM

Hi,
My carputer is almost done but i'm having one last problem. I just went out and got an FM Modulator and it comes with the options of using two AAA batteries to power it or you can plug it into a 12V cigarette lighter. Using AAA batteries would get pricey over time so I was wondering if there was a way to hook it up to the computer's PS some how?

Thanks!

**migel628** · 08-14-2004, 07:33 PM

I would imagine if it takes 12v that you could splice into the 12v off of the PSU. Better yet, get a Y-splitter & lob off one of the ends...That way there is in perm. damage to the PSU...Just an idea, I could be wrong though

I would also guess that somewhere in the 12v source there is some kind of resistor or step down network, b/c I beleive that 2 AAA only produce 3V (1.5V each).

Please correct me if I am wrong...I hate giving misinformation...

**MoniraInc** · 08-14-2004, 07:41 PM

I have no issues with splicing because it's an older computer and i got it for $40

. But which wires is the 12V? is it the connector that is plugged into hdds, cdroms, etc to power them? If so there are 4 wires which ones would be neg and pos?

**Fox_Mulder** · 08-14-2004, 07:52 PM

Use the end of the cigarette lighter (12v) and connect the positive part (the tip) to the yellow and the black wire closest to the yellow wire to the negative (the other bit on the side) indicated in the diagram. It would be preferable to splice/solder the wires into place.

**MoniraInc** · 08-14-2004, 08:05 PM

Sweet Thanks!!!

**MoniraInc** · 08-15-2004, 12:13 AM

Uh o,
So i got it to work but now it doesn't auto turn on when it receives power. I'm using the iRock 400FM - http://www.myirock.com. Any ideas?

**bosstone74** · 08-15-2004, 12:29 AM

does it have a switch on it?

you may have to remove it and hook some wire together from the switch

**Fox_Mulder** · 08-15-2004, 01:12 AM

It depends on what type of switch, i'm guessing it is a standard SPST switch. If this is the case you can replace the the switch with a cheap relay, and wire the relay onto your computers 12v line so when power is applied to the computer, the relay closes and the fm transmitter powers on.
Connect the 12v and The Gnd Wires to the same place that you conenct your fm modulator to the computer's power.
There are also other useful schematics in the Schematics/Pin Outs/Diagrams thread, especially the one by stimps which shows you various ways of emulating switches.