How to convert 12cDC (in car) to 5vDC?? Any clues?

[Silvia007]

Need to run some electronics that runs off of 5 volts DC.

[LuvMyJ]

Check the web for a DC-DC converter. Two companies I use at work are Lambda and Vicor.

Cheers,Bob

[Simmsled]

Go to Radio Shack and find the dorkiest nerdiest guy there (pocket protector a plus) and that guy will be the best help. Works every time.

[IveBeenBad]

resistor

[Silvia007]

I've tested a resistor with a volt-meter and it does nothing for dropping voltage... I was hoping you guys have some clue on how to make a simple device for doing so. My last option is a dc-dc converter but I don't want nothing too big. I guess I'll have to stop by Radio Shack.

[minutericesentra]

If your "electronics" will be pulling a consistent(staying at a certain level) amount of power you should be able to just use a resistor, If you tried measuring the resistor's voltage drop without a load you would get the source voltage(~12v) because the voltmeter isn't supposed to act like a load.

[Silvia007]

I see... so, you know what resistor I should get to drop 12 volts to 5? As you can see I'm not very good with this.

[minutericesentra]

Well actually using a resistor might not be the best option in this case if your "electronics" are very sensitive to the difference in voltage when the car is/isn't running, since your voltage can vary from a little over 14v to under 12v it would probably be best to go with the converter. But the size/value of the resistor will depend on the amount of power/current the load uses, so if you know that, you can use something like this chart( http://community.webshots.com/...apcmY ) to figure out what resistor to use, or I could figure it out for ya.

[Silvia007]

hmmm... couldn't I just get like an adapter for a cell phone or something liek that from like target or walmart! Doh, should of just done that, anyway, minutericesentra, if you can get me what resistance a resistor has to be to do what I want please tell me, I have no idea how to use that chart you linked to. When it comes to electronics, I'm clueless.

[minutericesentra]

I would have to know how much current(amps) or watts it uses.

[Silvia007]

very very little, just a 5 volt 2 port usb hub used to run accessories off of a laptop I integrated into the car as a dvd player, mp3 player, etc. etc. It draws about 500mA.

[MainEvent212]

woah, that sounds pretty trick man! i dont know anything about this but i always have fun reading this stuff...you should post pics

[Silvia007]

sure, once it's all working, I will.

[minutericesentra]

Sorry I haven't replied to you, the first time I tried to reply the forum was messed up and then I just forgot about it!Anyways, I figured that at 14v(engine running) you will need a 18 ohm resistor that can handle at least 4.5 watts, but at 12v(engine off) you would need a 14 ohms, 3.5 watt resistor to keep the 5 volts that you need, I didn't even think about the change in voltage between when the engine is/isn't running before I suggested the resistor idea. If you split the difference and used a 16 ohm 4 watt resistor you would get 6 volts with the car running ang 4 volts without. So it would probably be best to just get a conveter, they're easy to wire up and relatively inexpensive, usually solder into place, just make sure to get one that exceeds your power needs so it'll last a long time, sorry if I got your hopes up.

[Silvia007]

No it's fine, Thanks man, I'll try the resistor idea, if it doesn't work too well, then I'll just pick up a DC to DC converter. Main reason I would rather run a resistor is because I want to have as little electronics as possible because I already have a lot of Crap in there. But, if I have to, then I guess I have too. Thanks for taking the time to figure out what I need minutericesentra.