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I need to convert 12 volts to 5 volts, how?

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Old 04-29-2006, 06:20 PM
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I need to convert 12 volts to 5 volts, how?

I need to have a hard wired 5 volts supply to a monitor I'm trying to put in, What is the best way? a resistor?

*EDIT*

Here's what's going on, I got an alpine cva-1000 from a friend for free. He was just going to toss it out. A few years back we tried putting video to it, and we could get video but no sound, then sound but no video. I'm only planning on using it as a monitor, and sound will run through the aux input in the headunit i have now. I figured out that i need to "trick" the unit into thinking it's displaying an image and I need to send 5V to a wire. I tried 12V, but it'll only show the image for a few seconds.


Thanks-

Last edited by HOJU; 04-30-2006 at 05:36 AM.
Old 04-29-2006, 07:49 PM
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A transformer is the best way, should be able to find one at an electronic supply place.

Another option is some sensors and guages in Toyotas run on 5V, so there might be a +5V outlet on your ECU, don't know if it's a good idea to mess around with that though.
Old 04-29-2006, 08:04 PM
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Just go browse the power adapter aisle at Radio Shack. You should be able to find a 12v to 5v adapter in a suitable amperage for your purposes.
Old 04-29-2006, 09:22 PM
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Not sure how much power you need for your application but this site has several designs for 12VDC to 5VDC converters. Some soldering, although minor, is required.

I've used the one with the 7805 to power the buttons' backlight in my Gentex mirror.
Old 04-30-2006, 06:08 AM
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That 7805 looks like it might do the trick, but it's been almost 10 years since i took an electronics class, so what i have to do is attach the 12 volt, ground the center pin and I've got 5V on the other end??

Last edited by HOJU; 04-30-2006 at 06:20 AM.
Old 04-30-2006, 07:53 AM
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does the radio have a Foot brake wire and a E brake wire? If it does you have to activate them in sequence to get video displayed on it. I know the newer alpines have that safety feature but i'm not sure if the old ones have it. I have never heard of putting 5 volts to a wire on a alpine and i worked at a alpine dealer for 6 years.
Old 04-30-2006, 08:04 AM
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Originally Posted by HOJU
I tried 12V, but it'll only show the image for a few seconds.
Ummm, so, you fed an input with a 250% overvoltage? I wonder what you blew up inside? Not _if_, but _did_.


Anyway...

Originally Posted by HOJU
That 7805 looks like it might do the trick, but it's been almost 10 years since i took an electronics class, so what i have to do is attach the 12 volt, ground the center pin and I've got 5V on the other end??
The 7805 is a workhorse regulator and it should do fine for what you're looking at. Be careful to note that you MUST use a heatsink, so (like the article says) use an aluminum project box and mount the heatsink to it. Use thermal grease! And use those electrolytic caps!!!

Hookup wise, when you get the part from Rat Shack, it'll have a pinout diagram on the back of the card. You can't look at the schematic and discern which is "left" or "right" on the part. But in short, yes, the hook up is just as easy as it looks.
Old 04-30-2006, 11:39 AM
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I tried a 12v for only a brief moment, to see if the wire needed power. Then I found out that a 5V is needed so i'm not worried about that too much. I'll end up doing this crap through out the week so I'll see how it goes-
Old 04-30-2006, 09:39 PM
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Originally Posted by HOJU
That 7805 looks like it might do the trick, but it's been almost 10 years since i took an electronics class, so what i have to do is attach the 12 volt, ground the center pin and I've got 5V on the other end??
I'd take a look at my instal in the car but it's buried inside of the center console. Here's the link to its spec. sheet: link.
Old 05-01-2006, 04:44 AM
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Originally Posted by Tron
does the radio have a Foot brake wire and a E brake wire? If it does you have to activate them in sequence to get video displayed on it. I know the newer alpines have that safety feature but i'm not sure if the old ones have it. I have never heard of putting 5 volts to a wire on a alpine and i worked at a alpine dealer for 6 years.

Well If you remember, the CVA-1000 was never meant to have video, The CVA-1005 was really the first to offer this. I've located the video feed from the main brain and have soldered on a female rca end, and that works great. Appearently the wire in question is a green/white wire called the "Guide Control In" or something very close to this, It supposedly needs 5 volts sent to this when a DVD, Game, etc... are on and playing. This will trick the display into thinking the Nav system is hooked up and will diplay the video feed instead.




Who knows, I'll probably get it figured out and then want to take it out...

Last edited by HOJU; 05-05-2006 at 08:35 PM.
Old 05-05-2006, 08:37 PM
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The 7805 piece from radio shack worked like a charm....
Old 05-06-2006, 09:06 AM
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Originally Posted by HOJU
The 7805 piece from radio shack worked like a charm....
Right on! And you have it attached to a heat sink of some sort, right?
Old 05-06-2006, 10:11 AM
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Originally Posted by HOJU
The 7805 piece from radio shack worked like a charm....
Glad it worked out for you.
Old 05-08-2006, 06:56 PM
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Ok, I've got another problem.....
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