How can I easily reduce my 12v to 5v?

[Off Road SHO]

I'm trying to power up an onboard camera/DVR and the DVR needs 5 volts DC. Can I just insert a resistor of a certain size somewhere in the middle of the 12 v + line to reduce it down to 5V?

Thanks

Tom "the electronics challenged"

 

[hawkeye18]

A resistor will not do the job. You need a transformer.

Fortunately, every cellphone in the market currently runs on... 5 volts. You know what that means; any car cellphone charger will work. You will want to get an extra cigarrette outlet from AAP or AZ (they all carry them) and wire it into a switched or hot power source of your choosing. Then, simply insert the cellphone charger (the smaller the better, obviously), wrap it with tape of your choice to ensure it doesn't slip out (they generally don't), and cut the end of the charger to either directly splice wires or attach correct connector as desired. This will give you regulated, fused 5v.

There are also a couple of regulated 5v lines off the EEC if you want to go that route.

 

[shopartsnw]

Tom,

For the 24 Hours of LeMons, I bought a cheap 110 inverter for about $30 and then used the power supply that came with my camcorder. I mounted the inverter to the car and hard wired it to the battery (with a fuse). I thought about a universal voltage converter, but I did not know if it would give me enough current to power the camcorder. I know it is a bit of a Rube Goldberg design to do what I did, but it worked great. It also gives you the opportunity to polish the fins on the inverter heat sink

Mike

 

[93rev2sev]

I agree with the inverter idea. I have a larger (1400W) one and it powered my computer, cable modem, 3 compact flourescent bulbs, a tiny fridge, and charged my cell phone one night when the power was out...Ran all night at idle with my little 90amp MTX alternator.

 

[hawkeye18]

1400 watts equals about a 110A draw on the alternator at full load. I wouldn't do that too many nights!

 

[Off Road SHO]

There are also a couple of regulated 5v lines off the EEC if you want to go that route.

Are they unused?

Tom

 

[hawkeye18]

no, they're the ones that go to the TPS/MAF, etc. I don't know what they're fused to but I can't imagine the camera would draw that much current...?

 

[Pro*banshee]

ARE YOU GUYS EFFING SERIOUS?!!!


Tom, Radio shack makes a little chip called the 7805. It is a voltage regulator that takes any voltage from 7-37 volts and cuts it down to exactly five. If you bolt it to a grounded heatsink one of the pins is voltage in and the other is 5v out (only two pins+ground). These little babies cost about 2 bucks and can give you an amp or two of current. If you need more than 1 amp let me know and I can ship you a regulator that can handle a few amps

 

[hawkeye18]

Well I was trying not to go into individual componentry. There are endless options if you want to deal with individual chips.

 

[Pro*banshee]

Well it's just one chip; there's no other connections that you have to make.

http://www.electronicrepairguide.com/7808 voltage regulator.jpg

Your 14.4V goes in the left, you cut off the middle pin and voltage comes out the right. You have to bolt it to the ground

 

[Off Road SHO]

That would have worked great and I might still do that. I just went to Fry's Electronics and got a variable voltage cigarette lighter adaptor. Now I need to wire in a cigarette lighter.

Thanks guys.

Hopefully I'll have some good videos up on YouTube soon.

Tom

 

[ManySHOs]

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96515

 

[Racer X]

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96515

If that's true to the USB spec, it has a max output of 500ma.

 

[SASHO91]

I'm trying to power up an onboard camera/DVR and the DVR needs 5 volts DC. Can I just insert a resistor of a certain size somewhere in the middle of the 12 v + line to reduce it down to 5V?

Thanks

Tom "the electronics challenged"

Subtract 7v from 12v.....











:angelnot::wave:

 

[SeanMc]

Subtract 7v from 12v.....











:angelnot::wave:

Good thing I didn't think of it first

 

[Joe_SHO]

Zener diode. Basically the zener varies its resistance to ensure a constant, predetermined voltage drop across it and anything you put in parallel in it.
This site will calculate the resistor size you need.

http://www.reuk.co.uk/Zener-Diode-Voltage-Regulator.htm