198Views13Replies

# How to convert 12V to 5V for incar use ? Answered

I need to create a cable that will run from my car battery into a device that runs on 5V DC power.

It needs to look like this:

INPUT:

12V car battery

Simple bare +ve and -ve wires

OUTPUT

5V 1.25A barrel connector
5.5mm (I beleive)

like this one:

http://sgcdn.startech.com/005329/media/products/gallery_large/USB2TYPEM.C.jpg

Tags:

## Discussions

I found this video on youtube, hope it helps.

PS if u don't want the usb, just remove the usb module and solder a wire to the positive side and the negative side (for help look at diagrams of USBs online)

also i did not make this video

Purchase one of those cheap lighter-plug USB converters from a local drug store or Wallmart, etc.

Alternatively,if you need more current than they can provide, consider using a stand-alone 3-terminal or other semiconductor regulator. Your car operates on 12VDC, so it will be a relatively simple circuit. Google "7805 regulator circuits" and you should find plenty of examples to work from.

A USB converter may be a good option, but not all of them can deliver 1.25A. check the data before buying.

The 7805 will work, but you'll need a 78S05, the one without S delivers only 1A.

And even then ... When bringing 1.25A of 12V down to 5V, it has to convert (12V-5V)*1.25A = 7V*1.25A = 8.75W into heat. That is a lot of power for a TO220. You'll need a good heat sink.

Agreed, but many do advertise themselves as being able to deliver up to 2 or more amps. The local pharmacy sells one that's more than capable of delivering 1.25 (it advertises as capable of delivering 2.5A)

On second thought, the 7805 probably isn't suitable in any variant aside from the T0-3 package. And as you noted, a switching solution is probably best. 7805 was, as usually, suggested due to the lack of skills that result in questions like this in the first place.

I am happy to add the connector on myself . Could somebody send me a link to one of these usb converters you speak ok. One that I could simply snip the end off and be left with. +ve and -ve wire for me to wire my plug onto?

I can't recommend a particular one for you, but a simple google search for

"Car lighter USB adapter", "Car lighter USB charger", etc should produce many choices that you can select among.

https://www.bing.com/search?q=Car+Lighter+USB+Adapter&FORM=QSRE1

Lol, or Bing search for that matter. (forgot that I changed my default from google to bing)

Chec Ebay for 5V step down converters, I got one rated at 8amps for under 30 bucks.
If you need under 2A you can simply hardwire aUSB charger fr the cigarette lighter.
Be aware that phones and tablets with a SB charging connection also require a voltage on the data lines to get into full power charging, otherwise they only charge with 100/480mA.

"Be aware that phones and tablets with a SB charging connection also require a voltage on the data lines to get into full power charging, otherwise they only charge with 100/480mA."

+1

Look for a USB charger converter that can deliver the amperes you need as seandogue wrote or google for switching 7805 replacements. By switching they have to waste much less power - It's effectively what the USB converters do. But make sure they can handle the current (most are only 500mA or 1A)