Hard-wiring +5V for USB Power?

[Crickett]

Any EEs in the house?

I'm wanting to hard-wire a standard female USB A cable to a switched power source to power iPods & other USB devices. I've found a +12V switched line (the purple & white wire in the phone harness in the center console) & just need to step that down to 5V & ~1A.

From what I've been able to discover, I have a couple options:

1. Wire up a 7805 circuit like so:

2. Cannibalize an old 12V cigarette lighter cell / USB charger, one that uses an MC34063.

3. Find a switched +5V line in the car somewhere . . .

Option #1 looks pretty inexpensive (& kinda fun in a DIY way) but I've heard 7805s can get heatsink-requiring hot.

Has anyone already done something like this? Any hints or tips?

[spencers]

Our friend, nathancarter, did this and wrote up a tiny little how-to over on bimmerforums.
http://forums.bimmerforums.com/forum...7&postcount=12

[billschusteriv]

I just searched for 5 volt power in cars and found what I think this you were talking about above:



12V-5V DUAL USB CHARGER PLUG

Are you looking to cannabalize and DIY for something permanent... something clean... or something semi-stock?

Plans?

[Crickett]

[ . . . ]Are you looking to cannabalize and DIY for something permanent... something clean... or something semi-stock?

Plans?

I'm planning to hard-wire power to my iPod aux-in plug; I'm going to try to make it as reversible as possible (i.e. using existing plugs / sockets vs splicing or taps). I currently have the USB end of my iPod cable sticking out of the center console to plug into the cigarette lighter adapter (much like the one you found); I just want to clean it up aesthetically & be able to leave everything plugged in without constantly drawing on the battery (the cigarette socket isn't switched, IIRC).

[Oli77]

Are you sure you want to be able to draw a whole amp through there?
Won't 150 mA be enough for a phone?
Plus, it won't heat that much - maybe.

[Crickett]

Are you sure you want to be able to draw a whole amp through there?
Won't 150 mA be enough for a phone?
Plus, it won't heat that much - maybe.

Y'know, I'm not sure. I just pulled the 1A figure from the normal iPod AC adapter; I'm not sure what minimum current would be sufficient. I'm sure I could do a bit of trial & error.

[Oli77]

An iPod adapter is rated at 1 A? I didn't know that. I doubt our computer USB output lets us draw that much. Seems a little high.

[Crickett]

They are, indeed; modern Macs' USB ports can do up to 2A to charge the iPad, as do the iPad AC adapters.

[Oli77]

Darn, well you might need a "good cooling" heatsink then, according to the site you show up there.

You sure there is no 5 V anywhere else in the car?

[Crickett]

Darn, well you might need a "good cooling" heatsink then, according to the site you show up there.

You sure there is no 5 V anywhere else in the car?

Nope, I'm not sure. I haven't been able to find anything yet, but I'm hoping someone hereabouts knows!