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:

http://www.tkk.fi/Misc/Electronics/circuits/psu_5v.gif (http://www.tkk.fi/Misc/Electronics/circuits/psu_5v.html)

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/showpost.php?p=19698507&postcount=12

[billschusteriv]

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

http://ep.yimg.com/ca/I/yhst-11353365108554_2149_5956025174.jpg

12V-5V DUAL USB CHARGER PLUG (http://rcm.amazon.com/e/cm?lt1=_blank&bc1=000000&IS2=1&bg1=FFFFFF&fc1=000000&lc1=0000FF&t=zhpcom-20&o=1&p=8&l=as4&m=amazon&f=ifr&ref=ss_til&asins=B001OZMA08)

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!

[mimalmo]

I would just add on an additional cigarette lighter behind the dash by tapping into the existing cigarette lighter wiring then use one of these:

White Universal 12 Volt USB Car Charger for Apple iPod or USB Charging Device (http://rcm.amazon.com/e/cm?lt1=_blank&bc1=000000&IS2=1&bg1=FFFFFF&fc1=000000&lc1=0000FF&t=zhpcom-20&o=1&p=8&l=as4&m=amazon&f=ifr&ref=ss_til&asins=B000DCP4QK)

http://ecx.images-amazon.com/images/I/31MJ1PF3ZXL.jpg

[Oli77]

This one looks better, plus, it apparently does not draw power when device is charged.
http://www.x-tremegeek.com/media/catalog/product/cache/3/image/330x/9df78eab33525d08d6e5fb8d27136e95/p/1/p1310128a.jpg
from here (http://www.x-tremegeek.com/motormonkey-12v-dc-adapter-kit.html?&cm_mmc=Mercent-_-Google-_-NULL-_-1310128&mr:trackingCode=EB93DD07-70DD-DF11-9C39-001517B1882B&mr:referralID=NA)

That's if you o that way.

[mimalmo]

Apparantly you missed the part where I said it would all be behind the dash. :)

[Oli77]

Sure did!
Was just trying to help OP while looking around the net for an alternative 5V source in the headunit area when I came across that one.
I kinda like the low profile, apparently, you can close the ashtray door over it.

[mimalmo]

I'd like to do the Eurotray and inside of it install a USB charger along with an aux-in.

[pyreguy]

^Just ordered one. Thanks!

[Crickett]

I appreciate the suggestions, guys, but I'm already using a Belkin Micro USB Car Charger (http://www.belkin.com/IWCatProductPage.process?Product_Id=489767) that is small enough to close the ashtray cover on when not in use:

http://www.belkin.com/images/product/F8Z445ea/FUL1_F8Z445ea.jpg

But I'd still like to use a switched power source rather than the cigarette lighter socket. The only battery trouble I've had has been when I've left that plugged in (even without anything plugged into it); I'd like to be able to leave my iPod plugged in & know it's only drawing power when the car's on.

Also, I had considered a hidden second lighter socket tapped off the first to use one of these adapters, but I came across an article (perhaps it was the Wikipedia page) cautioning that the cigarette lighter electrical standards were never designed for powering of devices & that doing so (as has become ubiquitous) can be unreliable. Hence my search for a hard-wired solution. (Plus it's a lot of fun DIYing simple electronics!)

[johnrando]

Maybe this is too OT and deserves it's own thread, but now you've got me thinking about a USB playable source for our stock HK unit. Dice adds IPOD capability, and the Belkin port adds USB charging... how about a USB port that allows you to play music off of a USB memory stick (without changing the head unit)? The idea being that I'd feel much better leaving a USB stick in my VERT than an IPOD. John

[mimalmo]

I think the Dension lets you do all of that.

[johnrando]

I think the Dension lets you do all of that.

Thanks. I wasn't familiar with their products. I checked it out, it actually provides more capability than I need as I already have IPOD capability with my DICE, so I'd rather not spend the type of money they are asking... was hoping for something less expensive, unless I'm just not looking at the right product. Cool stuff though, would have definitely considered that instead of my DICE had I known, because I like the USB feature.