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#263182 - 22/08/2005 21:59 Carkarma
PaulWay
addict

Registered: 03/08/1999
Posts: 451
Loc: Canberra, Australia
Hi all!

I just recently drove down to Melbourne and I was using the Karma plus a Belkin Tunecast II to send FM to the car receiver. The Karma was better at keeping its batteries going (I just kept on forgetting to charge it before a trip) but the Belkin chewed through four AA batteries on the trip down and back. So I was thinking of rigging up a power supply to both for subsequent trips - to at least run both off the car battery rather than their own.

The Belkin, conveniently, takes 12V, but the Karma seems to only take 5V. How strict is this? It'd be great if I could run both without having to have a 5V regulator in there burning up (in both senses). I've bought the regulator, but I just thought I'd check...

(Yes, I haven't fitted the empeg yet. Once again I'm not a man of means, and the Subaru Liberty's dashboard has an integrated CD player so there's no way to put the empeg in without severe modifications - and I don't want to have a bodgy job. And Kate requires the use of the CD and radio...)

Thanks in advance,

Paul
_________________________
Owner of Mark I empeg 00061, now better than ever - (Thanks, Rod!) - and Karma 3930000004550

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#263183 - 23/08/2005 07:17 Re: Carkarma [Re: PaulWay]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31565
Loc: Seattle, WA
I recently used an iRock FM modulator on a trip in a rented U-haul from Sacramento to Seattle (aprox 12 hours), and a single triple-A battery lasted the entire journey. I never had to use the iRock's cigarette lighter adapter. Perhaps it's just a question of buying the right FM modulator?
_________________________
Tony Fabris

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#263184 - 23/08/2005 09:27 Re: Carkarma [Re: tfabris]
PaulWay
addict

Registered: 03/08/1999
Posts: 451
Loc: Canberra, Australia
Hi Tony!

Thanks for that. The Belkin is actually the least of my problems, since it takes 12V and I can wire up the plug easily for that. What I want is to power the Karma off the car supply. I'm guessing that I'll have to use the 5V regulator I bought, but I'm hoping that I'm somehow proved wrong...

Have fun,

Paul
_________________________
Owner of Mark I empeg 00061, now better than ever - (Thanks, Rod!) - and Karma 3930000004550

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#263185 - 23/08/2005 12:40 Re: Carkarma [Re: PaulWay]
eliceo
enthusiast

Registered: 18/02/2002
Posts: 335
so the liberty is the australia equivalent of the legacy? If you are really determined to install a din unit I have seen pictures of a JDM dash / climate control kit for the legacy. Im not sure about the price though and difficulty of installation. Plus You would probably have to further modify that din size to make room for the empeg sled.

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#263186 - 23/08/2005 20:26 Re: Carkarma [Re: PaulWay]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31565
Loc: Seattle, WA
Quote:
What I want is to power the Karma off the car supply.

Ah, gotcha.

My thing with the Karma on a road trip is:

If I pack the AC adaptor in my suitcase, then I can charge it up while I'm sleeping between legs of the trip. The Karma's battery life is long enough (supposedly 12-15 hours) so that if the Karma's battery runs down on the drive, odds are I'm long past needing to stop for a rest anyway.

But I understand the desire to have a car-adapter for the Karma. Usually the way they do it with Cell Phone adapters is just to put a bunch of diodes in series until the voltage is dropped down to the level the phone needs. Cheap trick, but it works if I'm understanding it correctly. Anyone else got more information on how the diode thing works?
_________________________
Tony Fabris

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#263187 - 24/08/2005 04:26 Re: Carkarma [Re: tfabris]
mtempsch
pooh-bah

Registered: 02/06/2000
Posts: 1996
Loc: Gothenburg, Sweden
Quote:
Anyone else got more information on how the diode thing works?


As you said, just a bunch of diodes in series... Each drops about 0.7V depending on exact current draw. Also to consider is the varying voltage in the car, about 12.6V with engine off and no [big, like amps] consumers on and up to 14.4V with the engine running, possibly even higher if the regulator isn't performing as it should.

That it works for so many gadgets is the fact that the gadget normally runs off batteries which lose voltage (especially normal non-rechargeables) as they are used, and the gadget must be designed to cope with that...

But a 7805 regulator and 2 caps will provide a vastly more stable voltage.

The Karma power supply says it can give 2A, which will cause a fair bit of heat (around )14-5)*2=18W) for any linear way of dropping the voltage(if it really draws that much), so a bit of heatsink is called form or at least don't bunch the diodes all up tight together.
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/Michael

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#263188 - 28/08/2005 03:13 Re: Carkarma [Re: PaulWay]
Ezekiel
pooh-bah

Registered: 25/08/2000
Posts: 2413
Loc: NH USA
You want a 12V to USB plug. I have one (a Belkin, I think) and Have used it with my Carbon and that works fine. I haven't tried with the wife's Karma. I'll give it a try tomorrow and let you know.

-Zeke
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WWFSMD?

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#263189 - 28/08/2005 06:13 Re: Carkarma [Re: Ezekiel]
msaeger
carpal tunnel

Registered: 23/09/2000
Posts: 3608
Loc: Minnetonka, MN
The Karma does not charge from the USB like the new players do.
_________________________

Matt

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#263190 - 28/08/2005 16:21 Re: Carkarma [Re: msaeger]
Ezekiel
pooh-bah

Registered: 25/08/2000
Posts: 2413
Loc: NH USA
Yeah...just confirmed that. However, shouldn't it be as simple as wire soldering to change the end on a standard USB cable into the small diameter pin used at the 5V DC in? The worst result would be blowing the 12V/USB adapter if the Karma is too thirsty for amperage. It's a cheap experiment.

-Zeke
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WWFSMD?

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#263191 - 06/09/2005 05:56 Re: Carkarma [Re: PaulWay]
paulw
new poster

Registered: 12/04/2002
Posts: 7
Loc: Woking, UK
If the regulator idea doesn't work BoxWave seem to have a variety of solutions apparently designed for the purpose. I've not tried these folks myself...

Alternatively one could use a mains charger and 240/110 volt inverter of course, but that usually results in too many wires

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#263192 - 30/09/2005 10:51 Re: Carkarma [Re: PaulWay]
altman
carpal tunnel

Registered: 19/05/1999
Posts: 3457
Loc: Palo Alto, CA
Don't go above about 5.5v on the Karma, it won't be happy (specifically, you'll probably kill the VCORE step-down). Get a regulated cigarette lighter adaptor!

Diode chains are dangerous, as they can drop almost nothing at very low current - and very low current is still plenty dangerous to low voltage electronics...

Hugo

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