HELP: 12v cigarette lighter question

russgunn

I've just wired in a new lighter barrel behind my existng one in my Golf IV so that I can plug the 12v power adapter into it and hide it behind the console, while still keeping the existing one in place for cosmetic reasons. I needed to do this because after looking inside the adapter plug I presumed what I was looking at was a resistor circuit to get the 12v supply down to 5v for the iPAQ, can anyone confirm this? Hence, I needed to keep using the power adapter instead of wiring straight into the car's 12v supply.

Anyway, back to topic...Can anyone tell me if there are any side effects of having the adapter powered constantly? Because it's on the lighter circuit there is power going to it all the time, in anticipation of me lighting a bifta while looking out into the sunset with the engine off no doubt!! So basically, my little red light on the adapter is always on, even when I'm not drawing power to charge the iPAQ. Is this OK, or would it be better to get a professional to wire it to the ignition so that it switches off?

Looking forward to your replies.

compaq dave

Russ,

If you have a proper charger, then it will have much more than just a resistor in it, because of the high current / low voltage there will be a transistor and mini transformer in there, the power drain leaving it on but not connected to your Ipaq should be very little, however I would install a fuse as close to the power take off point as possible and also a switch for piece of mind (what if the live lead touched something in the car with you not there to unplug it?)

hope this helps

Dave

Darren

When you say you have installed a 'new lighter barrel' I hope this is an accessory socket designed as such and not an additional lighter socket? You need to ensure that the socket is protected so that no part of it can short to earth behind your dash.

You are correct in thinking that you cannot simply remove the adapter as this contains the voltage transformer as well. For my installation I bought a cigarette lighter extension lead, chopped off the plug and tapped in to the supply to the center console socket. I also put an in-line fuse in the circuit (the adpater you have will already have one but better safe than sorry). On my car the socket is only powered when the key is in the accessory or ON position, if yours is not then you need to be able to isolate this circuit with a switch for safety.

If you have any doubts about your abilities and handiwork then I would urge you to get it double-checked by someone with auto electrical knowledge as a short could be disastrous.
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Darren Griffin

russgunn

Darren, where did you get your cig lighter extension lead from, Maplins?

Secondly, is there no way at all of wiring straight into the car's 12v supply and still use the adapters circuit?

Darren

Yes Maplins and No unless your handy with electronics as you need to drop the 12v to 5v hence the circuitry!
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Darren Griffin

russgunn

I was thinking along the lines of ripping the circuit board out of the adapter and soldering some cable straight onto its contacts from say the fuse box supply. Or perhaps after soldering onto the contacts placing it in a Maplins switch box or similar. I'm pretty sure that would do it.

For now though I've taken my secondry lighter barrel out from behind the console and routed the power cable so that the adapter plug just pops out above the ash tray. This way almost all of the unsightly spiral power cable is hidden. Can't afford to pay for my company car to be written off after a fire!

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