Permanent conection to the car

MikeRohan · Occasional Visitor Joined: Oct 08, 2003 Posts: 14

Hi all,

I'd like to be able to connect my TomTom BT to the car's electric system (not through the lighter) and I'd like to know if anybody could tell me where to get any info on how to do this.

I already have a cable that is supossed to be conencted the car's electric system (it came with my unit) but I do not know if I need any fuses or where to wire them

Thanks,

Mike

lbendlin · Posted: Thu Oct 21, 2004 12:01 am Post subject:

You MUST use the lighter circuit (or something equivalent) to get the car's 12 V down to the 5 V that the receiver expects.
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Lutz

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MikeRohan · Occasional Visitor Joined: Oct 08, 2003 Posts: 14

Thanks, but maybe I've should have been more explicit Embarassed

I have the cradle that comes with TomTom BT. It has a "12-24V Permanent power cable jack" as well as a "Permanent power cable" that has a head to connect it to the cradle and a different head at the other end...

Now, my problem is that I have no instructions at all on how to connect that other end to the car's electric system (maybe through the radio?)

Thanks again,

Mike

walms · Occasional Visitor Joined: Oct 22, 2004 Posts: 33

Hi,
I don't know if you have already sorted your problem but i just thought i'd let you know what i am doing.
Today I'm installing a Brodit active holder with a 12v lighter adapter on the end. Easy but what i am doing is using a Dual lighter adaptor. I've striped the end off the adaptor and will splice the cars 12v DC cigarette (spelling??? Non smoker) lighter and run everything behind the dash. the cable from the holder will run behind the dash and just plug into the dual adaptor, along with another device. that way i will be able to remove the holder when i change cars but it will still look like a completely hard wired solution! I plan to put some picture on the "Reader Mounts" page in a few days. I hope that that helps and is the same kinda thing that you want to do?
If you have any questions that you may have i'd be happy to try and answer them.

MikeRohan · Occasional Visitor Joined: Oct 08, 2003 Posts: 14

Thanks a lot,
I think that is a better idea (I was going for a truly permanent, but I like your approach)
I will take a look at your pictures once you post them.

Cheers,

Mike

bigfatjohn · Posted: Mon Oct 25, 2004 5:29 am Post subject:

Or you could put your BT receiver at the back of the car to keep it away from all the other junk at the front. :D

That is the point of BT after all. If you are keeping it all permanently wired at the front of your car then you might as well use a wired mouse and save yourself any potential BT issues.

My preferred method is to connect to the permanent live on the boot light switch.

Definately put a fuse in, as close as possible to wherever you source your power. For instance, take power from boot light switch, as short a cable as you can to a fuse then attach the TomTom BT receiver to the other side. This is as much to protect your car from catching fire if the cable shorts out anywhere as it is to protect the BT receiver from power surges.

MikeRohan · Occasional Visitor Joined: Oct 08, 2003 Posts: 14

Thanks again, :D

it's very nice being able to share these ideas.

I'l investigate about the boot light idea. What worries me is that if I turn the ignition off, that light is not "disconnected" (if I open the boot it lights up Wink

), Therefore could I risk draining the battery if I forget to go to the back of the car and disconect the GPS?

Cheers,

Mike

philip4242 · Regular Visitor Joined: May 26, 2004 Posts: 123

Mike,

If you're really worried about a flat battery, use one of these from Maplin Electronics:-

http://maplin.co.uk/Module.aspx?ModuleNo=37962&TabID=1&worldid=3&source=14&doy=25m10

I've got one wired in series with my Royaltek GPS mouse (even though it only takes about 200 milliamps, and would take weeks to flatten a car battery), wired directly from the battery, via a fused lead.

The advantage is that I get an instant fix when I connect my PDA and start the GPS software, since the GPS mouse always knows where it is.

PS Maplin sell 12v sockets and inline fuse holders, if you're going to follow John's suggestion to pick the supply up from the boot light feed.
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Getting older and more senile by the minute !

Philip

lbendlin · Posted: Mon Oct 25, 2004 11:19 pm Post subject:

That is a very smart device. Kudos for finding this gem!
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Lutz

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bigfatjohn · Posted: Tue Oct 26, 2004 3:53 pm Post subject:

Mike....

You DON'T need to disconnect your BT receiver.

If you leave it permanently connected, with the amount of current it uses, you will flatten your car battery sometime about the middle of the next Ice Age.

The whole point of a permanent installation, to me, is "fit and forget".

The other benefit is that you never have to wait for a fix. It's already got one.

Darren · Posted: Tue Oct 26, 2004 4:51 pm Post subject:

MikeRohan · Occasional Visitor Joined: Oct 08, 2003 Posts: 14

Thanks everybody!!!

I have tested connecting the BT to the boot light and it looks/works great! :D :D :D

It was just a quick thing. I have disconnected it as I have to go and get a fuse (and maybe route/hide a little bit the wire - you know just for looks).
I'll keep that Maplin link around just in case...

Thanks again,

Mike

Darren · Posted: Tue Oct 26, 2004 5:01 pm Post subject:

Just be careful it doesn't switch off when the boot is closed ;)
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Darren Griffin

MikeRohan · Occasional Visitor Joined: Oct 08, 2003 Posts: 14

Now that you mention it Wink

I had a moment of doubt until I figured out where to connect it so it by-passed the 'sensor' thingy.

It could have been truly embarrasing Laughing

philip4242 · Regular Visitor Joined: May 26, 2004 Posts: 123

Lutz,

Do you mean it's smart looking, or it's smart (as in clever) ?

I don't actually think it's smart looking, but it doesn't matter to me, as it's hidden away behind the car radio.

As for it being smart (clever) ?

Well, in this age of digital this and intelligent that, all there is inside the case is a couple of resistors, a couple of capacitors, a couple of transistors, a zener diode, and a relay - hence the 'click' when you plug the unit in.

If the voltage drops below a certain level, the zener diode ceases to pass current, so the transistors switch off, so the relay de-energises, disconnecting the connected equipment.

Gloriously simple electronics !
_________________
Getting older and more senile by the minute !

Philip

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