View Full Version : Car/ Electronics advice
Matblack
21-11-2006, 14:07
I have an idea that I want to carry through and I want to run it by you guys first.
I have a Bluetooth GPS reciever and I want to permanently wire this to my car in such a way that it is always on, even when the ignition is off. The unit requires a mini USB socket provided by a specially wired charger which goes in a cigarette lighter.
In my car the battery is in the boot which is handy because this would be the least obtrusive place for the GPS attached to the underside of the parcelshelf with Velcro.
Oddly there is already lighter socket in the boot but investigation shows that there is a relay AFTER the fuse to it, so I can't rewire it in the fuse box to be permanently on, besides it would mean messing with the existing wiring and possibly messing up my warrenty in the process.
So the idea is this; to wire a cigarrette lighter directly to the battery. I would fit a fuse inline with the positive terminal so any short would blow it and put some shrouded quick release connections after the fuse so that the lighter socket can be removed easily. I can then plug the charger into this socket and run the cable to the GPS.
Can anyone see a flaw in this plan?
MB
I did the same thing for a friend a few weeks ago on her 3 series. Worked like a charm.
If it's being hard wired I'd probably go without the cigarette lighter connectors altogether unless you particularly want to leave the charger unmolested.
At one time I actually installed USB port in my Cinq. It was power only but it was good enough for charging my iPod. You might be able to get away with similar and cut out using the charger altogether.
Matblack
21-11-2006, 14:35
How would you go about regulating the power to make a USB port?
MB
Matblack
21-11-2006, 14:39
The charger itself is a pain in the bloody arse, Holux took it upon themselves to use a non standard way of wiring the cable and when you plug it into a normal charger whilst the unit is on it switches itself off :/
Apparently the charger which comes with it is wired in such as was as to allow you to use it and charge at the same time but I'm going to have to have a good look for it as I'm not sure where its gone :(
MB
How would you go about regulating the power to make a USB port?
MB
Simple wiring diagrams are out there for that sort of thing although personally I just tapped it straight into the power supply that the head unit was already using, but then I like to live dangerously :p
I'd plumb straight onto the battery terminals, run a fused cable through into the car and hide it under the front passenger footwell carpet, as far back towards the engine compartment as you can. Terminate it with chocolate blocks.
Strip the charger apart so you lose all the unneeded excess plastic, solder wires in the appropriate place and screw the ends into the chocolate block, the charge will probably be small enough to also hide behind that same piece of carpet.
Then you just need to route the cable out and to wherever the GPS is.
This is exactly the same way I've done it in the Feekmobile, heavy duty fused cable out from the engine compartment to termination points.
Matblack
21-11-2006, 17:03
OK, I've had a look and found the cable I needed, why they decided to use a proprietry wireing in a mini USB cable I have no idea :angry:.
Anyway I've scouted the car and its a piece of the proverbial to get to the battery, its just under the carpet in the boot :)
I have thought about striping the charger down and making it more stream lined but because its not a normal one I can replace easily I'm going to keep it intact just incase I want to use it in another car at some point. The parts from Maplin are only £8 and that gives me a permanently on socket which could be used for something else if need be.
The only questions which remain are; a) how to attach some little wires to the bloody great terminals on the battery (I would use those cable taps but the wires coming out are too big and b) what amperage fuses to use :huh:
MB
If you're only using it for that USB GPS then something like a 500mA would probably be enough - But you may find the charger has one built in anyway, these things often do.
Spade terminals. Solder wires into them and affix to battery. Simple.
Matblack
21-11-2006, 17:13
Spade terminals.
OK you lost me, I have this
http://img296.imageshack.us/img296/4415/terminalho3.jpg
and you think one of these?
http://img296.imageshack.us/img296/2492/l211st42fdgad2.jpg
Do they come in massive sizes?
Sorry its a while since I use to upgrade car stereos and fit amps :embarassed:
MB
Aye, you'll be able to get them in the size you need. Maplins, Halfrauds or any place like that should be able to sell you them.
Sorry its a while since I use to upgrade car stereos and fit amps :embarassed:
MB
I was going to say, you don't get those blinging gold battery terminals as standard do you?
Matblack
21-11-2006, 19:08
Nah, thats just a pic I ripped off the net :D
MB
Matblack
21-11-2006, 23:08
Well that worked nicely :)
I put the fuse nice and close to the battery to prevent mishaps and all the gubbins fitted into the battery hole so the only thing sticking out is the cable for the sat nav and that is sat behind one of the panels in side of the boot. Absolutely nothing visible and nice and neat. I just hope the car doesn't blow up :shocked:
Thanks for the advice :)
MB
Matblack
22-11-2006, 11:12
Checked this morning and the car wasn't a steaming pile of molten plastic and metal and the satnav was still working :D
MB
So now you just have to wait for someone with a bluetooth mobile phone and a brick to walk past your car in a carpark to know you have satnav and steal it!
DRZ - Forum optimist :D
I live in Salford...
So now you just have to wait for someone with a bluetooth mobile phone and a brick to walk past your car in a carpark to know you have satnav and steal it!
Only if the GPS mouse is discoverable - and it would only be the mouse. The damage to the car would be more of a problem.
Matblack
23-11-2006, 09:02
I'm very careful about where I leave my car and there are certain places I refuse to park, Salford is one of them :p :D
MB
I've got to get into the habit of not leaving my car in dodgy places... I'm too trusting (or ignorant). Then again I've been quite used to leaving my car unlocked and windows open in Cyprus - it's a hard habit to break.
MB any chance of pics of your beeeeautiful installation? Sounds like it's all worked out fairly well. :)
Matblack
23-11-2006, 09:38
I've got to get into the habit of not leaving my car in dodgy places... I'm too trusting (or ignorant). Then again I've been quite used to leaving my car unlocked and windows open in Cyprus - it's a hard habit to break.
MB any chance of pics of your beeeeautiful installation? Sounds like it's all worked out fairly well. :)
I'll try and do some later when I get in from work :)
MB
Then again I've been quite used to leaving my car unlocked and windows open in Cyprus - it's a hard habit to break.
To be fair you've got a convertible so nothing in the car is secure anyway. You're just as well not leaving anything in it and leaving it unlocked. If anyone wants to take a look inside it'll save you and them the trouble of a slashed roof.
I wouldn't leave the windows open though, it rains in this country :p
Matblack
23-11-2006, 21:46
http://img20.imageshack.us/img20/189/img1256oo1.jpg
http://img58.imageshack.us/img58/7875/img1258nt1.jpg
http://img296.imageshack.us/img296/5923/img1257aa0.jpg
The boot floor sits on a lip so the full weight of anything in the boot (which isn't a lot due to its size :D) isn't on the unit. The GPS is stuck on with velcro and the battery is left in and is on constant charge, if this kills it it takes the same battery as some old Nokia phone and is about £4 to replace. I did screw up the wiring slightly and one of the cables sits over the battery securing bar but when I can be arsed all reroute it. The gubbins (socket and charger) sit beside the battery in the well :)
I'm quite pleased, for some one who isn't very practical it was a good idea :)
MB
I'm amazed you can pick up satellites inside the boot - I always thought you needed LOS - I guess I was wrong! :p
Cool install. :)
Matblack
23-11-2006, 22:13
I'm amazed you can pick up satellites inside the boot - I always thought you needed LOS - I guess I was wrong! :p
Cool install. :)
Nope this chipset is really sensitive, as long as you don't have too much in between you can get a full lock in that position :)
MB
The newer chipsets in combination with the new versions of Tom Tom have a really low point at which they accept a signal as valid, it's way below anything my Garmin would even consider to lock on to.
In some ways it's good because you can get a lock in places you'd never imagine (mine locked with the GPS sitting on my desk at work, on the first floor of a 3 story building about 15m from the nearest window) but you do start to suffer from accuracy issues. When mine was locked it thought I was about 300ft up the road and was creeping around a lot.
I'd much rather give it clear LOS to the sky to ensure a good clean lock.
On yachts you need LOS, but they're a lot more sensitive as it's used for very precise navigation. I must read up on them frequency and power they use, I'm genuinely impressed - I guess I shouldn't be but as an RF guy it's "cool" (then again it is my trade, and my professional certification). :embarassed:
Yes, indeed, as Feek says, without LOS you may lose a little accuracy and possibly be more prone to losing lock under difficult conditions (driving in areas with lots of high-rise buildings, for example).
I was very impressed to see a lock in the office, until I realised how inaccurate it was. Now even though I've got the unit, it still gets a clear view.
I have a USB Royaltek unit which is pretty good and works best with LOS, but gives good flexibility with lower signals
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