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lasvegas Occasional Visitor
Joined: Dec 28, 2005 Posts: 1
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Posted: Wed Dec 28, 2005 6:11 pm Post subject: Help cut plug off charger |
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Can you hard wire the tom tom one?
I have cut the plug off my tom tom one so i can hard wire it to my cigarette lighter and found that there is 3 wires.Red,black and white.
Is the red positive,black negative,what is the white wire for and how do i connect it |
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Andy_P Pocket GPS Moderator
Joined: Jun 04, 2005 Posts: 19991 Location: West and Southwest London
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Posted: Wed Dec 28, 2005 6:38 pm Post subject: |
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STOP!!!!!!!
What you are trying to do will fry your TomTom!
The TomTom works on 5 Volts, and the supplied cigarette lighter adaptor reduces the 12 Volts from your car battery down to 5 Volts.
What you need to do is rewire it back as you found it, quick.
If you want to do a neater install, buy a cable mounting cigarette socket from Maplins or some car accessory shops, and wire that in parallel with your existing socket. Then plug the complete TomTom adapter into that and hide it all behind the dashboard. |
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JimmyTheHand Frequent Visitor
Joined: Apr 16, 2005 Posts: 386
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Posted: Wed Dec 28, 2005 6:38 pm Post subject: Re: Help cut plug off charger |
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lasvegas wrote: | Can you hard wire the tom tom one?
I have cut the plug off my tom tom one so i can hard wire it to my cigarette lighter and found that there is 3 wires.Red,black and white.
Is the red positive,black negative,what is the white wire for and how do i connect it |
Not possible - the plug is actually a voltage converter - it takes the 12/14V DC from the car's electrical system drops it down to 5V. If you wish to hardware it in, you are best to get a assesory socket and wire that in, then plug the lead into that. _________________ J. |
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Andy_P Pocket GPS Moderator
Joined: Jun 04, 2005 Posts: 19991 Location: West and Southwest London
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Frazz Occasional Visitor
Joined: Dec 10, 2005 Posts: 40 Location: Gotham City
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Posted: Wed Dec 28, 2005 6:40 pm Post subject: |
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Not sure why there are three wires, but the adaptor also reduces the votage from 12V to 5V so if you wire it in directly you will fry it
Frazz |
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Frazz Occasional Visitor
Joined: Dec 10, 2005 Posts: 40 Location: Gotham City
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Posted: Wed Dec 28, 2005 6:45 pm Post subject: |
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Looks like we all got alarmed by this post at the same time - let's hope it isn't too late for lasvegas 8O
Frazz |
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Andy_P Pocket GPS Moderator
Joined: Jun 04, 2005 Posts: 19991 Location: West and Southwest London
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Posted: Wed Dec 28, 2005 6:59 pm Post subject: |
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The white wire is a voltage "sense" wire that measures the voltage actually at the input to the TT and sends it back to the circuit which adjusts it's output to allow for loss down the cable.
A common fault (a while back) was that the sense wire broke in the plug so the supply thought the voltage was low and increased it, thus frying the unit. |
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Oldboy Pocket GPS Moderator
Joined: Dec 08, 2004 Posts: 10642 Location: Suffolk, UK
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Posted: Wed Dec 28, 2005 9:59 pm Post subject: |
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Andy_P2002 wrote: | The white wire is a voltage "sense" wire that measures the voltage actually at the input to the TT and sends it back to the circuit which adjusts it's output to allow for loss down the cable.
A common fault (a while back) was that the sense wire broke in the plug so the supply thought the voltage was low and increased it, thus frying the unit. |
If that is the case, would not the same thing happen if you unplugged your TTG from it's mount? _________________ Richard
TT 910 V7.903: Europe Map v1045
TT Via 135 App 12.075: Europe Map v1120 |
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Frazzle Regular Visitor
Joined: Nov 05, 2004 Posts: 66
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Posted: Wed Dec 28, 2005 11:53 pm Post subject: |
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The white wire, as has already been stated, senses the voltage at the point where it eneters the TTG (the plug) Any voltage drop caused by the current flowing through the thin copper supply cable is detected and compensated for by the switching regulator.
When you remove the TTG from the cradle or power plug you remove the load and no current will flow. The sense wire sees a healthy 5v at the plug so all is well. Voltage drop will only be present when current is drawn.
When the white wire failed I understand that the switching regulator received no voltage sense input from the white wire so "thought" WOW there is a lot of voltage drop along this cable.... I'd better up the voltage a bit at my end to compensate.... this continued until it topped out at MAX volts out, which effectively supplied approx 12V to the TTG connector and TTG = very bad for the TTG.
The sense wire idea is common on high current xcomputer power supplies but if I'm hionest i think it's a bit OTT for a 5V 2A feed to a TTG
The solution to the old "broken sense wire" fault was to connect the switching regulator sense input directly to the 5V supply output and disconnecting the white wire completely. This works well. |
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