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Making your own Active Mount...?

 
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Daaave
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Joined: Jul 28, 2007
Posts: 15
Location: United Kingdom

PostPosted: Sun Aug 05, 2007 11:32 am    Post subject: Making your own Active Mount...? Reply with quote

Hi everyone,

I have a cubby hole in my car dashboard that the TT 720 fits nicely into. I would like to be able to have all the cables (power and line out) wired into the cubby hole so I can easily mount the TT and remove it when I want to for swapping to another car or whatever.

As there aren't any active mounts out there yet, I wondered how easy it would be to make my own... I don't use the USB PC docking unit (I have enough cables and proprietary 'mounts' for other gadgets crowding my desk) as I just use any mini-USB lead that's free.

So I wondered if I could take the docking unit apart and make my own active mount? I need to get a 90 degree 3.5mm jack for the line out, drill a hole and glue it in position, and I'm hoping that I'll be able to re-wire the cable for a 12 volt power supply rather than USB.

Has anyone ever tried this before?
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999tommo
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Joined: Feb 07, 2006
Posts: 616
Location: Midlothian

PostPosted: Sun Aug 05, 2007 10:08 pm    Post subject: Re: Making your own Active Mount...? Reply with quote

Daaave wrote:
Hi everyone,

I have a cubby hole in my car dashboard that the TT 720 fits nicely into. I would like to be able to have all the cables (power and line out) wired into the cubby hole so I can easily mount the TT and remove it when I want to for swapping to another car or whatever.

As there aren't any active mounts out there yet, I wondered how easy it would be to make my own... I don't use the USB PC docking unit (I have enough cables and proprietary 'mounts' for other gadgets crowding my desk) as I just use any mini-USB lead that's free.

So I wondered if I could take the docking unit apart and make my own active mount? I need to get a 90 degree 3.5mm jack for the line out, drill a hole and glue it in position, and I'm hoping that I'll be able to re-wire the cable for a 12 volt power supply rather than USB.

Has anyone ever tried this before?


I haven't done this, but before you wire up a 12v supply, remember that your car charger supplies 5v and not 12v. I have heard of others hard wiring their devices, but what they usually do is buy a lighter socket from Maplin's or another electronics supplier and wire this behind the dash with the Tom Tom car charger fitted in the socket. You should wire this to a switched power source, rather than 'always on' as it could either drain your battery or worse still cause a fire.
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Daaave
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Joined: Jul 28, 2007
Posts: 15
Location: United Kingdom

PostPosted: Tue Aug 07, 2007 9:27 pm    Post subject: Re: Making your own Active Mount...? Reply with quote

999tommo wrote:
I haven't done this, but before you wire up a 12v supply, remember that your car charger supplies 5v and not 12v. I have heard of others hard wiring their devices, but what they usually do is buy a lighter socket from Maplin's or another electronics supplier and wire this behind the dash with the Tom Tom car charger fitted in the socket. You should wire this to a switched power source, rather than 'always on' as it could either drain your battery or worse still cause a fire.


I have it all sorted and it almost works really well...

I have a buzzing noise on the audio signal from the TT 720 when the power cable is in the unit as well. Without the power plugged in it's fine, and the audio from the TT speaker is fine when the power is plugged in. It was making this noise before I mucked about with any of the cables / connections.

I've tested the audio cable in a portable mp3 player and there's no buzzing noise when the TT is plugged in. Seems like a problem with the 720.

I would really appreciate it if some other people please try their 720s with both power and line out plugged in at the same time to see if they get a buzzing noise too?
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mikealder
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PostPosted: Tue Aug 07, 2007 9:34 pm    Post subject: Reply with quote

What you need is a "Ground Loop Issolator" there is a problem with the ground (earth connection) between the supply feeding your 720 and stereo - the easy option is to fit one of These between the two devices or use the FM transmitter built in to the device and do away with both the cable and the problem - Mike
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Daaave
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Joined: Jul 28, 2007
Posts: 15
Location: United Kingdom

PostPosted: Tue Aug 07, 2007 10:04 pm    Post subject: Reply with quote

mikealder wrote:
What you need is a "Ground Loop Issolator" there is a problem with the ground (earth connection) between the supply feeding your 720 and stereo - the easy option is to fit one of These between the two devices or use the FM transmitter built in to the device and do away with both the cable and the problem - Mike


Thanks Mike.

One more question - would I not still get this noise when using any input device (TT or MP3 player) when the TT power is plugged in?
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mikealder
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PostPosted: Tue Aug 07, 2007 11:20 pm    Post subject: Reply with quote

If you use a ground loop issolator it will get rid of the type of noise you describe, the device is only required if you use the direct wired connection between the stereo and TomTom device.

I would try using the FM transmitter built in to the 720 and tune the cars radio in to the same frequency, you can have the sound through the car system without the problems of a direct wired connection, thus negating the need for the ground loop isolator - Mike
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Daaave
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Location: United Kingdom

PostPosted: Tue Aug 07, 2007 11:48 pm    Post subject: Reply with quote

Sorry I don't think I was clear enough, what I meant was as things currently are (i.e. without the isolator) shouldn't I get the same background hum on the stereo no matter what the output device was?

So no matter if I connected a TT, Ipod, PSP, walkman, etc, (and had the TT power plugged in) then I would have thought the noise should still be there, but it isn't. It's TT specific... Confused
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mikealder
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PostPosted: Wed Aug 08, 2007 7:41 am    Post subject: Reply with quote

Some devices will generate this type of hum, others do not so the Ground loop issol is ideal for those cases where a wired connection is providing noise on the speakers.
It is the physical connection that is causing the loop and associated noise, try switching the audio output of the TomTom to the FM transmitter and tune in the radio to the same frequency, do you still get the noise using this method? - if you do then it sounds like the TT is faulty - Mike
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markjohnson
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Joined: Jan 20, 2006
Posts: 41

PostPosted: Wed Aug 08, 2007 8:30 pm    Post subject: Re: Making your own Active Mount...? Reply with quote

Daaave wrote:
Hi everyone,

I have a cubby hole in my car dashboard that the TT 720 fits nicely into. I would like to be able to have all the cables (power and line out) wired into the cubby hole so I can easily mount the TT and remove it when I want to for swapping to another car or whatever.

As there aren't any active mounts out there yet, I wondered how easy it would be to make my own... I don't use the USB PC docking unit (I have enough cables and proprietary 'mounts' for other gadgets crowding my desk) as I just use any mini-USB lead that's free.

So I wondered if I could take the docking unit apart and make my own active mount? I need to get a 90 degree 3.5mm jack for the line out, drill a hole and glue it in position, and I'm hoping that I'll be able to re-wire the cable for a 12 volt power supply rather than USB.

Has anyone ever tried this before?


Hi,

I want to do this exact same thing. However, I need the device to be able to switch ON automatically whereas at present it just seems to switch OFF when power is removed (as long as that option is selected.

Until I can sort this I still rely on my Nuvi for speed cameras (as that does the ON/OFF thing just fine).

Kind regards,

Mark
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