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Re: SAT NAV SOCKET

My TomTom runs happily on 6v but I can't remember +ve or-ve earth.
Sorry.

Location: Bristol

Re: SAT NAV SOCKET

"My question is - does it make any difference to the sat-nav (TomTom) if the live feed is positive or negative. I should know but I can't fathom it out." - I have never tried it but suspect that if you get it wrong at best it will not work, worst case you will damage the sat-nav.


Is this the previous post you were looking for?

Old thread?

Re: SAT NAV SOCKET

Just pinched this from the Tomtom forum.


Wait for other replies, as others may disagree, but I think the TomTom should cope OK with being fed with 6 Volts directly from your battery. But that is at the top of it's acceptable range and might make the safety diode in theTT run a bit hot or go pop.


So you would need to make a cable from the battery to whatever plug your TT model requires (usually a mini USB with power on the outermost pins - you'll need to check the polarity).

To do it properly, you would want to add two diodes in series (each will drop about 0.7 V), or a little zener diode dropper circuit, or use a "low dropout" power regulator chip such as the LM2940, built into the cable, to get you down to a guaranteed 5V.

If you think your battery may ever produce more than 6V then I would not risk it without the above circuit. For example, if you have a charger for that 6V battery, it is likely to produce more than 6V so it should never be used at the same time as trying to power the TomTom unless you have added that power reduction circuit.

Location: Pembrokeshire

Re: SAT NAV SOCKET

Dave it does make a difference which way they are wired,they are all as far as I am aware negative earth and will almost certainly stop working if connected incorrectly.

Location: Pembrokeshire

Re: SAT NAV SOCKET

From a post by Martin J Booth, Feb 4, 2010 - 9:31PM


Re: GPS running on 6 Volts

"The tomtom power supply is trying to emulate a USB port in that it provides a max 500mA at 5volts. It uses switch mode technology which means it actually takes less peak current on 6v than it would on 12.

Trying to keep this simple, the idea is that it switches on and charges a capacitor until the output voltage rises to the required value, in this case 5v. It then switches the input off until the output drops slightly, discharging the capacitor below 5v, then switches back on again and repeats. It does this so fast that you don't notice any fluctuation in the output. The difference between connecting it to 6v or 12v is that on 12v it is switched on for a much shorter time and during that shorter time it draws a higher current. Lowering the input voltage would result in the device being switched on for a longer and longer time until eventually it would be on all the time. In this case the input current would be the same as the output current, ie 500mA. As I said to start with, this is the simplified version."


I have a cigarette lighter socket which I connect directly to the 6 volt battery with alligator clips, case to negative earth.
Using the converter supplied with the GPS/SatNav plugged into the socket the GPS works on 6 volts.

Tony.

Location: Malvern, Victoria, Australia.

Re: SAT NAV SOCKET

I use a
HiLetgo DC-DC adjustable LM2577 auto step down up power supply module solar power from Amazon
All of £1.45 including delivery. Albeit shipped from China.

http://tinyurl.com/gozggyx

When I first set it up I had a brain fail and adjusted it to 7v instead of 12 or a bit more. I was surprised to discover that the satnav and dash cam fired straight up. I now run it at 12.5v and also drive a phone charger. I was able to dispense with the small 12v battery that I formerly used.

My main reason for the satnav is the speedo and odometer function (until my speedo is repaired), and also it yells at me when I exceed the speed limit. Speed cameras have a much tighter tolerance than our speedos......

Roly

Location: Upton upon Severn

Re: SAT NAV SOCKET

I have been using a TomTom ONE version one in my (6 volt) Seven for some years. I've fitted a cigarette lighter socket discreetly below the passenger seat and then plug in the standard TomTom adapter. It also works with a USB plug to charge my very basic phone and also charges my son's Samsung 6 with no problems. The adaptors seem perfectly happy on 6 volts.
The centre pin is +ve.

Re: SAT NAV SOCKET

I can't in good conscience let this thread pass without relating my experience with SatNavs in 6V A7s.
First a little explanation about the make-up of the cigar lighter plug GPS chargers. These are usually simple 3 legged 5 volt voltage regulator. These things are cheap as chips and as common as muck but, there is something that needs to be taken into consideration. These little chips have what is usually referred to as a "dropout voltage"; this is the lowest voltage ABOVE the 5 volt output that will allow the chip to provide the regulated 5 volts output. This is almost always less than 2 volts but can often be around 1.5 volts. In effect this means that all will work fine as long as the applied voltage is in excess of about 6.5 volts (to be safe, lets say 7 volts)

Now, the on charge voltage of your average, lightly loaded, 6 Volt A7 battery is usually between 7 and 7.5 Volts - UNTIL YOU SWITCH ON YOUR (UPGRADED) QH HEADLIGHTS when, in a very short time, the battery voltage will drop to somewhere around 6.0 volts AND YOUR SatNav WILL STOP CHARGING.

I discovered this the hard way on minor roads in rural France some years ago.

So, if you will never be using your headlights and SatNav at the same time, you should be OK. If you want to use the SatNav whilst driving any distance in the dark you will need a "up convertor" to supply the cigar plug charger with never less than say 7.5 volts (or ideally about 12 volts) whatever the voltage across the battery terminals.

This isn't in any way a fault with the SatNav chargers, they were designed to a spec calling for them to work on nominally 12 volt and 24 volt systems. No-one ever envisaged that they might be asked to perform on 6 volt systems installed in 90 year old cars.

Ian Mc.

Location: Shropshire

Re: SAT NAV SOCKET

I fitted a simple cigarette charger from Maplins, cost about £3 if I recall.
The important thing is for it to be isolated, ie in a plastic sleeve rather than bare metal. Then all I did was connect the +6v to the centre terminal and the 0v to the outer case. So the Sat Nav is a isolated from the car and doesn't care whether the supply is positive or negative earth, it just has a 6v drop in the right direction.
Can't comment on Ian's clearly better knowledge on working voltage.
I would say that I have a Tomtom1 for the A7 and have no problems. I also have a new TomTom in my modern and have found that it needs more power to charge than the car USB can provide, so have bought a high current lighter adaptor. Might mean that newer Tomtom's will also pull more power than an A7 cigarette adaptor can deliver.
Andy B
Norf Essex

Re: SAT NAV SOCKET

Just to add about the polarity of the connection, it must be the correct way otherwise the USB connection will burn out and if you are running on +ve then the easiest solution is to be a weatherproof USB adapter (for a motorbike) in place of the cigar lighter socket and connect the wires to the correct polarity. The unit is totally isolated and you can simply plug the USB cable for the tomtom directly in. On my "modern", 1965 Rover P6, which is +ve, I replaced the cigar lighter with a USB adapter, this was the exact same size as the cigar light body, fitted this so the car has modernday electronics, I also fitted an on-off switch as the USB was on all the time otherwise. I will be fitting another USB adapter to my Ruby shortly so that too will be able to power all this electrickery (Catweazle), I am on 12V on both cars.

Location: Saltdean, Brighton