Gps In A Truck

Wayne3940 · January 30, 2005

Ok this is a long shot but can anyone help. I'm trying to fit GPS to a 24v system on a truck but the system requires a 12V input.

I need a circuit so I can build a voltage dropper. I know I could use a potential divider circuit or a regulator but this is a little crude and I don't want to flatten the Battery when left plugged in over night as the vehicle in question is a Fire Engine.

Can anyone technical help with the circuit or give me some advice on where to look

Cheers.......

Monster-Mat · January 30, 2005

i cannot help..but why would you need GPS in a fire engine surely by the time you have programmed it the house will have burnt down

Scorpion · January 30, 2005

i cannot help..but why would you need GPS in a fire engine surely by the time you have programmed it the house will have burnt down

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Cant help either as my truck has extra 12volt outlets in it which i run a phone charger and dvd player oh and a kettle. :D

Wayne3940 · January 30, 2005

i cannot help..but why would you need GPS in a fire engine surely by the time you have programmed it the house will have burnt down

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Its an experiment at the moment and would be great for out of area response. Could be called to anywhere in the country (in theory) and the postcode based software takes seconds to plot. Its more for location and access than directions.

They exist (must be the same as an in truck phone charger but I'd prefer to build it myself as there are other systems to consider...

Bazza · January 30, 2005

i cannot help..but why would you need GPS in a fire engine surely by the time you have programmed it the house will have burnt down

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Its an experiment at the moment and would be great for out of area response. Could be called to anywhere in the country (in theory) and the postcode based software takes seconds to plot. Its more for location and access than directions.

They exist (must be the same as an in truck phone charger but I'd prefer to build it myself as there are other systems to consider...

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i will send you a map of where i live in case it doesnt work :D

does the engine use two batteries ie: 2 x 12v ?

could you not tap off only one ;)

Scorpion · January 30, 2005

does the engine use two batteries ie: 2 x 12v ?
could you not tap off only one ;)

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I asked the same to the fitter at work,and he said no you cant do that ;) but was told from a mate that you can......so who knows ;)

Anyway i got a brand new truck with all mod cons B)

Geoffers · January 30, 2005

Yes, you can tap off one providing you put a diode inline with the positive feed. If not, the GPS system will just act as a big resistor.

Using a regulator should be ok with a couple of caps to take the spikes out, etc. Here's a circuit for you anyway, even though you sound as if you've thought about this already.

It will only supply 1a - what GPS system are you looking at? If it takes more current then you're going to have to look at a different regulator.

Wayne3940 · January 31, 2005

Yes, you can tap off one providing you put a diode inline with the positive feed. If not, the GPS system will just act as a big resistor.
Using a regulator should be ok with a couple of caps to take the spikes out, etc. Here's a circuit for you anyway, even though you sound as if you've thought about this already.

It will only supply 1a - what GPS system are you looking at? If it takes more current then you're going to have to look at a different regulator.

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Thats great thanks just what I wanted. Knew the basic circuit but never thought of the diode. Its based on one of these palm top computers with a GPS unit attached so one amp is fine. Might use a 78S12 because I think it'll run cooler. Been all over the net looking so cheers this should have been the first place i looked......