Hi,

got a Volvo XC90 with headrest screens. There was an RF audio transmitter for wireless audio on whatever was being shown on the screen.

When I purchased the car there was no transmitter so I was hoping to use some a domestic transmitter and headphones. They usually work on 12v supply anyway and I have the power leads from the old one in the car.

However, the transmitter has turned up and it requires an 8v supply.

Stupid question probably but can I hook this up to my car using the existing 12v leads or not?

 

i think you'll need to use a multi-voltage adapter

 

why not buy an RF transmitter designed for in-car use?

 

cheers mate - any pointers on which one?

Ideally if I can lop off the end with the jack plug I can connect to the adaptor?

 

Can't find one - they are predominantly designed for audio and video. Nothing for audio as far as I can see.

The car has two AV inputs - the factory fit is to have 2 transmitters operating on distinct channels but with some headphones that can switch between the two sources.

I looked for a dual channel RF transmitter but the only one was in the US.

 

What make are the screens? dealer option or aftermarket?

By RF are we talking about FM transmitter, or something else?

If you need detail on the factory headunit and A/V input options have you been on http://www.volvoforums.org.uk/ ?

 

They are fitted by VOlvo UK - I've actually been in touch with the guy who designed the system for them.

The transmitter transmits on one of 3 channels around the 863MHz range

Already scoured the volvoforums.org.uk

 

oh right ok

the domestic effort you bought, has a mains plug?

 

Yep - was considering an invertor if that's where you're heading?

But seems a contrived way of doing things? Stepping up the voltage to then step it down again?

 

it is a tad clumsy, but simple and should ensure no harm comes to the kit from supplying the wrong voltage / ampage / current etc.

Maplin otherwise do this sort of thing but the milliampage needs to be like for like http://www.maplin.co.uk/regulated-ca...ing-tips-37423

 

If you like soldering a standard voltage regulator chip should step down 12v with ease;

I have one on my 12v cooler bag to bring the fans down to 6volts so that its quieter at night in the tent (I replaced the fans for high performance ones after the originals seized so its was a fair bit noisier)

A NC37CA will give you 1amp at 9volts. But may require a heatsink to go with it at anything above half an amp.

http://www.maplin.co.uk/1a-positive-...gulators-46475


If you need more current, there are higher output chips that will do this, but they have variable voltage outputs and will need additional circuitry to get the correct voltage, so a little more work (just two resistors usually, but you need to calculate the correct values).