Invert a signal from 12V to 0V
 

Hey Everyone,

I was just wondering if anyone knows if there is a way to invert the signal on a wire from +12V to 0V and vice versa.

I am trying to hook up the mute wire for my Nokia Bluetooth car set to the factory deck.

The problem is that Pin #14 Factory Head Unit is expecting 12 volts to mute the volume when a call is received, and 0 Volts the rest of the time when it is used normally.

The mute wire on my bluetooth car set is putting out a constant 12 volts when it is on and and then 0 volts whenever I receive or place a call. I need to somehow invert the signal.

I have also thought about hooking the mute wire from the bluetooth car kit to the relay wire that turns on the factory amp, but I would rather not have my amp relay controlled by the bluetooth car kit.

Any have any ideas?

A 12V relay should do the trick as long as the output of the BT kit puts out enough power to drive one.

Connect the BT kit output to the relay input. Then connect a 12V source to the common terminal of the relay. Use the NC (normally closed) output of the relay to the factory deck. The 12V from the BT kit will power the relay normally and have it open and you'll have 0 V at the NC output, then when the call comes in the relay will turn off (0V from the BT kit) which will put 12V at the NC output of the relay.
Someone will probably have an easier solution but this would work.

Are you sure the BT kit doesn't have a way to invert the signal itself?

Bingo. I would also use a solid-state relay rather than a mechanical.

Thanks guys...

Where can I get one of these?

So the relay would have 3 connections?

Is the NC normally connected to the ground wire?

I dont' know much about relays, so I'm a little confused.

Thanks...Kenny

The relay has 4 connections - 2 on the input and 2 on the output.

The 2 input connections are wired to the output of the BT kit, or if there's just one output from the kit put that on the + side of the relay input and wire the - side of the relay input to ground.
The common conection gets wired to some +12V source.
The NC from the relay is your output to the factory deck input.

Thanks for the replies guys. I'm going with the diagram on the very bottom of the page that MusicBox gives a link too.

It shows how to wire it that relay will only turn on when the ground connection is made. So bascially, when I get a call BT kit will put out +0V to make the relay will turn on and send +12V to the factory deck pin #14.

I'll be hooking 12v terminals 87 & 85.
The BT kit to terminal 86, and the Factory head unit Pin #14 to Terminal 30.

Thanks for the info!

the BT kit does not have enough oputput current to drive a relay directly, you would be better off using a transistor.

I'd put a relay in.