Problem with Neon underbody lights and car dome light

[rvk2]

Hi everyone. A friend of mine recently purchased some neon underbody kits for his car. He has it hooked up to the dome light. When the dome light is on, the neon lights turn on. When it's off, they turn off. Now the neon light is wired up to a relay, which doesn't really work too well. The problem is that when the dome light starts to dim out slowly, the neon lights start acting funny.
He basically wants it so that the neon lights turn on at 12volts and turn off at 0. Since the voltage drops slowly when the dome light dims, is there any component he can use to simply keep the neon lights on at 12v and off at 0? This way, the lights don't screw up as the dome light is dimming down. Also, the neon lights are made up of several LEDs.

Any help would be appreciated in this matter.

 

[mramos1]

Neon lights made from LEDs? I need to keep up on technology..

You need to make a circuit that drives an FET (or transistor if really LEDs) from the dome light. The power from the dome light powers that FET gate (or transistos base) which powers the device which powers the lights..

Can you post a link to the item your friend has? You might want to power a relay to run it.

 

[gramo]

The IRL2203 is a decent FET. It can handle upto 30VDSS and 50Watts of power dissapation. at 12V, thats 4.1Amps, should be well within limits (can handle more with a heat sink)

**broken link removed**

Not sure if the pull down resistor is needed - but it would ensure immidiate cut-off when the switch is open

 

[gramo]

Its also a great FET to use with logic level voltages of 5V, I've used them a few times and havent had any dramas

I forgot to add;

FET's are like switches, they need a postive voltage at the Gate(as shown after the switch in the diagram) and when thier on, thier on (This model anyhow).

They have an 'on' resistance of about 7 milli ohm, and can handle massive current loads between the Drain(the upper connection) and the Source(Lower connection on the IRL2203 in the diagram), making them voltage controlled current regulators, unless the voltage is high enough to just make em 'digital switches' - like this design

Also forgot to add that the IRL2203 is 'on' with any voltage > 3V

 

[Hero999]

How is this wired?

Is the neon in paralell with the dome light?

You need to power it from a separate 12V power supply.

Is that what the relay's for?

Perhaps you need a buffer of some sort for the relay, the dome light might use PWM or something that's causing the relay to bounce?

How is it acting funny?

Is if flickering or something?