ok so i converted my dome light to LED's. it was a pnp kit that i found at my local automotive parts store. my problem is that when the switch for the dome light is turned to the door position, the leds tend to stay dimly on when the door is closed. does anyone know a solution to this issue?

 

same problem here

 

i've read some stuff about this on another forum. what it boiled down to was that there has always been that small amount of current but with a halogen bulb it was just undetectable by your eyes.

 

so will the led staying on wear the battery down?

 

yes, but its such a minute amount. plus the battery will be recharged everytime you drive

 

no more than it always has.

 

Correct, also part of the reason you disconnect your battery when storing the car for a long period.

Here'se the EE answer for you:

If you want the LED to be off completely, look at putting a reverse Zener diode in series with it, then it will be off even at low voltages (or any voltage below the breakdown voltage)

 

good work newbie! ha, i hadnt heard of a reverse zener diode...i know a few ways i could use one though....hmmmm!

 

I fail to see how your Zener diode is going to solve any problems here. Probably their most widely used position is parallel, as shown in the schematic on that wikipedia page. When used in this way, they act as an open until the voltage goes above their breakdown voltage, and then they act as a short allowing as much current as possible through them until the voltage drops below their breakdown voltage, at which time they turn back off. The only thing a Zener would do in that case is keep the LEDs from ever turning on.

If you add it into the circuit in series, then you've basically just added another voltage drop in the circuit before you get to the LEDs. In which case, you really didn't need a Zener to do that, any ol' diode would do that.

 

Series, not parallel.
Yes on the open until breakdown voltage, no on the second part. Well, assuming you don't leave it on until your battery starts to die and produces a voltage below the breakdown voltage. Also, this isn't a short, it's a pre-existing circuit in the car.

To break it down, look at it this way. The light circuit has two states--on and off. Off isn't really off as there is a small voltage (below the breakdown voltage) going through the circuit. This is what the reverse Zener will stop. On is way above the breakdown voltage (assuming you install the right diode) and will allow current to flow through to the LED, turning it on.

So while it's on the circuit will stay on because the battery is supplying a constant voltage above the breakdown voltage and therefore the circuit will remain on and you will have light.

Yep, series. Yes it will have a very small, unnoticable voltage drop, but so do wires--the whole V=IR stuff.

As for any ol' diode, think about what the D in LED stands for.

 

have faith in the newb