led's to courtsey light, to +?

I hope after all this that that was understood from the start.... I presumed it was from the original writings - it sounded like a basic test had been conducted.... But you are quite right.... In fact someone has just written about it at www.mp3car.com/vbulletin/lcd-display/137810-changing-cold-cathode-backlighting-leds-auto-brightness-control-4.html#post1365910

oldspark wrote: I hope after all this that that was understood from the start.... I presumed it was from the original writings - it sounded like a basic test had been conducted.... But you are quite right.... In fact someone has just written about it at www.mp3car.com/vbulletin/lcd-display/137810-changing-cold-cathode-backlighting-leds-auto-brightness-control-4.html#post1365910

I thought he was just looking for a solution to convert the voltage output of 0v (increased to +12v) when the door was open, and instead have it as 12v (fade to 0v) when the door was open. Not a method of pulsing the LED's so that they appear to fade... But maybe I read something wrong.

Yes - mtrhd0024 was just pointing out that LEDs do not dim like lights. As I understand it, Rowley was merely looking at a power source to drive the LEDs which he has - ie, the 12V when the courtesy lights are on, decaying to 0V as they extinguish. I took his LEDs to "fade the same way my current lights" meaning off the same supply etc - but not matching luminosities (since the LEDs will extinguish before bulbs). mtrhd0024 just clarified that last point. Is saw the issue as merely being one of confusion of LED ground voltage rising from 0V to 12V as opposed to the more conventional(?) LED supply dropping from 12V to 0V. (Both are the same as far as the LEDs are concerned.) If Rowley wants matched decay - that's easy. The 555 PWM circuit (in my earlier link) controlled by an courtesy-light mounted LDR (Light Dependedent Resistor). No switching necessary! It needs appropriate calibration - eg courtesy lights almost off may equate be a 20% LED duty cycle (though I think will be similarly close to 0%). Since the LDR value is proportional to courtesy lamp intensity, and LED intensity proportional to duty cycle, they should drop with similar intensity (electrically speaking!). (Alternatively maybe a LED could used as an LDR for a better match.... It's been years since I used a LED as a LDR....)