Auto dimming LCD

cproaudio · 09-19-2003, 12:37 AM

Since no one makes a VGA screen with dimmer input wire to dim the LCD when you turn on your parking lights, heres an idea for you programmers. Currently theres a program that dims the screen http://www.mp3car.com/vbulletin/showthread.php?t=14560 couldnt someone also write a program with resettable time to activate the dimmer program. You probably have to reset the time every few months or so. For example right now the sun sets around 7:30, you can set the time to dim your LCD screen at 7:45PM or 8:00PM. You'll have an auto dimming LCD but with no hardware installation required. just an idea

frodobaggins · 09-19-2003, 02:07 AM

I might code something up

iPal · 09-19-2003, 03:07 AM

i connected ground wire on inverter into stock parking light from dimming controller (ground wire with register)...
and it works light oem screen... it gets dimmer and even i can control the brightness of screen...

skassama · 09-23-2003, 02:35 PM

Could you please clarify what "ground wire with register" means.

I do unerstand ground but with register ???

also if you give some detailed explanation on how to do this ....

tnx

Alphared · 09-23-2003, 08:35 PM

http://www.mp3car.com/vbulletin/showthread.php?t=16142

2 times setting to automatically dim at night and regular brightness during the day

iPal · 09-24-2003, 01:34 PM

Quote: Originally Posted by skassama

Could you please clarify what "ground wire with register" means.

I do unerstand ground but with register ???

also if you give some detailed explanation on how to do this ....

tnx

'ground wire with register' is wire from your factor dimmer controller...
dimmer controller should have 3 wires... one is positive from parking light...
one is ground... and one is ground out put with register that you can cotrol...
and from lcd controller to invertor ther should 3 wires... one is 12v ingition and one is 3v trigger to turn lcd on... and one is ground...
that ground should be disconnected then rerouted to third wire from dimmer controller above...
i will get my digital camera back from my friend on friday...
i will post some video how it works...

gork · 09-24-2003, 01:49 PM

OK i get it, you're floating the Inverter power supply's ground to dim the screen, but doesn't the dimmer control wires voltage increase with brightness? ie the brighter your dash lights the dimmer the screen gets?

iPal · 09-24-2003, 02:05 PM

Quote: Originally Posted by gork

OK i get it, you're floating the Inverter power supply's ground to dim the screen, but doesn't the dimmer control wires voltage increase with brightness? ie the brighter your dash lights the dimmer the screen gets?

no that is the case your car controls dash light with positive wire...
with ground wire... higher register gets dimmer output...
so first you have make sure your car has ground type dimming controller...
if it is not you might want to play with power line to invert instread of ground...
but i am not sure how it would work...
i tried only on my car which is working just fine like factory setup...
btw nice setup... on your m3... most japanese cars are grounded type...
i am not sure of european cars...

gork · 09-24-2003, 02:11 PM

I will check again but I am pretty sure mine increases the voltage on the illum. wire relative to chassis GND.. and when illum. is off completely it's at 0V with GND..
Man it would have been easier your way

I hope I just measured incorrectly. I guess I didnt expect that behavior. I'll measure between illum and 12V battery and see what I get..

Do you have any suggestions for how to dim the inverter if the dimmer is changing the + supply instead of floating the GND?

Thanks a lot for the advice,

iPal · 09-24-2003, 02:33 PM

Quote: Originally Posted by gork

I will check again but I am pretty sure mine increases the voltage on the illum. wire relative to chassis GND.. and when illum. is off completely it's at 0V with GND..
Man it would have been easier your way

I hope I just measured incorrectly. I guess I didnt expect that behavior. I'll measure between illum and 12V battery and see what I get..

Do you have any suggestions for how to dim the inverter if the dimmer is changing the + supply instead of floating the GND?

Thanks a lot for the advice,

first with 12v positive try each wire from dimmer controller... and see if you could get controllable wire... if not yes you have to play with + supply...
try the + wire from invertor and leave ground wire...
try and let me know how it goes...

gork · 09-25-2003, 12:11 AM

iPal:

I ripped open my dash again tonight to take another look at this... I took apart the dash module where the dimmer is located. No luck. It's all electronic. On further inspection, this makes a lot of sense as the interior illumination is a mix of LED, EL backlighting, and Incandescent bulbs. It seems the illumination brightness is varied from 1-12V via PWM on the illumination wire, though I cannot 100% confirm that it is PWM since my multimeter reads true RMS and my oscilloscope is currently out of commission.

The problem I have with powering the inverter off of the Illumination wire is mainly that when the headlights are off, the wire is at 0V .. that would mean no backlight! also, at 1V the inverter would probably not even be able to power the CCFL.. I think what I really need is a circuit that somehow does this:

Illum wire at 0V -> Backlight powered at 12V
Illum wire at 1V (minimum dash brightness) -> Backlight powered at 5-6V or whatever the minimum voltage the CCFL lights at..
Illum wire at 12V -> Backlight powered at 12V

Unfortunately, I know only enough to be dangerous with circuits. I know there has got to be some simple solution to this problem, but I have no idea what it is :-/ This could help a lot of people too to have a workable way to dim the LCD backlight with the rest of the dash...

Again thanks for the help.. I wish my car had an easy solution like yours..

Mastero · 09-25-2003, 01:43 AM

nice my kind a place !

I am also looking for the same solution to control the backlit with a dimmer.

What i was thinking was to have a seperate 10k pot resistor to control the backlit seperatly. not through the factory dimmer.. dont know what my car works on its a MB shall know in a couple of days ..

Mastero

iPal · 09-25-2003, 02:24 AM

so u can not find any regular light bulb which controlled by dimmer in your whole interior?
i don't quite understand how your interior lights work...
what u mean by illum wire and backlight powered?
hope u finding way to do yours...
here is my video of my new interior...

http://www.imagestation.com/video/vi...210992480&dl=1

u have to click right then save it as different name to download... then play it~

Quote: Originally Posted by gork

iPal:

I ripped open my dash again tonight to take another look at this... I took apart the dash module where the dimmer is located. No luck. It's all electronic. On further inspection, this makes a lot of sense as the interior illumination is a mix of LED, EL backlighting, and Incandescent bulbs. It seems the illumination brightness is varied from 1-12V via PWM on the illumination wire, though I cannot 100% confirm that it is PWM since my multimeter reads true RMS and my oscilloscope is currently out of commission.

The problem I have with powering the inverter off of the Illumination wire is mainly that when the headlights are off, the wire is at 0V .. that would mean no backlight! also, at 1V the inverter would probably not even be able to power the CCFL.. I think what I really need is a circuit that somehow does this:

Illum wire at 0V -> Backlight powered at 12V
Illum wire at 1V (minimum dash brightness) -> Backlight powered at 5-6V or whatever the minimum voltage the CCFL lights at..
Illum wire at 12V -> Backlight powered at 12V

Unfortunately, I know only enough to be dangerous with circuits. I know there has got to be some simple solution to this problem, but I have no idea what it is :-/ This could help a lot of people too to have a workable way to dim the LCD backlight with the rest of the dash...

Again thanks for the help.. I wish my car had an easy solution like yours..

Audio Bandit · 09-26-2003, 04:11 PM

wut about using a phototransister?

Entcee · 01-02-2004, 01:38 PM

Quote: Originally Posted by gork

iPal:

I ripped open my dash again tonight to take another look at this... I took apart the dash module where the dimmer is located. No luck. It's all electronic. On further inspection, this makes a lot of sense as the interior illumination is a mix of LED, EL backlighting, and Incandescent bulbs. It seems the illumination brightness is varied from 1-12V via PWM on the illumination wire, though I cannot 100% confirm that it is PWM since my multimeter reads true RMS and my oscilloscope is currently out of commission.

The problem I have with powering the inverter off of the Illumination wire is mainly that when the headlights are off, the wire is at 0V .. that would mean no backlight! also, at 1V the inverter would probably not even be able to power the CCFL.. I think what I really need is a circuit that somehow does this:

Illum wire at 0V -> Backlight powered at 12V
Illum wire at 1V (minimum dash brightness) -> Backlight powered at 5-6V or whatever the minimum voltage the CCFL lights at..
Illum wire at 12V -> Backlight powered at 12V

Unfortunately, I know only enough to be dangerous with circuits. I know there has got to be some simple solution to this problem, but I have no idea what it is :-/ This could help a lot of people too to have a workable way to dim the LCD backlight with the rest of the dash...

Again thanks for the help.. I wish my car had an easy solution like yours..

I am looking for a circuit to do this:
Illum wire at 0V -> Backlight powered at 5V
Illum wire at 12V -> Backlight powered at 3V (may be different)

Does anyone know how I can go about doing this?