Xenarc Circuit Diagram for auto dimmer dev.??

**chuckster** · 11-01-2005, 10:55 AM

Anyone know or have the circuit diagram of the Xenarc touch screen?

I would like to work developing an auto CCFL dimmer based on brightness of the environment. I saw this on an Avic this past weekend where the screen would dim or brighten depending on how bright it was inside the vehicle.

The Gamma method works but does not dim the CCFL so I'm looking at trying to get extended life on the CCFL using a photo diode and my current 8051 circuit. I imagine the current Xenarc design goes through some D/A conversion and it should be straight forward to get this working independant of the builtin firmware.

***EDIT looks like a similar project has been in discussion LCD Backlight Upgrade Autodimming control

Thoughts?

Chuck

**PatO** · 11-01-2005, 09:13 PM

I will name my first born after the person who makes this work.

**chuckster** · 11-01-2005, 09:37 PM

Originally Posted by PatO

I will name my first born after the person who makes this work.

Now there's a challenge

**greenman100** · 11-01-2005, 09:39 PM

all you need is a photodiode and a transistor

the xenarc's inverter displays varying brightness dependent on a pin that goes from 0 to 5v

**chuckster** · 11-02-2005, 12:20 PM

Originally Posted by greenman100

all you need is a photodiode and a transistor

the xenarc's inverter displays varying brightness dependent on a pin that goes from 0 to 5v

Do you happen to know where this pin is located? The circuit is easy and I would like to make it adjustable through a Microcontroller I already use as part of my installation.

Thx,
Chuck

**PatO** · 11-04-2005, 12:37 AM

Hmmm... I think I shall name him Mini-Greenman!
However, we must find this pin first...

**greenman100** · 11-04-2005, 12:56 AM

there's a 4 pin cable going from the LCD controller to the mainboard. There's +12v, ground, the brightness, and a 4th pin that may be ground.

I could take a measuremnt and check

**chuckster** · 11-04-2005, 11:28 AM

Thanks.

Maybe I will purchase another Xenarc to mess with instead of removing mine at this time. Would really be bad if something happened and I had no display for my vehicle

.

I will order one and work on this. I think it will be easy, I think I may go the way of an OPAMP and Photodiode to adjust gain.

Thoughts.

Chuck

**Scouse Monkey** · 11-04-2005, 11:31 AM

how did i miss this thread?

it's easy. You want a couple of pots. one in series and one in parrallel with a photocell. the inverter pinout is giiven in a thread somewhere.