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 http://www.mp3car.com/vbulletin/hardware-development/50953-lcd-backlight-upgrade-autodimming-control.html

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

Quote: 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

Quote: 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.

PatO · 11-04-2005, 11:12 PM

Anyone have pics of this mod? I've killed things doing this type of work before, and I really really really don't want to kill a Xenarc!

chuckster · 11-05-2005, 05:37 PM

Quote: Originally Posted by PatO

Anyone have pics of this mod? I've killed things doing this type of work before, and I really really really don't want to kill a Xenarc!

Not yet. I don't want to kill one either so I am going to order another Xenarc to play around with just in-case. I don't think this should be too complex. I just simply want it to autodim and nothing else special.

A couple things come to mind though such as timing of the brightness. If going under street lights you don't want it to keep going up and down in brightness that quickly. This would be easy to to add using my existing 8051 circuit but most folks probably don't have this in there cars. Maybe some sort of RC network to add some time delay would be sufficient.

Chuck

chuckster · 02-21-2006, 03:56 PM

Been a while and I had not made any progress on this but I have a professor at school who is willing to help with a circuit.

I need some more information on the Xenarc circuit diagram or where I should tap into as well as the input voltage and output voltage requirements.

I'm thinking if I crank up the the brightness to full and leave it that way then the voltage would be ~5v at the inverter???

I will need to take that ~5V and use it as the input to my circuit where my circuit would then autoadjust it between 0 - 5 volts (possibly 1 volts or similar so it doesn't go black).

Circuit would utilize a cap for timing as to not quickly adjust it when going under traffic lights etc...probably not the best but it should work.

Anyone have info on this? I have someone to help with the circuit.

Thanks,
Chuck

chuckster · 02-28-2006, 12:11 PM

BUMP...

I have not located this thread that shows the inverter output. Does anyone know where it is. I really want to get this thing going and will post details but to get this thing off the ground I need to know the voltages levels I am dealing with. Supposedly it is 0-5V and I assume I will want to output my circuit directly to the inverter to adjust screen brightness.

Chuck

spaceskater · 03-26-2006, 01:26 AM

Ok, I took some measurements and found out the pin-out on my Xenarc.
As you can see in the image:

Pin 1 Yellow: 12V
Pin 2 Orange: Ground
Pin 3 Red: Brightness control (0V Max brightness 5V Min. Max value measured was3.4V I don't know if it dims more in 5V)
Pin 4 Brown: Back light On/Off (when High, measured 3.4V, Back light is ON. When low, 0V, it's OFF)

My 800TSV has three settings. Bright (0V), Middle (1.3V), Dim (3.4V)

Use this info at your own risk!!!

I'm going tho use the feed from my old head unit that comes from my headlamps. it gives a variable voltage according to the setting you have for the brightness of the console lights. It goes from 0-12V when the headlights are on. BTW my headlights are automatic which will make this automatic.

chuckster · 03-27-2006, 08:25 AM

This is great! Thanks a ton Spaceskater.

I'll let you know how my project goes. I'll share whatever I find.

Chuck

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