Auto Dim Xenarc/Liliput with illumination wire from radio harness?

Kamakazie2 · 03-26-2006, 09:47 AM

I was wondering if a simple relay circuit would allow for the dimming of the monitor. I use 2 settings in my xenarc. Full bright in the daytime and 0 bright at night. I wanted to tap the inverter wire and put a relay on it so when the relay is off it gets full conection which would get full brightness (or whatever the xenarc is set to) and once the headlights are on the relay will divert the circuit to a resistor to dim the backlight. Does this seem right? Any tips or suggestions?

h0tw1r3 · 04-21-2006, 08:05 AM

I am interested in this also.

fonseca · 04-21-2006, 11:54 AM

Quote: Originally Posted by Kamakazie2

Full bright in the daytime and 0 bright at night.

So you leave your backlight at max and only adjust the bright setting?

Scouse Monkey · 04-21-2006, 12:12 PM

its easy.

the pin-ins for the backlight inverter are onthe forum somewhere. I beleive it just takes a 0-5V signal for the dimming as there is pwm onboard.

All you need to do is intercept this 5V signal and have a circuit to chnage it when the headlights are on. Cant remember is 0V is ful or 5V is full.

If it is a PWM input (which I dont think it is) then you would need to have some kind of PWM (55IC circuit) that outputs a different signal depending on the healdights being on or off. You would lose the ability to control the brightness fromt he screen but it would allow you to have a thumb wheel or knob to do it instead as well as the headlight switched behaviour.

Kamakazie2 · 04-21-2006, 12:19 PM

Quote: Originally Posted by Scouse Monkey

its easy.

the pin-ins for the backlight inverter are onthe forum somewhere. I beleive it just takes a 0-5V signal for the dimming as there is pwm onboard.

All you need to do is intercept this 5V signal and have a circuit to chnage it when the headlights are on. Cant remember is 0V is ful or 5V is full.

If it is a PWM input (which I dont think it is) then you would need to have some kind of PWM (55IC circuit) that outputs a different signal depending on the healdights being on or off. You would lose the ability to control the brightness fromt he screen but it would allow you to have a thumb wheel or knob to do it instead as well as the headlight switched behaviour.

0v is brightest setting..

So it will operate like this
Monitor set at Full Dim

Lights are off: Relay is in the open position giving 0v to circuit causing backlight to be at max.
Lights are on: Relay is closed causing the origninal circuit of 3.3v (set at full dim) to dim the screen

Scouse Monkey · 04-21-2006, 12:46 PM

you may want the relay to ground the input pin. but I am not sure about this. dont blame me if you blow it!

visenri · 04-21-2006, 03:35 PM

Hello, i've recently done a modification to my xenarc 700IDT to dim the backlight with a 12V external signal in the RCA audio IN. I've also added attenuation control with volume digital potentiometer, i've used the internal potentiometer used for audio, the xenarc 700idt indash has no speaker, but amplifier and potentiometer are in the board!!!.

The backlight intensity is modulated by a signal from 0 to 3.3V (being 0V the brightest) located at the inverter conector. Note that in my screen 3.3V is backlight at 50%, if backlight is lowered more, backlight turns off!!!!!. I think it is a design problem.

This signal is produced by an LM358, a signal amplifier, configured with a gain of 2.

The input to this amplifier (4) is an analog signal provided by a filter (RF & CF , 10K and 39n), from a PWM signal around 800Hz from the main controller, PW113.

To make the screen dimm we need to mix this signal with the input to raise the voltage when input is 12V.

The circuit has two parts, first part is an input signal conditioning and level control, and second is a mixer and filter enhacement.

Gray parts are present in the board.

R1, DZ1 and R2 limit the point (3) voltage 3.11V.

R3 and CF2 are the mixer an filter enhacement (we need to raise the filter because we reduce the filter resistor with R3)

With screen set to full backlight and input set to 12V, the mixer point (4) raises from 0 to 1.244, multiplied by 2 (lm358), this makes 2.488, so backlight is at 60% (with pot at max value).

Location of LM358 and digital potentiometer

0 ohm resistor must be eliminated (this is the input from the audio RCA)

LM358 and filter

Final aspect:

My original post about this in solocarputer forum in spanish:
http://www.solocarputer.com/phpbb2/viewtopic.php?t=5122

vinzer · 04-22-2006, 12:32 AM

Great job man ! Thank you

Kamakazie2 · 05-22-2006, 02:37 PM

Quote: Originally Posted by Kamakazie2

0v is brightest setting..

So it will operate like this
Monitor set at Full Dim

Lights are off: Relay is in the open position giving 0v to circuit causing backlight to be at max.
Lights are on: Relay is closed causing the origninal circuit of 3.3v (set at full dim) to dim the screen

Relay installed and fully funcitonal.. just cut 1 wire and add a relay and you have full bring to full dim when lights come on..

dmurray14 · 05-30-2006, 03:56 PM

Quote: Originally Posted by Kamakazie2

Relay installed and fully funcitonal.. just cut 1 wire and add a relay and you have full bring to full dim when lights come on..

Just want to bump this because I'm interested in doing it too. What type of relay did you use? Which wire did you cut?

Thanks,
Dan

visenri · 01-06-2007, 11:02 AM

The wire you should cut is the control wire in the inverter conector, in the pictures labeled as CONTROL (it may be different in your model).

You can check it with a multimeter, the control wire changes from 0 to 3.3V when you adjust backlight from 100 to 0.

Any type of small relay will do the work.

Just be sure to connect as follows:
Cut the CONTROL wire.
Connect the wire that goes to the inverter to the COMMON of the relay.
Connect NO contact to the wire comming from the screen mainboard.
Connect NC contact to gnd.

When you close relay, inverter gets 3.3V (depends on backlight setting)
When you open relay, inverter gets 0V, full backlight.

kelmk · 03-15-2008, 11:24 PM

I have a CTF700-SH from cartft. It has a light sensor that is used for auto dimmer. How would I hook up this sensor to my dimmer wire from my radio harness?

kuo · 03-18-2008, 01:38 PM

just wondering... if it has a light sensor already built in, why do you want to hook it up to your car's dimmer? does it not work to your liking?

kelmk · 03-18-2008, 01:46 PM

It doesn't dim as low as I would like. I run 100 brightness during the day and at night I would like 50 but the auto dim only seems to drop it maybe to 70 or 80.

visenri · 03-26-2008, 04:45 PM

Quote: Originally Posted by kelmk

It doesn't dim as low as I would like. I run 100 brightness during the day and at night I would like 50 but the auto dim only seems to drop it maybe to 70 or 80.

In your case i would take one of these two solutions:

1- Build my new dimmer (with microcontroller)

check: http://www.solocarputer.com/phpbb2/v...201&highlight=

It has two working modes, in simple mode, if the dimmer input is activated (night mode) it dimms the screen brightness to what you have set in the backlight setting (limited to 1% to avoid CCFL powering off), if dimmer input is not activated, backlight is set to 100% (0 Volts day mode). All brightness changes are done smoothly. It has also a serial mode (advanced mode), to set the brightness from a serial transmitter at 15ms per bit (in this mode backlight screen setting has no effect).

2-Build a simple transistor or relay switch, to change between full backlight (0 Volts , day mode) or backlight set to screen setting (night mode). In my last post i have explained how to do it with a relay, if you want transistors, tell me.