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

I am interested in this also.

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?

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.

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

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

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

Great job man ! Thank you

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..

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