Hi,
I've been trying to reduce the strenght of the backlight of a ASUS VS197 old monitor i had laying around. I'm a noob in electronics and I've had some difficulties to understand the datasheet of the panel inside the ASUS VS197, a HM185WX1-400.
Page 7 and 12 give information about the backlight electrical specifications and connections.
I've been attempting through trial and error and i found that, pins 1,2,5, and 6 seem to be PWM, but actually i'm not sure whether they are inputs or outputs of the backlight. The backlight is in the right edge side and has 4 bulbs, which i believe correspond to the 4 Current Feedback channels. If i unplug one of this 4, the corresponding bulb turns off. By sending a PWM from a Arduino Leonardo it is possible to adjust the brightness, where analogWrite (0) gives more brightness and analogWrite (255) gives less brightness. The intermediate values (25-225 aprox) produce heavy flickering if a resistor is not used.
So indeed i was able to adjust the brightness through a Leonardo connecting the Current Feedback channel pins to the PWM pins on the board, but the backlight will not turn on unless at least one (any of them) of the feedback chanel pins is connected to the original monitor controller board.
In this way i was able to reduce the brightness of 3 of the 4 bulbs significantly by attaching a 2.2k Omh resistor between the arduino and the current feedback pins on the backlight. But, if i try to attach in series another resistor to that pin connected to the monitor controller board, the backlight will not turn on, will only flash a couple times.
I'm also still able to adjust the brightness with the built-in monitor HUD.
So i'd appreciate if someone could help i'd like to be able to control all 4 bulbs evenly..
thanks
.