Warning: I'm completely new to Raspberry Pi, and not even sure if it's the right solution here.

I'm trying to make a better digital picture frame. Got almost all the way there by just buying a nice flat-bezel 4k display, connecting a Chromecast, and putting a nice picture frame on it. Voila!

But I want it to adjust its brightness in response to ambient light -- and turn itself off when the room is dark. So now I need something to check a light sensor and control screen brightness.

  • Video drivers with Raspberry Pi?
  • Disassemble the monitor and wire it up with Arduino?
  • Off-the-shelf-HDMI-screen-dimming-device?

I would greatly appreciate any recommendations/suggestions/ideas.



turn itself off when the room is dark. So now I need something to check a light sensor and control screen brightness.

In this part, you need to do the next two steps.

First. Buy a BH1750FVI I2C sensor and configure this light sensor hardware to the RPi by this link - Using the BH1750FVI I2C Digital Light Sensor.

Next. For the brightness control feature, don't concern about any driver. There is a lot of methods to do that, Although, try one that has written in python the same as your light sensor hardware by this link - Brightness Controller.
To change the brightness level by command line, try it by this Github issue:

xrandr --output "your connected display name" --brightness "required percentage brightness/100"  

After all of this, you can get the brightness level of the room when it's dark. Next, convert the value in the standard of your brightness controller. Finally, write a while bash script and run it as a crontab job that checks the value of brightness level then if the light sensor value is "0", turn the brightness level to "0".


If I understand good.

  • You have a 4K tv.
  • You have a chrome cast connected
  • You want an independent way to control the brightness and ON/OFF.

I would look if your tv has a way to control it by serial port or something similar, like this: https://www.openhab.org/addons/bindings/lgtvserial/. If it has it you can build a light sensor with a raspberry pi or Arduino (BH1750FVI I2C as has said M. Rostami) and send commands by serial protocol to your tv to control brightness and ON/OFF.

  • 1
    Thanks, this is cool! Any idea if there's a list somewhere of which LG monitors have a serial control port? (I looked, but couldn't find one.) Dec 30 '19 at 20:25
  • 1
    You can see look here: github.com/suan/libLGTV_serial
    – jcardenas
    Dec 30 '19 at 23:24

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