Posts: 6
Joined: Thu Jan 16, 2020 6:10 pm

Controlling LCD Screen Backlight Project

Tue May 18, 2021 2:46 am

Hi all,

So I am working on upgrading my Raspberry Pi 4 based media center and have managed to cross quite a few hurdles, but have one major one to tackle still and am at the limits of my technical skill to work on.

Here is the setup. I have a Raspberry Pi 4 that serves as media client, I have compiled Plex on it and have a 3.5" LCD screen to provide an interface for the stereo so I don't have to use the TV.
The issue lies with the screen, which is always on by default and cannot be turned off by software.
Having a look through the drivers, etc. I decided that it would be exceptionally difficult to go the software route so I am trying to build a hardware switch.
My concept works like this, the LCD panel has a momentary switch which is used to adjust screen brightness and turn it off completely. I wish to operate that switch remotely. To do this, I had in mind a transistor wired in parallel to the existing switch. To control the transistor I intend to use the CAM_GPIO method recently published here ... /#comments
Where I am unsure is how to wire the transistor, and what other components, resistors, diodes, etc. if any should be included in the schematic.
I have attached a draft schematic of the proposed plan, which is hopefully clear enough on what I am proposing to do.
RPI 4 LCD Switch.jpg
RPI 4 LCD Switch.jpg (25.83 KiB) Viewed 270 times

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