7” lcd screen always on

Discussion about this major DATV Project. See https://wiki.batc.org.uk/The_Portsdown_Transmitter
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g6hfs
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7” lcd screen always on

Post by g6hfs » Wed Jul 12, 2023 1:48 pm

Hi,

I have been using these commands in ssh to turn the 7” screen off and on is there a way to do this via the touch screen, or could an option be added.

sudo sh -c 'echo "0" > /sys/class/backlight/rpi_backlight/bl_power'

sudo sh -c 'echo "1" > /sys/class/backlight/rpi_backlight/bl_power'

Brian
G6HFS

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G3GJA
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Re: 7” lcd screen always on

Post by G3GJA » Wed Jul 12, 2023 3:27 pm

How would you turn the backlight on from the touch screen if it is not lit?

I don't think I could navigate the menus without being able to see the buttons!

Clive

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gm1mfn
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Re: 7” lcd screen always on

Post by gm1mfn » Wed Jul 12, 2023 3:46 pm

A toggle switch in the backlight power path seems like the best option to me.
Doppler effect: The tendency of stupid ideas to seem smarter when they come at you rapidly.

g6hfs
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Re: 7” lcd screen always on

Post by g6hfs » Wed Jul 12, 2023 4:42 pm

Hi,

Using those commands turns off the back light only, the touch screen is still active, so touching it could bring the back light back on.

Brian

g6hfs
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Re: 7” lcd screen always on

Post by g6hfs » Wed Jul 12, 2023 4:45 pm

Hi,

Removing power does not work have tried that, when power is switched back on the pi does not see the screen, when you remove power the pi assumes there is no screen.

Brian

G8GKQ
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Re: 7” lcd screen always on

Post by G8GKQ » Sun Jul 16, 2023 7:44 pm

Hi Brian

Why do you want to turn the screen off?

Dave

g6hfs
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Re: 7” lcd screen always on

Post by g6hfs » Sun Jul 16, 2023 8:27 pm

Dave,

Thanks for the reply, I think it's a worry about the same image on screen causing damage or burn type of image on screen, perhaps these screens do hot suffer the same.

Brian

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Re: 7” lcd screen always on

Post by G8GKQ » Mon Jul 17, 2023 2:50 pm

Hi Brian

These 7 inch screens do not seem to suffer from burn-in. I certainly can't see any problems on my development Portsdown 4 which is generally powered up for about 8 hours each day - mostly on the main menu.

Not sure that turning the backlight off would have any effect anyway - the pixels are still switched to the displayed image state even without the backlight.

Dave, G8GKQ

g6hfs
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Re: 7” lcd screen always on

Post by g6hfs » Mon Jul 17, 2023 4:03 pm

Dave,

Thanks for the reply, if I need to turn the back light off I will carry on using the commands to turn off and on.

Cheers

Brian

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