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Scenario

I'm building several wall mounted kiosk that will be placed in remote locations and i'm trying to find a way to build in some longevity / power saving options (IE put them to sleep when the location is outside of operating hours).

I'm running the standard raspbian wheezy image on them.

Currently what I have working is running xset dpms force off to disable it and xset dpms force on && xset s reset && xset s off && xset -dpms $$ xset s noblank to wake it back up and disable the blanking again (it resets to the default of going to sleep after 10 minutes after forcing it on / off).

I was hoping to be able to put the display (a Westinghouse 32" HDTV connected over HDMI) to sleep with tvservice -o which works with one small problem. I'm powering the Pi off of the TV USB port and when the monitor goes to sleep power is cut to the Pi so that won't really work.

I could tell the location personnel to power off and on the tv when they open and close which would in-turn cut power to the Pi; while I've yet to have any problems with hard power-offs like that, I don't really want to make that the standard operating model for units that would require two day shipping of a new drive to restore should something happen to them. Having it truly offline through the night also means I can not push large video content to them over night and in general introduces new problems with the potential of it being powered off in the middle of receiving a large content update (I do have protections build in to the process by which it checks in for new content to recover from this but again, would prefer to minimize the potential problems this could introduce).

I'm mostly happy with the dpms setting method with the exception that the backlight stays on. I attempted to install and use xbacklight -set 0 to dim the display but it reports that there are no configurable displays detected.

Questions

The man page for xbacklight indicates that it only supports particular video cards and that you may want to look for a card specific utility to handle this issue.

Does such a utility exist for the Raspberry Pi's video card specifically?

  • Please ask each question seperatly. Combining questions is not allowed. This is not a forum but a Q&A. Some of these questions do not even belong here. You tlaking mostly about backlight issues.. How is that related to Raspberry Pi? – Piotr Kula May 28 '13 at 12:31
  • edited to be more specific about raspberry pi hardware – JoshHetland May 28 '13 at 12:45
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Back light uses the most power, blanking the LCD will save a bit of power on large screens but it has to be power saving mode and not just black screen(cause that still uses power)

You can try and use CEC commands with your TV. Also just use the TV's power supply cord (220v/110v) and piggyback a power supply of that rather than relying on the TV.

The Pi does not have any power saving modes... because it is already very efficient.

  • 1
    Thanks for the information about backlighting power consumption. based on your and leniks responses I reached out to one of my electrical engineer friends and they are going to modify the power cord for the tv to have a 5v regulator and usb plug built into it so i can maintain a single cable running off the back of the TV and be able to keep the Pi powered full time and use the tvservice utility to sleep and wake the display as needed. – JoshHetland May 28 '13 at 20:11
  • Thank you- I am glad that that my answer helped out. Good luck with the DIY job. – Piotr Kula May 28 '13 at 20:27
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Backlight is the main power consumer in the contemporary TV sets, if you set the screen to black, it is the worst combination from the power consumption point of view, because backlight shines full power and all this becomes heat when cut by LCD panel in front of the backlight.

If I were you, I'd power up RasPI from the USB adapter connected to the outlet and let it run 24/7, and then check RaspBMC sources regarding powering TV on/off over HDMI link.

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