Turning monitor on/off when not in use.

  • Hi All -

    I’m using a dual approach to turn my monitor off when it is not in use. The first is a cron job that turns it off at 9:30PM and back on at 5:00AM.

    I am also using MMM-Remote-Control and MMM-NetworkScanner to turn the monitor off when both my wife and I are not home, and back on when one of us returns.

    I am thinking there will be an issue when we are gone overnight. The cron job will turn the monitor back on in the morning and it will stay on all day since the network scanner will think that the monitor is still off from when we left.

    Trying to think of a solution to this, has anybody else encountered this or does anybody have a solution? Is there a way to set the network scanner to run the vacant command at a certain time, like 5:01AM, if no devices are found on the network?


  • i would think the other way…

    let the cronjob execute a script which checks if there are mobile phones online.

    the script should do it like this:

    1. is there a phone nearby?
          yes --> turn on the monitor
          no --> don't do anything

    need to google for this kind of script, but shouldn’t be too difficult.

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  • @wi_brewer Hi I have a dual approach.( FYI my mirror turns the monitor off with the command vcgencmd display_power 0 (raspberry pi 3, Philips monitor on HDMI). and on again with vcgencmd display_power 1. Your mileage may vary. )

    In crontab I put my mirror off during the night and on again in the morning. My /etc/crontab has added the following:

    # m h dom mon dow user	command
    30 0	* * *    root	mmscreenoff
    00 6	* * *    root	mmscreenon

    The script mmscreenoff is a shell script that I put in the standard path that does the following:

    touch /var/lock/displayscreenoff.lck
    vcgencmd display_power 0 >/dev/null

    As you can see it turns off the screen and puts a lock file, so other programs will know that the screen really need to be turned off, whetever else.
    The mmscreenon script does the opposite.

    rm -f /var/lock/displayscreenoff.lck
    vcgencmd display_power 1 >/dev/null

    So… These are the basics… The screen goes off every night.

    Now I want during the day also to see if me, my wife or my son is at home. For this I adapted the script from https://github.com/RpDp-git/PiDisplaySleep (thanks!). I have my router assign IP …100,…101 and …102 to the three phones of myself, my wife and my son. The script is modified to first check if there is a lockfile, in that case it waits but does nothing useful. If there is no lockfile it will scan the network.

    from os import popen,system,path
    from time import sleep
    state=3 #State of the display 1 On 0 Off, 3 = unknown
    ip="" #Enter the IP address of the device that should keep the display awake
    while True:
        if not path.exists('/var/lock/displayscreenoff.lck') :
            nmap_out=str(popen('nmap -sP '+ip).read()) #nmap command to scan on the given IP address
            if nmap_out.find('latency') == -1:  #looks for the word "latency" in the output
                if state==0 :                   #this nested if makes sure that commands are not repeated
                else :
                   system('vcgencmd display_power 0')  #Bash command that turns off the display
                   state=0                             #Updating the display state variable
            elif nmap_out.find('latency') > 1:
                if state==1:
                else :
                   system('vcgencmd display_power 1') #Bash command to turn on the display
                   sleep(900) #keep on for at least 15 minutes
        sleep(10) #Scan rate in seconds

    I run this script via pm2 start mmdaysleep.py or any other way you want to keep the script running. If nmap isn’t installed at your system you should install it via sudo apt-get install nmap.

    For the purists: it has grown this way, with the crontab job first and the python script later. Variations of the python scripts being stopped and started by crontab and/or having system timing considerations in the python script are also possible and maybe more logical. I just happen to like the relative simplicity and modularity of this solution.

    Hope this helps.

  • Thanks for the input, @cruunnerr and @martinkooij.

    I ended up going with @cruunnerr’s approach as it required fewer changes to my existing setup.

    Here is what I did:

    1. Created a file that lists the devices and their IPs that we want to evaluate. Filename: “devices”.
    1. Created a perl script, “ping.pl”, that pings the devices listed in the file. If it gets a response it will write the results to a file named “ping_results”.
    use Net::Ping;
    open(INFILE, ";
    #open(OUTFILE, ">", "ping_results") or die("unable to write output: $!");
    $p = Net::Ping->new();
       if($_ =~ /\d+.\d+.\d+.\d+/)
                open(OUTFILE, ">", "ping_results") or die("unable to write output: $!");
                print OUTFILE ("$`is responding to ping.\n");
    1. Added a crontab job to run the perl script at 04:55.
    # m h  dom mon dow   command
    # Execute Perl Script to check for devices
    55 4 * * * perl /home/pi/ping.pl
    1. Created a shell script, “rpi-hdmi-on.sh” that will check to see if “ping_results” exists. If it does it will turn the monitor on and then delete the “ping_results” file. Added a crontab job to execute this script at 05:00.
    if [ -e ping_results ]
            vcgencmd display_power 1 >/dev/null
            rm -f /home/pi/ping_results
    # m h  dom mon dow   command
    # Turn HDMI On (05:00/5:00am)
    0 5 * * * /home/pi/rpi-hdmi-on.sh
    1. Created a shell script, “rpi-hdmi-off.sh” that will turn the monitor off. Added a crontab job to execute this script at 21:30.
    vcgencmd display_power 0 >/dev/null
    # m h  dom mon dow   command
    # Turn HDMI Off (21:30/9:30pm)
    30 21 * * * /home/pi/rpi-hdmi-off.sh

    I’ve done some testing and it seems to be working well.

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