I think I may have found a simple solution. According to the discussion here: https://forums.raspberrypi.com/viewtopic.php?t=254875 <https://forums.raspberrypi.com/viewtopic.php?t=254875>
The pi can be configured to turn off the 3.3v power when shut down. This is not configured by default as it also disables the option of starting the pi by any signal. You need to cycle the power, which is fine for this use case. All I need to do now, is latch a relay that is held in the latched state by 3.3v system power. > On Feb 16, 2022, at 12:46 PM, Chris Albertson <albertson.ch...@gmail.com> > wrote: > > The shut off needs to have a delay otherwise you are killing the power in a > running system. The delay gives the OS time to do an actual shutdown. > > On Wed, Feb 16, 2022 at 10:38 AM Roland Jollivet <roland.jolli...@gmail.com> > wrote: > >> On Wed, 16 Feb 2022 at 16:17, Thaddeus Waldner <thadw...@gmail.com> wrote: >> >>>> Just use a simple 10A relay with 5V coil >>>> As a latch, you press a button to power up, ie power the coil, then the >>>> same line gets dropped by the Pi to power off.. >>> >>> How does the pi drop the 5v line after shutting down? >> >> >> The circuit can be similar to attached.. >> But I've got no idea if there are 'hooks' in Linux so you could add code to >> drop the relay at the end-of-shutdown. >> Or whether you can get Linux to pull in the relay on power-up >> >> I presume this has to be in Linux, not LinuxCNC. >> Ok, I did a quick search and found this; >> >> https://stackoverflow.com/questions/45128655/where-does-acpi-hook-into-the-shutdown-sequence-on-linux-to-soft-off-the-pc >> >> Roland >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > > > -- > > Chris Albertson > Redondo Beach, California > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
