Automated mains socket power-off for OSMC on a Raspberry Pi

I’ve chosen to replace an ageing mini-PC which I’ve used since 2010 with a new Raspberry Pi 3 B+ running OSMC. It makes for a really capable media centre which can playback newer h.265 HEVC video files at 1080p without any problems, or it can serve 4K files over NFS to a box with a hardware h.265 chip like the Fire TV Box.

This form factor is easy to take on holiday and you can use an old infrared remote control (or Harmony learning remote) with it too.

However, the one thing I’ve struggled with is how to make it easy for my family to use in regard to switching it on and off. The Pi doesn’t have a power button. Some power supplies have an inline rocker switch, which almost fits the bill. I wanted something more automated.

Fortunately I had a spare Energenie power socket from a previous project where I use one to turn off our bass speaker when the TV isn’t on. These power sockets are controlled remotely (over RF) from a Pi which you attach an Energenie control board/shield to.

What I’ve done with the Pi 3 is have it powered through an Energenie socket, and set up a service that executes when it detects OSMC is shutting down. That service will make a quick HTTP call to the Pi with the Energenie controller shield, which will in turn send an RF signal to turn the mains socket off.

 

 

Here’s how you can set it up like I have…

Scripts for the Pi running OSMC

First, add a new service script.. create a new file in this folder;

/etc/systemd/system/callenergenie.service

	[Unit]
	Description=Energenie Remote Call to Secondary Pi
	Before=multi-user.target
	After=network.target
	Conflicts=shutdown.target
	[Service]
	ExecStart=/bin/true
	ExecStop=/bin/sh /home/osmc/callenergenie.sh
	Type=oneshot
	RemainAfterExit=yes
	[Install]
	WantedBy=multi-user.target

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callenergenie.service

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Then enable it with;

sudo systemctl enable callenergenie.service

There are a couple of useful things happening in this service, the After parameter makes sure the code runs before the network code is shut down, and Conflicts parameter is looking for OSMC shutting down.

Now add a helper script… this will make the webserver call as a background task, so control will be given back to the service immediately, rather than it waiting for the wget to complete.

/home/osmc/callenergenie.sh

	echo Calling energenie socket…
	wget –quiet –background –output-document="callenergenie.log" "http://192.168.1.99/callenergenie.php?delay=10&switch=2&state=off"
	echo Sleeping for 2 seconds
	sleep 2
	echo Done.
	exit 0

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callenergenie.sh

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This calls the PHP script, telling it which socket to turn off, and how long to delay before sending the command, which we’re doing so that the Pi has time to shut down before the power is cut.

Scripts for the Pi with the Energenie shield

This is the PHP script I added to the other Pi which was already configured to be a PHP web server.

/var/www/html/callenergenie.php

	<?php
	/* MattC – Call this with various parameters..
	callenergenie.php?
	delay = time in seconds to sleep before calling Energenie
	switch = which socket to talk to
	state = turn socket on/off
	e.g. callenergenie.php?delay=5&switch=2&state=off
	*/
	print ("Waiting ".$_GET['delay']." seconds");
	sleep($_GET['delay']);
	print ("Switching socket ".$_GET['switch']." ".$_GET['state']);
	exec("sudo python /var/www/callenergenie.py ".$_GET['state']." ".$_GET['switch']);
	?>

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callenergenie.php

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To allow PHP to run the script as root, I needed to add the Apache user to the list of sudo-ers.. not that secure tho :( I’d be interested in anyone who knows how to run the Energenie scripts a regular user.. their Python doesn’t like it when it’s not root.

nano /etc/sudoers

www-data ALL=(ALL) NOPASSWD:ALL

The nice thing about the PHP script is that we can actually call it to turn the Pi on remotely too.. so you could configure that into a widget on your phone, or add it to Alexa.

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Home Automation Project – Raspberry Pi Heating Controller – Part 1

I’m going to build a home automation project which connects a Raspberry Pi to control my central heating. I wasn’t particularly happy ripping out all the existing controls, and wanted to piggyback onto them.. which helps if the Pi ever fails (I’ve still got the old controls to fall back on).

I also didn’t want to mess with the existing heating control board, so bought a duplicate unit (British Gas UP2) from eBay for about £12.. I can perfect the project on that, and install it when I’m ready.

This set of videos goes through each step of the project.. starting off with opening the control board, an overview of what I want to do, and testing out the changes.

Opening up the Control Panel

This was a bit tricky.. it wasn’t quite obvious which plastic clips needed pushing in to pull the board out.. if you were doing this on your actual panel (not an eBay-bought duplicate) then this video should help work out what you need to do to get into it without damaging anything.

 

Project Overview

Next up, I’ll quickly go over what I intend to do to piggyback onto the control board. There’s a project here which did exactly what I wanted to do. He’s not using a PiFace 2 like I intend to use, and he wants to be able to control the hot water as well, but everything else is the same.

 

Safety First – Masking off the High Voltage Area

In this second video, I’ll show how I’m masking off the high voltage area of the board to make it a bit safer when I’m testing things out. Obviously most of the time the board is off, but this helps keep things safer when it is on without the cover.

 

Identifying Solder Points

Luckily this blog gave me a good starting point, but it wasn’t clear where to get the status of the central heating.. I used a multimeter to find a spot which changed voltage when the system was on, and this diagram shows you what I found;

Soldering

Since I only needed 4 wires for this project (2 for the switch, and 2 for the system state), I took an old USB cable, cut the ends off, stripped the wires and soldered it to the board without much trouble.

Soldering Complete!

This shows the control board after the soldering has been completed.. it’s pretty simple soldering; the only tricky part was finding the points to connect to for the system state (on/off). I’ve stuck down some of the wires so that they don’t catch or get stuck underneath the control boards buttons.

 

Testing the Wiring

Now that I’ve done the soldering, I’m testing out the wiring.. seeing whether connecting the two wires for the switch turns the central heating on, and when it is on, whether we get voltage on the other two wires to indicate the system state.

 

Controlling from Software

I’ve now hooked it up to the Pi Face 2 board, which can be controlled with a few lines of Python to simulate a button press, and detect the state of the system.

With these basics in place, the rest of the control software can be written to do scheduling, bring in temperature readings, and allow the system to be controlled remotely.