The Official Raspberry Pi Projects Book - Projects_Book_v4

Tutorial

raspberrypi.org/magpi The Official Raspberry Pi Projects Book 111

PIHUE: CONTROL PHILIPS HUE LIGHTS

LIGHT

CHANGES

For rooms with

both dimmable

and coloured

lights, alter

the brightness

as well as

the colour of

the room.

We can also change the alert patterns in the section
following # Alert Patterns. These are Python lists;
the first number is how many times to repeat the
pattern. The second is the delay between changes –
the recommended minimum delay is 0.4 (seconds).
The remaining values are Python dictionaries of the
light status changes.
Use any valid Hue status, e.g. on, bri, xy, ct,
sat, hue, transformationtime (see the Hue API
for details: magpi.cc/2vEpXfH).
Dimmable lights do not accept any of the colour
changes (xy, ct, sat, hue), so just change their
brightness instead.
We can specify as many changes as we want.
For Light Lists, the status changes are Python
dictionaries that contain the changes for each light
type (e.g. Extended color light and Dimmable
light). Other light types can be added if you have them
(e.g. Color Light, Color Temperature Light).
There is one special dictionary that is used by the
Touch pHAT’s Enter button to set all lights to bright
white: allwhite. We could redefine this to be a
preferred colour and brightness.

Running the code
The line # b.connect() must be uncommented the
first time the code is run. Just before running it, we
must press the Bridge connect button. Run with:

python3 PiHueRoom.py

...or:

python3 PiHueLightList.py

The Pi should connect to the Bridge and save the
Bridge details in the file /home/pi/.python_hue.
If we ever need to change the Bridge, we just need
to delete this file. We can now re-comment the
b.connect() line by adding # at the front..

Running on boot

There are a few ways to run Python code when

the Raspberry Pi boots. A good method is to

use systemd. In this case, we need to create a

configuration file (aka a ‘unit’ file) that defines

a new systemd service:

sudo nano /lib/systemd/system/PiHue.service

...and type in the following (replacing PiHueRoom.py

with PiHueLightList.py if required):

[Unit]

Description=PiHue Service

After=multi-user.target

[Service]

Type=idle

User=pi

Restart=always

ExecStart=/usr/bin/python3 /home/pi/PiHue/

PiHueRoom.py

[Install]

WantedBy=multi-user.target

Exit and save using CTRL+X, Y, then ENTER.

The permission of the unit file needs to be set to 644:

sudo chmod 644 /lib/systemd/system/PiHue.

service

We need to instruct systemd to start the service

during the boot sequence:

sudo systemctl daemon-reload

sudo systemctl enable PiHue.service

When we reboot the Pi, the PiHue service should run.

Check service status

We can check the status of the PiHue service using:

sudo systemctl status PiHue.service

The last line should look like:

Jul 10 23:26:52 PiHue systemd[1]: Started

Start the Touch pHAT Hue controller.

Sometimes the Raspberry Pi disconnects from

the network, especially when using WiFi. Once

disconnected, it will remain disconnected unless the

interface is restarted or the Pi is rebooted. That makes

this light switch a bit useless. But help is at hand: we

can reboot the Pi if it cannot see your home router!

Follow the instructions by Thijs Bernolet on his blog

to enable reboot on network loss: magpi.cc/2uC0iny.

Language

>PYTHON 3

NAME:

PiHueRoom.py

PiHueLightList.py

DOWNLOAD:

magpi.cc/2vBxtoI

CONTROL

YOUR OWN

WORLD!

Don’t just use

the code as

is – why not

experiment

and make

your lights

match your

own colour

schemes?

Above It’s alive!