January 14, 2019

cheatsheet DIY home automation

This cheatsheet shows the steps to a DIY project and was used to make my heater smart. This guide is only readable to technical people.

In the past I worked with primitive setups like Arduino or tried to get an ESP8266 wifi relay working. In my opinion, too limited and only worth considering if you need analog or economies of scale. Therefor, all my DIY home automation have a Linux kernel.

To understand this cheatsheet, this is my point of view;

  • Love cheap solutions for home automation
  • Love being able to write custom code
  • Hate it when stuff is dependent on the vendors’ server (most smart products)
  • Don’t like the physical aspect, get me the CLI over SSH ASAP

Step00: hardware

Get the required hardware.

  • USB to TTL
  • Board with wifi
  • dupont cables
  • power supply
  • relay
  • SD card
  • Laptop
  • etc.

Step01: bootable

To get the board up and running, we need the server version of the OS booting from the SD card.

Download it and dd or xz it to the SD card. (google ‘create bootable sd card YOUR-BOARD-NAME’)

Get a local CLI, via HDMI, usb serial console (build in or a separate USB to TTL). Confirm that it is booting.

 RX -v- RX
 TX -^- TX

I made this picture very unclear to highlight that RX connects to TX.

screen $(ls -tr /dev/tty*|grep -i usb|tail -1) 115200

step02 SSH

We will now configure the wifi. The name of the interface can be found using ip link, mine is called wlan0. On the sd card, add the following to /etc/network/interfaces:

allow-hotplug wlan0
auto wlan0
iface wlan0 inet dhcp
  wpa-ssid "my wifi network name"
  wpa-psk MyPlainTextPassWord

step03 install

Install the basics

apt update
apt dist-upgrade -y
apt install -y python-dev git python3-pip vim tree

step04 GPIO

We now find the right GPIO library for our board, for the OrangePI Zero we do:

# https://opi-gpio.readthedocs.io/en/latest/api-documentation.html
pip3 install OPi.GPIO

We search on google for ‘BOARD-NAME BOARD-VERSION pinout’, from which we learn the pin numbers to use.

The following code is based on the example code that came with OPi.GPIO:

root@OrangePI:~# cat /usr/local/bin/set-relay.py 
#!/usr/bin/env python3

import OPi.GPIO as GPIO
import sys

pin = 24 #which is PA13 on pinout

GPIO.setup(pin, GPIO.OUT)

val = sys.argv[-1:][0]
if val == '1':


Don’t forget to:

chmod +x /usr/local/bin/set-relay.py

We can now test this script with:

set-relay.py 1 # turn on
set-relay.py 0 # turn off


  • connect the jumper on the relay board between ‘VCC’ and ‘JD VCC’
  • connect the ‘VCC’ near the ‘in1’ to 5V on the controller board
  • connect GND to GND
  • connect ‘in1’ to the GPIO using a resistor

step05 create

Create whatever you like.

Example: Smart heater controlled via Dropbox

This example controls a heater. The heater unit is located on the attic, while the thermostat is located in the living room.

We keep the thermostat in place, enabling us to control the temperature there, but we make a cut in the line to insert the wifi relay. This enables us to turn the heater on or off, which will heat until the desired temperature set on the thermostat.

This makes the heater smart; we can control it from the web or set a timer, but not control the temperature.

We create the timer script, which will turn it on during specific times. Outside these time frames, we check a shared (with housemates) dropbox file, which contains either a ‘1’ or ‘0’.


# The following can be a link to a shared dropbox file or a file on your server
TIME=`date +%H%M`

# during the following time blocks
# we always want the heater on
if [ $TIME -gt 0430 ] && [ $TIME -lt 0615 ]
  # morning
  echo 1

if [ $TIME -gt 1530 ] && [ $TIME -lt 2045 ]
  # evening
  echo 1

curl --silent -L $FILELOC \
  | grep 1 \
  || echo 0

pay attention to dl=1.

This script is saved and tested:

root@OrangePI:~# vi /usr/local/bin/get-heater-val.sh
root@OrangePI:~# chmod +x /usr/local/bin/get-heater-val.sh
root@OrangePI:~# get-heater-val.sh

We connect the ‘get-value’ with ‘set-relay’:

root@OrangePI:~# cat /usr/local/bin/trigger-relay-update.sh
/usr/local/bin/set-relay.py `/usr/local/bin/get-heater-val.sh`

root@OrangePI:~# chmod +x /usr/local/bin/trigger-relay-update.sh

We would like to have a systemd timer, but since we are on an old machine, we will use a cron job:

root@OrangePI:~# cat /etc/issue
Ubuntu 14.04.5 LTS \n \l
root@OrangePI:~# mkdir -p /etc/cron.d
root@OrangePI:~# apt install cron
root@OrangePI:~# vi /etc/cron.d/relay
root@OrangePI:~# cat /etc/cron.d/relay 
*/3 * * * * root /usr/local/bin/trigger-relay-update.sh 2>&1

We now have a smart heater, controlled by time and multiple people can change the dropbox file, turning the heater on.

This is a very simple example, a better way would be ifttt or using Google Assistant.

NOTE: you may want to google ‘/etc/timezone’

actual implementation

The example above was to illustrate how one could do it, the actual code:


# turn on during these times
30 5,16 * * * root echo 1 > /run/relay

# turn off during these times
15 7 * * * root echo 0 > /run/relay
45 21,23 * * * root echo 0 > /run/relay

# dropbox only checked when current state is off
*/3 * * * * root /usr/local/bin/check-dropbox.sh

# set state
* * * * * root /usr/local/bin/set-relay.py `cat /run/relay`


# this allows the device to reconnect after a possible router reboot
4 4 * * * root /bin/sleep 60; reboot



# The following can be a link to a shared dropbox file or a file on your server

grep 0 /run/relay \
  && curl --silent -L $FILELOC | grep -q 1 \
  && echo 1 > /run/relay


#!/usr/bin/env python3

from flask import Flask
from flask import request
app = Flask(__name__)

homepage = '''
Turn the heater
<a href="/setrelay/1">on</a>
or turn it
<a href="/setrelay/0">off</a>

@app.route('/', methods=['GET'])
def serve_homepage():

@app.route('/setrelay/<int:value>', methods=['GET'])
def update_relay(value):
#  print(request) # debug
  inp = str(value)
  with open('/run/relay', 'w') as f: 

if __name__ == '__main__':
  app.run(debug=True, port=80, host='')


pip3 install flask

The server is started in a tmux session. Or one could make it reboot proof:

# Old Ubuntu, systemd is used nowadays
tail -2 /etc/rc.local 
/usr/local/bin/run-relay-webserver.py &
exit 0

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