Connecting DIY sensors to Home Assistant

Since Home Assistant (HASS) runs on raspberry Pi, I can easily extend it using my cheap home built sensors.

Temperature Sensor:

The first sensor I attached was a temperature. My thermostat is outside the room and if the door is closed, the difference between the room and outside can be as high as 4°F. The sensor I used is DS18b20 (it has high accuracy — 0.5° and is quite cheap <$0.5) and HASS supports it out of the box using one wire plugin. The schematic is:

Schematic for DS18B20 temperature sensor

You need to add “dtoverlay=w1-gpio” to “/boot/config.txt” and reboot the device. Execute the following commands:

sudo modprobe w1-gpio
sudo modprobe w1-therm
ls /sys/bus/w1/devices

You will see the 28-xxxx which is the ID of the device and you can now add the following to the HASS configuration.

sensor:
  - platform: onewire
    names:
      28-xxxx: Bedroom

Motion Sensor:

The next step was connecting motion sensor which I can use to track when the room is empty. PIR Sensor (HC-SR501) is one of the most fascinating pieces of technology. It uses a fresnel lens to focus the IR on the sensor, can detect movement 7m away and cost <$1! The schematic is:

Schematic for HC-SR501 motion sensor

Note that you can directly connect the Data Out of PIR Sensor to GPIO of raspberry pi but I added a LED and 220Ω resistor so I can easily test the range of the sensor. You also need to add the following to the HASS config:

binary_sensor:
  - platform: rpi_gpio
    pull_mode: DOWN
    ports:
      19: Bedroom Motion

I now have complete history of motion in the room :).

Red=motion detected

Changes:

• Add motion and temperature sensor to the room
• Expense: ~$1.5