serfSwitch

An Arduino-based smart "switch" that fits over a regular switch and physically flips it on demand (because we're all just renters these days).

Uses MQTT to integrate with Home Assistant.

My first electronics project!

Requirements

• Arduino Nano ESP32
• Small servo motor
• Tools and other materials:
  • Soldering kit
  • Wire stripper/cutter
  • Jumper wires (male/female)
  • Aluminium strips
  • Strong double-sided tape
  • Optional breadboard
• Infrastructure
  • Mosquitto or other MQTT server install
  • Home Assistant install with the MQTT integration connected

Usage

0. Setup the Arduino IDE with the ESP32 and MQTT libraries (on Linux, you may need to add SUBSYSTEMS=="usb", ATTRS{idVendor}=="2341", ATTRS{idProduct}=="0070", MODE:="0666" to /etc/udev/rules.d/60-arduino-esp32.rules).
1. Copy template.creds.h to creds.h and fill it in if you want to (if not, you'll need to configure connection settings via Bluetooth).
2. Strip a centimeter or so of insulation off each of the three wires of the servo (power, ground, control).
3. Do the same for 3 wires that end in female jumper pins. Coordinating colour with the 3 servo wires is recommended.
4. Manually twist the exposed end of the power wire from the servo motor with a corresponding female jumper wire for a loose attachment.
5. Do the same for the servo ground wire.
6. Solder the 2 power wires (that were twisted together to form "one wire") to the VIN pin on the Arduino.
   • You could use the breadboard to prototype everything first.
7. Solder the "merged" ground wire to one of the GND pins on the Arduino.
8. Solder the servo control wire to either the D3, D6, or D7 ports on the Arduino.
   • Only one pin is technically used but the code outputs to all 3 - this is a lazy way to "correct" a soldering error in my builds.
9. Solder the remaining hanging wire (the third female jumper wire) to the VBUS pin on the Arduino.
10. Connect a USB-C power supply to the device. It should show up in Home Assistant with a permanent randomly-generated ID, and should be usable immediately.
    • Depending on the motor used and how you set it up, you may need to modify some variables under // Hardware config - experiment with what values work for you.
    • Note that the code does support a push button connected to pin D5, but I ended up not using one for my build.
11. Use the aluminium strips and double sided tape to securely mount everything over your existing dumb switch.
    • Obviously, skip this in the prototyping stage.
12. The female jumpers are used to power a second switch without needing a second USB-C power supply.
    • Using a male-male wire, connect the VBUS-attached pin of the USB-powered switch to the VIN-attached (power) pin on the second switch.
    • Do the same to connect the GND-attached pins of both switches.
    • Due to power constraints, only 1 switch can be attached in this way.
13. After the board is plugged in, it should automatically connect to the configured MQTT server. If you did not put configuration variables in creds.h, you can use a Bluetooth LE scanner app to configure the switch via Bluetooth (as instructed in the Bluetooth characteristic). The blinking lights you see on boot represent a 6 digit code you will need to include when configuring the switch.

Result

Hey, I never said it was pretty.