I built an ESPHome project to sense the mains voltage inside my turntable to sense whether it was swtiched on.

esphome-sensing-mains-voltage-turntable.md

ESP-Home Turntable

A quick morning project I did to detect whether my turntable was turned on so I could automate powering on my monitors (speakers). Note - the easiest and safest way to do this was probably with an energy detecting smart plug but I didnt have enough space for one. Another advantage is that it resulst in having an esphome close to my turntable which may come in helpful for future automations. Another better alternative is probably just using a CT clamp.

Ingredients

• ESPHome device - I used an ESP32 DEVKIT 1
• Optocoupler
• Project box
• I also got some heatshrink
• Electronics essentials: Soldering iron, jumper leads etc
• Hot glue gun

Method:

0. Work out what you're dealing with
   • 
   • This seems to show two terminals that get energised to mains voltage
1. Prototype on a breadboard, Note that this is HIGH VOLTAGE, stay well clear when the mains side is energised.
   • 
2. Solder and assemble into project box, cut holes for connections, glue components into place.
   • 
   • N.B in the finished project I put a non conductive space between the ESP and the highvoltage circuit.
3. Solder the HV side - I also had to put a cut out to let the wires through, then wrap in heatshrink
   • 

References

• ESP32 doit DEVKIT V1 pinout https://www.circuitstate.com/pinouts/doit-esp32-devkit-v1-wifi-development-board-pinout-diagram-and-reference/
• ESP8266 pinout https://randomnerdtutorials.com/esp8266-pinout-reference-gpios/
• ESPhome Hardware design channel https://discord.com/channels/429907082951524364/951213660905287761

turntable-monitor.yaml

esphome:
  name: turntable-monitor
  name_add_mac_suffix: false
  friendly_name: Turntable monitor

esp32:
  board: esp32doit-devkit-v1

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password
  # use_address: 192.168.0.128
  # Optional manual IP
  # manual_ip:
  #   static_ip: 192.168.1.100
  #   gateway: 192.168.1.1
  #   subnet: 255.255.255.0

  ap:
    ssid: "Turntable Fallback Hotspot"
    password: "some_fallback_password"

logger:

# Enable Home Assistant API
api:
  encryption:
    key: yourkeyhere=

ota:
  - platform: esphome
    password: "somepassword"

binary_sensor:
  - platform: gpio
    pin: 
      number: GPIO4 # D4 contains neither a pull up or pull down internally
      mode: INPUT
      inverted: true # our optocoupler has a 47k resistor between the 3.3V VCC and the collector, which is directly connected to 'out' so when there is no high voltage input, out is pulled up
    name: "Turntable"
    device_class: running

bluetooth_proxy: #because why not, will only work on boards that support it (not an esp8266)