D1 Mini Pro based vehicle detection sensor utilizing QMC5883L magnetometer. Features vehicle detection using megnetometer, gate staus with reed switch, battery voltage detection with voltage divider, and relay for gate actuation.

Compile using ESPHome from esphome/esphome#671 for QMC5883L support.

D1 Mini Pro: $4
D1 Mini Dual Base: $1.00
D1 Mini Relay Shield: $1.20
D1 Mini DC Power Shield: $1.40
D1 Mini Proto Board: $0.30
QMC5883L Triple Axis Compass Magnetometer: $6.59
Sonoff IP66 Junction Box: $6.99
Voltage Divider: $1.38

QMC5883L: 3v or 5v, GND, D1 (SCL), D2 (SDA)
Reed Switch: GND, D7
Relay: D8 (you can modify the pin # on V2, or physically cut D1 pin and add bodge wire)
Voltage Divider: GND (if not shared ground), A0

Voltage divider and reed switch terminals were connected to a shared proto board

Don't forget to connect the external wifi antenna if needed!