Smart intercom

Simple and cheap circuit for transform the old intercom into a home assistant compatible smart intercom.

Circuit (pdf)

For the Urmet 1131/1133:

• 9 -> Buzzer
• 6 -> GND
• CA -> electric lock

Urmet 1131

Urmet 1133

Components:

• AC/DC -> LM2596HV AC/DC to DC Buck Step Down Converter Module (Aliexpress)
• Relay -> 1 Channel Relay Module 5V High Level Trigger (Aliexpress)
• Optocoupler -> PC817 (Aliexpress)
• ESP8266 MOdule -> Wemos D1 mini

It's strongly recommended to use a High Level Trigger Relay to avoid accidental opening of the door in the event of blackout.

Home Assistant / EspHome (YAML)

There are two entity:

• switch for the door opening
• binary_sensor triggered when the intercom buzzer rings.