Now to the fun part. Connecting all parts together according to the wiring on the left. The Entrelec relay is directly connected to the garage opener board. The control supply is provided by the Homematic relay. The switch input of the Homematic relay is provided by the hardware button and finally some 230V to feed the relay. That’s it.
Making the best out of Corona-wise cancelled sports evenings, there was suddenly enough time to smartify my garade door. It already has connectors on the garage door hardware. That way, I could connect a button to the board that is used to open and close the garage. But what was missing is a way to control it remotely. Since the remote went missing it was nearby to integrate the button into my smart home setup: Homematic actuators and a raspberry pie transferring all traffic via MQTT.Since that’s quite a boring interface, the next step was to write a control app, fooling around with Combine and SwiftUI. But that’s a story for another time 😉
As there’s already the possibility to control radio-relays via MQTT, the next move was to replace the connection from the button to board with a circuit integrating the relay HM-LC-Sw1-FM. https://de.elv.com/homematic-unterputzschalter-1fach-hm-lc-sw1-fm-fuer-smart-home-hausautomation-076793
But there was one problem. The relay works with an input and output voltage of 230V. That’s too much to control the board on the garage opener. So I had to integrate another relay that could switch an arbitrary input voltage but works with a rated Control Supply Voltage of 230V. I finally came up with an relay by Entrelec.
In order to test it, there’s no faster prototyping than to use Node-Red. It enables visually wiring up a control that either automates a workflow or provides a rudimentary GUI. https://nodered.org In this case, it’s a simple UI consisting of one toggle labeled „Garage“ sending out a message to the MQTT broker to fire up the Homematic relay.