Run Electric Door Openers With 2 Wires Instead of 4 Wires

When retrofitting electric door openers such as the Effeff Mediator Linear Door Opener, the wiring can sometimes be the biggest problem:

Most of the time, only two wires run to the door, but four are needed: two for the supply and two for the switch.

However, with a simple pole changer using a relay and some diodes, it can be done.

Add a relay with two switching contacts to the supply/switch side. This will produce -12V when the opener button is not pressed and +12V when it is.

The +12V and -12V go on two wires to the door.

A small rectifier produces +12 V for supplying the lock (stabilised by a capacitor).

A half-wave rectifier produces +12 V only when the button is pressed against the lock's contact.

The powersupply should produce around 13,5V as the rectifier has a 1,5V drop.

See https://www.tinkercad.com/things/cBRLRgXW4j6-2-draht-ansteuerung-motorschloss-statt-4-draht-mit-polwechsler