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Outdated design! Update coming soon!

Tests show that there is an issue causing short circuits in this design. When coupled, the couplers are not fixed in the relative, vertical position. This may result in a coupler raising a whole row over the over coupler, shorting the pins C1 to C2. A new version of the coupler will be released soon, fixing this issue with promising results in the testing so far.
New and old versions of the coupler will not be able to drive in traction.

Before you start

The parts list can be found on the design page. The wiring is explained there as well.

Mechanical coupler

We start by building the mechanical coupler.

Two housings and the magnet Step 1: starting with the magnet and both 3d printed parts

The magnet is inserted into one of the housings Step 2: insert the magnet

Closing process of the housings Step 3: close the coupler

Step 4: closed coupler

Coupler connected to a Plate, Modified 2 x 3 with Hole, Item No: 3176 with a Technic, Pin 1/2 without Friction Ridges, Item No: 4274 Step 5: insert pin

Pogo pin

Assembly of a pogo pin contact.

Brown wire with crimped pogo pin Step 6: crimp the single wire with pogo pin.

Mind that one coach can only have one C1 / brown and one C2 / blue with pogo pin on one side, and the same wire will have a fixed pin on the other side!

Wire with crimped pogo pin with copper foil around the pogo pin Step 7: use some copper foil to adjust the diametre of the pogo pin to the pin hole in the coupler.

Step 8: isolate the end of the pin.

Coupler with the pogo pin inserted Step 9: insert the pin in the coupler

Step 10: glue the pin in the coupler.

Make sure there is no glue on the moving part of the pogo pin!

Fixed contact

Assembly of a fixed contact.

Stripped wire Step 11: starting with the wire.

Stripped blue wire with lots of copper foil around it Step 12: use some copper foil to adjust the diametre of the pogo pin to the pin hole in the coupler.

Stripped wire with lots of copper foil around it with isolation tape on the cable facing half of the copper foil Step 13: isolate the end of the pin.

The assembly inserted into the coupler Step 14: insert the pin in the coupler.

The copper foil on the coupler side is flattened Step 15: flatten the pin.

The fixed contact is glued into the coupler Step 16: glue the pin in the coupler.

Connected contact

Assembly of a pair of contacts.

A long stripped red wire as well as a short double stripped red wire Step 17: starting with the wire.

The long stripped wire is connected to the short stripped wire with copper foil similiar to above. In plus, the other end of the short stripped wire has a pogo pin attached Step 18: same procedure as above, but the fixed pin will hold both ends of the wire.

Step 19: isolate the end of the pins

The whole assembly mounted in the coupler Step 20: glue the pins in the coupler.

Make sure there is no glue on the moving part of the pogo pin!

The whole assembly, but made of a black wire, mounted in the coupler Step 21: do the very same with the black wire and attach the coupler to a train.

Have fun with it!

Mounting the coupler to the train.

Electrical coupler on a tender Step 22: mount the coupler to your loco / tender / wagon / coach.

A loco and a tender are connected with the electrical coupler. Lights are on. Step 23: have fun with the coupler!

Electrical coupler for LEGO trains - Building instructions