Lego Power Function (PF) Motor Speed Controller

Inspired by this product I made my own versions of a speedcontroller for Lego PF motors.

This product contains a commercial HW-70 PWM Motor Speed Controller Module.

It is based on the well known NE555 timer-IC to make a PWM ouput signal.

I bought a couple of these modules on AliExpress (for approx. 1€20 each incl shipping).

Then I made a small snapfit enclosure for it in FreeCad and 3D printed it.

The cable entry on the lid is marked with "wire".

The bottom (= lid) fits on lego studs.

You can find the the native files on my github

On AliExpress I bought a couple of PF connectors and 4 core wire and made my own DIY Lego PF connection cable.

Before assembling the PF cable, I removed the C1 and C2 contacts from the Bottom part of the connector so that only 1 connector is required to connect both the battery box (via the 0V and 9V contacts in the BOTTOM part) and the motor (via the C1 and C2 contacts in the TOP part).

See here the working of de Power Function cable

Because the output voltage cannot be reversed with this version, this module is actually more suitable as an LED dimmer than as a speed controller for a motor.

The addition of a DPDT switch does allow the motor to change direction - The type I found on AliExpress has 3 positions (FORWARD-STOP-REVERSE).

For this version I designed a larger snapfit enclosure in FreeCad

You can find the the native files on my github

First of all I replaced the screw connector on the HW-70 Module by a header connector (removed 3 pins first).

After that I soldered and tested all connections - The assembly of the PF cable is described in Step 2.

Finally I 3D printed the enclosure and mounted the circuit into this housing.

The cable entry on the lid is marked with "wire".

To make the stripes on the potentiometer scale, color in the lines with a black marker and then wipe it clean with alcohol, leaving the stripes.

The result is a full function speed controller for Lego PF motors.

The bottom (= lid) of the module fits on lego studs.