Powering Vintage Motors
EV3 motors are a great invention, allowing precise motion with built in encoders and gear reduction. But sometimes a simpler, smaller motor is needed. And it's worthwhile to learn to build gear systems from a simple motor. LEGO has made several types of motors over the years, two of which are in the photo above from my collection. On the left is the 2838 9V Motor, which I bought in the mid-1990s. LEGO later changed the 9V motor design to that shown on on the right of the 71427, many of which I bought in the late 1990s. The 71427 was in some of the Znap sets of 1998-1999. Znap was a flop as a product line, and in 1999 I found the sets at drastic clearance prices as my local Toys R Us store was trying to unload them. I bought several of the Znap sets just for the motors.
These older motors can be used with EV3 designs by providing a voltage from EV3 as described in my other blog post on EV3 Voltage Source. To connect to the motor the cable from the motor has to be modified by cutting off one connector to expose bare wires, much like the description provided in Chapter 3 of LEGO Optics. With higher applied voltage, the motor will spin faster. Reversing the polarity of the connection will reverse the direction of the motor.