Introduction: Electronic Pendulum Made Into Brushless Motor

Picture of Electronic Pendulum Made Into Brushless Motor
I had built this electronic pendulum for an earlier project and decided to make it into a single pole brushless motor by doubling the length of the armature and adding magnets to both ends. After balancing the armature it worked first try. Slow running motor, abut 60 RPM and very little torque though this motor will run for weeks or months on three AA batteries. If you could use the power used to light the LED it would even run longer. Interesting project.

How it works:  as the armature rotates and one end with the magnets comes close to the coil of wire, the circuit senses the magnets and turns power on to the coil to make an electromagnet which then attracts the magnet. When the magnet passes to the center of the coil the magnet is turned off, the polarity of the coil reversed and then the coil pushs the magnets away so you get this pull then push effect which rotates the arm.
This simple electronic circuit is about one of the most interesting I have ever built and the only time consuming part is winding the coil of wire which I did by hand and took about an hour. Well worth it.

This link shows how to build this electronic driver circuit

Photo 1: Shows complete motor assembly.
Photo 2: Closeup of end of armature. I hot glued magnets to end of arm which is a piece of hollow fiberglass tube (fishing pole).
Photo 3: View of axle which is a bicycle spoke inside smaller tubing which goes through center of armature. Notice red tape which is just a counterweight so both sides of armature are balanced.
Photo 4: Close up and hand wound coil.
Photo 5: Close up and electronic circuit that drives coil and armature.
Photo 6: Circuit diagram from website that describes how to build electronic driver circuit.


TinkerJim made it! (author)2017-03-21

Thank you, Jim, for posting this Instructable. I made a Gasparovic pendulum 17 years ago from his article in Nuts & Volts magazine. It has essentially the same circuit as the one you showed in your Instructable. The pendulum has been swinging away more or less continuously since then, changing the 2 AA batteries every 3 months or so.

I thought many times of doubling the arms and making a motor of it, but your Instructable finally provided the motivation get on with it. Still wanting the pendulum to keep on swinging, I made a separate motor - shown in the video at . It runs beautifully and I thank you again for your help…TinkerJim

PS: I slightly modified the circuit as shown here:

About This Instructable




Bio: I am an American teaching English at Shangluo University, Shaanxi. I like making machines that do interesting but fairly useless things - I call them Quixotic ... More »
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