Cool Motor Kits for Future Engineers

October 30, 2009

4 Min Read
Cool Motor Kits for Future Engineers

Greetings fellow gadgeteers! In this blog post, I will take a look at some electronics projects for kids. Like many of you, I have kids that are at that impressionable age where they can hopefully be steered towards an honorable life spent in a field such engineering, science, or plumbing, and away from such disreputable activities as ticket scalping or lawyering. To that end I present some projects that are kid friendly and which hopefully can stir an interest in electronics as a hobby or career.

The first electronic motor kit I built was a conventional permanent magnet DC motor with brass brushes and commutator. I had to wind the coils by hand (and rewind! I learned that polarity matters!). Then the brushes had to be carefully bent to properly touch the commutator. It was some frustration to get going, but once it worked I spent many hours spinning things with it, and experimenting with the phasing of the commutator to see how fast it would go. As it turns out there are much simpler ways to build motors that don’t involve brushes or paying close attention to which direction the windings are put on.

Homopolar motor

homopolarmotor.jpg

The simplest electronic motor that I’ve been able to find on the internet is called the homopolar motor, so named because the polarity of the current never changes. It runs off DC current and does not use brushes or otherwise change or interrupt the current. This motor is simplicity itself, and you can find the build directions at the Evil Mad Scientist website.

The full explanation is available with the build instructions, but in brief this motor uses the magnet as the rotor, and the conductor as the stator. The magnet itself is part of the circuit, and motion is produced by the cross product of the current flowing through the magnet and the magnet’s own magnetic field. I haven’t built a working version of this yet since I don’t have a round magnet at hand, and the oblong ones I’ve scavenged from dead hard drives don’t seem to work (Even when coupled with a round steel washer it only twitches, it doesn’t rotate). Despite this setback I am rating this project “easy” and (based on other motor experiments I’ve done with my kids) with a high “cool factor”. I’ll search out a round magnet and report back via the comment section below.

A simple DC motor

I ran into this design over at instructables.com, billed as a simple electric motor. This one actually worked when I built it, and my four sons were also able to each build one. The instructable says to coat the wire with nail polish, but I wasn’t able to get that to work. My wife obviously does not buy motor rated nail polish. We found that the nail polish wasn’t necessary, it was enough to simply scrape all the enamel from one end of the coil, and only the enamel from one side of the wire on the other end of the coil. In this motor the field formed by the coil is opposite in polarity to the field of the magnet, which causes the coil to flip over. In this orientation the coil would be attracted to the magnet, except that the circuit is broken by the presence of the enamel on the wire. The motor relies on angular momentum to keep the coil spinning through this dead phase until it is again energized and repelled by the magnet. This project is also rated “easy” and “fun for kids”.
My oldest son recently attended a Boy Scout “merit badge workshop” where he coincidently built another version of this same motor.

Brushless DC motor

brushlessdcmotor.jpg

This is another DC motor that cleverly replaces the brushes with a reed switch. The circuit is the same as the simple DC motor above in that the current is only applied to the coil when the coil and magnet are opposite polarity, but in this motor the coil is the stator and the magnets are the rotor. Kits are available, and there is also a slightly more complicated hall effect motor also.

Build some of these motors and see what your kids (or your co-workers) think of them and let me know! Post your comments below.

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