Motor Makeover

Does it feel like your motor is a little wound up? Time for a makeover!

Motors are everywhere, from appliances to toothbrushes to tools. Just about anything that uses electricity and moves. This exploration takes a look inside them to see how they work and experiment with making a more powerful one. And it's going to look great.

• What: Motor Makeover
• When: Oh, it's time.
• Concepts: electromagnetism, physics, circuits
• Time: ~15 minutes to make
• Cost: ~$3, all re-usable
• Materials:
  • DC Motor
  • Batteries and Pack with leads
  • Magnets x 2
  • Small pieces of wood
  • Alligator clip leads (optional)
• Tools:
  • Hot glue gun / hot glue

Let's motor!

Let's see how this puppy runs!

Make a flag of tape to put on the motor spindle to make spinning easier to see. Load up your batteries, attach them to the clip leads, and attach the other ends to the rear tabs of the DC motor. Feel the tape with your finger (it makes great shapes, too). What happens when you change which leads the black and red go to?

Time to pop it open.

Turn your motor over to look at its bottom. Use a pair of pliers to bend the two metal tabs out, which were holding the plastic bottom. Then grip the plastic with the pliers, and pull to remove. What do you see inside? Let's pull it out and examine.

Starting from the metal tabs, the first stop is at the brushes. If you follow from each tab, you'll see that the brushes are made of springy metal and have grooved blocks at the end. This allows it to have constant contact with the motor as it spins.

The brushes are in constant contact with the commutator, which has three panels on most simple DC motors. As the motor spins, the brushes slide over the panels of the commutator, and at certain points in the rotation reverse the polarity of the current. It's an incredible trick, and also involves the way the armature windings are oriented as they connect to the rotor.

The motor functions as an electro-magnet, but which flops polarity halfway through its turn. The permanent magnets on the outside provide a common field. The electro-magnet moves partway attracting north to south. As it gets there, instead of locking in that orientation like most magnets do, suddenly its poles flop and it wants to be in the opposite orientation. With the rotational momentum it has, the motor simply keeps on spinning in the same direction.

A couple of things to examine include:

• the wiring pattern of the windings
• what having three commutators means as the spindle rotates
• what north-south orientation are both of the permanent magnets

Raise your motor to the sky!

With some wood extras, it isn't too hard to make a base for our motor to spin on. There are many solutions to this, but I cut two short pieces of dowel, glued them on a stirring stick, and glued the motor base on to that. I left the two motor tabs exposed on the sides for easy connecting.

Here's the fun part!

You can set up your motor however you like. You can put a tape flag or leave it, but the essential part is grabbing your two extra magnets to play with. Use the gator clips to hook up your motor. Putting them close to the rotors in the right orientation will get the motor running elegantly and extremely quickly.

Here are some wonderful things to try and notice:

• What orientation do the magnets have to be in to make the motor spin? Try flipping them mid-way.
• What happens when they get closer? Farther away?
• What happens when just one magnet moves away?
• Try starting your motor with one hand with only one magnet. Why does it do what you see?
• What happens to the circuit if you don't put magnets near? (heat)
• What happens when you add more magnets in a ring?
• Try substituting your magnets for stronger ones. What happens?
• Notice the spark and arcing happening where the brushes are touching the commutators.

Hope you enjoy this electronics take apart, which gets at the core of how electricity and motion play nice together. Open things up, get amazed, and as always, keep exploring.