Drill bit that matches the size of the motor shaft (we use AWG#50)
Fan or windy day
Optional: other motors and LEDs, hookup wire, alligator clip leads
Cut the sides of the small cup into four equal parts. Remove the base to create four curved pieces that will be the blades of the wind generator.
Use hot glue to attach two craft sticks together at the center so they make a plus sign.
Once the glue is dry, drill a small hole the size of the motor shaft in the center of the craft sticks. This will serve as the frame for your blades (see below).
Glue a blade to each of the craft stick ends, as shown (click to enlarge image). The blade design has the greatest impact on the efficiency of the wind generator; this is just one way to do it. Feel free to try materials other than a cup to construct something you think will best utilize the wind to yield the most rotations per second.
The hobby motor should have two small prongs sticking out of the back that serve as the terminals where you would normally attach a power source. Instead, attach an LED to the back of your motor by twisting each leg of the LED through a different terminal on the back of the motor. The correct orientation of the LED will depend on whether the blades spin clockwise or counterclockwise, so you will know if you need to switch it once you test the windmill. Slide your blade frame onto the shaft of the motor (see below).
Glue one end of each of the other two craft sticks on either side of the larger cup to make a stand that holds the motor above the cup like chopsticks. Glue the other ends of the craft sticks directly to opposite sides of the motor to hold it in place. Make sure the motor is positioned so that the stand does not obstruct the ability of the blades to turn freely.
To Do and Notice
Test out your wind generator with a fan or on a windy day. Can you generate enough power to light an LED?
Note: LEDs only work in one direction in a circuit. Your motor will output DC current, but it may be in the reverse of the direction your LED needs. If you have trouble getting the LED to light up, try switching the leads to make sure it’s connected in the correct orientation.
What’s Going On?
A generator is a device that converts mechanical energy into electrical energy. This is the opposite of how a motor works, which uses electricity to create motion. This activity uses a hobby motor in reverse to create an electric current. By attaching blades to the motor, wind can be used to provide mechanical energy to the motor so that it works like a generator and supplies electricity. This electrical output could be measured with a multimeter, but an LED provides an easy readout that shows power is being generated. This simple wind generator is a model for wind turbines used to generate electricity around the world. Though they operate on a larger scale, they use the same physical principles to convert wind energy to electricity.
This Snack provides a basic template for constructing a wind generator, but there are many opportunities to engineer a better design. What adjustments can you make to the overall design to solve these problems:
By using a high voltage motor, the wind generator should readily light a red LED with a room fan. Can you design a generator that works with a 3-5V motor?
Some wind generators allow the blade frame to rotate to optimize its position depending on the wind direction. Can you design a stand that will turn into the wind?
When testing your design, it helps to make the parts of the wind generator modular so components can be readily swapped in and out. For example, you can use alligator clip leads or hookup wire to make it easier to change the LED if you are testing different load devices. Can you design an easy way to test different wind blades?
Depending on the torque of your motor and the intensity of your LED, it may be difficult to see the light turn on. Play around with different materials to find a combination that works for you and your wind source.
This Snack is adapted from an activity developed by the CuriOdyssey museum at Coyote Point, near San Francisco. Check them out at www.curiodyssey.org.