Create a windmill by cutting four windmill blades out of thin cardboard. You can use a manila folder, food packaging or similar material (see image: cut blades from a used waffle box). You can use the design provided, or create your own design. You can build, test, and compare them to see what shapes work best.
LEGO Spike Prime Windmill Design
How could you use a sensor to measure the wind speed?
In the above example, notice how a color sensor has been attached to the windmill to detect and count each time a blade is detected.
Sample code is provided below.
Here’s a brief explanation of the code:
- We start by setting the count variable to 0 and resetting the timer. For 10 seconds, we count how many times a blade passes the sensor
- To detect each blade, we wait for the reflected light to go above 5% (i.e. a blade is in front of the sensor) and then wait for it to drop below 5% (the blade has moved past the sensor)
- After 10 seconds, we play a beep, display an estimate of the windmill’s RPM (revolutions per minute), and repeat the process.
- Note that to estimate the RPM, we have multiplied count by 10 (to get an estimate for 60 seconds) and then divided by 4 because there are four blades on the example windmill.
Here’s another approach to constructing a windmill using LEGO bricks, a LEGO wheel, a toilet paper roll, and a rubber band.
Turn ordinary paper into decorations with a paper crimper.
There are many ways to construct a paper crimper—as long as it has a set of meshed gears to crimp the paper. The stand, the crank, and the number and type of gears are up to you.
Once your paper crimper is working, crimp some paper and use the strips for a creation of your own design—a mask, a hat—anything you wish.
Benham was a toymaker in the 1800’s who discovered an illusion while experimenting with spinning tops. He found that when he spun a black-and-white disk, he sometimes saw flashes of color. See if you can produce this effect.
The attached Benham Top Design Sheet contains two ready-made patterns and one blank template for creating your own design. (Look for the paperclip icon in the top-right corner of this post.)
Cut out one of the disks from the design sheet and sandwich it between a large gear and a small gear on a LEGO top made from gears stacked on axles.
LEGO spinning top.
LEGO spinning top with Benham's disk.
The colored-flashes effect is produced by differences in the cones of your eyes. You have three types of cones, one for detecting blue light, one for red, and one for green. The three types of cones have different response patterns, and the flashes of white light on the spinning disk activate them in different ways. Their varying responses create the illusion of color.
Thanks to Kat Kelly (Windmills) and Barbara Bratzel (Paper Crimper, Benham's Top) for their contributions to this post.