Henry wanted to know how traffic signals work. He learned a ton about them and what makes them function. Just so you know, there are lots of books about crystals (rocks & minerals). We found only 1 book that even mentioned traffic signals. Not a lot of info about them out there. That made this project a little challenging.
But Henry was determined to learn about them. He even rigged up this little model using the Snap Circuits Jr. set. There is a photo sensor under the truck that turns the red light on and off and he added a second switch that makes the other light change. Cool.
I'm really proud of them too!