Science Buddies: "Ask an Expert"

There is a problem with my speedy light seeking robot. The wheels are going at different speeds somehow. We did finish building and put all of things in the right spot on the bread board. Its just the motors that are moving at different speeds. We did have to switch one motor wires because the wheels went opposite ways. Heres a picture.

Moderator note: Related Project: https://www.sciencebuddies.org/science- ... wing-robot

Hello!

Basically, each wheel has its own little “speed knob,” so if the knobs are not set the same, one wheel goes faster. Point both light sensors the same way, turn both blue knobs all the way down, then slowly turn one knob up until its wheel starts spinning. Turn the other knob until that wheel spins at the same speed. If it still turns to one side, twist the slower wheel’s knob a tiny bit more.

I will add to calixte's answer that sometimes there are just small physical differences between motors (different amounts of internal friction, wheel may be mounted slightly differently, etc) that make them run at slightly different speeds. But as calixte described, in this project you can use the two potentiometers (knobs) to adjust each motor's sensitivity to light independently. It can be difficult to hit each photoresistor with EXACTLY the same amount of light, so it can be hard to get the robot to go perfectly straight, but it does help if they are pointed in the same direction. In your picture, one of the photoresistos is facing off to the side.