Line Following Snack Serving Robot

by rory_littleBits

Published on March 11, 2015

A robot built with littleBits that follows a drawn line and serves treats from the snack bowl mounted on top.

How it works:

The Line Following Snack Serving Robot is a robot made with littleBits that does exactly that, serve delicious snacks along a path drawn by the maker. This project requires no programming.

The robot has two DC motors controlled by a respective light sensor. The bright LEDs illuminate the surface below the robot and more light reflects from the floor surface than from the drawn line. When the bright LED shines on the floor, more light reflects into the light sensor telling the DC motor to turn fast. When the bright LED shines on the drawn line, less light reflects into the light sensor telling the DC motor to turn slowly. Each light sensor controls its respective DC motor in effect steering the robot along the drawn black line.

The inspiration for this project came from one of our active users on the project’s portion of our website, Yoo-bin Lee. She created the original littleBits line follower robot in December of 2013.

Credits: Sean Schumer

How To Make It


Take the two mounting boards and sandwich them together so their mounting sides facing outward. Zip tie the two mounting boards together by placing a tie through the mounting holes at each corner (four zip ties total).


Begin building your circuit, start by placing the following on one side of the mounting boards: P1-Power → Branch → 2 x Wire


On the other side of the mounting boards, you are going to build two identical circuits along the long side. Keep in mind the orientation of the DC motor will be different on each side. The DC motor shaft must face towards the outside of the board. The circuit is: Bright LED → Light Sensor → Wire → DC Motor


Attach the Pololu wheels to the shaft of each DC motor.


Warm up your hot glue gun and place your caster on the mounting board somewhere between the two bright LEDs. Hot glue it into place.


Set the direction on each DC motor so they turn in the correct direction. The right motor’s direction should be set to “left”. The left motor’s direction should be set to “right”.


Set the light sensors to “light” mode.


At this point, it may be a good idea to test your robot and see how it’s operating. The light sensor will likely need its sensitivity adjusted and may need to be shielded physically from outside light.


A wooden floor may be fine for your robot but a surface with high contrast is ideal. White foam board or white poster board is recommended. Once you’ve selected your surface, use black electrical tape to draw a path for your robot. You can either use a single long piece of tape to gracefully draw curves or you can cut pieces of varying lengths and draw a path with lots of straight lines. Very sharp angles may be difficult for the robot to navigate so try and keep the angles obtuse.


How did your robot do? Did it navigate the path successfully or did it run off the path? It’s likely your robot ran off the path and will need adjusting to suit your track. This will take some trial-and-error to get right. Here are some suggestions:

 -- On the underside of your robot, turn the sensitivity down on each light sensor and test again. This will slow your robot down but will let you know if it’s able to navigate your path.

 -- Does your robot drive off the path at specific points? If so, the path may be too sharp of an angle, or you may have bright lights in your area creating glares on the surface. Try turning off these lights.

 -- If all suggestions don’t seem to help, it may be worth building some blinders for your bright LED and light sensor. You can use any stiff material you have around. Cardboard is easiest to work with. We used scrap acrylic. Lining the inside of the blinders with black electrical tape will cut down on light reflections.

 -- In addition to building blinders, a skirt for the entire robot will help block out more ambient light. Construction paper worked well here.


Once your robot is working well, it’s time to attach your snack bowl! Build a platform on the top side of your robot to support your bowl. We used scrap acrylic to create several posts beneath a flat, horizontal panel, like a table. Cardboard will also work here just fine. Use your hot glue gun to put it all together.


Fill your bowl with tasty treats.


Place the robot back on its path. Enjoy autonomous snack serving!

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