Light Following Robot




About: Engineer, Clemson grad, writer, maker of random contraptions for fun and profit.

This instructible will show you how to make a light following "robot" using only a couple batteries, light dependent resistors, and a pair of motors. Robot is a bit of an exaggeration, as this is quite a simple beast, but it reacts to stimuli, so that's close enough!

Video of the process can be found here, and I'll embed it at the end of the tutorial as well.

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Step 1: Materials Needed

  • (2) Gearmotors
  • (6) LDRs (light-dependent resistors)
  • Wire
  • (2) Coin cell batteries
  • Perfboard
  • 1/2" MDF
  • Toy car or other source of wheels

This is what I used, but nearly everything on this list can be substituted.

Step 2: Cut Out Frame

This can be made out of nearly anything you can think of, but I decided to cut mine out of a piece of 1/2 inch MDF. A 1/2 inch slot was first cut down the middle of the frame in order to accommodate motors on either side, then the body was cut out with a 2 3/4 inch hole saw.

An area was also cut out in the back for the coin-cell batteries.

Step 3: Source Wheels

Wheels were sourced from a broken toy truck. Lock the axle in a vise, then pry with pliers.

Step 4: Install Batteries

Like everything else in this project, you could substitute something different (like a LiPo pack or two), but after carving out space for my coin-cell batteries, I stripped a piece of wire then wrapped it around, connecting it to the positive battery terminal on the bottom. The top negative side was connected by the ends of a wire run through the PCB and sticking out the bottom slightly.

Technique is somewhat similar to these shrink wrap battery packs outlined here.

Step 5: Electrical Connections

Electronics are quite simple. Positive from the batteries goes to the LDRs as shown, then the bank of LDRs on the right feeds the motor on the left and vice versa. Three LDRs in parallel were used here to allow more current to flow to each motor.

Step 6: Assemble

Assemble the motors with hot glue, along with the circuit board that forms the top. And that's it, you now have a little robot that will follow a light around!

Step 7: Enjoy!

Thanks for checking this tutorial out. If you enjoyed the video, I'd invite you to check out a lot of other contraptions I've made here!

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    16 Discussions


    1 year ago

    Google the work of Rodney Brooks. He has written extensively and intriguingly on subsumption architecture in robotics in which light seeking (photophilic) and light avoiding photophobic behaviors can be modeled using NO microcontroller and only a few photocells and transistors. Your project would benefit from using a left and right photocell to controll the base drive to transistors which would vary their conductance in response to or lack of available light.

    Good post.


    1 reply

    1 year ago on Introduction

    would it be possible to use this to only follow a certain IR light? im quite new to electronics and im building an r2 d2 and id like it to be able to follow me

    1 reply

    Reply 1 year ago

    Hi, if you were to put some sort visible light filter on the LDRs or if there are LDRs made that only respond to certain wavelengths, I would think it would be possible. I haven't tried this though.


    1 year ago

    Why 6 LDR's ??? What will happen if i put 2 LDR on front side and 2 on back side ???

    1 reply

    Three LDRs in parallel were used here to allow more current to flow to each motor. You might check out the video for more of an explanation.

    It wouldn't work too well that way - would turn one way when light is in back and the other when light is in the front.


    1 year ago

    nice, I love the simplicity of the electrical works. Since these LDR's vary quite a bit, would it be possible to add a variable resistor to both sides, so you can tweak the robot to go straight when light is equal?

    1 reply
    Penolopy Bulnick

    1 year ago

    I don't think I've ever seen a light following robot before! What a fun idea :)

    1 reply