A Mini Op-Amp Based Line Following Robot


There’s no denying it. Super small robots are just cool. [Pinomelean] has posted an Instructable on how to create a mini line following robot using only analog circuitry. This would make a great demo project to show your friends and family what you’ve been up to.

Analog circuitry can be used instead of a microcontroller for many different applications, and this is one of them. The circuit consists of two op-amps that amplify the output of two phototransistors, which control each motor. This circuit is super simple yet very effective. The mechanical system is also quite cool and well thought out. To keep things simple, the motors drive the wheel treads, rather than directly through an axle. After the build was completed, the device needed to be calibrated by turning potentiometers that control the gain of each op-amp. Once everything is balanced, the robot runs great! See it in action after the break.

While not the smallest line follower we have seen, this robot is quite easy to reproduce. What little robots have you build lately? Send us a tip and let us know!

[via Embedded Lab]


  1. You sir…deserve the slow clap….

  2. k says:

    Lovely and elegant.

  3. theo says:

    It doesn’t hurt that this is physically beautiful

  4. Mike Szczys says:

    I think everyone should build a line follower at some point. They’re simple enough to be approachable, but as the beginning of the video proves, complex enough to be worth perfecting.

    The size and appearance of this one put it on a pedestal of craftsmanship. the body bent out of flat stock, and that mini-ball-roller for the third wheel. Fantastic!

    • medix says:

      We used to build these out of LM339’s with photoresistors as inputs driving a pair of transistors to control the motors. The frames were made ‘freeform’ out of paper clips soldered together. Very cool to see this design!

  5. wetomelo says:

    I opened this commercial product and is almost the same circuit


  6. Stephen says:

    This was the final project in our (Scottish Certificate of Education) Fifth Year Physics analogue electronics book. I still remember the circuit.

  7. justice099 says:

    At a previous job, we built surgical lamps that followed around a pendant and it worked pretty much the same way. In this case, op-amps are a bit more simple than PID in a microcontroller and the motion is much smoother.

  8. Liam Jackson says:

    I love how the motor spindle drives the wheel, total minimalistic “why didn’t I think of that” design.

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