Let's Make Robots!

Herbie the Bristlebot

Goes towards the brightest light

Here is a little bot I made last week. He is a Herbie (original circuit by Randy Sargent) light seeking robot. A very simple freeformed circuit, only a lm386 audio amp, a 7805 linear regulator (to keep from blowing up the lower voltage motors), two photodiodes, a few led's, a resistor, a switch and two vibe motors. I built another herbie about a year ago with the typical motor configuration you usually see, and I like that bot quite a bit. I also made a solar bristlebot / photopopper which I posted here... and well this is a mash-up of those two bots. It works suprisingly well, tracking light and turning is very responsive.

For construction I used 'Plumbers Strap' and rivets. Along with super glue to hold wires and the photodiodes in place. I used double sticky foam tape to fasten the toothbrush heads and the motors. The 'eyes' are subminature panel mount red led's from Radio Hack. The actual eyes are large area photodiodes from goldmine electronics. The motors were scavanged from cell phones.

I have found you dont need a special toothbrush to achieve forward motion, just take regular toothbrushes and bend the bristles back and set a book on it for a while. These toothbrushes were the 6 for a dollar type. The battery fastener is one of those hook and loop (velcro) cable straps for your computer cables. It worked out great.

Anyway, I teach robot classes at the local library, and this is my next project. This guy is the prototype, now I am going to do some work on making the circuit easy to assemble in a library (without a soldering iron).

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

great robot. simple, but realy cool.

being able to steer so smoothly, great!!!

bonus points for the plumber straps.

Unless I ovelooked it. Where is the schematic?


Good Call. I just added the circuit for this guy as built. If you are using more voltage tolerant motors than mine you can drop the 5v regulator. If you google "Randy Sargent Herbie" you can see the original schematic and other peoples versions.

Thanks guys for the kind words.

If I can, I'll get some video of 10 of these guys at once @ the class. Bristlebot herding...


Your analisis is pretty much right. The circuit is not just bang bang (on / off) though. It varies the voltage to the motors and allows for straight movement, but I have found on this bristlebot platform the only way to achieve it is with very even lighting. I had to use the 5v regulator to avoid burning out the vibe motors I had found, which were happy with 1.5 to 5 volts. So the circuit divides that 5v between the two motors. The deadband from 0v to where the motor actually turns on, and the low total voltage, give this guy the back and forth waggle. At least thats my take on it.

I see.


Now I know what to do with my old toothbrushes ;)

Very nice :)


As Frits said, I have not seen a bristle-bot that was so responsive. I believe I see how you did it. one side stands still, so the robot tend to rotate around that point, then when the other side gets more light, it turns back the other way. This happens so quickly that the effect is to move in an "almost" straight line.

Great job.

Awesome, I never managed to make a controllable Bristlebot! Nice! :)