Project of the Week: Mini robot

I got my new 3D printer up and running recently. After some tuning, some improving, and some printing of backup parts (an ongoing process, I decided I was confident to move forward.

First a picture of said printer:


Pretty nice, huh? It’s a large Delta printer called a Kossel. I printed the vast majority of the parts on my Makerbot Cupcake, which just very recently found itself a new home at Ctrl-H, the local Hackerspace.

When I originally got a 3D printer (2010!) my dreams were of building robots. Motors and circuits were one thing but with this I could actually print wheels, frames, grippers, or whatever else I could come up with. Now that my printer is reliable, those dreams can come true! With MakerFaire coming up in a few weeks, I started to think about what I can take and what I can do.


I bought these motors sometime last year. They’re super small, probably for some toy. They have a 10mm diameter, and a planetary gear in the head that transfers the speed into torque. I bought them because I wanted to explore swarm-robotics. I hadn’t really gotten anywhere though, so they lived in a plastic bag, waiting for a better day.

Fishing them out, I worked through a wheel script you can find on Thingiverse. It took some experimentation, but I managed to finally output a wheel that fit the shaft of the motor.


With wheels, I was in a good spot to print something for the motors to sit in. I spent a couple hours (maybe even 3) re-learning OpenSCAD and figure out how to capture the motors reasonably eventually, I came up with this:

Screen Shot 2015-08-25 at 10.20.51 PM

I printed it, and looked to see how it’d turned out. To my surprise, I found that it actually made more sense the other direction. The mounting holes and housing is pretty tight, and with the bottom as the top, you actually have a nice platform to place stuff on.

This is the physical object printed out, and placed “Rightside-up” (This one with a flash because the detail’s easier to see.)

And that’s where I am on the project. I’ve hit a little bit of a snag because I don’t know what I’m going to do about electronics. I’ve got plenty of Arduinos, but they’re all much too big, and I need a motor driver on top of that. I came across Monty Goodson’s MEGABitty, which puts an ATMega8 on a surprisingly small space – but the Mega8 is a little less than what I want. Currently I’m looking to see if I can adapt the Arduino Micro into a small form factor with a couple of motor controllers and maybe some simple sensor input.

  1. You could work with something like a Teensy or a Trinket Pro or a Nano. And a motor driver chip isn’t that much. Think about doing it on a solderless breadboard for a base, because you will need sensors and so forth. (Or if you’re serious about swarms, why not one of those little wifi chips on a breakout? They’ve got oodles of ram and processing power)

    • I have a couple of Teensys at home, but they’re way overpowered for my application, and too expensive to deploy on more than a few robots.
      The Trinket and Nano are just a little underpowered for what I want, which is why I was eyeing the Micro. The 32u is a nice little chip, has USB onboard, and plenty of GPIO to mess around with. There’s an added advantage that I can repurpose the Arduino layout into my own formfactor.

      Which Wifi chip are you thinking of? The ESP8266 is an option, but again, not enough GPIO.

      For longer term, I was thinking about trying the Nordic nrf51822 – it’s an ARM M0 that has bluetooth built-in, and Nordic gives you a drop-in BT stack. I’ve not done anything with Arm in the past, so it’d be a new experience for me.

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