Micro:bit Robot Turtle

In this article we're going to make a robot turtle named Donut. Why is it named Donut? Well, one look at it us enough to understand why.

This robot's mechanical structure draws inspiration from another project on Instructables, a Robot Rat made by David, a 14-year-old boy living in Spain. It was really cool to see such simple mechanical structure able to move in all directions, so we decided to take the original design and make it work with micro:bit. Also it became much cuter!

micro:bit 2 (the first generation will also work)

Bitmaker Lite Expansion board

Grove Servo * 2

3D printed parts

M3 self locking screws * 6

Li-Ion battery * 1

Grove cable * 1

We used regular FDM printer to print the parts, with the following settings:

Nozzle diameter 0.04 mm

Layer height 0.2 mm

13 % infill

Raft+supports

As you can see, with layer height 0.2 mm the glasses on the model are not printer properly, so if you'd like you can decrease layer height to 0.1 mm - that will slow the printing speed, but allow for finer details to be printed.

After printing is finished, peel off the supports and raft. Then install Grove servos in the sockets, as shown in the picture. Use M3 self-tapping screws to fix the servos in place.

Next, use zip strips or glue gun to neatly tuck in the servo wires inside robot's frame.

Solder the Grove cable to Li-ion battery and install the battery on top of the servos. Then place Bitmaker Lite expansion board on top of the robot frame, so the two outer holes in the expansion board are above the screw sockets in the robot frame. Use M3 self-tapping screws to fix Bitmaker board in place. Insert micro:bit in Bitmaker Lite, the front of micro:bit board facing Grove sockets on Bitmaker Lite board.

Attach servo arms to robot turtle legs, as shown in the picture. Use the longer servo arms(most of servos, including Grove servo have a few arms included in the package).

Before legs installing on the robot, we need to make sure the servos are set to 90 degrees. Connect the battery Grove wire to I2C socket on Bitmaker Lite board, then upload the calibration code to micro:bit. After servos are centered you can install the legs. When legs are installed on the robot, you might notice that they're still not perfectly perpendicular to servos - then you need to adjust init_front or(and) init_back variables in code until legs are perpendicular to servos.

Congratulations! The mechanical structure is finished now.

Finally upload the test code to the robot. Notice that the values for init_front or(and) init_back variables need to be the same as you obtained during calibration in the last step.

Look at Donut go! The test code will make the robot go forward, left and right. Of course, the experimentation and improvement doesn't stop here - you can improve on that by adding remote control with second Micro:bit or even voice control, if you're using new micro:bit 2!

The possibilities are endless and implementing your own ideas in hardware and software is the soul of Maker movement. If you come up with some new and interesting ways to improve this project, please do share in the comments below. Also, Bitmaker Lite comes with an online course you can access at TinkerGen's online course platform for free! For more information on Bitmaker Lite and other hardware for makers and STEM educators, visit our website, https://tinkergen.com/ and subscribe to our newsletter.