I have always thought small robots were great and creating one with the cost effective Microbit would be ideal. I wanted to create a robot that didnt use a ready made IO boards like I have used in the past to drive motors or get sensor inputs, I wanted something smaller. This small Microbit robot is one I will base a series of tutorials on. Starting first with how I made it using "The Really Useful Box Companies boxes" for a chassis, and using very small motors and motor drivers. I will use this base model to explore things like bluetooth control shown in the video, using the accelerometer and magnometer to determine direction, and adding things like Neopixels and IR distance sensors. There are plenty of boards you can buy to just plug your microbit into that will run motors and servos, but for this we will use the main components you will need to replace these add on boards.The same principals will apply to using any microcontroller when driving motors.
I used the small boxes from the "Really Useful Box" company for the body of the robot, I used 3 of the lids to make it, so you would need some of those or something similar. I like the idea of using items you have already to build containers for electronics and motors.
Step 1: What You Will Need
For this project I used my usual tools comprising of a soldering iron, small screwdrivers, wire cutters and a small drill, I also like to have a hot glue gun available for fixing and securing some of the parts.
I managed to find some really small motors with a gearbox the only problem was there were no wheels I could find that fitted the tiny shaft. After some searching through what I had I found 4 small blue plastic gears which were just right.
I also wanted where possible for this robot to use ready available parts and so I used female to female short 10cm jumper wires, so they could be plugged in or out easily when required, if you want to make a much neater robot then these can be cut to size and soldered instead of plugging in.
2 x Small Motors https://www.robotshop.com/en/gm24-tiny-geared-moto...
10cm jumper wires https://www.amazon.co.uk/sourcingmap-Female-Jumper...
1 x DRV8833 Dual Motor Driver board http://www.hobbytronics.co.uk/drv8833-motor-driver...
3 x Really useful box company lids https://www.amazon.co.uk/Really-Useful-Box-0-3-Lit...
Small bits of 2mm sheet plastic
1 x Adafruit neopixel strip https://www.adafruit.com/product/1426
1 x Kitronik Microbit edge connector https://www.kitronik.co.uk/5601b-edge-connector-br...
4 x gears or something to use as wheels ( you could always 3D print something better.
1 x Pololu ball caster https://www.amazon.co.uk/Ball-Caster-Metal-3-8-Bla...
1 x BBC Micro:bit https://www.amazon.co.uk/BBC-BBC2546862-micro-bit-...
1 x battery - I used a rechargeable 1S lipo, but you could use the small 2 x AA holder that comes with the Micro:bit go kit as well.
Step 2: Building the Motor and Ball Caster Assembly
First I built the motors and ball caster assembly as that makes up most of the chassis.
1. First I superglued the 4 gear wheels I had to the motor output shafts
2. Next I glued the motors to a small strip of 2mm plastic I had, you can use any plastic material for this.
3. Once the glue had set I placed the assembly on an upturned really useful box company lid.
4. The next part was fitting the ball caster, I used the screws and nuts that came with this to go through both the plastic sheet I was using and the lid of the box, so this with some glue held everything in place.
5. At this stage I also soldered the headers on the DRV8833 Motor board ready for assembly.
Step 3: Connecting and Mounting the Motor Driver Board
The wires that come out of the motors are tiny, they seem not much thicker than a hair. So to make them easier to work with and not break I soldered them to 4 strips of a veroboard, so two wires from each motor, this meant that each wire was on its own copper track, this I then soldered some cut in half female to female jumper wires to. This with the addition of some hot glue allowed me to place the motorboard and veroboard where I needed them, and protected the delicate motor wiring.
The motor driver board and veroboard are all on top of the lid, and I drilled some holes to get the motor wires through to the top of the lid.
Step 4: Fitting the Micro:bit Edge Connecter
The edge connector is on its own lid, it is fitted by drilling 2 holes in the lid and screwing it in place, or if you prefer hot glue is also an option.
It was at this stage in the build I also worked out where to position the battery so it all fitted in the tiny space available.
Once this was done it was time to move on to wiring up the motor driver board
Step 5: Wiring the Motor Driver Board
At this stage using the female to female jumper wires the wiring diagram can be followed. I cut out small sections of the front of the lids which will rest on top of each other, this was to allow the jumper wires to come out the front and go and plug into the microbit edge connector, I bent the pins of the edge connector forwards so the jumper wires didnt stick up, but that isnt required it just makes the robot a little taller when finished.
Micro:bit / Motor driver board
PIN 1 --> B1
PIN 8 --> B2
PIN 11 --> A2
PIN 12 --> A1
0V /GND --> GND
3V --> VIN
Adafruit Neopixel connections
Micro:bit / Adafruit neopixel
PIN 2 --> DIN
0V /GND --> GND
3V --> VIN
Step 6: Adding the Adafruit Neopixel Strip
The box final lid is then ready to be fitted with the neopixel strip
First solder the wires to the VCC+, GND- and DIN side of the neopixel strip
In my case I also added soldered wires to the VCC, GND and DOUT side of the neostrip while I was there as I have plans to expand this in another instructable.
Step 7: Final Assembly
Now all 3 layers are complete, It take some careful moving around of the jumper wires so the base lid with the wheels attached lines up with the next layer ontop, It was also necessary at this stage to drill 2 holes to add long thin screws and nuts so I could hold it all together like a 3 layered sandwich.
I used black tape to hold the bottom 2 layers together wrapped around the outside
I then fitted the 2 screws and nuts to hold it together, the one thing I like about this approach is it allows quick taking apart and adding new sensors to the edge connector, just by removing the 2 nuts on the top layer.
One final modification I made was then to cut a section out of the lid so you could access the micro:bit buttons and see the display more clearly. I also added a small piece of black plastic to hide seeing some of the untidy wiring through the transparent top layer lid.
NEXT: I will be adding a next step on the programming and software side of things, as well as adding more sensors such as an IR distance sensor, to make the bot more useful.
You can follow more of what I do here at my website: www.inventar.tech