Microbit and junkbot?


What is a Junkbot?
For this project, it is a moving ‘bot’ made from waste materials, combined with an electric motor and a programmable device (in this case a Micro:Bit) to control (or try) it. An example is shown below. More details on junkbots can be found at http://junkbots.blogspot.co.uk/


Stage 1 - The start of a Junkbot
This stage is relatively simple. Tape some pens or straws to a drinks can.




Stage 2 - Physical arrangement of Microbit and motor control board

The control part is this via a Micro:bit (http://www.bbc.co.uk/programmes/articles/4hVG2Br1W1LKCmw8nSm9WnQ/the-bbc-micro-bit). Kitronik produce a motor driver board, and provide quite a bit of support for it, for the Micro:Bit (the latest version of the board can be found at https://www.kitronik.co.uk/5620-motor-driver-board-for-the-bbc-microbit-v2.html ). A 6v battery pack is connected (see on the left of the image) and wires going to a motor are attached to the first block on the front left (marked as motor A).



The overall arrangement is show below, including a broken propellor as an unbalanced load to make the motor vibrate - the propellor was to hand but if you can secure something a clothes peg this could be used.


Stage 3 - Built Junkbot
Now we just need to put them together by taping (or fixing somehow) the motor to the junkbot built in stage 1. A further possibility is to attach the Micro:Bit, motor driver board and battery pack to the junkbots; but this adds weight.








Stage 4 Code
 Using Micropython via the online editor https://www.microbit.co.uk to program the board and therefore the junkbot. 
An example piece of code is shown below:

from microbit import *

def startIt():
   pin8.write_digital(1)
   pin12.write_digital(0)
   pin0.write_digital(1)
   pin16.write_digital(0)    

def leftTurn(duration):
   pin8.write_digital(0)
   pin12.write_digital(1)
   sleep(duration)
   
def stopIt():
   pin8.write_digital(1)
   pin12.write_digital(1)
   sleep(2000)

while True:
   startIt()
   
   if button_a.is_pressed():
       leftTurn(100)
   
   if button_b.is_pressed():
       stopIt()

Unplug the Micro:bit from the motor driver board and download the code to the microbit. Unplug the download cable and plug the Micro:Bit back into the motorboard, with the battery pack attached there is enough power for the Micro:Bit and the motor - don't plug in any other power including the programming cable when it is in the motor driver board.


Stage 5 In action



Suggested Resource List
  • Small Electric Motor
  • Kitronik Motor Board
  • Battery Pack
  • BBC Micro:bit
  • Pens
  • Junk (Can or Bottle)
  • Wires
  • Tape
  • Scissors
  • Broken Propeller or un-balanced load
  • Screw Driver

Stage 6: More control
In the remained of this post I want to show a modification to it, to use one Micro:Bit to control the junkbot controlled by another Micro:Bit. A nice feature of the Micro:Bit using micropython, is it can send and receive simple messages via radio - so here is my take on it.

The first problem is the Python editor available on https://www.microbit.co.uk/ does not seem to work with the radio API. One solution to this is to change to the mu editor.


Two pieces of code are needed.

Stage 7 Sending Code for the 'remote' control:
Essentially it is set up to send two messages, via the built-in radio module, spinl or spinr depending on which button is pressed.

import radio
from microbit import button_a, button_b

radio.on()

while True:
   if button_a.is_pressed():
       radio.send('spinl')
   if button_b.is_pressed():

       radio.send('spinr')

Satge 8 Junkbot Code
This takes an adapted form of the previous Junkbot code to work by; on receiving spinl or spinr via the radio link; spin the motor clockwise or anticlockwise.
import radio
from microbit import pin8, pin12, sleep

def leftTurn(duration):
   pin8.write_digital(0)
   pin12.write_digital(1)
   sleep(duration)
   
def rightTurn(duration):
   pin8.write_digital(1)
   pin12.write_digital(0)
   sleep(duration)
   
def stopIt():
   pin8.write_digital(0)
   pin12.write_digital(0)

radio.on()
while True:
   incoming = radio.receive()
   if incoming == 'spinl':
        leftTurn(500)
        stopIt()
   if incoming == 'spinr':
        rightTurn(500)
        stopIt()







All views are those of the author and should not be seen as the views of any organisation the author is associated with.

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