QR Code Recognition System

A QR code is a square of black and white blocks that hides a message, like a word or a web address. Scan Sense reads QR codes through your computer's webcam, with no internet needed. In this project you make five command cards: go, left, right, dance and win. Show a card to the camera and MIEO obeys it, once each time a card appears. Lay a trail of moves to lead MIEO to a treasure, then play it back card by card.

• What a QR code is: a picture that stores a message
• Starting a script when a particular code is seen
• Planning a route as a list of commands
• Why the robot acts once per card, not over and over

• Mieo board
• Two N20 motors and their wheels
• Battery
• 3D-printed mountings
• Caster wheel
• Screws and screwdriver
• Five printed QR codes saying go, left, right, dance and win
• A webcam; most laptops have one built in
• A computer with Bluetooth
• The Robolab app (free)
• A webcam (most laptops have one built in)

1. Build MIEO with both N20 motors, their wheels, the caster wheel and the battery, as in Switch Motor Start.
2. Ask an adult to make five QR codes with a free QR code maker, one for each word: go, left, right, dance and win. Print them on card, one per card.
3. Put a small “treasure” on the floor a short way from MIEO, round a corner.
4. Switch MIEO on and connect it to your computer over Bluetooth.

Want MIEO Bot to guide you?

Robolab's built-in tutor has a lesson on the same idea, “Code Card Driver”. Open MIEO Bot in Robolab, pick Pro, then Mieo, and it shows you the blocks one at a time and checks your work as you go.

About MIEO Bot's lessons

1. Open Robolab, choose Mieo, connect and set the switch at the top right to Arena. Add the Scan Sense extension.
2. Start with “when green flag clicked”, “switch camera on with picture 0 % faded”, “show code outline” and “show think”, then a “forever” loop with “scan camera for a code” inside.
3. Add “when a code saying go is found” with “show happy”, “go forward at 40 % speed for 1 seconds” and “show think”.
4. Add the same kind of script for left and right, each with “go left” or “go right” at 40 % speed for 0.5 seconds.
5. For dance: “show disco pattern”, “play sound happy” and “go right at 50 % speed for 2 seconds”. For win: “show heart” and “play sound win until done”. End each with “show think”.
6. Click the green flag, allow the camera, and hold up the go card.

Arena mode: the program runs on your computer and talks to MIEO live over USB or Bluetooth, so keep MIEO switched on and connected.

when green flag clicked
switch camera [on v] with picture (0) % faded
[show v] code outline
show [think v]
forever
  scan [camera v] for a code
end

when a code saying (go) is found
show [happy v]
go [forward v] at (40) % speed for (1) seconds
show [think v]

when a code saying (left) is found
go [left v] at (40) % speed for (0.5) seconds
show [think v]

when a code saying (right) is found
go [right v] at (40) % speed for (0.5) seconds
show [think v]

when a code saying (dance) is found
show [disco v] pattern
play sound [happy v]
go [right v] at (50) % speed for (2) seconds
show [think v]

when a code saying (win) is found
show [heart v]
play sound [win v] until done
show [think v]

Click the green flag and the camera picture fills the stage. Hold up the go card: an outline appears round the code and MIEO drives forward for a second. Take the card away and show it again to repeat. Left and right make MIEO turn, dance makes it spin under disco lights, and win shows a heart with a fanfare. Use the cards to steer MIEO to the treasure.

If it doesn't work

• Nothing happens when you show a card? Hold it flat and still, close enough to fill about a quarter of the picture, in good light.
• A card works once and then stops? That's on purpose: take it out of view and show it again.
• MIEO turns too far or not far enough? Change the 0.5 seconds in the left and right scripts.

1. Easy: add a card for back, with “go backward”.
2. Medium: make a card that says a number, and use “code text” to drive forward for that many seconds.
3. Hard: hide clue cards around the room so each one tells the next player where to go.