Precision building with Auto Builder

 Building instructions  Python code  Improve project

Image credit: LEGO

The Auto Builder builds LEGO figures autonomously. These Python scripts make it work smoothly and accurately.

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Coding instructions

This program resets the motors to known positions, and then constructs the LEGO figure brick-by-brick.

This works by repeatedly:

• moving the belt motor to the given brick;
• picking the brick up by moving the arm down and up;
• moving the belt back to the base position;
• putting the brick down.

The brick positions are given as the degrees the belt motor turns relative to the base position. You can tweak these values by a few degrees if needed.

from pybricks.hubs import MoveHub
from pybricks.pupdevices import Motor
from pybricks.parameters import Port, Stop, Color
from pybricks.tools import wait

# Initialize the arm motor
arm = Motor(Port.D)
arm.run_until_stalled(-100, duty_limit=30)
arm.reset_angle(0)

# Initialize the belt motor
belt = Motor(Port.B)
belt.run_until_stalled(-100, duty_limit=30)
belt.reset_angle(0)

# Component positions
FEET = 0
BELLY = 365
HEAD = 128
ARMS = 244
NECK = 521
BASE = 697

# Place all the elements
for element in (FEET, BELLY, ARMS, NECK, HEAD):

    # Go to the element
    belt.run_target(speed=200, target_angle=element)

    # Grab the element
    arm.run_time(speed=300, time=2000)

    # Lift the element by going back to nearly zero
    arm.run_target(speed=300, target_angle=55)

    # Go to the base
    belt.run_target(speed=200, target_angle=BASE)
    wait(500)

    # Put the element down
    arm.run_time(speed=300, time=2000)

    # Lift the arm back up
    arm.run_target(speed=300, target_angle=0)

# When we are done, eject the result
belt.run_target(speed=200, target_angle=FEET)

Further exploration

The provided program is very basic, demonstrating only the core principles. Here’s a few ideas and challenges for further exploration:

• Change the order of the bricks in the for-loop to build something else.
• Instead of pushing the element down for two seconds, you could stop sooner. Try experimenting with the run_until_stalled method. This can speed up the build process.
• Speaking of increasing speed, how fast can you make it? Optimize this robot and set a new world record!

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This project was submitted by The Pybricks Team.