This year for Halloween, I decided to build a mini chocolate throwing machine using the LEGO BOOST kit. This one spins up the candy in a mini centrifuge before launching it across the room. You can see it in action, with an explanation of how it works, in the video. Continue reading for instructions on building and programming your own.

For this model I decided to bring the mini chocolates up to speed in a spinning armature, which acts much like a flywheel to store kinetic energy. Once it reaches top speed, an arm is raised under the armature to trigger the launch of the candy from the tray it is sitting in.

Building the Model

Below you can find a PDF file with step by step instructions on how to build the model. All the pieces you need to build it come in the BOOST set 17101 Creative Toolbox.

The external motor needs to be connected to port D and the light/colour sensor needs to be connected to Port C. You’ll also want to ensure the wires are out of the way of the spinning armature. This is only really an issue with the motor wire, and I’ve built a small bracket on the side of the conveyor support in order to route the wire, which you can see in the video.

Build It Yourself

Free Building Guide (PDF)

Parts List

Rebrickable Page

You might have to tweak the model depending on what you are trying to throw, but it should work reasonably well with anything that is roughly the same size as the mini chocolates that I am using.

Programming the Model

The BOOST program is fairly straight forward, and below you can find a screenshot of it, which you should be able to use to recreate it on your own device. I describe each programming block in detail below.

Edit: It seems with a recent update to the app, the orange ‘wait for color’ block in my original program above may not be available to everyone. Below is an alternate program that achieves the same logic using more basic blocks.

The program follows a linear execution path, executing the following steps in order.

• Rotate the external motor 180 degrees – This will move the conveyor belt to drop a mini chocolate onto the launch tray. You can adjust the rotation amount to suit the size of the items you are launching.
• Start motor A at 100 percent power – This will start spinning the armature.
• Wait 0.4 seconds – This will give the armature some time to reach maximum speed.
• Rotate motor B -90 degrees – This will raise the arm, in order to trigger the launch of the candy.
• Stop motor A – Stop the armature from spinning.
• Rotate motor B 90 degrees – This will lower the arm back down.
• Start motor A at -10 power – This will start the spinning the armature so that we can return to the start position.
• Wait 0.5 seconds – This gives the armature some time to rotate smoothly. Technically this isn’t necessary, but it seems to help give more reliable results.
• Wait until the colour sensor detects blue – This will wait until the light sensor detects the launch tray above it.
• Stop motor A – Stop the armature. Since there is a small delay in program execution, the armature will ‘overshoot’ the correct position, which is why the next loop is necessary.
• Repeat rotating the motor A 5 degrees until the light sensor detects blue – The loop is set up to continue repeating while the light sensor doesn’t detect blue, which means as soon as it does detect blue it will stop. Each time it repeats it will rotate motor A 5 degrees.