Introduction: Marble Sorter

An autonomous marble sorter which raises marbles to a height then separates based on type (glass or metallic) and colour (white, yellow and black). Can be easily modified to sort different colours.

Created as a year 11 engineering project. While this took one school year to complete from its inception, should take less than a month to build using these instructions.

Total cost under $200.

Step 1: Flowchart

Using four mechanisms the marble is lifted and sorted based on colour and type.

Step 2: Lifting Mechanism [Structure]

The lifting mechanism is comprised of three sheets of acrylic separated by acrylic washers.

Use CAD software to design component as per given dimensions (or adapt as desired) and cut using a laser cutter or similar. Ensure that a clear front is used so that marbles can be viewed.

Connect together using M4 nuts and bolts.

Connect the rotating disk to a geared motor with extended spindle.

Step 3: Type Sorter [Structure]

Same as lifting.

Connect the disk to a geared motor using an aluminium hub.

The final pathway is intended to house two metal rails which will act as probes to test marble conductivity. These can be attached using a hot glue gun. While aluminium was used in this iteration, the rails did need to be sanded occasionally to obtain a better contact. If available copper rails should be used.

Step 4: Colour Sorter [Structure]

Same as lifting.

Connect the bottom disk to a stepper motor using an aluminium hub.

Step 5: Supports

Use pine to create the support pieces and use a chipboard base.

Connect the lifting mechanism using bolts, the rest can be connected using screws.

Once structure is created take apart and spray-paint using several layers. Connect everything back together, use a strong glue (e.g. liquid nails) to attach each mechanism.

Use a plastic container to catch marbles. Hot glue into place.

Step 6: Circuit Boards

Create the required interfacing circuits and micro-controllers.

PICAXE was originally used although later an Arduino Uno was also added (PICAXE ran out of output pins).

If possible use a single Arduino unit and shield since this will greatly reduce build time.

Step 7: Electronics Integration

Connect sensors and actuators to the interfacing circuits using wire.

Keep project looking neat by connecting wires to the supports using hot glue (or similar).

Step 8: Programing

Follow flow diagrams to achieve the appropriate function.

Use logic most suitable to the micro-controllers used.

May need to re-calibrate sensors from time-to-time depending on light levels.

Since two micro-controllers (PICAXE and Arduino) were used, two wires run between the boards to allow for communication. This can be avoided by using a larger control board.

Step 9: Conclusion

Marble sorter project is complete.

Try modifying the light sensor components to check for other colours.

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