Science Play And Research Kit: Lego Robotic Claw
    By Steve Schuler | December 6th 2013 08:35 AM | Print | E-mail | Track Comments
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    In a previous article I demonstrated how to build a conductivity tester out of Snap Circuits for your Science Play and Research kit.

    You can use the same circuit with a small modification to build a simple magnetic stirrer. You can also further modify the circuit to make a reversible motor driver. Reversible motor drivers are often used in robotics to drive the robot forward or reverse, turn it right or left, to raise or lower a robotic arm, to open and close a robotic gripper, and so on.

    You can use this circuit as an introduction to H-bridge ICs as well as an introduction to micro-controllers and how their output pins can be used in robotics to drive robot motors for forward/reverse motion, right/left motion, and robotic claw attachments. To demonstrate the reversible motor driver I will use the Lego robotic arm from Robot Invasion by Dave Johnson.

    To keep the circuit as simple as possible, I’ll only demonstrate driving a single motor on the robotic arm to raise and lower it. I have removed the parts and motor that move the arm right or left and mounted it on a different base to make it more stable. On account of copyright I don’t think I can demonstrate how to build the robot arm, but I suggest you include a similar project in your Science Play and Research Kit. When I have more time I’ll try to rebuild it using the more current Lego Mindstorms parts.

    This is Mr. Johnson’s robotic arm that I have modified for this demonstration (I've taken the motor out to show the Snap Circuits jumper wire to Lego Technic motor conversion cable):

    Parts Needed:

    1 555 Timer IC
    1 DC motor (mine was the older Lego Technic motor used to drive a Dave Johnson’s Lego robotic claw)

    1 Base Grid (11” x 7.7”) # 6SC BG
    1 Eight-Pin IC Socket # 6SC ?U8
    0.02uF Capacitor # 6SC C1
    1 Variable Resistor #6SC RV
    1 SPDT Switch # 6SC S5 (Single Pole Double Throw)
    1 4.5 Volt Battery Holder # 6SC B3
    1 Slide Switch # 6SC S1
    Jumper Wire 18" (Black) # 6SC J1
    Jumper Wire 18" (Red) # 6SC J2
    1 Single Snap Conductor # 6SC 01
    11 Conductor with 2-snaps # 6SC 02
    3 Conductor with 3-snaps # 6SC 03
    2 Conductor with 4-snaps # 6SC 04
    2 Conductor with 5-snaps # 6SC 05
    2 Conductor with 6-snaps # 6SC 05

    Build the circuit shown:

    You can make a Snap Circuits Jumper Wire to Lego Technic motor conversion cable. I used a Snap Circuits Jumper wire and a Technic motor cable (note: for this demonstration, I did not finish the cable with wire glue or shrink tubing so you see the raw wire twisted together). Cut a Technic motor cable in half, split the cable about 4 cm down the middle and strip about a half an inch (13 mm) of insulation from each wire exposing the braided copper wires. Cut a Snap Circuits Jumper Wire in half and also strip 13 mm from the wire. Twist the exposed wires of the Technic motor cable and the Jumper Wires together.

    The following video demonstrates the 555 timer IC reversible motor driver circuit used to raise and lower the robot claw:

    In the magnetic stirrer circuit the motor is connected to the positive side of the battery and spins in only one direction (forward). For the reverse motor driver circuit one side of the motor is connected to pin 3 (the output pin) of the 555 timer IC via the red jumper wire. The other side of the motor is connected to the single pole double throw switch (at point “A” on the SPDT switch S5) through the black jumper wire. When I slide the switch to point “B” on the SPDT switch, the motor is connected to the positive side of the battery and turns in the forward direction. When I slide the switch to point “C” on the SPDT switch, the motor in connected to the negative side of the battery and the motor turns in the reverse direction.


    For more information about the Science Play and Research Kit (SPARK):

    SPARK press release

    SPARK competition web site

    For more articles regarding SPARK, type "science play and research kit" in the search box above and click the "Go" button.