LEGO MINDSTORMS - The Unofficial Guide to Robots - Jonathan B. Knudsen Part 6 potx

90 Grabber Arm In Step 17, the half-bushings go between the center block and the cams (pear-shaped pieces). 91 92 Make sure that the two sides are at the same angle. They should mirror each other. 93 94 Structural Support 95 Idler Wheel 96 97 Drive Motor While you're putting the motor in, hold on to the worm gear so it doesn't slip off. 98 Grabber Arm Motor 99 [...]... Attach the RCX on both sides as shown 101 Wiring First, attach the left motor, which powers the arm, to output A Then use a wire brick to attach the right motor (the drive motor) to output C 102 Attach the light sensor to the front of the arm The wire attaches to Minerva's side as shown Next, use a wire brick to attach the touch sensor to the light sensor wire Then use a longer wire brick to attach... look at the simple parts first The grab() and release() inline subroutines take care of the grabber arm All they do is run the arm motor in one direction until the limit sensor is pressed Running the motor forward causes the arm to descend, the grabber to close, and the arm to lift again Running the motor in reverse makes the arm descend, the grabber open, and the arm lift again The mechanics of the arm... explain later in the chapter All we have to do is wait for the arm to lift, which presses the switch when it's finished You might have noticed that the light sensor and the touch sensor are both attached to the same input I'll talk about how this works later For now, just be aware that it's necessary for grab() and release() to move away from the touch sensor to use the light sensor The calibrate()... wires to input 3 103 Programming Minerva's basic program is straightforward: find something to pick up bring it back to the starting point The program assumes that the objects to pick up will be dark and that the surface Minerva is driving on is light To return to the starting point, Minerva measures how long it has to drive forward to pick something up Then it turns around and drives back for the same... transmission is shown in Figure 5-3 The bottom shaft is the input A 24t gear mounted on this shaft drives another gear that is mounted on a beam that rotates on the input shaft Depending on which direction the input shaft turns, the beam swings to the left or right; the top gear on the beam engages the gear on either the far left or far right These gears are on the output shafts You could create variations on... cutaway view is shown in Figure 5-4 Figure 5-4 Cutaway view of a worm gear directional transmission The input shaft drives the worm gear, which slides freely along the shaft In fact, it's easier for the worm gear to slide on its shaft than to turn one of the output shafts Depending on which way the input shaft turns, the worm gear slides as far as it can in one direction or the other When it can't slide any... can be used to link pulleys together This type of linkage is similar to using gears to transmit motion from one shaft to another By using pulleys of different sizes, you can achieve the same power and speed tradeoffs as with gears The only difference is that pulleys connected by a band turn in the same direction, while two gears meshed together turn in opposite directions If you twist the band around... two ways to build a directional transmission with the parts included in your RIS The first design uses a pair of gears on a swinging arm The second design uses a worm gear Minerva uses the worm gear design, but I'll briefly explain the fundamental ideas of both types of directional transmission Swing-Arm Design A cutaway view of a swing-arm directional transmission is shown in Figure 5-3 The bottom shaft... threshold - 3); Once a dark object is found, Minerva moves forward a little farther to position the grabber over the object She records the forward movement time for the return trip Finally, Minerva turns off output C to stop the robot's forward motion: Wait(20); // Move up on it a little returnTime = Timer(0); Off(OUT_C); Having found something interesting, Minerva picks it up: grab(); 1 06 Now she wants to. .. gear hog The drivetrain alone sucks up all of the 8t gears, all of the 16t gears, and most of the 24t gears that come with RIS If you decide directional transmissions are useful for your robot, you may want to have some extra gears handy from other sets Pulleys Pulleys are an interesting alternative to gears A pulley is simply a slotted wheel, like the ones used with outdoor clotheslines The RIS comes . wire brick to attach both wires to input 3. a wire brick to attach the touch sensor to the light sensor wire. Then use a l 103 Programm Minerva's forward: nd ng it back to the. Wait(TURNAROUND_TIME); . All they o is run the arm motor in one direction until the limit sensor is pressed. Running the motor forward causes the arm to descend, the grabber to close, and the arm to lift again 90 Grabber Arm In Step 17, the half-bushings go between the center block and the cams (pear-shaped pieces). 91 92 Make sure that the two sides are at the same angle. They should