Memorial University of Newfoundland Faculty of Engineering and Applied Science

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Memorial University of Newfoundland Faculty of Engineering and Applied Science ENGR 1040 Mechanisms & Electric Circuits Prof. Nicholas Krouglicof Prof.

1 Memorial University of Newfoundland Faculty of Engineering and Applied Science ENGR 1040 Mechanisms & Electric Circuits Prof. Nicholas Krouglicof Prof. Dennis Fifield Laboratory Exercise ML3: Assembly of the Wall-Following Mobile Robot Platform Wallee II Figure 1: Wallee II ENGR 1040 Mechanisms & Electric Circuits Lab ML3 Page 1 of 5

2 Introduction The purpose of this is lab exercise is to assemble and test the wall-following mobile robot Wallee II. Assembly PreLab The mechanical assembly of the robot platform is relatively simple. The driver board and the MUNder board are secured to the frame using the eight Aluminum Spacers (Hexagon), four nuts and four screws. The two boards are stacked with the MUNder board on top. Four spacers are fastened to the frame with screws. Then the driver board is stacked on top and spacers are inserted between each board. Four nuts secure the complete board assembly. The two stepper motors are secured to the frame using the Philips head screws provided in the kit. Two screws per motor should suffice. The drive wheels are mounted directly on the motor shafts and are held in place by set screws. The rubber O-rings must be stretched over the drive wheels to provide traction. The roller ball is located towards the front of the platform. A brass spacer provides the required height. A machine screw and washers are used to secure the roller ball in place. Wiring Tips It is of paramount importance to the success of your project that the robot platform be wired properly and reliably. Do not under any circumstances shorten the motor or sensor leads. Simply coil up the excess wire and secure it to the frame using tape or tie-wraps. Do not under any circumstances have bare wires extending beyond the terminal blocks on the MUNder board or driver board. Strip off only 1/8 inch of wire to make the connections. Do not over tighten the terminal blocks. Use only stranded wire. Be neat! ENGR 1040 Mechanisms & Electric Circuits Lab ML3 Page 2 of 5

3 Wiring Procedure: The stepper motors each have two windings. Since each winding has a centre tap, there are three wires per winding: Winding 1: Blue, Red, White (C.T.) Winding 2: Green, Black, Yellow (C.T.) The driver board consists of 12 solid-state switches. Only 4 are required to drive a stepper motor hence 8 switches are required for the two motors. Connect the two winding of the right-hand side stepper motor to the driver board as follows: Blue Wire Digital Output 0 Red Wire Digital Output 1 Green Wire Digital Output 2 Black Wire Digital Output 3 Yellow Wire White Wire Connect the two winding of the left-hand side stepper motor to the driver board as follows: Blue Wire Digital Output 4 Red Wire Digital Output 5 Green Wire Digital Output 6 Black Wire Digital Output 7 Yellow Wire White Wire On the input side of the driver board, connect digital inputs 0, 1, 2, and 3 to D0, D1, D2, and D3 of the MUNder Board (RHS motor). On the input side of the driver board, connect digital inputs 4, 5, 6, and 7 to D4, D5, D6, and D7 of the MUNder Board (LHS motor). ENGR 1040 Mechanisms & Electric Circuits Lab ML3 Page 3 of 5

4 Connect GND on the input side of the driver board to GND on the MUNder Board. Under no circumstances should the input and output side of the driver board have a common ground. Install the two Sharp 2D12 optical proximity sensors on to the platform using two short socket head cap screws per sensor. Use the nuts supplied in the kit. One sensor should be installed on the front and the other on the left-hand side of the platform. Install the two wire harnesses. The red wire on each wire harness should be connected to VCC on the MUNder board. The black wire on each wire harness should be connected to GND on the MUNder board. The signal (yellow wire) should be connected to input A1 (left sensor) and A0 (front sensor) on the MUNder board. These inputs correspond to the onboard Analog-to- Digital converter. Have a technician or lab demonstrator check you circuit before applying power. Two rechargeable nickel-metal hydride battery packs are included in the kit. Each pack provides approximately 7.2 volts. The two packs must be connected in series using the two snap-on connectors provided in the kit. This configuration will provide 14.4 volts to the driver board. Use two Velcro fasteners to secure the batteries to the underside of the frame. Connect the positive terminal of the series connected battery pack to VCC on the digital output side of the driver board. Connect the negative terminal of the series connected battery pack to GND on the digital output side of the driver board. The 9 volt battery in the kit is used exclusively to power the MUNder board. Make up a small wiring harness using a third snap on connector and the power jack included in the kit. Use heat shrink or electrical tape to insulate your connections. Install the 9 volt battery holder to the frame using a Velcro fastener. When it s time to activate the MUNder board simply insert the power jack into the corresponding receptacle on the MUNder board. Note that the MUNder board can be powered via the USB connector for development purposes. ENGR 1040 Mechanisms & Electric Circuits Lab ML3 Page 4 of 5

5 Each group will also need to prepare a recharging cable using a fourth snap-on connector and the power connector that is included in the kits. Once again use heat shrink or electrical tape to insulate your connections. Testing Laboratory Exercise If the cart was assembled correctly, the rightturn.hex file should drive the robot in a straight line and execute a right turn every time an obstacle is detected in front of the robot. Using the bootloader, download rightturn.hex file to the MUNder board and verify the operation of the robot. Open the rightturn project using the MPLAB development environment and change the delay between steps to achieve a slower operation. This can be done by modifying the instruction: Delay1KTCYx(20). Programming Write a main program that calls the two functions repeatedly so that the robot travels a square path and comes to a stop. ENGR 1040 Mechanisms & Electric Circuits Lab ML3 Page 5 of 5

Memorial University of Newfoundland Faculty of Engineering and Applied Science

Memorial University of Newfoundland Faculty of Engineering and Applied Science ENGR 1040 Mechanisms & Electric Circuits Prof. Nicholas Krouglicof Laboratory Exercise ML2: Stepper Motor Torque Testing Unipolar