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Amphibionics 06  3/24/03  9:02 AM  Page 229
                                       Chapter 6 / Crocobot: Build Your Own Robotic Crocodile
                                                                                   FIGURE 6.45
                                                                                   Robot remote control
                                                                                   device.























                        The schematic for the transmitter remote control is shown in Figure
                        6.46. The circuit functions by using the PIC 16C71 to monitor the
                        position of the control stick and then send serial commands to the
                        transmitter module. When the control stick moves along the X and
                        Y axis, the resistance values of two 100K   potentiometers are var-
                        ied.  The  control  stick  and  the  two  attached  potentiometers  are
                        shown in Figure 6.47. Each potentiometer is configured as a volt-
                        age divider so that a unique voltage represents each position along
                        the X- and Y-axis. The voltages from the potentiometers are con-
                        verted to 8-bit values by the internal analog to digital converters on
                        the  PIC  16C71  and  then  interpreted  by  the  microcontroller.
                        Depending on the values, certain movement commands are sent in
                        a serial format from the transmitter to the robot. The remote control
                        also has a programmable push-button switch and a light-emitting
                        diode (LED) that can be turned on when certain events occur, such
                        as during the transmission of a movement command. The transmit-

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