Douglas H. Williams. PDA Robotics. 2003. 256p
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Once the gearboxes have been mounted, push the motor wires through
the holes and solder the Molex wire connectors to the leads. Ensure
that the ground wire is inserted on the left of the plastic housing. See
Figure 6.22.
PDA Robotics
128
Figure 6.24
Assembling the gearbox.
Figure 6.25
The assembled
gearbox.
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Secure the L-brackets and mount the wheels using wheel hub #1 and
a 1" 4-40 bolt with a washer so that there is not too much wobble.
Figure 6.28 shows the side profile. Note: You may want to substitute
the L-brackets for casters that will allow the front and back wheels to
swivel freely. I found that the L-brackets work well on smooth surfaces
Chapter 6 / Building PDA Robot
129
Figure 6.26
Mounting the wheel
hub.
Figure 6.27
Mounted gearbox
with wheel
attached.
PDA 06 5/27/03 8:37 AM Page 129
or loose surfaces such as ceramic tile and gravel. The wheels may grab,
hindering the turn ability of PDA Robot when the carpet pile is not
low and tight. Another solution is to use smooth, hard plastic wheels
on the front and back that don’t grab.
Drill holes in the circuit board to correspond with the hex spacers
attached to the main platform, and mount them with 4-40 bolts. Pass
the IR range finder wire through the wire hole in the center of the plat-
form, and insert the presoldered wire connectors into the plastic
Molex housing.
The Ribbon Connectors
To connect the main board to the IR transceiver and the motor con-
troller, we need to prepare the ribbon connectors. For the main board
to motor controller connection, cut a 6" piece of ribbon six wires wide,
and secure the connector to it by sliding the wire into the groves and
pressing down on the top firmly until it is tight. Then slide the lock-
ing key in to hold everything together permanently. It is important that
pin 1 of each connector goes to pin 1 of the other. Secure one connec-
tor to the ribbon, flip it over and connect it the same way on the other
side. The red wire (wire 1) is always on the left. Figure 6.29 shows the
process of preparing the ribbon connector. Do the same for the IR
transceiver. A shorter piece of cable about 4" should work.
It is important that the connectors are placed in the correct orienta-
tion or the circuit will not function. The pins of one connector must
match up with the pins of the other. Figures 6.30 to 6.33 show the
connector’s orientation and how the cables should be aligned. As a
general rule, the red wire (wire 1) should always be over pin 1 of the
connector.
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130
Figure 6.28
Side profile of PDA
Robot.
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Attach all the connectors and drill the holes in the top plate that will
support the PDA. Figure 6.34 shows the position of the drill holes
used to secure the top platform (7" ⫻ 5-1/4") to the hexagon spacers of
Chapter 6 / Building PDA Robot
131
Figure 6.29
Preparing the ribbon
connectors.
Figure 6.30
The IR transceiver
connector
orientation.
PDA 06 5/27/03 8:37 AM Page 131
PDA Robotics
132
Figure 6:31
The IR transceiver
connector
orientation to main
board.
Figure 6.32
The motor controller
connector
orientation on the
motor board.
PDA 06 5/27/03 8:37 AM Page 132
Chapter 6 / Building PDA Robot
133
Figure 6.33
The motor controller
connector
orientation on the
main board.
Figure 6.34
Top platform drill
holes.
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the main platform. Secure a piece of sticky Velcro to the top plate
(where you would like the transceiver to go) and to the transceiver
itself. We need to program the 16F876 microcontroller, so it’s best to
leave the top plate off until this is done (see the next chapter).
The Camera (Accessory) Mount
Drill two holes in the 1" ⫻ 1/2" ⫻ 1/4" piece of aluminum. One hole is
used to secure it to the hex spacer positioned on the front of PDA
Robot and the other to mount the camera. Figure 6.35 shows the cam-
era mount attached to the hex space. A X10 wireless video camera will
be mounted here to provide vision when PDA Robot is being con-
trolled remotely from a PC connected to the wireless network.
Now that PDA Robot’s physical body is complete, we need to give him
a brain. Information on how to program the microcontroller and the
PDA software is in the chapters to follow. Figures 6.36 and 6.37 show
PDA Robot fully assembled.
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134
Figure 6.35
Camera mount
attached to the 2"
hex spacer.
PDA 06 5/27/03 8:37 AM Page 134
Chapter 6 / Building PDA Robot
135
Figure 6.36
PDA Robot being
controlled by a Palm
OS device (Visor
Deluxe).
Figure 6.37
PDA Robot being
controlled with a
Pocket PC device
(iPAQ).
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137
The PIC compiler is used in this project to write the software running
on the PIC16F876 microcontroller, and the EPIC Plus Programmer is
used to download the software to the PIC16F84A. The PIC16F876
receives input data and commands from the infrared (IR) module and
the PDA via the MCP2150. It sends information such as range data and
motor control confirmation codes back to the PDA. The PIC16F876
could be considered the main node of the robot’s nervous system.
Figure 7.1 shows the EPIC Plus microcontroller programmer with the
PIC16F876 inserted into the ZIF adapter.
The pocket-sized EPIC Plus Programmer quickly and easily programs
most PICmicro microcontrollers, including the PIC16C55x, 6xx, 7xx,
84, 9xx, PIC16CE62x, PIC16F62x, 8x, 87x, PIC14Cxxx, PIC17C7xx,
PIC18Cxxx, 18Fxxx, the 8-pin PIC12Cxxx, PIC12CExxx, and the 14-
pin 16C505 microcontrollers. The basic programmer includes an 18-
pin socket for programming 8-, 14-, and 18-pin PICmicro microcon-
troler unit (MCUs). (It will not program or read the baseline PIC16C5x
or high-end 17C4x series.) A wide variety of adapters allow the EPIC
Plus to program devices in many different package formats such as
DIP, SOIC, PLCC, SSOP, TSOP, etc.
The EPIC Plus Programmer is software upgradeable for future PICs. It
includes DOS and Windows 95/98/Me/NT/2000 programming soft-
ware and a PIC macro assembler that works with both the Microchip
Programming
the PIC16F876
Microcontroller
7
PDA 07 5/27/03 8:44 AM Page 137
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