A License Plate Recognition and Speed Detection System - Index of

V.B.3. Serial Interface Circuit Board
The optical character recognition system stores the processed images on a laptop
computer. We wanted to store the speed data from the Ramsey Radar Gun on the same computer.
The Radar Gun kit was not designed to provide a computer interface, so we decided to solder an
eight wire ribbon cable to the output pins of the dual BCD decade counter IC chip. The ribbon
cable could then be brought to the outside of the Ramsey Readout case. This entailed drilling two
one-sixteenth inch holes into the top of the case with the holes spaced far enough apart to allow
the ribbon cable to slip smoothly between them. The plastic between the two holes was carefully
filed away until the two halves of the case would close without binding or cutting into the ribbon
cable. An eight pin breakaway header was soldered to the opposite end of the cable.
The laptop computer has a serial port available for communication with peripheral
devices. To convert from the parallel output on the ribbon to a serial input needed by the
computer, we used a module from Parallax, Inc (figure 36).
Fig. 36 Parallax HomeWork Board
This unit is from a Parallax training kit for embedded microcontrollers. It contains a
programmable PIC microcontroller (μcontroller), a MAX232 chip, and a serial port. The Max232
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