A License Plate Recognition and Speed Detection System - Index of

we set pins 8 to 15 as input pins and pause the program for 200 milliseconds. This pause time
was chosen because it is somewhat longer than the cycling time of the BCD counter, which
requires ~143 milliseconds to update itself. After pausing, the DEBUG routine sends the value
on each input pin out the serial port to the laptop via an RS232 connection. The value on pin 15
represents the most significant bit and the value on pin 8 represents the least significant bit in the
Binary Coded Decimal. The laptop computer takes this binary input and converts it back to the
decimal value of the vehicle’s speed.
When the Ramsey kit was assembled, we used IC sockets to mount the IC chips instead
of soldering them directly to the printed circuit board. This allowed us to solder the ribbon cable
to the BCD counter chip without having to worry about damaging the chip (or any other chip
during assembly). In testing the Radar Gun – BasicStamp combination, it was noticed that the
digital readout on the Radar Gun went blank, which meant we did not have an independent
confirmation of the vehicle’s speed. The problem appeared to be caused by too large a drain at
the BasicStamp connection. To remedy the problem, we first unsoldered the ribbon cable from
the Readout’s BCD output pins. Then we purchased a second dual BCD decade counter and
mounted it on the HomeWork module’s breadboard. Next, the input signal was taken from the
Readout’s Quad NAND gate IC chip at pin 11. The second BCD counter was wired on the
breadboard exactly as the one on the Readout’s circuit board, except it draws power directly
from the lantern batteries and the second BCD’s output pins were now connected to the
HomeWork board’s input pins.
51