indicating the race can begin. When the RC car passes
through the laser beam, the unit will display the completed
laps and the time needed to complete them (Figure 10).
After 15 laps are completed, the LCD will clear itself
and begin to display the next 15 laps. If the laser beam is
interrupted for more then three seconds, timing/counting
stops and the message seen in Figure 11 will be
displayed, indicating an error, but completed laps can
still be reviewed. During the race recording, a small
clock icon will scroll down the display, indicating proper
operation. Lap counting will continue until the unit’s
function button is pushed, which stops the timing
process and enters the review process. Additional
presses of the button will display lap information that was
recorded during the test session, 15 laps at a time.
Lap review looks exactly like Figure 10, except that
the last lap in the review will have the word “END”
printed next to it. The timer/counter can store up to 124
lap times in its EEPROM, but it will continue to display lap
information on the display after the memory is full. One
additional push of the button will provide test session
statistics (Figure 12). You can continue to review all of the
stored data by continually pressing the timer/counter
function button. I did not use an ON/OFF power switch;
instead, I just disconnected the wire from the 12 V battery
to start a new test session.
The DB9 cable seen in Figure 13 is connected to
the STK500 serial connector for use with an optional
computer interface that can be used to record race data
to a file for later analysis. The STK500’s RS232 port will
print serial data during the lap timing/counting and
review processes (Figure 14). This is a convenient way to
record those hard-to-believe track times.
NUTS & VOLTS
STK500 boards, Atmel
components, and laser
Graphic and character displays.
Graphic and character displays.
Everything for radio control.
This project was my first attempt at using a graphic
LCD. A lot of the graphics are not really necessary, but
they really made the user interface more interesting.
Character only displays still have their place in the
electronics world, but this enthusiast is sold on graphic
displays for all future projects.
A multi-car counter could be created by adding flags of
different horizontal widths that intersect the laser above the
vehicles. The timer/counter could then be programmed to
use flags of varied sizes to respond to the different lengths
of time that the beam was broken. Each flag would produce
a different pulse width that could be used to distinguish
several cars. I will not try this any time soon, but I would be
interested in hearing of an ingenious reader’s success story.
It was rewarding to have a project that was
considered useful by my kids. Their boring RC cars were
now fun again because of the added incentive to race the
clock. There will be no more doubt as to who the “RC
Champion” is in my house! NV
Alonzo Trueland currently works as a PBX programmer for
Kennedy Health Systems. He develops microcontroller solutions
on a part-time basis; most of his work is in the area of data
acquisition and control, but radio controlled projects are his
hobby. He holds an FCC license and a certification in industrial
control (CET). You can reach him at email@example.com