27404 Parallax Inc, 27404 Datasheet - Page 94

• Manufacturer Part Number: 27404
• Description: COMPETITION RING FOR SUMOBOT
• Manufacturer: Parallax Inc

Specifications of 27404

• Accessory Type: Hobby and Education
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: SumoBot®
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

Page 90· Applied Robotics with the SumoBot
Figure 3-5 Opponent vs. Distraction
If your SumoBot has a tendency to get distracted by nearby objects, there are ways to
make it more nearsighted. The sensitivity of the IR receivers can be adjusted by
changing either the resistance in series with the IR LED or the
command's
FREQOUT
frequency. A larger series resistor would make the IR LED headlights dimmer, and
different frequencies would make the IR receivers less sensitive to reflected infrared.
However, changing the resistance in series with the IR LEDs isn't really a good option
because the SumoBot board has 220 Ω IR LED series resistors built-in. So, we'll take a
closer look at changing frequencies to make the IR object detectors more near/farsighted.
The way to test the relationship between near/farsightedness and IR LED frequency is to
write a program that displays the detection results at a number of different frequencies.
Then, test with objects outside the ring at different distances. Finally, test with an
opponent SumoBot inside the ring at different distances. In some cases, the goal will be
to find a frequency for each IR object detector that will be most likely to see its opponent
and least likely to see objects outside the competition ring. This might also be the goal if
the most sensitive IR frequency causes the IR object detectors to see the reflection of the
floor outside the ring. On the other hand, if onlookers stay a meter or more outside the
ring, and the reflection of the floor around the ring doesn't interfere, use the most
sensitive frequency.
It will give your SumoBot the best chances of detecting its
opponent.
Figure 3-6 shows two examples of the Debug Terminal output from the next example
program. The program makes the IR LED send frequencies ranging from 36 to 42 kHz,