27404 Parallax Inc, 27404 Datasheet - Page 83

• 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

Figure 3-2 IR Object Detection Circuits
to the header. The right column shows the components that you plugged into the header,
the IR receiver, and shielded IR LED.
Testing the front left IR detector involves sending a 38500 kHz signal to P4, then
immediately storing the value sensed at P11 in a bit variable. Here is an example of some
PBASIC code that will do this:
irLF
FREQOUT 4, 1, 38500
irLF = IN11
The SumoBot's IR receivers are designed to send a low signal to the BASIC Stamp
whenever they detect infrared light flashing on/off at frequencies in the neighborhood of 38.5
kHz. 38.5 kHz is 38,500 on/off cycles per second. The IR receivers send a high signal if
they do not see IR flashing on/off at that rate.
To detect objects, the SumoBot's BASIC Stamp has to use its IR LED headlights to shine
infrared flashing on/off at 38,500 times per second. If the infrared is reflected off an object
and bounces back, the IR receiver will detect it.
The command FREQOUT Pin, Duration, 38500 actually sends a harmonic signal at
38.5 kHz. The IR receivers can't really tell the difference between a fundamental and a
harmonic. To learn more about this and other IR object detection techniques, see Chapters
7 and 8 in Robotics with the Boe-Bot.
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Bit