Build Your Own Combat Robot

290 Build Your Own Combat Robot
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pulsout 0, 200 'Send a 2 ms pulse to the right servo
pulsout 1, 200 'Send a 2 ms pulse to the left servo
pause 15
back: 'This routing causes the mini sumo to back up.
for b2=1 to 25 'This loop determines how far the mini
pulsout 0, 200 'sumo backs up. Increasing the value
pulsout 1, 100 '(25) will cause the robot to back up
pause 15 'more, decreasing the value will cause
next 'the sumo the back up less.
return
Object Detector
The goal of the object detector is to enable your bot to detect or “see” your opponent
while it is far away from your bot, so that your bot can position itself to push
the opponent out of the sumo ring. There are many different ways to locate your
opponent, including bump switches, infrared reflective sensors, ultrasonic sensors,
laser range finders, and vision cameras. The most common are infrared reflective
sensors.
An infrared reflective sensor consists of an infrared LED and phototransistor.
They are placed next to each other, facing the same direction. When the LED turns
on, infrared light is emitted forward. If an object gets in front of the infrared light,
some of the light is reflected back toward the phototransistor. The transistor turns
on when it detects the infrared light. This type of sensor will actually work with
any type of light, as long as the phototransistor is sensitive to the same wavelength
as the emitted light.
Because normal light usually contains all wavelengths in the visible light spectrum
and light in the near infrared wavelength spectrum, it becomes difficult to
distinguish the difference between natural light and the light we are trying to detect.
One way to distinguish a man-made (or bot-made) light source from natural
light is to modulate the light source at some frequency that is not found in nature.
A sensor tuned to this frequency will ignore all of the light sources except for the
light source of interest.
The easiest way to make this type of object detector is to use the same type of
infrared sensor that is found inside a standard TV remote control. You probably
already know that you can change the TV channel just by aiming the remote at a
wall opposite the TV set. The TV detects the reflection of the infrared light off of
the wall, which in essence is the same way your object detector should work. Inside
the TV is a small sensor that contains all of the filters and amplifiers needed
to act as a stand-alone infrared sensor. Most of these sensors are tuned to receive
a modulated infrared light source operating at either 38 kHz or 40 kHz.