Build Your Own Combat Robot

248 Build Your Own Combat Robot
tube rotates past horizontal, the ball will roll off the contact, thus opening the circuit.
The figure shows a bracket at some angle. The smaller the angle becomes, the
more sensitive the robot becomes to angular tilting.
Bump Sensors
A bump sensor is nothing more than a mechanical lever action switch that is attached
to the underside of your robot’s bumpers or armor. When another robot
hits your robot, the bump switches will tell the robot that it was hit. One implementation
of a bump switch is to place it on the sides and the back of your robot.
When your robot is moving forward and the bump switches indicate that something
is hitting the side of your robot, your robot can initiate an automatic spin
move to face the attacker. To implement this type of sensor, the armor or bumpers
must be semi-flexible so that when they get hit, they will move a little to trigger
the switch.
Implementing Sensors in Combat Robots
Although many sensors have a few problems when used in the combat environment,
the following techniques can help you overcome these.
Sensors obviously cannot be placed where they could be damaged by an opponent.
In general, this means recessing them with the robot’s structure. If you do recess
the sensor, be aware that some varieties of optical, IR, or ultrasonic sensors
will “detect” the sides of the exit hole, especially if this hole is too small. To help
eliminate this problem, for optical or IR sensors, paint the inside area that faces
the sensor flat black.
If you place the sensor too close to the floor, it is possible that the floor will return
a distance measurement, which will be depend on the roughness of the floor.
To help prevent this, try to mount the sensor so that it doesn’t angle downward.
Sometimes people will want to protect the sensors by placing them behind a
clear plastic (Lexan) shield. If using a plastic shield, the shield must be placed close
to the sensor to prevent the plastic’s refection from affecting the sensor’s readings.
Remember that IR sensors will not work behind glass and some plastics, so choose
your shield accordingly.
Optical sensors are not completely immune to ambient light. The sensor data
sheets show what happens to the sensors under “normal” lighting conditions. In
normal lighting conditions, the sensors have a range out to 31 inches (80 cm).
What happens when the sensors are used in bright light conditions? Or what happens
when an arena spotlight hits the sensor or the object that is being sensed?
The range is reduced! In bright light conditions, this range can be reduced to
about 16 inches (40 cm). Here, again, recessed mounting helps this problem, because
it will limit the spotlights from directly hitting the sensor. However, recessed
mounting does not help when the spotlight hits the object that is being sensed.
The 16-inch (40-cm) range is still usable. You can set up the sensors to work
within a short range and not depend on them for long range. Alternatively, you