Crater
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A low-cost Fire Fighting robot

Drive system uses two motors, with encoders and a caster. Sensor array 
consists of a panning servo with IR ranger and a phototransistor and shield. 
Incorporates a single UV sensor on top of the robot to detect flame in a room. 

Speed - 88RPM, 2.75” Wheels, yields 12.5” per second.

To minimize external components and port usage, we use the internal 8mhz clock, 
and share the programming and LCD ports (we can pop the LCD off to program if 
necessary.)

Navigation
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We use an a priori topological map with limited metrics for navigation. We 
define the neighborhood of the node to be approximately 24 inches in diameter. 
In hallways, we turn the head 30 degrees to a side and follow the wall. If 
we are looking for a forward wall, we begin forward wall checks when we enter 
the neighborhood of the node. If we are looking for a wall loss, the robot does 
periodic checks for wall loss (about every 3”) when it is in the neighborhood 
of the node. Turns are encoder-based. Speed is not regulated.

Fire Detection
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We use a UV LED, with reverse bias, to detect UV put off by a flame. We charge 
the negative end of the LED, and time the fall. Once we have detected the 
presence of the fire, we pan the robot and scan with a photodiode for the 
fire’s appearance. 

Schematic for OP599a sensors 
 
          5V
          |
          R = 47K
  analog__| 
          |
          C (flat side)
          + op599a
          E 
          |
         Gnd