Foundation | Welcome

How to detect a fire

The extinguishing subsystem, shown to the left, displays the interaction between the x-axis and y-axis stepper motors and the UVTron input to the microcontroller. The timing of the water pump is elucidated as well, with a state also including the firing algorithm consisting of modulating both stepper motors together.

The water pump

To extinguish the fire, a standard TOPSLFO Micro Gear Pump was used to launch water across the room. By creating a 12” by 6” by 6” water tank out of ultravioletresistant clear extruded acrylic sheets, a maximum volume of 7.079 L (1.87 gallons) of water can be stored for a fire. Once a fire has been detected, 12 V can be applied to the motor to supply a max flow of 2.5 L/M. By connecting the end of the water pump’s tubing to a nozzle and motor, aiming the flow of water is easily achieved to reach up to 25 feet.

Aiming the water

The hose of the extinguisher will be mounted on the same servo driven platform as the UVTRON detector. This means that the x-radial position of the hose, for the purposes of extinguishing, is in line with the fire once the fire has been detected and the sensor stops scanning. The same loops used for scanning are used for the extinguishing algorithm, namely, the stepper motor controlling y-radial position will cycle through 90° of movement reflected by a function call to the stepper motor function while alternating left and right on the x-radial position.

Shortened firing algorithm rendering with y-stepper Upon reaching the center of a room, the fire detector will sweep a near 360° radial distance. Upon positive identification of the flame, the sensor will cease the sweep and remain pointed at the fire. The fire extinguisher then is primed to begin the aforementioned algorithm, beginning the y-radial sweep with the stepper motor and then setting pin P1.3 to high and activating the relay, powering the MCP355 water pump. The MSP430 monitors the status of the UVTRON, and when the UVTRON particle detector no longer senses a flame, pin P1.3 will be reset and the extinguisher will cease at the zero degree mark of motion.

Aiming motors

To control the aiming capabilities of HeatSeekr, two 39BYG302 stepper motors are used for the X and Y axis control of the water tubing and UVTron fire detection device. By mounting the UVTron on top of the X axis motor, and the Y axis motor above the UVTron with the water tubing, HeatSeekr is able to detect a fire and extinguish it within 30 seconds of its arrival into an active room.

The NEMA 16 step motors, model 39BYG30, are small step motors with a step angle of 1.8° and 200 steps per revolution. With a small dimension of 0.98” by 0.511”, they easily fit onto the chassis while keeping a sleek appearance. Despite their small stature, they provide a moderate amount of torque at 1.0 N/cm. This torque has proved to easily carry the lightweight UVTron and shroud for detection. To run each step motor, a Texas Instruments DRV8811 stepper motor controller was used. The DRV8811 provides two H-bridge drivers and microstepping indexing logic to control each stepper motor.