A Smart, Servo-Controlled Fire Extinguisher




Introduction

We have created an autonomous, servo-controlled fire extinguisher that is capable of aiming photo sensors and a water nozzle along two axes to detect and extinguish candle fires a short distance (about 1 ft.) away using a small burst of water.

Our inspiration originally came from thinking about an automated toy sentry turret that could fire at intruders (like a NERF® gun), but given ECE 4760’s ban on weapons and projectiles we thought that project was unsuitable. Additionally, we wanted to create something that might actually be useful. So, considering that current indoor fire prevention systems (such as ceiling sprinklers) can cause excessive damage by spraying everything in the room upon a whiff of smoke, we took the NERF® turret idea and turned it into a smarter fire mitigation system that sprays water only at fires. Of course, since our potential users (eg., home owners) would most likely not be around when our fire-extinguishing sentry’s vigilance would be most helpful, our system had to be autonomous. We thought that driving an autonomous system like this one would be a good application of the microcontrollers topics we learned in ECE 4760.

A Smart, Servo-Controlled Fire Extinguisher

Although what we have actually built serves only as a proof-of-concept, we think that a device operating on similar principles could be useful both indoors and outdoors as a smart, home fire prevention system or a forest fire mitigation system, respectively.

High-Level Design

The system has three major actuators: a water pump that sends a burst of water from a nozzle up to a few feet away, a servo motor that controls the horizontal position (angle) of the water nozzle, and a servo motor that controls the vertical position (angle) of the water nozzle. We use an ATmega1284p microcontroller (MCU) to manage both the “on” signal sent to the water pump and the positioning signals sent to the servos.




In order to detect fires, our system employs three major sensors: a central sensor that sees directly in front of the device approximately where the water nozzle is aiming, a sensor that sees diagonally upward from the approximate location of the water nozzle, and a sensor that sees diagonally downward from the approximate location of the water nozzle. We adjust for defects in the mechanical positioning of our sensors via software offsets. The upper and lower sensors are sensitive to visible light, and consequently they detect more than just fires. The center sensor, which is sensitive to infrared (IR) light, is activated more specifically by fires; consequently, it has the final say in whether a threat picked up by any of the sensors should be extinguished. The sensors all have their horizontal field of views (FOV) restricted so that we can think of our sensor array as analyzing a single patch of vertical space at a fixed horizontal position. The center sensor also has its vertical field of view restricted. The idea is that by sweeping the sensors along a horizontal axis, the center sensor will see only the point where the water nozzle is directed, while the upper and lower sensors can alert it to any other points that the system might want to check out with the center sensor. While scanning, if our system detects something via its center sensor, it immediately considers it a fire and activates a brief spraying routine to extinguish it. If it instead detects something via its upper or lower sensors, it pauses its horizontal scanning routine and begins sweeping the water nozzle (and the collinear center sensor) vertically in the direction of the activated sensor(s), giving priority to the upper sensor. By passing the center sensor over the source, our system can determine whether it is actually a threat and initiate an appropriate response (spray the source with water or ignore it). When the vertical scanning routine is done, the system resumes its horizontal scanning routine and the process repeats. Figure 1 (below) illustrates the basic operation of our system:

For more detail: A Smart, Servo-Controlled Fire Extinguisher




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