Electronics Projects: May 2013

The main aim of the project is to build an autonomous vehicle (robot) that can detect a fire source, move towards it and extinguish the fire.

Major Components:

Arduino Uno, H-bridge circuit (L293D) – 2 nos. , IR photo diodes – 2nos. for detection, Fire sensor – 1 No (Can be another IR photodiode) and a Fan

Principle:

Fire sensors:

The spectral characteristics of the fire source depends on the source (or the burning material) of the fire. Most common fire sources emit radiations in the IR region of the spectrum and sensors that can sense radiations in this region can serve ideally for the purpose of detecting them.

Typical IR photodiodes have their sensitivity to be very high in the region from 870nm to 950nm wavelength, with daylight blocking filters to prevent any false triggers due to sunlight. These serve us ideally for fire detection purpose.

In this project, we intend to use three IR sensors –

Two on either sides in the front of the vehicle (Detectors) – This is for the initial fire detection and also for the purpose of guiding the vehicle in the direction of the fire source.

One in the centre with a high threshold (Activator) – This acts as a trigger for detecting the proximity of the fire and to take action (in our case switch on the fan) to extinguish it.

Controller:

An Arduino Uno is used here for controlling the robot. The main functions of the controller would be:

1. Initially be in scanning mode until any of the Detectors sense radiation.

2. Guide the vehicle by controlling the Left and Right motors based on the analog voltage levels from the Detectors.

3. When the fire source is close by, align the vehicle such that the fan faces the source (i.e the Activator is aligned to the fire). The Activator output is connected as an interrupt source to the Controller. Hence the extinguishing of fire takes place as part of the Interrupt Service routine (ISR)

4. Switch on the fan until fire is extinguished. H-bridge circuits are used for the purpose of motor and fan controls.

5. Return to scan mode

Circuit Diagram

Sensor Circuit:

1. The Value of R1 and R2 can be tuned based on the sensitivity requirement.

2.The 5V and GND can be derived from Arduino Uno board pins for convenience.

3. ANALOG_INPUT_LEFT, and ANALOG_INPUT_RIGHT can be any two analog pins on Arduino, say Analog 0, and Analog 1.