Fire Detection Algorithms Using Multimodal ... - Bilkent University

CHAPTER 5. FLAME DETECTION USING PIR SENSORS 69based system or a regular IR sensor based system is in the order of one thousanddollars.In this chapter, wavelet domain signal processing is also used, which providesrobustness against sensor signal drift due to temperature variations in the observedarea. Regular temperature changes due to hot plates and radiators areslow variations compared to the moving objects and flames. Since wavelet subsignalsof a waveform are high-pass and band-pass in nature they do not getaffected by the slow variations.Events are classified into two different classes in this approach. The firstclass represents fire events, on the other hand, the second class represents nonfireevents. PIR sensor circuits are designed for detecting the movement of hotobjects. Therefore, we include regular human motion events such as walking orrunning in the non-fire event class.The PIR sensor can be considered as a single-pixel camera without loss ofgenerality. Therefore, the proposed PIR based fire detection algorithm is obtainedsimply by removing the spatial analysis steps of the video flame detection methodsdeveloped in Chapters 2 and 3.Data acquisition and the PIR systems are described in the next Section. Theproposed algorithm and the experiments are presented in Sections 5.2 and 5.3,respectively.5.1 PIR Sensor System and Data AcquisitionCommercially available PIR sensor read-out circuits produce binary outputs.However, it is possible to capture a continuous time analog signal indicating thestrength of the received signal in time. The corresponding circuit for capturingan analog signal output is shown in Fig. 5.1.The circuit consists of 4 operational amplifiers (op amps), IC1A, IC1B, IC1Cand IC1D. IC1A and B constitute a two stage amplifier circuit whereas IC1C