Point smoke density measurement system design based on photoelectricity

Point smoke density measurement system plays the most important role while calibrating fire detector. Based on dimmer principle and photoelectricity technology, a measurement system is designed in this paper. As the emitting device, infrared LED provides light into the smoke measured. Corresponding driving circuit is designed to control On/Off of the LED and provide constant current. As the receiving device, photodiode is chosen to convert infrared light into weak current. The conditioning circuit converts the weak current into standard voltage to be measured. As the central unit, Sing Chip Microcomputer (SCM) acquires the standard voltage and communicate with PC by RS485 interface. The system designed possesses such advantages as high accuracy, more flexibility, lower power consume.