Infrared-Based Motion SensorsObjects that radiate heat, radiate infrared.Motion sensing feature on most lights and security systems is a passive system that detects infrared (Ir falls between visible light and microwaves). These sensors are known as PIR (passive infrared) detectors or pyroelectric sensors.PIR sensors that detect human motions are designed to be sensitive to the temperature of human body. Humans have a skin temperature of about 93o F & radiate with a wavelength between 9um & 10um. ECGR 2252Mehdi MiriECE Dept.UNC CharlotteInfrared-Based Motion Sensors - continuedPIR sensor is made from ceramic material that generate surface charge when exposed to Ir.This charge is proportional to intensity of Ir radiation.Single element PIR detector:ECGR 2252Mehdi MiriECE Dept.UNC CharlotteGRsRSDVcc+-0VirOpticalfilterDetectorelementFETtransistorInfrared-Based Motion Sensors - continuedSingle element PIR would be sensitive to static Ir radiation (sunlight) not just dynamic radiation (motion).Multiple element PIRs are used to cancel effects of “background noise” (sunlight, vibrations, RF, lighting).Two element PIR detector (side and front views):ECGR 2252Mehdi MiriECE Dept.UNC Charlotte+-GRsRVccDS-+0Vir++ --Directional SensitivityInfrared-Based Motion Sensors - continuedQuad element PIR are used to detect all directions of motion.Quad element PIR layout (front view):ECGR 2252Mehdi MiriECE Dept.UNC Charlotte-+-+-+-+ -+-+ -+-+-+--Infrared-Based Motion Sensors - continuedFresnel lens can be used to increase sensitivity:Vir output:ECGR 2252Mehdi MiriECE Dept.UNC Charlotte+-GRsRVccDS-+0VirFresnelLensInfraredradiationPIRInfrared-Based Motion SensorsPIR-325 motion detector design (GloLab):ECGR 2252Mehdi MiriECE Dept.UNC Charlotte+3-2V+4V-11OUT1U1ALM324+5-6V+4V-11OUT7+10-9V+4V-11OUT8+12-13V+4V-11OUT14R1R2100kR310kR4 1MR510kR61MR71MR8 1MR91MR101MC1C210uC3 0.1uC410uC5 0.1uC61uD1D2D3D4Vcc000000PIRT = RCRetriggerableMachine +Edge