Sensing unit consists of infrared emitter OP295 to produce the infrared beam, & two detectors in front of the emitter to detect the infrared beam OP598. Since the main idea in this device is to know person direction; and so, to get this approach, we have to use tow pieces of infrared detector in order to identify the direction of the person. When Infrared beam become brokendue to any body, the output signals from these detectors will be changed in unique sequence. Controller will identify the direction of the person by analyzing these signals as shown in the table at right `from 1 to 5 passed IN, 5 to 1 passed OUT`
Since detectors output signals are analogue while the controller can only process digital signals, these signals must be converted to digital through the analogue comparator LM393.
Controller will increase the number of the persons in side the room by one, or decrease it by one when the appropriate sequence of signals have occurred. If this number is greater than zero, light will be turned on otherwise it turned off.
After this, controller will stop scan sensors for one second to allow the whole body to pass. Fig 3 describe the whole algorithm
Sensors circuit is so sensitive in Light Control System, that mean any external noise or any small variation in voltage will change the sensors circuit status. While these signals are changing due to these reasons, microcontroller will assume that some one pass in front of sensor and so a fault will occur. In order to solve this problem I have used soft and hard components "capacitors" to make Light Control System stable as much as possible. A soft component is an algorithm in the control code to separate the noises signals from the real signals. If you have a camcorder, or just a camera mobile phone, you can see the infrared light! Just point the infrared emitter at the camera then you will be able to see the infrared light in the viewfinder. If you point your remote at the camera and push a button, you will see flashing light!