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.

  Notes:
- You have to isolate detectors from any kind of light, except the infrared radiation.
- Use TIP110 to drive relay current; it has Base-Emitter Shunt Resistors built in. Diode D1 is acting as a freewheeling diode.
- Analogue reference voltage should be less than voltage produced by the detectors; otherwise, the system will not function properly . "Less than 0.1V is recommended"
- The maximum speed of the body to be detected by the Light control System is 1.67 metersecond = 0.462 KmHour this value is accurate only if the depth of the passing body in front of sensors is equal to the distance between these two infrared receiver, if this depth is more, the maximum speed will be increased.
- Light Control System is unable to detect any body with a depth less than the distance between 2 receiver.
- By adding an auxiliary switch, Light Control System can be disabled if any failure has occurred after installing. This auxiliary switch disables the functionality of Light Control System and restores the wall light switch to the previous state as shown in figure 4.