Automatic room power control / Maizatul Sahrina Mohd Busri and Suhaiza Mahamat

Automatic room power control is used to switch ‘ON’ and ‘OFF’ the light automatically.
In this circuit we use two LDRs, which are placed one after another. So that they may separately sense the person going into or coming out of the room. The output of two LDR senses are used in conjunction with a bicolor LED that when the person get into the room it emit green light and when person goes out of the room it emit red light and vice
versa.
These outputs are simultaneously applied to two counters. One of the counter will count as +1, +2, +3 etc that when the persons are getting into the room and the other will count as -1, -2, -3 etc when persons are getting out of room. These counter make use of Johnson decade counter CD4017 ICs. The next stage comprise two logic ICs which can combine the output of two counters and determine if there is any person still leave in the room or not. The output of the two counters are ended by AND gates and the wired ORed.