31-07-2012, 03:56 PM
AUTOMATIC SWITCHING OF LIGHTS
AUTOMATIC SWITCHING OF LIGHTS PROJECT.pptx (Size: 361.07 KB / Downloads: 31)
DIFFERENT PARTS OF THE CIRCUIT
COMBINATION OF D Flip Flops
Four D Flip Flops are connected to the outputs from the two sensors, for understanding let us consider them to be A0 towards the exit and A1 towards the entry into the room and both the sensors are placed close to each other there comes a moment when both the sensors respond simultaneously. The four Outputs from the D Flip Flops are ANDed and connected to UP and DOWN of the counter.
UP-DOWN COUNTER
An up-down counter counts the numbers of persons entering the room and leaving the room. So basically it is responsible for switching of lights and switching it off when the count becomes zero i.e 0000. It consist of four JK flip flops, and gates, Or gates and a Not gate. The outputs A4 A3 A2 A1 are connected to white LED and it glows even if any one of the output is one.
SHORTCOMINGS OF THE CIRCUIT
THIS CIRCUIT CAN COUNTS NUMBER OF PERSONS FROM 0-15 BUT ONE SEVEN SEGMENT DISPLAY CAN SHOW NUMBERS FROM 0-9, SO IT CAN COUNT ONLY NINE MEMBERS.
WHILE MAKING THE CIRCUIT, A DELAY FROM OUTPUT OF D FLIP FLOP CIRCUIT IS NOTICED AS COMPARED TO INPUT FROM AND GATE TO THE CLOCK OF THE COUNTER, BUT IT HAS BEEN RESOLVED USING THREE AND GATES.