NOT Gate (IC 7404) :
It takes the 6-bit output form 4:16 Decoder into its Pin 1,3,5,9,11,13 and produces the inverted output at Pins 2,4,6,8,10,12.
Here we connected output Pins 6,8,10,12 to LEDs and Pins 2,4 to J-k Flip Flop.
Pin 7 is grounded while Pin 14 is connected to Vcc.
J-K Flip Flop :
IC 7473 contains two J-K Flip Flops. It is used to latch the output state and toggle it for the next valid input.
It takes 1st J-K Flip Flop input at Pins 3,14 and 2nd J-K Flip Flop input at Pins 7,10. 1st Flip Flop output is present at Pin 12 and 2nd J-K Flip Flop output is present at Pin 9. These outputs are fed to Relay Driver.
Two clear inputs at Pins 2,6 are connected to Vcc.
Clock input to two Flip Flops is provided by IC 555 timer at Pins 1 and 5 respectively.
Pin 11 is grounded while Pin 4 is connected to Vcc.
IC 555 Timer :
It is configured at astable state to produce a train of clock pulses of desired frequency depending upon the value of resistance and capacitor. This clock is used to drive the J-K Flip Flop IC.
Clock output is produced at Pin 3 and fed to J-K Flip Flop IC.
Vcc is connected to Pin 4,8 and Resistance R1 whose other end is connected to Pin7 and to R2. R2 is then connected to Pin 2,6. Capacitor C1 is connected to Pin 2 and Pin 1 which is grounded. Capacitor C2 is connected to Pin 5 and other end is grounded.
RELAY DRIVER (ULN 2003):
A relay driver is a monolithic high voltage and high current Darlington transistor arrays, used to drive relays by input from TTL or CMOS devices like microcontroller.
Outputs from J-K Flip Flop IC is fed to relay driver at Pins 1 and 2.
According to the input signal fed, relays connected to driver at Pins 15 and 16 are operated.
Pin 9 is kept high by Vcc and Pin 8 is grounded.
In our project, two relay have been used to connect the devices and to operate them.