4027 Dual JK Flip-Flop

Light Controlled Toggle Switch

4027 IC has four inputs (J, K, Set, Reset, and Clock) and two outputs (Q1 and not-Q). Here, a 4027 IC is designed in the toggle mode. The LED turns on or off and remain in that state whenever the resistance of the LDR changes. The 741 IC acts as a comparator. When light falls on LDR, Vin (pin 3) rises above or falls below Vref (pin 2) and the output changes polarity. The output is then sent to the clock input of the 4027 IC. According to the truth table, the output Q (pin 1) will toggle from one state to the other when both the J and K inputs are HIGH. Set (pin 7) and Reset (pin 4) are connected to the negative battery terminal. These pins are not dependent on the clock.