Flip Flop based Staircase Switch

In many cases, the stairs have a power switch at the bottom which is often left switched on during night. No one wants to go down to switch it off and hence, unnecessary on, it leads to wastage of electricity.

To solve this problem we have described a simple staircase circuit which contains two micro switches; one at the top and other located at the bottom of the staircase that can be pushed and released easily during climb-up from the bottom of the staircase or climb-down from the top of staircase. In short you can use any switch to on and off the light.

This simple circuit is built around a CD4013 IC which has two independent D type flip flops which exist in complimentary states and can store information.Each module is further equipped with a group of pin outs assigned as data, set, reset, clock input and a couple complementary output Q and Not Q. As we know, it has couple of output that change or toggle state as response to trigger applied to input terminals.

CD 4013 comes in 14 pin dual inline package. To understand the working of circuit first we have to understand its pin lay out.

Fig. 1: Pin Diagram Of CD 4013 IC

1. Pin no1, 2, 13 and 12 are complimentary outputs. This set of output changes state while setting and resetting the IC producing opposite logic level at any instant when operated in bistable mode.

2. Pin 5 and 9 are called Data pins and are generally connected to one of the outputs for the purpose of lengthening the applied input clock for square wave. For other waves, they may be terminated to any other logic level or they may be connected either connected to supply or to the ground of the circuit. In this circuit we have connected Not Q and Data pin 5 together.

3. Pin 3 and 11 are called as Clock input. These are input pins which are used to receive clock signals generally in the form of square wave. These signals may be provided by the transistor in the form of astable multivibrator or with the help of NAND or NOR gate. This input will produce effect on any of the output pins, the other being connected to Data pin as explained above. In our circuit we are providing clock signal through transistor circuit.

4. Pin 4, 6 and 10, 8 are called as set and reset pins. Whenever any of the pin goes high, we will get the output. When set and reset are low, output shows that data at input at the time of last low to high clock transition means output is held till the next transition. For safety, these are also assigned to a logic level generally they are grounded with a high value resistor. Once this is done, the input can be made to alternately respond to positive peak pulses to toggle the logic stage of the Q and Not Q outputs, alternately.

5. Pin 14 and 7 are called supply and ground pin respectively. Pin 14 receives the positive supply input which should not exceed 15V otherwise it will destroy the IC and pin 7 is ground or connected to negative supply input of IC Now you can also see this in truth table-

CLk	D	R	S	Q	Q-
*low-hi*	0	0	0	0	1
*Low-high*	1	0	0	1	0
Hi- low	X	0	0	Q	Q
X	X	1	0	0	1
X	X	0	1	1	0
X	X	1	1	1	1

From the above explanation of pin outs we can see that when you press switch S1, clock input goes high and high input is transferred to output. It further drives a transistor which in turns energizes the relay and as a result device connected to it start working. Similar action will take place when you use switch S2. We have used resistor R1, R2 diode D1 and Capacitor C1 to eliminate the effect of switch bouncing and combination of C2 and R3 provides power ‘on’ reset. Before connecting the bulb through relay, verify the voltage and current rating of relay. Also check CD 4013 based two way switch