TOGGLE SWITCH

Summary
Many times we require a circuit which will on and off the device by the touch of our hand the benefit using touch sensor is we will not receive shocks. If you want to switch off you night lamp or you want to on or off your motor you can use it by simply connecting a relay at the output.
Description
This circuit is based on NAND gate CD4011 in this we are utilizing only 2 gates of NAND gate and rest two are not used. To understand the working you should know about the truth table of NAND gate are as follows-

Input		Output
A	B
0	0	1
0	1	1
1	0	1
1	1	0

In NAND gate we will get output when any of the input signals go low and if both are high we will not get output in that case.
Working of the circuit is very simple in standby mode both the switch are closed and the current follow through R1 and R2 to ground. When you touch the ON switch pin 1 receive the logic zero at its input now whatever may be the input at pin 2 we will get the high at pin 3.  As you can see from truth table. At this time input at pin 6 is high as OFF switch is not pressed and we also get high at pin 5 because of output from pin 3 is feedback to pin 5 as result we will get 0 at pin 4. And the LED connected to start working.
When you again touch the OFF switch then reverse action will take place means when you press the switch pin 6 will receive 0 at its input and whatever may be the input at pin 5 we will receive a high at pin 4.And at this time pin 1 is at logic high and pin 2 is also high therefore we will receive 0 at pin 3. As a result LED connected at the output will go OFF.
In place of LED you can also connect a relay with the help of a transistor. In this you can use BC547 transistor and use supply voltage according to the relay voltage rating. Always remember that working voltage of IC vary from 5V to 15V so do not supply or use relay of more than 16V otherwise it will destroy y your IC.
If you want to make a touch sensor at your home than take conducting plate it may be copper and glued it to some non-conducting material like wood or plastic in a close proximity to each other so when we touch the sensor with the tip of our finger circuit start working. You can also find the readymade sensor available in market or you can also use push to on switch.
The above application can be done with single touch switch as shown in the circuit diagram below-
Component used

IC
CD4011	1
Resistor
R1,R2(4.7K)	2
R3(330E)	1
C1(.1uF)	1
Miscellaneous
LED	1
Touch switch	1