Simple Touch Sensor Switch Circuit

A simple touch sensor switch circuit can be built using a single IC 4017 and a few other passive components, the procedure is explained in the following article.

Referring to the below given circuit diagram for the proposed simple touch sensor switch, we can see that the entire design is built around the IC 4017 which is a 10 step johnson's decade counter divider chip.

 

Simple Touch Sensor Switch Circuit

The IC basically consists of 10 outputs, starting from its pin#3 and randomly ending at pin#11, constituting 10 outputs which are designed to produce a sequencing or shifting high logics across these output pins in response to every single positive pulse applied at its pin#14.

The sequencing does not need to finish at the last pin#11, rather could be assigned to stop at any desired intermediate pinout, and revert to the first pin#3 to initiate the cycle afresh.

This is simply done by connecting the end sequence pinout with the reset pin#15 of the IC. This makes sure that whenever the sequence reaches this pinout, the cycle stops here and reverts to pin#3 which is the initial pinout for enabling a repeat cycling of the sequence in the same order.

For example in our design pin#4 which is the third pinout in the sequence can be seen attached to pin#15 of the IC, implies that as the sequence jumps from pin#3 to the next pin#2, and then to pin#4 it instantly reverts or flips back to pin#3 to enable the cycle again.

This cycling is induced by touching the indicated touch plate which causes a positive pulse to appear at pin#14 of the IC each time it's touched.

Let's assume at power switch ON the high logic is at pin#3, this pin is not connected anywhere and is unused, while pin#2 can be seen connected with the relay driver stage, therefore at this moment the relay stays switched OFF.

As soon as the touch plate is tapped, the positive pulse at pin#14 of the IC toggles the output sequence which now jumps from pin#3 to pin#2 enabling the relay to switch ON.

The position is held fixed at this point, with the relay in the switched ON position and the connected load activated.

However as soon as the touch plate is touched again, the sequence is forced to jump from pin#2 to pin#4, which in turn prompts the IC to revert the logic back to pin#3, shutting of the relay and the load and enabling the IC back to its standby condition.



31 thoughts on “Simple Touch Sensor Switch Circuit

  1. Have questions? Please feel free to post them through comments! Comments will be moderated and solved ASAP.
  2. Does the touch plate work when it is placed under a glass panel? LIke if we touch the particular area on the glass which is placed above the touch plate, the relay should response.

  3. sir
    is there any progress in my request
    can you tell me how to buy parts for making these projects online individually..i dont want bulk quantity.can you tell me any site..this ia because nowadays all parts are not available in my nearby electronic shops..please help me

  4. Sir good morning Hope you fine. I requested u to design a circuit for boost the heart beat sound from stethoscope via condensor mic to 8" speaker.Is there any chance to design.
    Thank you
    Sridhar

  5. what is that touch plate..is it an ordinary metallic plate to which base of transister is connected..sir im new to these type of circuits thats why i asked

    • it can be any metal end, even a small 1 inch stripped wire will do.

      this wire should be as small as possible, longer wires might produce erratic results due to stray disturbance pick up

  6. Sir I made a touch switch using 4013 ic and its works fine but suppose if switch is OFF and main power goes and when power comes back again switch turns ON (vice versa). How can I avoid this. or how to keep the same state of switch when power goes OFF or comes ON.

    • Janak, to rectify the issue you can connect a high value capacitor across the ICs suply terminals via a 1M resistor, and also make sure to connect a 1N4148 from the supply to the (+) of the capacitor, that is at the junction of 1M and capacitor positive, cathode will go at this point, and the anode to the supply positive.

  7. Sir i tried it using 1000mf cap with 1m resistor and also diode. but now it works only if switch is in off state. suppose before power goes if switch is off and power comes it remains off but if switch is ON and power goes and when power comes back it is off. Sir is there any other way to keep same state of switch even if main power goes and come it remains in previous state.
    circuit description for two touch switch.
    Ic used cd 4013. Two output taken from this Ic 1st output from pin 1 and 2nd from pin 13.Input given through M397 TTP223 Capacitive Touch Switch Button Self-Lock Module(http://www.ebay.in/itm/M397-TTP223-Capacitive-Touch-Switch-Button-Self-Lock-Module-/112442397140?hash=item1a2e16d1d4:g:JEsAAOSwgv5ZQNAL)to both input pins 3 & 11 with 2k resistor to I/O of touch module other end of resistor goes to pin 3 of ic 4013 and one more resistor of 100k from pin 3 goes to ground. . short pins of Ic 2 with 5, 4 with 6&7, 12 with 9 and 10 with 8 which is then shorted to 7 as ground & 14 is vcc.
    output of this Ic given to ULN2004 ic and output through this ic is given to relay circuit. Input supply is 5v
    sir pls let me know if any other modification to be done so that switch remain in same previous state even if power goes and come.



Leave a Comment