Touch switch using CD4011.

john March 6, 2010 22 Comments

Description.
A simple touch switch circuit using CD4011 is given here. The IC CD4011 is wires as a flip flop here. The 9, 13 pins of the IC works as the set and reset contacts respectively.CMOS ICs like 4011 require requires a very low current for controlling its gates. Since the pins 9 and 13 are connected to the positive via resistors R1 and R2, the logic gates of the ICs will be in high state. When we touch through the points A, B the gates of the IC will be closed and the output becomes low. This switches ON the transistor Q1 and the relay gets activated. When we touch through the points C, D the gates again becomes high and switches the transistor OFF. This makes the relay OFF. Thus by touching through the contact points A,B and C,D the appliance connected through the relay can be switched On and OFF.

Circuit diagram with Parts list.
touch-switch-circuit-using-cd4011

Notes.

  • The circuit can be assembled on a general purpose PCB.
  • The circuit can be powered from 12V DC.
  • The IC must be mounted on a holder.
  • The relay can be a 12 V, 200 Ohm SPDT relay.
Comments
  • Nishant
    April 18, 2017

    sir,can you please help me in making single button push to in/off switch which maintains its previous state after power failure.

  • boudabudka
    July 8, 2014

    AS FOR THE DIODE: it is used to “kill” the negative voltage which is produced by the solenoid (the coild of the relay) if it is powered off. If not used, this voltage can destruct the transistor.

    To be honest, there are two serious bugs:
    – There is no protection against overvoltage or static electricity at the IC inputs, so I guess the life of this circuit will be really limited to a couple of days…
    – The transistor is connected wrong way and can be destroyed easily by exceeding its allowed voltage between base and emitter. Use an NPN tansistor (BC557 etc) and connect its emitter to the ground and its collector to the relay/diode.

  • Subhendu jana
    February 18, 2014

    Why the diode 1N4007 is conect with the relay? Thnks

    • ismail
      June 27, 2015

      it is called a fly-back diode to protect the rest of the circuit against over-current due to the relay suddenly losing power when it is switched off

  • veera babu
    November 4, 2013

    what is advantages of ic cd 4011

  • SARANSH
    June 25, 2013

    WHAT IS THE WORK OF D2 CONNECTED TO RELAY IN THE CIRCUIT?

  • March 20, 2013

    Is this circuit working or its a bug

  • Brandon Cooper
    March 8, 2013

    Can I use this as a main switch, is there any leakage current?

    • Seetharaman
      March 9, 2013

      Yes you can use but take care of relay contact ratings.

  • Manish Kumar
    December 30, 2012

    Sir,I have a camera detached from a touch screen mobile as well as its big screen. So sir I need a circuit to see via the camera on the screen wireless.I request you to suggest me some sort of circuit suitable for this. Thank You.

  • seetharaman
    September 27, 2011

    Hi Sourabh repeat the same circuit for any number of circuits

  • September 24, 2011

    I NEED TO activat MANY RELAY(5 TO 10) USING MANY(5 TO 10) Touch switch.

    REPLY ME ON “SOURABHKUMAWAT20@GMAIL.COM”

  • manoharan
    August 24, 2011

    thank you verymuch Mr.seetharaman

  • sugiman
    July 28, 2011

    sorry. if i use the circuit on motor cycle, example for turn on and off with a touch sensor. how i connect it to the key plug on DC CDI motor? thanks

  • Seetharaman
    June 2, 2011

    Hi Manoharan it is sufficient

  • manoharan
    June 1, 2011

    PLEASE ANSWER THAT SKIN RESISTANCE ENOUGH TO CONTACT A-B AND C-D.THANK YOU

  • carlos ferreyra
    March 30, 2011

    lo voy a experimentar , aunque ya antes lo construí y funciona de maravilla

  • February 19, 2011

    Hi pls send me any railway station used mini project circuits..

  • seetharaman
    April 21, 2010

    Hi Karthick PCB can be specified by copper track thickness width, base material as phenolic, hylam laminate or glass fibre (depends on voltage and insulation level required and fire retardent etc)single sided, double sided or multi layer etc. solder masking. aluminum heat sink based
    you can visit the following site
    http://www.lpkf.com/applications/rapid-pcb-prototyping/working-examples/double-sided-pcbs.htm

  • karthick
    April 21, 2010

    how can we specify the pcb board.

  • pradeep
    August 25, 2009

    thank you

  • M fadel
    March 6, 2009

    my dear I have two resistance 300 ohm and four 100 ohm and I want circuit to conect to select. with selctor switch 20 step frst step 50 ohm secnt 100 ohm and 250 and 300 ohm and 350 going to last step 1000 ohm you can help me to make this circuit thank you.

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