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    This is a very simple touch sensor switch that is build with the 555 timer IC.
    You just need to touch the metal plate and the relay gets energised and is kept in this state for about 100 seconds, then is released.

    This kind of sensor switch is suitable for making touch operated bells, buzzers of small toys which operate for a small time and then switch off automatically.

    The input impedance of the trigger is very high and the touch sensor switch can be triggered by the voltage induced in the human body. The relay is a 12 V DC relay operating at currents less than 200 mA.

    555 Touch Sensor Switch Schematic

    555 touch sensor switch circuit schematic


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    25 Responses to "Touch Sensor Switch Circuit with 555 timer"

    1. Thanks as soon as my laziness get healed I want to build this and use it as an alarm

    2. I’ve built one linked to a 555-auto-off-blinking-led.
      I built it for my kid’s truck. I use 9V battery instead of 12V source.
      The idea is they always forget to turn off their toys, so I make one with auto off and touch sensor on instead of switch.
      But the next day, there was 5V remain in the battery.
      Maybe I should link it to another solar charged battery instead of 9V battery. Any other idea how to avoid battery drains with a touch sensor?

    3. i tried a breadboard prototype of above circuit but not working relay energises without touch when powered on and keeps on even when capacitor is full charges.
      Whats the matter can u help?

    4. Hello Dear Mr P. Marian

      I’m ineresting to buid a similar circuit but with a small diference.
      Touch the plate and the relay stays energised (for as long as you want).
      Touch the plate again and the relay deenergised (for as long as you want).

      first touch – state ON
      next touch – state OFF
      next touch – ON
      next touch – OFF
      next touch – ON
      next touch – OFF
      …… and so on

      Thanks a lot for listening me.
      Best regards.

    5. sir i want pcb layout for this.. plz kindly send this

    6. whats 1M???

    7. Hello Rocky,
      You want a Touch circuit that can remain on for as long as you want.Yes this is possible if you let the relay operate a Digital on/off switch.Download a digital on/off switch.
      Best Regards,
      George Karitu
      Kabethi Holdings Ltd.

      • Hi, thanks for the reply but I am wondering what a digital on/off switch is? is that RS flip flop you are talking about or something else. please tell me ASAP I will be highly appreciate for your reply.

        Thabnks,
        Rocky

    8. please can the above circuit b fixed to motor car fo anti theft, if yes, hw do I fix the touch plate? you knw d body of a car is carrying negative voltage

    9. please can the above circuit b fixed to motor car fo anti theft, if yes, hw do I fix the touch plate? you knw d body of a car is carrying negative voltage

    10. pls sir, i want to know what makes the touch not to function except i touched the negative line before touching it?

    11. What does the size of the “touch plate” have on the sensitivity and operational reliability? I want to wire a touch sensor to my front door, which is metal… or run a wire to the door knob assembly. Has anyone tried something like that? [The object is to light a floor lamp via relay/driver, and delay-off circuitry (all of which I’ll add) when the door knob is touched.]

    12. How much amount of relay we can use

    13. Why are we using 1M resistor… Kindly tell me pls..

      It s very interesting circuit, am going to implement this on my metal gate, and am going to use 12V DC siren.

      Kindly let me know any changes has to be done on circuit…

    14. Got it, 1M is used for 100 secs timing. More t resistance more the secs…

      Can we hook this with 12v siren straight away with out relay?

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