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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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    12 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. chienline chienline says: on January 11, 2014 at 4:25 am

      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???

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