proximity sensor circuit schematic

Proximity Sensor Circuit – Detect Human Presence

This presence detector or proximity sensor circuit reacts in presence of any conductor object including humans. Sensitivity is adjustable with P1 which will be located at a great distance from the rest of the presence detector circuit. This circuit does not detect object movement but can act as an proximity sensor!

Presence, Proximity Sensor Circuit Schematic

proximity sensor circuit schematic

proximity sensor circuit schematic

The sensitivity of the proximity sensor circuit can be adjusted with P1 for the desired “distance”. One of its obvious uses is to open a door automatically. For this the sensor must be placed on the front of the door.

The presence detector is made of one oscillator with T1 and a monostable. The oscillator is a Clapp one, well known for its frequency stability. The surface of the sensor acts as a capacitor for the oscillator circuit and in this configuration the frequency is around 1 MHz.

The switching time can be adjusted with P2. Do not bring metallic objects in the proximity of the circuit because if doing so the relay will stay closed! This circuit can be used as a detector of aggressive liquids, the advantage being that the surface of the sensor will not come in contact with the liquid.


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  • tidustpygmail-com

    dear sir, could you please let me know whether it is possible to run with 3V battery, for ex CR2032?

  • John

    Thank you for all these interesting projects.
    Can you show me a project for sounding a buzzer in my pocket if I forget to take my sports bag with me when I leave my training centre..or a train.

    Thank you.

  • fr33d0m

    good day sir! May i ask if there is a capacitive proximity sensor that uses the negative/ground as the touch/trigger sensor? Is there a circuit that detects a change in capacitance when battery negative is touched? We know that a car’s battery negative is connected to body/chassis. I want to make it as a car touch/proximity sensor. Thank you so much Sir.

  • Name *

    What is that square thing below the L1? .im not familiar of that, sorry

  • fr33d0m

    good day sir! May i ask if there is a capacitive proximity sensor that uses the negative/ground as the touch/trigger sensor? I want to create an alarm for car and use the body/chassis as sensor. So that when someone comes near, or touch the car, the alarm will sound off. Thank you so much.

    • soundman

      I’m interested in the same project as ‘fr33d0m’ above (ie. touch sensor using a vehicle body as the sensing element). If anyone has any thoughts, perhaps you could make suggestions here. Thanks.


    sir i m going to make a 5kw automatic step up/down steolizer pls send circuit diagram and all riquired component

  • Steven


    Can be this circuit used as a human presence sensor? Say, if I put a sensor above the ceiling, would the circuit work?


    • P. Marian

      I really do not know what is the distance, sorry. I have updated the article with some missing information.

  • edrian

    can you please list down the components?
    I need for my research. thanks

  • Homoud

    Hahaha, I was just thinking if I could attach a circuit to my pen that would light an LED when I say “LUMOS”.

    Get it? Harry Potter.

    I was also thinking about “Homenum Revelio”; it’s used to reveal human presence. This would be perfect for it.

    Big pen though……….

  • prashant

    i’m going to make a project which will be the presence detector…its better if u helps me in someway that what sensor tech.. should be used like PIR,Microwave,ultrasonic

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