Radio constructor Relay capacitive K104

  The capacitive relay is assembled on a specialized chip KS1025KP2. This microcircuit has a complete set of necessary components: a sine wave generator, sine wave detectors, a reference voltage source, a differential amplifier, a voltage stabilizer, a threshold circuit, a protection circuit, a triac control circuit.
frequency and amplitude of the generator, the frequency-setting element of which is the circuit L1-C2-C1-sensor. When a person approaches, the capacitance of the sensor changes, as a result, the natural frequency of the oscillatory circuit drops. A change in the frequency of the generator registers the detector of sinusoidal oscillations, which gives the command to turn on the triac. A transformerless power supply is assembled on diodes VD1, VD2, capacitor C8 and resistor R4, which allows you to power a capacitive relay from a 220V network.
  After mounting the device in the housing, as well as after changing the dimensions of the sensor, it is necessary to adjust the coil L1 for the desired sensitivity of the circuit operation. In some cases, it may be necessary to select capacitor C2. It is desirable to make the adjustment with a small capacity of C6-10 microfarads. The capacitance of the capacitor C6 affects the opening and closing time of the triac VS1. The sensor is a rectangular plate of foil fiberglass. The sensor can be installed in any place convenient for a person, as well as under any insulating material (plastic, wood, drywall) with a thickness of no more than 10-12 mm, which allows you to hide the sensor and not violate the integrity of the interior. When installing the sensor outdoors, please note that changes in humidity can lead to false alarms of the device.

  The maximum length of the wire leading to the sensor should not exceed 50 cm. be triggered by any impact that changes the capacitance of the sensor (metal objects, some liquids, a person, an animal, a change in air humidity. To a lesser extent, dielectric materials).
 

WARNING! The device is not galvanically isolated from the mains! It is forbidden to touch the elements and metal foil of the sensor of the switched on circuit!