Schema proximity sensor
Schema proximity sensor:
The circuit consists of a transistor NPN BC107 TR1 (or equivalent) oscillation and driving a Darlington NPN BC517 TR2 used to drive a relay 12 V.
The principle is very simple: TR1 is an RF oscillator whose frequency is determined JAF1 by the inductor and the parasitic capacitance of a metal plate connected to its collector.
The HF generated is taken from the emitter of the capacitor C3 680 pF and applied to two diodes
in silicon DS1 and DS2 which, in the straightened , provide a positive DC voltage.
This voltage reaches the base of TR2 which thereby leads and excites the relay connected to its collector.
As the oscillator operates near its critical point, as soon as a person approaches or touches the plate as sensor, the oscillator stops and the base of TR2, no longer receiving a positive voltage to maintain conduction, ceases to conduct, which relaxes the relay.
To the oscillator to its critical point working , mounting a capacitor C1 adjustable 60 pF
between collector and emitter of TR1. DL1, in parallel with the relay winding, turns off whenever the latter is relaxed.
The choke JAF1 is 1 mH, a frequency of about 500 kHz is obtained. In modified ant the value of the self, the circuit works as well, but on another frequency.
To make the sensor, you can take a PCB rectangle (or a metal sheet, eg aluminum) 10 x 20 cm (smaller it would be difficult to stop the oscillator). List of electronic components: R1 .......... 10 kW R2 .......... 470 kW R3 .... ...... 3.3 kW R4 .......... 1 k C1 .......... 10-60 pF capacitor C2 .......... 10 nF polyester C3 .......... 680 pF ceramic C4 .......... 10 nF polyester C5 .......... 100 uF electrolytic C6 .... ...... 10 nF polyester JAF1 self ....... 1 mH DS1 ........ 1N4148 diode DS2 ........ 1N1448 diode DS3 ....... . 1N4007 diode DL1 LED diode ........ TR1 ........ NPN BC107 TR2 ........ NPN BC517 RL1 ........ 12 V relay 1 RT .......... switch S1 (Unless otherwise specified, all resistors are 1/4 W 5%)
The circuit consists of a transistor NPN BC107 TR1 (or equivalent) oscillation and driving a Darlington NPN BC517 TR2 used to drive a relay 12 V.
The principle is very simple: TR1 is an RF oscillator whose frequency is determined JAF1 by the inductor and the parasitic capacitance of a metal plate connected to its collector.
The HF generated is taken from the emitter of the capacitor C3 680 pF and applied to two diodes
in silicon DS1 and DS2 which, in the straightened , provide a positive DC voltage.
This voltage reaches the base of TR2 which thereby leads and excites the relay connected to its collector.
As the oscillator operates near its critical point, as soon as a person approaches or touches the plate as sensor, the oscillator stops and the base of TR2, no longer receiving a positive voltage to maintain conduction, ceases to conduct, which relaxes the relay.
To the oscillator to its critical point working , mounting a capacitor C1 adjustable 60 pF
between collector and emitter of TR1. DL1, in parallel with the relay winding, turns off whenever the latter is relaxed.
The choke JAF1 is 1 mH, a frequency of about 500 kHz is obtained. In modified ant the value of the self, the circuit works as well, but on another frequency.
To make the sensor, you can take a PCB rectangle (or a metal sheet, eg aluminum) 10 x 20 cm (smaller it would be difficult to stop the oscillator). List of electronic components: R1 .......... 10 kW R2 .......... 470 kW R3 .... ...... 3.3 kW R4 .......... 1 k C1 .......... 10-60 pF capacitor C2 .......... 10 nF polyester C3 .......... 680 pF ceramic C4 .......... 10 nF polyester C5 .......... 100 uF electrolytic C6 .... ...... 10 nF polyester JAF1 self ....... 1 mH DS1 ........ 1N4148 diode DS2 ........ 1N1448 diode DS3 ....... . 1N4007 diode DL1 LED diode ........ TR1 ........ NPN BC107 TR2 ........ NPN BC517 RL1 ........ 12 V relay 1 RT .......... switch S1 (Unless otherwise specified, all resistors are 1/4 W 5%)