Infra-Red Proximity Detector Circuit Diagram

Introduction

Infra-red proximity detector circuit is one of the most popular gadgets these days. This circuit uses an LM567 IC that is specifically designed to detect the presence of infra-red rays. This technology is extensively used in various security systems, automatic door openers, and household gadgets to sense nearby objects.

The detector is intended for sensing obstructions at distances of a few millimetres to a few centimetres. The industry and health services also use similar detectors for instance, to open a water tap via a magnetic valve.

Circuit Diagram

of Infra-Red Proximity Detector Circuit

This amplifier can be designed using a few basic components. The circuit diagram of this project is shown below.

**Infra-red proximity detector circuit diagram**

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Infra-red proximity detector SFH900 Pins — Infra-red proximity detector **SFH900 Pins**

Working Explanation

of Infra-Red Proximity Detector Circuit

IC2 is the sensor, which is a Type SFH900 optoisolator manufactured by Siemens or similar. A phase-locked loop (PLL) in decoder IC1 compares the frequency of the input signal from IC2 with that of an internally generated signal. When the two signals fall within the same band, the output at pin 8 of IC1 changes state (from high to low).

A signal at a frequency of about 4.5 kHz is generated by the internal oscillator which is determined by time constant R1-C1. The rectangular signal at pin 5 switches on the light-emitting diode in IC2 via T1. The diode then transmits an infra-red light signal pulsing at 4.5 kHz.

When an item near to it reflects the infra-red light, IC2’s photo transistor generates a signal that is sent to pin 3 of IC1. When the frequency of the signal matches the internal generator’s band, pin 8 is linked to the ground, and diode D1 illuminates. The PLL comparison method ensures that the system isn’t affected by unwanted interference. P1 can be adjusted to alter the detector’s sensitivity.

The detector with components as specified draws a current of 10-30 mA.

The optoisolator may be one of several types, as stated earlier. It may also be built from a discrete LED and phototransistor, but great care should then be taken to ensure that the photo transistor cannot receive light transmitted by the LED.

A suitable solid-state relay at the output enables larger loads to be switched. The Circuit of the IC1 can switch currents of up to 100 mA to the earth. Diode D1 should then be omitted.

Conclusion of Infra-Red Proximity Detector Circuit

In conclusion, the Infra-red proximity detector circuit using LM567 IC is a sophisticated, yet simple system that can sense the presence of objects by using infra-red technology. It is an effective and affordable way of providing security to homes and offices. With a range of applications, this circuit has become an essential component in modern-day electronics.