What is the work principle of inductive electronic welcome device?

With the development of electronic technology, the electronic welcome device that uses pure electronic technology to realize the welcome function in many shopping malls or some brand stores is now produced.

Circuit working principle

When a person walks through the welcoming device, a shadow is generated, and the resistance of the photoresistor changes by the principle of the light resistance of the photoresistor. The sensor is produced by receiving the photoresistor signal. The schematic diagram of the inductive electronic welcome device circuit is shown below.

Inductive electronic welcome circuit schematic

Note: AC 220V power supply is used in the actual production process. Please design the specific power conversion circuit.

The inductive electronic welcome device is powered by a battery, and the system enters a wait state after power-on. Since the light is not blocked and directly irradiated on the photoresistor RG1, RG1 exhibits a resistance value. When the human body blocks a part of the light that is irradiated to the photoresistor, the intensity of the light received by the photoresistor changes, and the resistance value of RG1 changes. The current flowing through RG1 is coupled through the electrolytic capacitor C2, and amplified by the high gain of the transistor Q1 and the like, and then input to the inverting input terminal of the integrated circuit IC1. This signal and the output number input to the non-inverting input terminal are operated and amplified in the integrated circuit IC1.

After processing, a control signal is formed to drive the audio generating circuit inside the integrated circuit IC1 to work, resulting in "Hello, welcome“ audio signal, through SP1 to complete the electro-acoustic conversion, so that the human ear can hear this greeting.

This article is from Allicdata Electronics Limited. Reprinted need to indicate the source.