Application of Photoelectric Sensors in Energy-saving LED Lamp Design

[Source: Gaogong LED 's " LED Good Products" magazine March issue ]

LED lighting fixtures have entered a new milestone in system design technology innovation. The LED light source realizes a new state of high voltage and small current operation due to multi-core packaging, effectively reducing the heat generation of the LED lamp; the LED driving constant current power source is highly integrated due to various functions of the driving chip, and the application circuit is more compact; the introduction of the plastic heat sink is solved The high-voltage safety isolation technology problem of LED lamps. The advantages of LED lamps in terms of energy saving, longevity and environmental protection make LED lamps widely used.

Nowadays, various LED lightings have been widely used in public places. How can public lighting fixtures be intelligently controlled in order to save energy and electricity more economically? The photoelectric sensor can assist the LED lighting of the public lighting to realize the automatic opening and closing of the light, can intelligently sense the entry and exit of the person and the vehicle, and automatically switch the light, can intelligently control the opening time of the LED light and control the brightness, and even automatically adjust the light according to human desires. The color temperature creates the light atmosphere that humans want.

Photosensitive sensors, infrared sensors, and color sensors have entered the design of various self-control energy-saving LED lighting systems. Their independent control and convenient application have made many public lighting LED lamps and home lighting fixtures intelligent.

Photosensitive sensor application

The simplest electronic device in a photosensor is a photoresistor that senses the change in light and darkness, outputs a weak electrical signal, and can be controlled by a simple electronic circuit to control the automatic switching of the LED fixture. For remote lighting fixtures, such as street lights, garden lights, lawn lights, etc., energy-saving automatic control can be realized economically and simply.

The solar street lamp itself is an LED lighting device that uses solar energy to generate electricity and store energy. It does not need the power supply of the grid, and there is no need to set up a costly transmission line. Therefore, the use of the photosensitive sensor can realize energy-saving management of extremely low cost and automatic opening and closing.

The automatic switch of the solar street light is shown in Figure 1. The left side of the figure indicates that the photosensor can be installed at the corner of the solar panel, and the space occupied is very small. In the lower part of the figure, the working circuit diagram of the photoelectric sensor is shown. The entire control board is very compact and can be mounted on the back of the solar panel.

Infrared sensor application

Infrared pyroelectric sensors (PIR) have been used in LED lighting for nearly a decade. The infrared sensor has a limited viewing angle and requires a Fresnel lens to expand the field of view (detection area) to monitor the moving heat source (person or car). The working principle of the infrared pyroelectric sensor is shown in Figure 2.

The Fresnel lens has two functions: one is the focusing action, which refracts the pyroelectric infrared signal on the PIR; the other is that the detection area is divided into several bright and dark areas to make the moving object (person) entering the detection area A modified pyroelectric infrared signal can be produced on the PIR in the form of a temperature change.

The typical design of the infrared LED downlight is shown in Figure 3. A small hole is opened on the panel side of the LED downlight to install an infrared pyroelectric sensor. The detected signal is amplified and can automatically turn the LED tube on and off. Lights to save energy and electricity.

Unfinished , please refer to the March issue of Gaogong LED 's " LED Good Products" magazine.

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