Design of universal intelligent switch based on LED-EEWORLD

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1. Introduction

With the development of China's economy and society, lighting electricity consumption has accounted for 10% to 12% of the total electricity consumption. Lighting energy saving has become an important aspect of energy conservation and environmental protection today. The purpose of lighting energy saving is to reduce energy loss in the lighting system and make the most effective use of electricity while ensuring the lighting scale and lighting quality.

Mainstream lighting energy-saving technologies include energy-saving lighting sources (such as LED lighting) and energy-saving circuits (such as dimming circuits and energy-saving switches). The integrated application of these two technologies is a new trend in lighting energy-saving technology. In my country, LED lighting equipment has a good development prospect, but the existing energy-saving circuit technology generally has the following two shortcomings:

(1) Most dimming circuits are composed of chips such as single-chip microcomputers, which are expensive and not conducive to installation and replacement of the original circuit;

(2) Energy-saving circuits are relatively complex. When installing related equipment, it is necessary to make major modifications to the existing lighting systems in indoor or other application locations. The installation and maintenance costs are high and the implementation is difficult.

In view of the above shortcomings, this paper designs and implements a universal intelligent switch for LED lighting equipment, which is low-cost, miniaturized, environmentally friendly and energy-saving, and easy to install and maintain, using simple components commonly used in analog and digital circuits.

2. System circuit and working principle

2.1 Working Principle

The LED intelligent switch designed in this paper mainly consists of two parts: intelligent control circuit and intelligent dimming circuit, as shown in Figure 1.

The intelligent control circuit interfaces C and D are connected to the control circuit that can control on and off according to the light intensity, and the control is mainly completed by thyristors D1 and D2; the intelligent dimming circuit interfaces A and B are connected to the control circuit that can change the thyristor conduction angle according to the light intensity. The working principle of the intelligent switch is shown in Figure 2.

2.2 Intelligent control circuit

The intelligent control circuit can automatically turn on and off the light according to the brightness set by the user. The circuit connected to its C and D interfaces (see Figure 1) is mainly composed of LM339 and 74LS02, as shown in Figure 3.

Among them, the resistance value of R6 can set the sensitivity of the switch according to different environments, and LM339 mainly compares whether the voltage across R5 is between the voltage across the photoresistor and the voltage across R6; 74LS02 mainly converts the comparison result into high and low levels, and then controls the conduction and shutdown of the thyristor through the transistor and relay; adjusting the adjustment knob 1 can set the brightness limit of continuous on and off of the light. The intelligent control circuit mainly controls the lighting equipment to become brighter and extinguished by controlling the conduction and cutoff of the thyristors D1 and D2 (see Figure 1), and its working principle is shown in Figure 4.

2.3 Intelligent dimming circuit

When the LED lighting device starts working, the intelligent switch designed in this paper will automatically change the brightness of the lighting device through the intelligent dimming circuit according to the changes in the ambient lighting conditions. The circuit connected to interfaces A and B of the intelligent dimming circuit shown in Figure 1 is shown in Figure 5.

The user uses the adjustment knob 2 to continuously set the brightness that the environment needs to maintain; the intelligent switch automatically changes the brightness of the LED lighting device according to the set brightness and the change of the actual light intensity of the environment to maintain the set brightness requirement, thereby playing a role in energy saving.

The working principle of the intelligent dimming circuit is shown in Figure 6, where the change in the resistance value of R19 causes the oscillator frequency to change, and this frequency change can change the charging time of capacitor C3. The resulting sharp pulse can control the conduction angle of thyristor D13, and then control the effective voltage across the lamp to achieve the purpose of controlling the brightness of the lamp.

3.Work performance testing and analysis

In order to test the actual working performance of the smart switch designed in this article, the author built a test environment indoors.

The environment is kept consistent with the outdoor brightness through transparent glass windows, and the change of outdoor brightness is simulated by artificially blocking the light entering the room. The light brightness that needs to be maintained indoors is set between 40lx and 50lx. The simulated outdoor environment brightness, the actual indoor brightness, and the actual brightness of the LED light are measured by a photosensitive sensor. The experimental curve shown in Figure 7 is the average result of more than 20 experiments repeated under the same configuration environment.

The curve shown in Figure 7 shows that when the brightness of the outdoor environment gradually weakens, the intelligent switch in this paper can automatically adjust the brightness of the LED lamp to gradually brighten it, so that the brightness of the indoor light remains within the preset range. Similarly, when the brightness of the outdoor light gradually becomes stronger, the intelligent switch can control the brightness of the LED lamp to gradually dim to maintain the preset indoor brightness. It can be seen that under the premise of maintaining the indoor brightness, the use of the intelligent switch designed in this paper can save the power consumption of the LED lamp.

4. Conclusion

This paper proposes a design scheme for a universal intelligent switch based on LED lighting equipment. This scheme integrates simple analog circuits and basic components of electronic circuits, designs and implements an intelligent switch suitable for LED lighting equipment, and conducts experimental tests on the working performance of the intelligent switch. Different from the intelligent switch based on single-chip microcomputer, the intelligent switch in this paper has the following characteristics:

①Pure hardware circuit implementation, no software programming and setting is required during manufacturing and use;

②Easy to operate and control, simple to install and easy to use;

③The switch has low cost and is suitable for occasions with high cost control requirements.

Keywords：LED Reference address：Design of universal intelligent switch based on LED

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