LED lighting system has the characteristics of power saving, light weight, long life and high durability. In recent years, it has been increasingly used in street lighting systems. The trend is to replace the street lighting of high-pressure mercury lamps that are widely used.
Aiming at the more advanced LED street lamp control system, the design of the analog street lamp control system is realized, and the LED street lamp timing control switch lamp, automatic switch lamp, independent control switch lamp and fault alarm of the whole branch are realized. The adjustable constant current driving power supply for the 1W LED street lamp unit can adjust the LED output power according to the setting requirements to realize the dimming function.
1 system hardware design 1.1 system overall design In order to truly simulate the actual LED street light control, the analog street light control system is designed. Using AT89S52 MCU and DS1302 real-time clock chip, using 5V power supply, with button control, time correction can be performed, and the switching time of LED lamp can be controlled and adjusted. The VCC2 of the DS1302 incorporates a 3V lithium rechargeable battery for clock power-down protection. The program power-down protection function is realized by the AT24C02 storage clock information.
1.2.2 Photosensitive detection circuit Photosensitive detection mainly detects whether the intensity of light should be switched on or off.
The photosensitive detection circuit mainly works by utilizing the photosensitive characteristics of the photoresistor.
As shown in the photodetection circuit, when daylight is irradiated to the photoresistor, the resistance of the photoresistor is lowered, and the voltage at the inverting input terminal is lowered. When the threshold voltage of the inverter 74HC04 is lower, the inverter is flipped. A high level is provided to the microcontroller, and the control LED is turned off. When there is low light or no light (at night), because the dark resistance of the photoresistor is very large, the voltage at the inverting input terminal is high, so that the output of the inverter is low, and the single-chip microcomputer controls the automatic opening of the LED light.
Photosensitive detection circuit. 2.3 Fault detection and sound and light alarm Sound and light alarm device is a circuit device that controls the buzzer and LED to emit sound and light alarm in the branch controller. IO is the menu function key, the corresponding menu has time correction, set the LED branch switch, independently control the dimming function of each street light switch time and power adjustment; it is the shift key; K3 is the addition and subtraction key; K4 is the confirmation button. The LCD data line is connected to the P1 port of the microcontroller; the RS register selection signal terminal is connected to P2.0; the RW read/write terminal is connected to P2.1; and the E enable terminal is connected to P2.2.
1.4 unit controller output voltage to control the adjustable constant current source drive circuit. The adjustable constant current source driving circuit is composed of an operational amplifier LM358, a relay, a high power tube TIP41, and a switch tube 9013, as shown. The single-chip microcomputer P3.0 control port outputs high and low level signals to control the relay switch, and provides +12V voltage to the constant current source circuit, and the constant current source circuit drives the LED to emit light. When the output is high, the relay is turned on, supplying +12V to the constant current source circuit, otherwise it is opposite. The microcontroller adjusts the size of the constant current source by controlling the output voltage signal of the TLC5615D/A.
Serial number constant current source Vi / V LED lamp power P / W 2 system software design to determine whether to open the street light according to ambient light. When setting by the button, enter the set mode, including: LED street lamp output power setting, setting range is 20% 100% current date and time modification and setting; street lamp working mode setting; Detection of street lamp failure and display of corresponding unit failure.
3 test results can display the clock and display menu on the LCD screen. Set and display the switch light time, control the entire branch (test to turn off the lights at 6:00 in the morning, turn on the lights at 7:00 in the evening) or independently control the LED lights and LEDs to turn on and off.
Simulated test of automatic switching lights for ambient light and dark changes. When the ambient light is less than 0.1lx (blocking the photoresistor by hand), the LED light is automatically illuminated, and the hand is released to automatically turn off the LED light.
The innovation of this design lies in the detailed design of the system based on the single-chip AT89252 analog street light control. Through the actual measurement of the power parameters, the output power of the LED street light can be accurately controlled; the street light can be automatically switched according to the light intensity; Time switch street light; can automatically detect faulty street lights and display the fault location. A variety of control methods play a role in energy saving and intelligent control. The designed program has been successfully run on the hardware platform of the analog LED street light control system.
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