During busy traffic, voltage drops, making streetlights appear insufficiently bright. Meanwhile, at night, when traffic is quiet and vehicles are sparse, streetlight brightness rises excessively, resulting in unnecessary lighting waste and even light pollution. This has long been a common challenge for urban streetlight management. However, with the advent of intelligent dimming technology, this problem has been effectively resolved.
In practice, managers can remotely control the on/off status of streetlights and adjust their output power, such as to 80% or 60%, across various roads. This prevents wasted illumination caused by excessive voltage in the middle of the night. Furthermore, all of these adjustment functions include a timer option, making streetlight management truly intelligent. Compared to the uniform lighting pattern of traditional streetlights, this new type of intelligent streetlight can optimize lighting according to actual needs. Operational data shows that with intelligent dimming, intelligent streetlights can achieve energy savings of approximately 40%, a significant improvement, making them a leading choice for green and energy-saving lighting.
1. Types of Dimmable Power Supplies
Currently, the LED dimmable power supplies widely used on the market include: LED thyristor dimmable power supplies, LED 0/1-10V dimmable power supplies, and PWM dimmable power supplies. These dimmable power supplies operate on different principles, but all achieve brightness adjustment for LED lamps by precisely controlling current, voltage, or frequency. Below, we will delve into the detailed principles of each dimming method.
1.1 LED Thyristor Dimmable Power Supplies
Thyristor dimming technology, initially used primarily for dimming incandescent and CFL lamps, has now become one of the most widely used methods for LED dimming. Its operating principle is to chop the input voltage by adjusting its conduction angle, thereby generating a tangential output voltage waveform. This technology reduces the effective value of the output voltage, thereby enabling power regulation for common loads (such as resistive loads). The outstanding advantages of thyristor dimming lie in its high efficiency and stable performance.
1.2 LED 0/1-10V Dimmable Power Supply Design
This dimmable power supply has a built-in control chip. When connected to a 0-10V dimmer, adjusting the 0-10V voltage changes the power supply's output current, thereby adjusting the light brightness. Specifically, when the dimmer is set to 0V, the output current drops to zero, and the light brightness is off, acting as a switch. When the dimmer is set to its maximum value of 10V, the output current reaches 100% of the power supply's output, and the brightness also reaches 100%. It is important to note that in this dimming mode, the output voltage remains unchanged. Similarly, the 1-10V dimming principle is similar, except that the dimmer range is 1-10V. When the resistor dimmer is set to its minimum value of 1V, the output current changes by 10%. At 10V, the output current reaches 100% of the power supply's output, and the brightness also reaches 100%. However, please note that the 1-10V dimming mode does not have a switching function and cannot completely shut down the lamp to its lowest brightness.
1.3 PWM Dimming Power Supply
PWM dimming, also known as digital dimming, is a technology that uses PWM waves to control the brightness of LEDs. It adjusts the on-time of the LED's forward current to achieve brightness adjustment. This technology exploits the human eye's insensitivity to brightness flicker, creating a flickering effect when the LED is under load. As long as the frequency of this flicker exceeds 100Hz, the human eye perceives average brightness and is unaware of the LED flicker. PWM dimming changes brightness by adjusting the ratio of bright and dark periods. Within each PWM cycle, the perceived brightness is cumulative: the greater the proportion of bright periods, the higher the perceived brightness. However, it should be noted that some devices with high-frequency sampling, such as high-frequency sampling cameras, may capture images of LEDs when they are dark.
II. Intelligent Dimming Technology in Smart Streetlights
Intelligent dimming is a key technology in smart streetlight systems. It dynamically adjusts streetlight brightness by monitoring real-time data such as ambient light, vehicle traffic, and pedestrian activity, achieving the dual goals of energy conservation and comfort. Intelligent dimming technology automatically adjusts streetlight brightness based on time of day and scene requirements, ensuring adequate illumination at night or in low-light conditions while avoiding unnecessary energy waste.
2.1 Linked Dimming Mode
The linked dimming mode in smart streetlights encompasses multiple components, including the lamp head, individual lamp controller, environmental detection module, remote communication module, and linkage module. These modules work together to enable streetlights to adjust brightness in real time based on vehicle and pedestrian activity. The lamp head integrates an LED matrix, a constant-current LED driver circuit, and a current-voltage feedback circuit, ensuring stable and energy-efficient lighting. The environmental detection module, through the precise coordination of infrared sensors, infrared motion detection sensors, camera motion detection sensors, and radar motion detection sensors, further improves recognition accuracy and reduces the possibility of false positives. This linked dimming mode not only enables intelligent control of approaching and exiting lights, but also features automatic dimming based on occupants and vehicles, thus meeting lighting needs while maximizing energy savings. Furthermore, its compact structure, comprehensive functionality, and energy-saving and environmentally friendly features make it a standout in the smart streetlight market. 2.2 Comprehensive Dimming Solution
2.2.1 Implementation of Brightness Adjustment
In smart streetlights, brightness adjustment is achieved by finely controlling the output current of the white LED driver. This adjustment is closely related to the duty cycle of the PWM signal: as the duty cycle increases, the output current increases; as the duty cycle decreases, the output current decreases. This flexible adjustment mechanism enables streetlights to adjust brightness in real time based on the environment and demand, ensuring adequate lighting while effectively conserving energy.
2.2.2 Streetlight Electrical Parameter Monitoring and Fault Warning
The ZigBee module in the streetlight is responsible for real-time acquisition of key electrical parameters such as voltage, current, and power factor to monitor the streetlight's operating status. Current and voltage transformers convert the current and voltage of the 220V AC transmission line into low-voltage electrical signals, which are then transmitted to the CC2530 processor. The CC2530 samples the voltage and current signals at 64 points and analyzes them using an FFT algorithm to derive key data such as active power, reactive power, apparent power, and power factor. This data is used to determine whether streetlights are operating properly and whether there are any potential faults.
2.2.3 Adaptive Brightness Adjustment
Currently, many cities' streetlight systems lack intelligent dimming capabilities, resulting in streetlights remaining on at night regardless of pedestrians or vehicles, resulting in unnecessary energy waste. To address this issue, we have proposed an adaptive dimming solution. This solution uses a ZigBee dimming module to monitor road conditions in real time. Upon detecting a pedestrian or vehicle, the module ensures that streetlights within their field of view maintain their normal brightness while dimming lights outside of their field of view to 10%-20%. This approach achieves energy conservation and emission reduction while meeting basic lighting needs.
Luxsky light's new street light is good quality and affordable. Click the link to view
