After installing street lamps, their dimming control and maintenance are two of the most crucial things in road lighting. Not to mention, these two require a lot of labor costs. Currently, the control methods for LED street lights mainly include Photocell switch on/off, Timing Dimming, and Smart Controller system. In this article, ADNLITE will introduce the advantages and disadvantages of these three street light control methods. This way, you will know how to choose the appropriate control method for road lighting projects.
What is a Photocell?
Photocell is also called a light sensor switch or dark-to-dawn sensor. It can turn on or off street lights according to the presence and brightness of natural light. This all happens automatically, without human intervention. So, if a street lamp is not equipped with Photocell, you need to turn it on and off through the main switch manually.
Principle of Photocell
Generally, the induction head is connected to the dimming joint switch of the street light power supply. Usually, there are photosensitive electronic components on the sensing head. Photosensitive electronic components can change the voltage or current value based on the brightness of natural light. The street light power supply lights up or turns off the LED light source through the current or voltage change of the sensor switch.
Considering the need for outdoor waterproofing, you must install the street lamp and the Photocell sensor switch through a 3-pin Nema socket, 5-pin Nema socket, or 7-pin NEMA socket. When installing street lights, check if the photosensitive switch can receive natural light. To avoid the influence of foreign objects, such as leaves, you must clean the sensor switch’s surface regularly.
Additional Cost of Installing Photocell for Street Lights
An optical switch and waterproof base usually cost around $6. Be guided that installing the photosensitive switch also requires additional processes. It might include opening holes in the back of the street lamp housing. Therefore, from the factory production perspective, installing an optical switch will cost between $8 to $10.
You might encounter some issues in your solar street light’s photocell, but do not worry. In most cases, if the solar street light is placed near the highway, it may accumulate dust from the road. The huge peck of accumulated dust on your solar lamps can cover the sensor head after a long time. Not cleaning it will prolong the solar lamp’s lighting time as it will not detect enough natural light. The shading of leaves or surrounding buildings might also be the reason why your street lights turn on during the day. The irradiation of external light sources such as car lights on the sensor head can also make the street lights automatically turn off at night.
What is the Timing Dimming Control System?
The Timing Dimming Control system is a functional module of the street lamp power supply. After a long time and the street light brightness is set, everything can remain the same. For example, within 6 hours after the lights are turned on when traffic flow is at peak, and the LED power is set to 100%. After 6-10 hours in the middle of the night, the LED power will be set to 50% to save energy. However, this mode starts timing from the moment when the street lights are lit, and cannot be adjusted accordingly as the season changes.
Fortunately, the current timing dimming control system of some brands like Philips, Osram, etc., has an automatic adjustment function. Their system will automatically adjust the dimming point in the second half of the night, which is based on the sunset and sunrise conditions of the previous two days. The following is the lighting schedule of street lights in 4 seasons.
|Date||Sunset (turn on)||Lighting Curve|
The Disadvantage of Using Timing Dimming Controls Only
If a street light only has the function of time dimming, it cannot be perfect in the following situations. In rainy weather, if the natural light is too dark during the day, the street lamps will not light. Remember that the times of sunrise and sunset vary with the seasons. But, the time of street lamp time-controlled dimming is fixed.
So, in this case, you cannot adjust the dimming settings of the street lamps based on seasonal changes. Therefore, the combination of light-controlled switches and time-controlled dimming is a must. These two functions enable street lights to adjust the dimming schedule automatically according to seasonal changes.
What is Smart Control System?
The Smart Control system is made to complete the remote control, remote dimming, remote monitoring, and remote real-time dynamic management of each lamp. This system makes municipal street lamps monitor the center and on-site remote distributed RTU, with the help of a powerful GPRS/CDMA mobile communication network. The system can monitor the operation of a single lamp, and the data includes the voltage, current, power, power factor, power consumption, lamp failure, and other data.
Benefits of Smart Control System
- Smart control system reduces labor costs. Usually, the distribution of street lamps is scattered, and the number is large. You need to invest a lot in the manual inspection cost and replacement of lamps every year! But with the use of street light intelligent control systems, you can save labor, management, and vehicle inspection costs.
- When the original clock control mode is running, it is necessary to periodically adjust the time setting of the clock controller to turn on the light. Due to limited manpower, the adjustment cycle should not be too short, generally 1-2 times a month. This will allow about 15 minutes of headroom for each adjustment. With that, it turns on 15 minutes earlier and turns off 15 minutes later, totaling about 30 minutes. In this way, the lights are turned on for an average of about 30 minutes a day during each adjustment cycle, which undoubtedly wastes energy.
- According to the road traffic conditions, the brightness of the street lights can be automatically adjusted. It can save 30 to 40% of the electricity bill.
- Eliminate abnormal lighting during the day and save electricity. According to the empirical data of the street lighting industry, troubleshooting abnormal lighting functions during the day requires a lot of manpower and material resources, which can reduce a considerable amount of expenses every year.
Three Major Sections of Smart Street Lamp Control
- Monitor Control Center
The monitoring center is an office area where lighting managers monitor and control the operating status of street lights. Managers can access and control the city/district lighting transformers/distribution cabinets and street lamps through the main control software. The control content includes switch light command sending, parameter configuration, status query, fault detection, etc. Through the monitoring center, it is convenient and intuitive to know the operation status of lighting equipment in the city/district.
- Centralized Controller
The centralized controller is installed in the power distribution cabinet. It usually manages and controls the line by receiving commands from the monitoring center through wireless GPRS. It sends commands (single lamp control) and information feedback to the single lamp terminal through the power carrier technology. This is to realize the control of a single street light and the collection of various state information on the line. When the communication failed in the monitoring center, the switch light operation at the power distribution cabinet level can be automatically performed according to the preset time curve. This controller can be connected to the single lamp controller.
- Single lamp controller
The single lamp controller is installed on the street lamp pole and used together with the Centralized Controller. The device adopts power carrier technology and receives instructions from the monitoring center through the Centralized Controller. This helps to realize switching lights and voltage regulation at the single-light level. Also, the single-lamp controller can actively collect single-lamp fault information for reporting. Thus, the entire control system can realize functions such as single-lamp networking, single-lamp control, single-lamp energy saving, single-lamp data collection, and single-lamp electric energy metering.
The table below is a summary of the three street lamp dimming control methods.
|Control||Photocell switch||Timing dimming||Smart control system|
|Advantage||Reduce labor; can adapt to the season to automatically switch operations.||Save electricity; no extra cost.||Smart， Save a lot of operation and maintenance labor costs|
|Disadvantage||Requires additional cost; easily disturbed by the external environment.||Not smarter||The cost is high and the operation is relatively complicated|