LED "anti-aging" several small coups, intelligent control LED light strips off the principle scheme

LED conventional aging test comparison

In general, especially for high-power LEDs, the luminosity will be attenuated in the initial lighting stage. In order to provide stable products for the application manufacturers, or for the LED manufacturers, in order to obtain stable LED materials, Do some aging tests. Of course, LED aging tests can be performed in a variety of ways, such as conventional aging, overcurrent shock destructive tests, and the like.

1, multiple tubes in series aging: constant voltage aging circuit and constant current aging circuit

2, multiple tubes connected in parallel

3, multiple tubes in series and parallel aging: string and constant pressure aging and series and constant current aging

4, single tube constant current aging

Comparing the above four kinds of aging methods, as long as one LED has quality failure in one or three ways, such as LED short circuit or open circuit will affect the working current parameters of other LEDs. The second method is better than 1, 3 kinds. Any change in LED characteristics will not affect other LED aging parameters, but in fact, the method of resistor current limiting is unreliable, the resistance of the resistor itself drifts and the voltage of the LED itself. Changes in characteristics can seriously affect the LED parameters. Obviously, the fourth single-tube constant current aging captures the LED current operating characteristics and is the most scientific LED aging method.

Aging should be a very important process in the test process, but in many enterprises, it is often neglected and cannot be properly and effectively aged. The analysis of all parameters including brightness, wavelength, etc. performed by the LED itself will be uncertain. . Over-current impact aging is also an aging method often used by manufacturers. It is usually used for constant temperature sources with adjustable frequency, adjustable current and adjustable duty cycle. It is expected to judge the quality and expectations of LEDs in a short time. life.

We often have such problems when applying LEDs. LED soldering works normally at the beginning of the product, but after a period of lighting, dark light, flashing, malfunction, intermittent light, etc. will appear. Bring serious damage. The reasons for this phenomenon are:

1. When applying the product, there are problems in the welding process. For example, the welding temperature is too high, the welding time is too long, and the antistatic work is not done. More than 95% of these problems are caused by the packaging process.

2. The quality of the LED itself or the manufacturing process.

1. Do a good job in welding process control.

2. Perform an aging test on the product.

Aging is an important guarantee for the reliability of electronic products and is the last essential step in the production of products. LED products can improve performance after aging and contribute to stable performance in later use. LED aging testing is a very important part of product quality control, but it is often overlooked and cannot be properly and effectively aged. The LED aging test is based on the failure rate curve of the product, that is, the characteristics of the bathtub curve, to improve the reliability of the product, but this method is not necessary. After all, the aging test is to sacrifice the life of a single LED product. For the price.

LED aging methods include constant current aging and constant pressure aging. A constant current source means that the current is constant at all times. If there is a frequency problem, it is not a constant current. That is AC or pulsating current. The AC or pulsating current source can be designed to have a constant rms value, but this power supply cannot be called a "constant current source." Constant current aging is the most suitable LED current working characteristic, and it is the most scientific LED aging method. Overcurrent aging is also the latest aging method adopted by manufacturers. It can be used for such aging by using constant current source with adjustable frequency and current adjustable. In order to judge the quality life expectancy of LED in a short time, and can pick out many hidden LEDs that can not be picked out by conventional aging.

Urban road lighting is increasingly using LED lighting technology instead of traditional lighting technology, the purpose is to reduce the consumption of electrical energy. Since the LED uses a low-voltage DC power supply, it is convenient to add additional detection and control circuits, which facilitates the intelligent management of the street lamp network and further saves energy and reduces consumption. For the management and control of streetlight networks, both power carrier communication technology and rapid development of technology can be adopted, making short-range wireless communication technology superior to power carrier communication technology in terms of application cost, reliability and communication rate, for example. Zigbee short-range wireless communication technology. This paper proposes a solution to build a LED street light wireless sensor network using short-range wireless communication technology. It can control the switching, dimming, etc. of any single or multiple lamps in the LED street light network. , current parameters and other tests to achieve intelligent management of the LED street light network. As a wireless sensor network, its architecture should include four basic levels: the physical layer and the data link layer, the network layer, and the application layer. The LED street light wireless sensor network adopts the IEEE 802.15.4 standard as the technical standard of its physical layer and data link layer. The network layer is integrated with the application layer, and three relay communication modes of single-hop, double-hop and variable-hop are adopted as the network. The basis of the agreement. This paper focuses on the architecture of LED wireless sensor network, based on the network topology and the composition of communication nodes, discusses the protocol packet format of the network layer, the working principle of routing, and the design flow of node communication.

The network system of the LED wireless sensor network is the basis for the network layer to implement routing, including node composition and network topology.

The LED street light network consists of a number of street lamps with even spacing. Each LED street light is a communication node of the network used to construct a wireless sensor network. As shown in FIG. 1 , in order to construct a wireless sensor network LED street light node, in addition to the circuit of the illumination part, circuits for sampling the LED current, detecting the brightness of the LED light, and PWM control of the brightness of the LED light are added. Each LED street light is both a sensor node and a network routing node; each node contains a microcontroller (MCU, such as cc2530), which has RF communication function, which can both transmit signals and receive signals; each node has 32 bits (bits) The unique ID number of ). By adopting the IEEE 802.15.4 protocol standard at the physical layer and the MAC layer, and combining the protocols of the network layer and the application layer, all of these nodes are organically combined to form an LED street light wireless sensor network. Since some existing network layer and application layer protocols such as Zigbee and RF4CE are not well suited for LED street light sensor network applications, network layer and application layer protocols need to be redesigned.

Figure 1 The composition of the LED street light node

According to the distribution rule of LED street lamps, each LED street lamp forms a wireless communication network as a network node. Its topology is shown in Figure 2. (a) is a signal point-by-point (single-hop) relay transmission topology diagram, and (b) is a signal. The separation point (double hop) relay transmits the topology map. To facilitate the design and discussion of the following network application protocols, the following definitions are made:

(1) All nodes can be divided into two categories, namely LED street light nodes (referred to as LED nodes, such as a1 a2 ... an , b1 b2 ... bn) and street lamp controller nodes (referred to as control nodes, such as a, b);

(2) The distance between adjacent nodes is L, and the wireless signal coverage radius of each node is greater than or equal to 2L;

(3) According to the relative position of the node, the node can be divided into the predecessor node and the successor node, the predecessor node is close to the controller, and the successor node is far from the controller. For example, a1 is the a2 precursor node, a3 is the a2 successor node; the same b2 is the b4 precursor node, b6 is the b4 successor node, and so on.

Figure 2 Schematic diagram of network topology

(4) Between the control node and the LED node, the LED nodes can communicate with each other as long as the wireless signal can be covered, without the need for a base station or a dedicated route coordination device.

(5) The 32-bit unique ID number of each node consists of two parts, namely the network ID and the node address (number), both of which are 16 bits. The network IDs of all nodes in the same streetlight network are the same; starting from the control node, the node addresses are arranged in order from small to large.

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