LED lighting has been in the field of landscape lighting for more than ten years, and its control technology has also developed several stages. At each stage, many problems have been solved, and at the same time, new problems have been brought up. The following is a further discussion on the development of LED control technology.
The first stage, the way LED display drive control mode is transferred
A serial shift communication method using a similar chip such as 74HC595, DM115, MBI5026, etc., each chip is cascaded, and each of the lamps is cascaded. There are both constant voltage driving methods and constant current driving methods. The problem caused by this communication method is that there are too many signal lines on the luminaire, reaching 4 or 5 (including ground), which not only increases the time and material cost of the company's production, debugging, but also increases the time cost and material cost of the engineering installation. At the same time, the failure rate is increased. The biggest problem is that the chip or signal is damaged at the front end of a string of lamps, and the back end is also affected. Of course, its advantages are also indelible. The HC595 is inexpensive, the chip is mature, the lighting and programming are easy, and there are many controllers on the market.
The second phase, the RS485 bus form of the DMX512 protocol
RS485 chip plus MCU (MCU) is used to form a RS485 parallel system with 512 effective points on the bus. Each lamp is numbered by address to receive different data respectively, achieving the purpose of dimming and color adjustment. Compared with the first stage, the method reduces the number of signal lines, basically eliminates the phenomenon that a certain lamp failure affects the subsequent lamps, the signal transmission distance is relatively long, and the distance between the lamp and the lamp is not several meters, tens of meters limit. However, this method also brings other negative problems. Firstly, the cost of the DMX decoder is high. When it is outsourced, it is not only a little higher. It requires a good design engineer to do it yourself. Then each lamp is numbered, and the number is not automatically numbered. Signal lines, and sometimes it is difficult to find problems when a decoder has a problem affecting the bus. Then there is a limited number of lights per main controller, which increases the hardware cost of the entire system. These negative problems are also the reasons for the large-scale use of the DMX512 system, which can only be used in some high-end projects.
Third stage, single line communication
A large number of 3-port, 6-port driver chips make LED luminaire design easier
Single-line chips are represented by ZQ1111, TLS3001, TM1803, SDMX5124, etc. They are serially cascaded between the chip and the chip through a single signal line. The I/O output ports of each chip can automatically perform PWM scanning, so the signal line The communication rate can be greatly reduced, and the HC245 can be omitted in the case where the distance between the chip and the chip is less than 2 meters. This type of chip can meet the high gray level (256 levels) data transmission and increase the number of series lamps. At present, it is widely used in point light sources and light strings (strips). Because of the need for segmentation, the guardrail tube uses more chips, and the first stage of the chip is mature and stable, and a step-by-step replacement requires a process. The innovative advantages of this stage are obvious. Only three output ports are designed for the point source and the light string (strip), and the PWM output is provided inside, which greatly improves the data transmission efficiency, greatly reduces the data transmission speed, and improves the reliability. The amplification of the components has increased the number of cascades, and the flexibility of the luminaire design has been greatly improved. However, the shortcomings of the United States also exist. First of all, most of the chips have just been listed, stability is still a generation of consideration and improvement, a slightly stable price is expensive, single-lamp requires multi-chip application is limited. Secondly, the data is transmitted in cascade mode. The front-end chip or signal failure affects the chip and signal behind. Again, there are not many controllers supported on the market, and customer choice is still limited.
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