Nowadays, more and more machines are controlled by PLC. Using PLC control can simplify the circuit and make the design more simple, safe and reliable. Some advanced PLCs have a variety of interfaces to achieve connected machines, Internet access and other functions. Enables people to remotely control the device. So, how can we design a PLC controlled machine? Based on my own experience, we must at least understand the following aspects of knowledge:
1 Know the working principle of PLC
PLC is also referred to as PLC for short. It is similar to relay system. PLC is also composed of input part, logic part and output part. The input part collects and saves the actual running data of the controlled part, and the logic part processes the information obtained by the input part. And judge those functions need to make output response. The output section provides many devices that are being controlled and which devices require real-time operation processing. PLC uses a large-scale integrated circuit microprocessor and memory to form a logical part. Although the function of the logic part is similar to that of the relay control system, its composition, working principle, and operation mode are totally different from those of the former. Through programming, its control program can be flexibly changed, which is equivalent to changing the hard wiring of the relay. This is called “programmableâ€.
2 master the PLC language and instructions
Knowing the working principle of PLC, understanding its language is easier. PLC language is the most common ladder and statement table two. The ladder diagram is the most intuitive and easy to use. To understand in detail the relevant textbooks, it should be emphasized that, although the principle is the same, the basic instructions are similar, but the manufacturer's different PLC instruction symbols will be different, for example, the same as the rising edge differential, Mitsubishi's products with PLS, Omron The company is called DIFU, and Siemens is │P│. These specific differences will depend on the programming manual for various products.
3 Learn to use a variety of programming software
After a program is programmed, it should be input into the PLC. In the past, a lot of hand-held programmers were used. To manually input, it is troublesome and error-prone. In recent years, with the popularity of computers, it has gradually been replaced by various programming software. For example, Yonghong's WinProladder editing software, Ohm's CX-PROGRAMMER. Siemens STEP-7-MICRO-WIN32 and so on. These tools can run in WINDOWS environment, it is very convenient to use, when you choose a factory PLC, be sure to learn to use its programming software, because it will greatly save your programming and debugging time. Take Yonghong's WinProladder editor software as an example. It can provide you with an input range for operands and quickly search for special instructions. According to the ladder diagram, the statement table is automatically generated, and the syntax error is pointed out. In the debugging, it passes the data line to the PLC quickly and accurately, and then monitors the execution status. It can forcibly set/reset the input/output points. You can also edit online. In short, when you are proficient in the use of programming software. The design task that must be done with half the effort.
4 understand that PLC control signals have those
The PLC controls the output signal according to the input conditions. The input signals are the buttons on the console, limit switches on the machine, pressure relays and photoelectric switches, and the output points control the on/off of the relays or contactor coils, the light of the indicator light, the solenoid of the hydraulic valve. Pull-in and output of the signal terminal of the inverter. When designing a machine tool, we often encounter two problems. One is that the PLC expandable I/O points are limited, and the other is to increase the I/O points to increase the cost. So we need to know what the control signals are, how many are each, and how many input and output points are needed.
LCD Display Module
High resolution
In order to realize a large-area high-resolution Liquid Crystal Display, it is usually necessary to use low-impedance metal materials, high-performance switching elements, and high-precision processing techniques. Aluminum is the most researched and used material for making TFT buses with low-impedance metals. By solving the problems of easy formation of hillocks, chemical corrosion and oxidation of aluminum, alloy methods (such as Al-Cu, Al-Si, Al-Nd and Al-Ti, etc.) and interlayer methods (such as Mo/Al/Mo) have been reported successively. , Cr/Al/Cr and Ti/Al/Ti, etc.), the alloy method is relatively simple in process, but the material has a higher resistivity. In May 1998, IBM developed a 16.3-inch ultra-high resolution (200ppi) a-Si TFT Display using Al-Nd alloy as the gate electrode, and mass production has been achieved. In April 1999, Toshiba introduced the 20.8-inch 16-SVGA (3, 200 × 2, 400) a-Si TFT-LCD, which can be said to represent the highest level of a-Si TFT-LCD in terms of high resolution and high capacity. .
According to Display Search in the third quarter of 2011, the global flat panel display research report "QuarterlyWorldw ide Flat Pane l Dis play Fore cas t Re port" pointed out that the average pixels per inch (ppi) in large-size LCD panels (>9.1 inches) ) Will grow from 88ppi in 2010 to 98ppi in 2015. The ppi of small and medium-sized LCD panels (<9.0 inches) will grow from 180ppi to 300ppi in the same period. With the rise of smart phones, mobile phones will be the most obvious application product for ppi's growth.
Another important way to realize high-resolution liquid crystal display is to develop LT p-Si TFT technology. The resolution of published p-SiTFT-LCD products is generally around 200ppi. Compared with a-Si TFT-LCD, LT p-Si TFT-LCD has a smaller volume of thin film transistors and storage capacitors. Therefore, it has a larger penetration area per inch, resulting in a brighter display. , And save more power. When the market demands higher ppi, low-temperature polysilicon (LTPS) technology becomes the best choice for manufacturing high-resolution thin-film transistor liquid crystal displays.
Contrast
The control ICs, filters and oriented films used in LCD manufacturing are related to the contrast of the panel. For general users, a contrast ratio of 350:1 is sufficient, but such contrast in the professional field does not satisfy users. Demand. Compared with CRT monitors easily reaching 500:1 or even higher contrast, only high-end LCD monitors can achieve this level. The first-tier LCD monitors on the market, such as Samsung, Asus, LG, etc., can reach a contrast ratio of 1000:1. However, because the contrast is difficult to accurately measure with instruments, you have to go and see it yourself when you pick it.
Tip: Contrast is very important. It can be said that the selection of LCD is a more important indicator than bright spots. When you understand that your customers buy LCDs for entertainment and watching DVDs, you can emphasize that contrast is more important than no dead pixels. We When watching streaming media, the brightness of the source is generally not large, but to see the contrast of light and dark in the scene of the character, the texture change from gray to black hair must be shown by the level of contrast. The 256-level grayscale in the test software In the test, more small gray grids can be seen clearly when looking up, which means that the contrast is better!a
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