PLC LED digital tube dynamic scanning data display -

PLC data revealed function has always been a problem in PLC application. In PLC application, often need to monitor some important data, but manifest the PLC data usually use external devices, such as the screen or touch screen, which show the price of the equipment is generally expensive, more waste for some small system. Therefore, how to manifest the PLC data, and as far as possible do high efficiency, high stability, strong anti-jamming capability, hardware, less investment, many problems need to consider in planning. The author used Siemens S7 - 200 PLC is controlled by the specific instructions IN the LED digital tube, SEGIN, OUT instruction is four bytes IN the input low active converted to determine the hexadecimal number that corresponds to the 7 segment LED digital tube paragraphs, code, and sent to the output bytes OUT side. If using static LED digital, PLC appeared a decimal data needs 7 dots to control, if you want to show n bits of data, the demand for 7 n dots. So, using this way to show the data of digits is large and needs a lot of dots, and the price of the PLC is based on the input and output points to calculate, this led directly to the hardware capital of rise, in view of this reason, looking for a cheap emerging technology is particularly necessary. Learn microcontroller LED digital tube dynamic scan revealed principle, combined with periodic sweep to catch the characteristics of PLC, PLC controller digital output directly drive the digital tube, PLC switch output can be divided into two parts, some are used for data output, the other part is used as the manipulation of the digital tube public end signal output. Using the afterglow effect of the human eye, circular light each digital tube, this method briefly and low capital operation.

1 planning completed

dynamic scanning is to use the features of PLC scan periodically, to do each cycle only when programming a digital tube can form the electric circuit, and electric light, because of a scan cycle time is too short, only a few tens of ms, so the human feeling every digital tube is uniform electric light, without trailing phenomenon together. 1 hardware program

planning method of the hardware circuit to complete is a starter button SB1 and a stop button SB2, two digital tube of a, b, c, d, e, f, g period of separation together, with the PLC output Q0 again. 0 ~。 7 after connect resistor, two public digital tube end com1 or com2 separation after the output of the transistor by PLC Q1. 0 and Q1. 1, the wiring principle is shown in figure 1.

by PLC output end Q1. 0 and Q1. The bump 1 level of working condition of the control in a switch triode, digital tube to com1 or com2 end circulation and M conduction output PLC public end, to select different digital tube, by PLC output Q0. 0 ~。 7 output corresponding data and based on common signals make corresponding digital tube a, b, c, d, e, f, g. Through software programming can be done with a set of start-stop button manipulation of the two groups of digital tube show the corresponding data. 2 planning software

after two software programming example of complete different function on the same hardware circuit design software to complete. Software programming example 1

this program to complete the 0 ~ 99 s repeatedly counting function, press the SB1 start counting, bearing in counting the pause button SB2 make count, press the start button again from the beginning start from 0, counting from the beginning start from 0 to 99. The program ladder diagram as shown in figure 2.

the above software for special storage SM0. 1 s happened 5 clock pulse counting, using the data of PLC, transfer, transform the function of transmission, processing, change of count data, then use period of decoding SEG command driven seven segment digital tube, made up of two timer cycle is 200 ms, separation shows reverse phase clock pulse to manipulate each other change of count data. Planning software example 2

this program complete 50 s countdown function, press SB1 starting time, press the SB2 suspend time, digital tube out together, and then press the start button from the 50 s the countdown, timing to 0 s, digital tube be extinguished. 2 conclusion

planning is mainly a double-digit can be divided into two groups of data separation appeared in 10 and bits digital tube, program USES the loop control method, then a scan cycle appeared a group of data, the two groups of data cycle. Assume that the program scan cycle for 100 ms, timer timer 100 ms, then each set of data update cycle is 100 * 2 = 200 ms, appeared such frequency enough to meet general industrial control requirements, can be used as a real-time show thoroughly. Appeared in the same way, if multiple sets of data, the data line connection is the same, only need to increase the control signal output points of PLC, digital tube common PLC output points of 7 + n, n number of digital tube; Software can be changed slightly. In this paper, the way of planning software and hardware debugging success in the laboratory, completely meet the requirements of planning, and reduces the hardware capital, has achieved good effect.

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