Foreword: The cement mixing plant adopts the programmable logic controller Ikondrives well T series PLC and weighing module H01WG, which realizes automatic, cutting, unloading and mixing. The automation of the equipment helps to improve the management level and concrete system. comprehensive scheduling capabilities, reducing costs and improving efficiency. Input the corresponding proportion of water and cement according to the demand, and achieve precise and control on the output and cement mixing.
1. The control requirements are as follows
Now the PLC is required to control two motors, one air compressor, and multiple relays to realize the start, stop, forward and reverse actions of the equipment; according to the formula cement and water set on the HMI, weigh and feed materials, and after unloading, after stirring Concrete is being delivered.
Figure 1 Field equipment diagram
2. Hardware configuration
T16S0R: 8DI 8DO relay output PLC, with two communication ports, supports 2 channels of 200K high-speed input, and can be expanded to 7 modules.
H01WG: One weighing module, 24-bit AD, supports multi-segment calibration, and supports single-channel multi-sensor applications.
The system needs two motors for feeding and stirring, and two weighing modules on the parallel port can realize high-speed communication with two H01WGs, read weight and realize tare. Output the action requirements of feeding and feeding of the connected motor control system. Therefore, choosing one T16S0R host and two H01WG modules can easily achieve the above functional requirements, improve efficiency and save costs.
Figure 2 Equipment electrical cabinet
3. Introduction to some functional programs on site
3.1 School name
H01WG calibration supports 3-segment calibration, the operation steps are as follows:
① When no heavy objects are placed on the weighing platform, write 1 to CR26H (decimal 38) of the weighing module;
② Put down the standard weight, and write the current weight value to CR27H (decimal 39) of the weighing module. If multi-stage calibration is not required, go to step 5;
③ If the second stage calibration is required, add another standard weight to the weighing unit, and write the current chassis weight into CR28H (decimal 40), if not, go to the fifth step;
④ If the 3rd stage calibration is required, add another standard weight to the weighing unit, and write the current chassis weight into CR29H (decimal 41), if not, go to step 5;
⑤ Write a value of 2 to CR26H to end the calibration process.
Figure 3 Calibration program diagram
3.2 Reading Weight
① The weight read by the module is divided into average weight and real-time weight. The CR of the average weight is 10H (decimal 16), and the real-time weight is 12H (decimal 18).
Figure 4 Read Weight Program
3.3 Peeling function
① Write 2 to the CR of the weighing module as 1AH (decimal 26) to display the net weight, and to 1AH of the weighing module
Write 0 to show gross weight
Figure 5 Gross/Net Weight Display Program
When the weighing platform or equipment causes dust or residual material to be scattered during the weighing process, causing the platform to not place any weighing items, the current weight is not zero, and the automatic tare function can be used at this time. , as long as the current weight is less than the set automatic tare weight value, the weighing module will automatically tare the current value:
3.4 Automatic peeling
① Write the weight value of automatic tare to the CR of the weighing module as 2AH (decimal 42) (judgment every 5S)
Figure 6 Automatic tare program
Of course, the stability and responsivity adjustment of the weight read by the module will have different requirements according to the actual application, and these two factors are affected by the sampling frequency (CR 1BH), the average number of times (CR 1EH) and the filter ratio (CR 1FH). Therefore, you only need to adjust the above three parameters to realize the adjustment of stability and responsiveness; there is also a special CR 9FH to restore the factory settings, you only need to write 0 in 9FH to restore the factory settings.
1. After calibration, the real-time value will occasionally jump. After checking the user manual of the module, increasing the filter ratio and reducing the sampling frequency can improve the stability of the read value. Here, increase the filter ratio and reduce the sampling frequency, and read Change the value to the average value, and the read value has no beating; after that, there is a problem in the on-site debugging, the value read before is normal, but the value cannot be read after a while, first test whether the module is normal, then test After the module is normal, remove external factors and find that the signal line of the external sensor is pressed, the gravity is pulled up, and the contact is poor. After dealing with the problem of disconnection, the read value is normal and the module works normally. The effects of downsampling frequency, average times and filter ratio on stability and responsivity are also introduced here:
① The faster the sampling times, the faster the average value is calculated, so the average value and real-time weight of the weighing are updated faster. However, the stability will decrease as the sampling times increase.
② The larger the filter ratio, the more stable the average weight value is, but the delay will increase and the sensitivity will decrease. The function of filtering is to filter out the sharply changing abrupt value, so that the obtained filtered average value will not be affected by the sharply changing abrupt value.
③ The more average times, the more accurate the average weight value, but the slower the update speed.
2. In terms of programs, as long as two simple FROM and TO instructions can be used to read and write the module, plus the rich CR number resources that come with the module itself, complex weighing requirements can be controlled, and The programming software is simple to operate and easy to use.
3. After the on-site use and operation, its stability is very high, and the calculation processing speed is fast. Accurately completes the control action requirements of the equipment, and has been highly recognized by users.