2020.01.18
Summary:The weighing and batching system uses the low-cost ARM processor stm32f051 as the core controller, uses a TFT touch screen to design the human-machine control interface, sdio for information storage, and monitors the size of the liquid batching by calculating the generated pulse frequency.
1 Overview
Currently there is a need in industry for dynamic dosing and metering of highly viscous liquids such as chemical raw materials, edible oils, additives, etc. Especially when dosing in the workshop there is a need to dynamically track the raw material preparation status as well as the temperature of the medium being measured. The feeding system calculates the amount of compensating medium according to the demand for materials and the rapid conversion of temperature data. And can be calculated in real time out of the amount of material, daily cumulative, total cumulative amount of data, convenient for production management and cost statistics. Can make the calculated quality of the media to avoid the impact of temperature changes, to ensure the accuracy of the dosage, to eliminate manual dosage of errors and dripping and other phenomena, simple and fast operation, than manual operation to save time and effort, improve efficiency, effectively reduce production costs, the whole operation is more clean and hygienic, so that the production environment is more standardized.
2 overall program design
Automatic dosage system using arm as the core processor, temperature measurement platinum resistance temperature information acquisition, design of weighing and dosage system monitoring circuit Hall dosage meter information acquisition, and finally according to the demand for materials combined with temperature information to control the solenoid valve on and off.
Feeding system meter based on Hall weighing module metal sensor design, through the calculation of the pulse frequency generated to monitor the size of the system. Platinum resistors are commonly used in industry for temperature detection and measurement modules, but there is a relatively obvious nonlinearity between its temperature and resistance value, and its sensitivity becomes smaller as the temperature rises. The design adopts the use of the conversion characteristics of the A/D converter to realize the nonlinear correction of platinum resistance.
The solenoid valve is a direct-acting solenoid valve, with the center of the valve as the closing member and the solenoid coils at both ends. When energized, the solenoid coil generates electromagnetic force to lift the closing member from the valve seat, the valve opens; when the power is off, the electromagnetic force disappears, and the spring presses the closing member on the valve seat, and the valve closes, this control method is relatively simple and reliable, and it is easy for the processor to control multiple valves.
Overall automatic dosage system junction measured temperature for the liquid raw material temperature, through the Hall system to monitor the liquid, after the collection of dosage information and temperature information into the ARM chip for processing, real-time calculation of the amount of material, daily cumulative total cumulative amount of data and so on, and stored in the sd card, according to set the temperature requirements for the conversion of the temperature change on the amount of the media, and according to the dosage amount of the requirements of the integrated control of the individual to the amount of solenoid valves on and off. According to the requirement of dosage quantity, it can control the on and off of the solenoid valve of each dosage port. Weighing instrument through the touch screen TFT display real-time temperature status, and used to set the relevant control parameters.
3 automatic feeding system hardware design
3.1 Core processor selection
The measurement of the dosage system in the core processor selection, in order to meet the design requirements, choose the best cost-effective processor to realize the whole dosage machine core control. stm32f051 series arm is based on armcortexm0 kernel launched the high-performance real-time processor. The kernel has a 32-bit compact instruction set, and can run at a maximum frequency of 48MHZ. The chip has a maximum of 64K bytes Flash, 8K bytes of sram, and has a 12-bit ADC converter, 16-bit timer, SPI communication interface, and up to 55 high-speed I/O ports, is very suitable for this dosage system.
The system power supply is supplied through 24V, which is divided into two channels, one channel outputs the solenoid valve power supply. A way to step down, through the LM2596T and asm1117 respectively, step down to 5v and 3,3v, of which 5v through the hall module, 3.3v to the main control arm power supply. 8M crystal is provided to the main chip as a clock crystal, at the same time due to the use of the internal rtc, while connected to the low-speed 32.768khz crystal.
3.2 Temperature detection part of the design
The monitoring of the liquid temperature using temperature measurement platinum resistance to achieve, the program can be used for high temperature temperature monitoring, but when the temperature range is larger, the platinum resistance to detect the temperature of the nonlinearity of the stronger, so in order to reduce the nonlinear in high temperature conditions on the detection of the accuracy of the impact of the dynamic feedback to adjust the excitation current through the temperature measurement of the platinum resistance, so as to achieve the nonlinear compensation of the voltage output.
