Control Design Of The Liquid Feeding System In The Portable Drop Analyzer

In the past of the droplet analyzer, the design of Liquid Feeding System, generally has a big volume, manipulation of the complex, and isn’t easy to carry. In order to solve the problem of inconvenience for integration and operation complexity, the micro-flow fluid supply system based on STC12series MCU is presented and implemented. STC12has many advantages such as ultra-low power consumption, rich chip designs, high performance cost ratio, high speed, etc. In this system, including hardware design and software design.In part of hardware design, mainly including control circuit design and mechanical structure design of liquid feeding system. In the part of hardware circuit control, by selecting the stepper motor and TC8640micro-stepping driver, designed MCU control circuit, stepper motor drive circuit, LM7805voltage conversion circuit, keyboard control circuit, and unify the various circuits together to build the circuit system, realize the function of the hardware circuit to control the motor. In addition to the hardware part of the circuit, the mechanical structure of feed liquid system is designed, it make the Liquid Feeding System to form a complete entity. After measurements and calculations, the use of aluminum panel as a raw material of mechanical structure. Mechanical structure consists of a base, motor fixtures, fixtures syringe components. After using CAD software for the mapping and processing, assembly and commissioning all components, and finishing the work of mechanical design parts.In part of software design.The software program is written by Keil to manage the feeding process of the start-stop, rotation direction, acceleration and deceleration of the motor. Both the flow rate and the flow flux can be controlled precisely and flexibly, so as to ensure that the test liquid is slowly delivered under quasi-equilibrium condition to shape into a satiated and uniform drop.Control design of the micro-flow liquid feeding system in the droplet analyzer in this article has completed processing production, assembly and system debugging, and has been proved in the experiments. When the motor’s speed is slow, it can meet the requirements of feed liquid by this control system:The growth process of the drop is smooth, uniform micro, low velocity and speed-controlled. Serial communication in this system employs the USB to TTL level serial port connecting to the control chip to simplify the serial communication circuit. When serial port connects to PC, the control program can be downloaded to the microcontroller, so as to realize the control of the entire system. And the stepping motor subdivision driver TC8640this paper selected has small volume and powerful segment. It is not only effectively solves the mutual conversion for feed liquid and drain liquid by controlling the motor reversing, but also better solves the shortage of low frequency oscillation and high frequency output of the motor by controlling acceleration and deceleration. In addition, the system not only can be used in the droplet analyzer for fluid system, also can be used in the aspect such as drug testing which needs the micro for fluid. This system has small volume, low cost, and it is operated easily. So it is the efficient solution for control design of the micro-flow liquid feeding system.