Stepper motor driven micro-infusion instrument of a new way

1, introduction

Stepper motor is a digital signal directly into angular displacement or linear displacement control-driven components, quick-start and stop.

Its mechanical displacement and speed are the number of input pulses and pulse frequency is proportional. Stepper motor in industrial production and life aspects of the application is very wide, and microprocessor control stepper motor has the function of flexible, accurate, real-time pulse output is stronger, and the system is less expensive.

Existing small stepping motor driver circuit, the basic use of OC door drive and push-pull driver transistor.

OC gate circuits driven motor weakness is driving current enough, responding slowly, but the best work in OC door + 5V voltage, low voltage conditions, job insecurity. Transistor push-pull drive stepper motor weakness is NPN and PNP transistor's choice. Two transistors of the pn junction switch point to the same, otherwise the transistor will be breakdown, no security risk.

This article for a traditional small stepping motor drivers exist for these issues, combined with a miniature infusion equipment of motor drive device design, proposing a new scheme the stepper motor driven.

This programme uses the MSP430 microcontroller, through its control software running on MAX4685 high-speed analog switch output to enable stepping motor control.

This low-cost, high stability, high-performance drive way, suitable for low voltage, high current, high response frequency comparisons.

2, micro-infusion equipment of motor-driven programmes

Development of this micro-infusion apparatus consists of three parts: the infusion fluid containers, a small battery-powered pump, for accurate control pump infusion dose of computer chips.

The above parts packaging, form a size like a pager of infusion equipment, pump container control by entering the instruction by the thin plastic infusion liquid.

The equipment of the motor-driven devices, including directive Input Panel and driver circuit, stepper motor control board.

Driver circuit control panels with integrated circuit MAX4685; its driver control panel output connection Mini Stepper Motors of the input. The micro-infusion equipment of motor drive block diagram shown in Figure 1.

Figure 1 motor block diagram Input Panel is by pressing the set parameters, run by microcontroller intelligent software control MCU IO port output.

SCM IO port connected to the input of IC MAX4685. Integrated circuits for high-speed analog switch MAX4685, entered as square wave pulse, control MAX4685 analog switch action so that the output pulse MAX4685 square wave. This can provide 500mA MAX4685 pulse current of. MAX4685 chip for dual analog switch, the switch is closed with 0.8 ω resistor (2.7V work), 1.8V to 5.5V voltage range. The response speed of up to 1MHz, driving currents up to 500mA. MAX4685 specific parameters are as follows:

NC-closed resistance up to 0.8 Ω (working voltage 2.7V); NO-end closed resistance up to 0.8 Ω (working voltage 2.7V); two channel matching resistance up to 0.06 Ω; work voltage range 1.8V-5.5V; trap-bit voltage 1.8V, maximum input signal voltage 5.5V.

This instance is driven two-phase DC stepping motor.

Use of single-chip models for MSP430F149. This type of microcontroller with FLASH function of ultra-low power 16-bit microcontroller, the working voltage of 1.8V-3.6V. Use keys to select a menu feature, set the parameters. Through the intelligent software control MCU P50, P51, P52, P55 4 IO port output drive stepper motor with pulse waveform, the control switch MAX4685. Use the output for driving MAX4685 stepper motor current is required. Motor speed depends on the output pulse waveform frequency control. Motor rotation driven syringe infusion.

Specific connection as shown in Figure 2.

Figure 2-chip, MAX4685, stepping motor connection diagram

This design with microprocessor control of switches, use MAX4685 MAX4685 output provides a stepping motor pulse waveform, ensures stable output voltage waveform, driving current large, interfering with small.

Achieve low-cost, high stability, response speed, low-voltage micro-motors. OC door and triode push-pull driver not easily integrated.

3, motor-driven program design and implementation of specific

Close the instance of the motor-driven part of the connection between the input status such as MAX4685 table 1.

Table 1 MAX4685 input status table

This article uses MSP430F149 microcontroller MAX4685 analog switch action, to achieve control of stepper motor.

MSP430F149 MCU P50, P51 IO ports via MAX4685 drivers, connect to the phase of A stepping motor; P52, P55 IO port via drivers, connect to the phase B stepping motor. Stepping Motor rotation mode to full step mode, the selection of a two-phase, every ring 20 step by step motor. Each step of angle of 18 degrees. Each ring rotation accuracy of ± 10 degrees.

Stepper motors of the phase of the input signal and turn the relationship shown in Figure 3.

Phase A and phase to signal if B plus 1-4, counterclockwise, from 4-1 to Rotate clockwise.

Figure 3 phase stepper motor

Input signal and the rotation of the relationship

Use MSP430F149 IO output output signal, control of movements, produce MAX4685 phase A and B the desired signal.

As shown in table 2. The signals listed in the table for motor rotation every step of the desired signal. Motor rotation through transmission device, push the syringe filling.

Table 2-chip IO port output signal and rotation of relational tables

The micro-infusion instrument motor driver specific processes, as shown in Figure 4, including several key steps:

(1) single-chip related IO port definition P5.0 P5.1 P5.2 P5.3 P5.4 P5.5 P5.6 P5.7 A B C D Data Vdd

(2) motor related timer timer initialization TBCCR0 = IntTime; //Primary timer total time TBCCR1 = IntTime1; //Timer 1 motor to electricity, high level time TBCCR2 = IntTime2; //Timer 2 electric outage, low level time

(3) start motor related timer TBCCTL1 = 0x10; //Open the timer 1 TBCCTL2 = 0x10; //Open the timer 0x0114 TBCTL = 2; //Open the primary timer

(4) off motor related timer TBCCTL0 = 0x00;

TBCCTL1 = 0x00; TBCCTL2 = 0x00;

(5) interrupt handler function interrupt [TIMERB1_VECTOR] void Timer_B1 (void) depending on the timer interrupt vector value adjustment motor TBIV walk direction, or the motor to the appropriate location.

Figure 4-motor-driven flow chart

4. conclusions

This design change of existing OC door driving and triode push-pull driver mode, using a high-speed analog switch MAX4685 directly driven mini stepper motor.

This driver programme response speed can reach 1MHz, driving current up to 500mA, can be designed as a low-cost, high stability, high response speed of motor driver circuit, direct drive small stepper motors. At the same time has the principle is simple, easy-to-implement features.

Reference documents

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MSP430 series FLASH type ultra-low power 16-bit microprocessor [M]. Beijing: Beijing University Press, 2002, 3. [2] huda can. MSP430 series MCU C language programming and development [M]. Beijing: Beijing University Press, 2003, 1. [3] Chen longchang. Control of the motor (third edition) [M]. Xi'an: Xidian University Press, 2000. [4] Sun sensitivity, often more. MSP430 stepper motor driven based displacement detection system [J]. Electric drive, 2003 (5): 31-33. [5] Zhang Peng Tao, Xiao Shi de, Wong springs. MSP430 microcontroller based stepper motor control system design [J]. Electromechanical engineering technology, 2005 (11): 36-37. [6] guowei, Cui group. Single stepping motor control system design [J]. Journal of Anhui University, 2006 (3): 59-62. [7] Wei yan wave, Wang Wei guilian, long day's journey. Single stepping motor control system [J]. Explosion-proof motor, 2005 (4): 25-26. [8] Meng Wusheng, Li Liang. AT89C52 MCU based stepper motor control system design [J]. Micro motor, 2007 (3): 64-66. [9] Sun Xiang countries. Based on the arm of the stepping motor control system design [J]. Electromechanical engineering technology, 2007 (6): 71-73.