Read 1168-datasheet.docx text version

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Document: Datasheet

Date: 6-Jul-12

Model #: 1168

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Stepper Motor Driver - Bipolar

This stepper motor driver offers a compact, reliable stepper motor control system. An integrated chopper drive circuit safely provides the maximum motor torque for a given drive voltage, even one many times over the manufacture-specified voltage, offering tremendous torque and speed improvements over traditional stepper motor control circuits. Maximum coil current(2A) is easily set using a potentiometer, and can be dynamically adjusted. The highly efficient design of the drive circuitry makes it the ideal motor control solution for nearly any application.

Motor current for each phase is set using an on-board potentiometer and the controller is capable of handling motor winding currents of up to 2 Amps per phase. It operates from a DC supply voltage of 9-24V. The drive provides all basic motor controls, including full or half stepping of bipolar steppers and direction control. All signals (Step, Direction, Enable) can be interfaced to external logic or a microcontroller. You can easily control the motor from your computer's parallel port or microcontroller. Stepper motors are rated by current and not by voltage. This is a chopper driver because it is switching on and off current allows a set current to be fed to the coils and not be dependent on the voltage of the power supply. The Chopper Driver also allows for the use of higher voltage power supplies (up to 24V) overcoming the effects of the inductance of the coils giving better performance and a higher top speed. Full & half stepping, directional control, motor enable/disable, and automatic current regulation provide a powerful, easy-to-use motion control system. The built-in chopper frequency generation and current sensing circuitry drives the motor at a presettable coil current. This controller is perfect for desktop CNC applications.

Features

· · · · · · · · · Easily adjustable motor current (0.3A to 2A) Full and Half stepping mode selection Step and Direction inputs directly from parallel port or microcontroller Enable input can be connected to ground to disable motor (Optional Input) Connections via screw terminals Develops maximum possible motor torque by using dual coil-current sensing & control loop circuits Allows use of drive voltage beyond rated motor specification for enhanced torque & speed Diodes and large filter capacitors for enhanced noise suppression Primary drive circuit thermal overload protection

Initial Setup

The Stepper Motor Driver can be used with a power supply up to 24V. Connect the power supply negative wire to a GND terminal and positive wire to the 9-24V terminal. The bipolar stepper motor is connected to the A, /A, B and /B terminals. The stepper motor will have two separate phase windings and optionally a center tap wire. The center tap wire should be left unconnected. The wiring phase of motor can be identified with multimeter and measuring resistance of motor windings. From the two phase 1st phase has to be connected to A and /A terminal and 2nd phase of motor has to be connected to B and /B terminals. If incorrect wires are connected, motor will not rotate properly. More about motor connections are on following pages. Control signals are connected to the STEP and DIR terminals. Connect a GND terminal to the GND terminal of the source of the signals as well. The EN terminal is pulled high internally, when a connection is made to ground through this terminal current is removed from the motors coils, allowing it to turn freely. This can be used as a kill switch input. This is optional input can be left unconnected making it always enable. STEPPER MOTOR

PC Parallel Port/MCU

9 to 24V DC Power Supply +

+5V out for other circuits if required

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Setting the Bipolar Stepper Current

The current that will be passed through the motors coils is set using the preset VREF and Multi-meter. The voltage in volts at the test point labeled TP VREF will be half the current in the motors coils in amps. That means 1V will give 2A, 0.5V will give 1A and so on. For a given motor, higher driver current will make the motor to output more torque, but at the same time causes more heating in the motor and driver. Therefore, output current is generally set to be such that the motor will not overheat for long time operation. Since parallel and serial connections of motor coils will significantly change resulting inductance and resistance, it is therefore important to set driver output current depending on motor phase current, motor leads and connection methods. Phase current rating supplied by motor manufacturer is important in selecting driver current, however the selection also depends on leads and connections which is covered in later pages.

Full and Half Stepping

When the jumper labeled STEP is in the F position the motor will move one step for each pulse on the STEP input if the jumper is set to H the motor will move half a step for each pulse on the STEP input. This jumper should be set before power is applied to the circuit. Half step produces a much smoother performance and less motor resonance.

Motor Connections

The driver can drive any 2-phase and 4-phase hybrid stepping motors. Connections to 4-lead Motors 4 lead motors are the least flexible but easiest to wire. Speed and torque will depend on winding inductance. In setting the driver output current, multiply the specified phase current by 1.4 to determine the peak output current.

F IGURE 1 S TEPPER M OTOR - 4 L EAD

Connections to 6-lead Motors Like 8 lead stepping motors, 6 lead motors have two configurations available for high speed or high torque operation. The higher speed configuration, or half coil, is so described because it uses one half of the motor's inductor windings. The higher torque configuration, or full coil, uses the full windings of the phases. Half Coil Configurations - Higher Speed Low Torque As previously stated, the half coil configuration uses 50% of the motor phase windings. This gives lower inductance, hence, lower torque output. Like the parallel connection of 8 lead motor, the torque output will be more stable at higher speeds. This configuration is also referred

F IGURE 2 S TEPPER M OTOR 6 L EAD H ALF C OIL

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to as half chopper. In setting the driver output current multiply the specified per phase current rating by 1.4 to determine the peak output current. Full Coil Configurations ­ Higher Torque Lower Speed The full coil configuration on a six lead motor should be used in applications where higher torque at lower speeds is desired. This configuration is also referred to as full copper. In full coil mode, the motors should be run at only 70% of their rated current to prevent overheating.

F IGURE 3 S TEPPER M OTOR 6 L EAD F ULL C OIL

Connections to 8-lead Motors 8 lead motors offer a high degree of flexibility to the system designer in that they may be connected in series or parallel, thus satisfying a wide range of applications. Series Connections ­ Higher Torque Low Speed A series motor configuration would typically be used in applications where a higher torque at lower speeds is required. Because this configuration has the most inductance, the performance will start to degrade at higher speeds. In series mode, the motors should also be run at only 70% of their rated current to prevent overheating.

F IGURE 4 S TEPPER M OTOR 8 L EAD F ULL C OIL

Parallel Connections Low Torque at Low Speed/High Torque at High Speed An 8 lead motor in a parallel configuration offers a more stable, but lower torque at lower speeds. But because of the lower inductance, there will be higher torque at higher speeds. Multiply the per phase current rating by 1.96, or the bipolar current rating by 1.4, to determine the peak output current.

F IGURE 5 S TEPPER P ARALLEL C OIL

M OTOR

8

L EAD

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Heat

The Stepper Motor Driver is provided with a Heatsink. Care should be taken when using the driver to ensure that the driver IC on heatsink does not overheat. When the driver is first used monitor the temperature of the heatsink. If it begins to get too hot to touch a fan or larger heatsink will be required. This is quite important if the motor is turning slowly or is stopped for long periods.

Noise

The switching of currents to the motor can radiate electromagnetic interference. To reduce radiated noise the motor leads should be shielded and as short as possible. The motor body should be grounded and a grounded metal housing for the PCB can be used.

Power Supply Selection

The stepper driver can match medium and small size stepping motors (from NEMA frame size 17 to 43) from motor manufactures around the world. To achieve good driving performances, it is important to select supply voltage and output current properly. Generally speaking, supply voltage determines the high speed performance of the motor, while output current determines the output torque of the driven motor (particularly at lower speed). Higher supply voltage will allow higher motor speed to be achieved, at the price of more noise and heating. If the motion speed requirement is low, it's better to use lower supply voltage to decrease noise, heating and improve reliability. Regulated or Unregulated Power Supply Both regulated and unregulated power supplies can be used to supply the driver. However, unregulated power supplies are preferred due to their ability to withstand current surge. If regulated power supplies (such as most switching supplies.) are indeed used, it is important to have large current output rating to avoid problems like current clamp, for example using 3A supply for 2A motor-driver operation. On the other hand, if unregulated supply is used, one may use a power supply of lower current rating than that of motor (typically 50% 70% of motor current). The reason is that the driver draws current from the power supply capacitor of the unregulated supply only during the ON duration of the PWM cycle, but not during the OFF duration. Therefore, the average current withdrawn from power supply is considerably less than motor current. For example, two 2A motors can be well supplied by one power supply of 3A rating. Multiple Drivers It is recommended to have multiple drivers to share one power supply to reduce cost, if the supply has enough capacity. To avoid cross interference, DO NOT daisy-chain the power supply input pins of the drivers. (Instead, please connect them to power supply separately.) Selecting Supply Voltage The motor driver IC can actually operate within +9 ~ +30VDC, including power input fluctuation and back EMF voltage generated by motor coils during motor shaft deceleration. Higher supply voltage can increase motor torque at higher speeds, thus helpful for avoiding losing steps. However, higher voltage may cause bigger motor vibration at lower speed, and it may also cause over-voltage protection or even driver damage. Therefore, it is suggested to choose only sufficiently high supply voltage for intended applications, and it is suggested to use power supplies with theoretical output voltage of +9 ~ +24VDC, leaving room for power fluctuation and back-EMF.

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Control Signals Step and Direction

The requirement of control signals to drive stepper motor through this driver are DIRECTION and STEP signals. These signals are of 3 to 5V level signals. The signals can come from various sources. You can also input from parallel port running software like Mach3. Most CNC software that output STEP and DIR signals on parallel port can generate these control signals. DIR signal: In single-pulse mode, this signal has low/high voltage levels, representing two directions of motor rotation; For reliable motion response, DIR signal should be ahead of STEP signal by 5s at least. Please note that motion direction is also related to motor-driver wiring match. Exchanging the connection of two wires for a coil to the driver will reverse motion direction. Making DIR signal high will make motor rotate one side and making DIR low will make motor rotate other side. Direction signal input is internally pulled high so it can be left unconnected if only one direction is required from the motor. Enable signal: This signal is used for enabling/disabling the driver. High level for enabling the driver and low level for disabling the driver. It is internally pulled high. Usually left UNCONNECTED (ENABLED). Using LM555 as Step Input To test the driver or have a stand alone application you can simply use a simple square wave oscillator based on LM555. The preset can be used to vary the frequency of step signal. The higher the frequency the higher speed. Square Wave Oscillator You can use following board as step input to the stepper driver.

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Using Microcontroller/PC Parallel Port as Control Signals Input Since control signals requirement are at 3~5V level you can use any microcontroller to generate HIGH/LOW pulses for step and direction. Step pulse is a square wave signal like HIGH and LOW. Each high going pulse will advance the motor one step. For parallel port most PC software has options to set as to which pin to make STEP/DIR signals. MCU/PC PP DIR STEP GND Stepper Motor Driver DIR STEP GND

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Wiring Notes

· · In order to improve anti-interference performance of the driver, it is recommended to use twisted pair shield cable. To prevent noise incurred in STEP/DIR signal, pulse/direction signal wires and motor wires should not be tied up together. It is better to separate them by at least 10 cm, otherwise the disturbing signals generated by motor will easily disturb pulse direction signals, causing motor position error, system instability and other failures. If a power supply serves several drivers, separately connecting the drivers is recommended instead of daisy-chaining.

·

Typical Applications

Suitable for a wide range of stepping motors, from NEMA size 17 to 43. It can be used in various kinds of machines, such as X-Y tables, labeling machines, laser cutters, engraving machines, pickplace devices, and so on. Particularly adapt to the applications desired with low noise, low heating, high speed and high precision. · · · · · · CNC / Milling Machines Robotics Industrial Equipment Remote-Positioning Equipment Scientific Apparatus Valve Controls

Troubleshooting

In the event that your driver doesn't operate properly, the first step is to identify whether the problem is electrical or mechanical in nature. The next step is to isolate the system component that is causing the problem. As part of this process you may have to disconnect the individual components that make up your system and verify that they operate independently. It is important to document each step in the troubleshooting process. You may need this documentation to refer back to at a later date, and these details will greatly assist our Technical Support staff in determining the problem should you need assistance. Many of the problems that affect motion control systems can be traced to electrical noise, controller software errors, or mistake in wiring.

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Dimensions

Board Schematic

VCC 1 3 RA1 10K R-ARRAY R1 470R + C2 100nF U1 LM7805 OUT GND 2 IN 1 C3 100nF + C4 100uF 25V D1 1N4007 CN1 PBT2

9-24V DC Ground

P1 10K Preset

Current Control

C6 100n

R2 22K C7 3n3 U2 L297 12 C5 100nF

9 8 7 6 5 4 3 2

D2 LED

C1 100uF 25V C8 100nF U3 L298 9

OSC VREF

VCC

TP

2 1

Imax=VREF/0.5

16 15 1 18 19 10 20 17

INH1 INH2 A B C D SEN1 SEN2

5 8 4 6 7 9 14 13

6 11 5 7 10 12 1 15

VCC

CN2 TP2

Stepper Motor

4 2 3 13 14 D3 BY399 D4 BY399 D5 BY399 D6 BY399 CN3 PBT2

ENA ENB IN1 IN2 IN3 IN4 SENA SENB

VDD OUT1 OUT2 OUT3 OUT4 GND

A B

CN6

STEP DIR ENB +5V GND

CN4 PBT2 CN5 PBT3

SYN CLOCK H/F EN RESET CW/CCW HOME CNTRL

C D

PBT2 D7 BY399 D8 BY399 D9 BY399 D10 BY399

VCC VCC

3 11

GND

HALF FULL

J1 JUMPER3P

2

R3 0R47 3W

R4 0R47 3W

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Sheet 1 Rev of 1 1

Title Bipolar Stepper Motor Driver based on L297/L298 Code 1168 Date: Friday, March 18, 2011

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