RoHS Compliant Stepper Driver from Lin Engineering

Morgan Hill, Cal. – A new RoHS compliant version of Lin Engineering’s R325 stepper motor driver is now available. Combining compact size with high performance, the R325 can be used with stepper motors of many shapes and sizes. 

The R325 microstepping driver is capable of output currents ranging from 0.3 to 3.0A peak while handling +15 to 48VDC of input voltage. Selectable step resolutions from Full, 2x, 4x, 8x, 16x, 32x, 64x, 128x, and 256x microstepping are also available. The R325 has hold current reduction capability with adjustable current and timeout settings. It also features three optically isolated inputs and one optically isolated control output that can be used for step, direction, disable/enable, and fault detection.

The R325 features Pole Damping Technology™ (PDT) which enhances a step motor’s performance by creating a more accurate and smooth motion profile. PDT optimizes the microstepping performance of the step motor by outputting the correct amount of run and hold current to the motor, at the right time. Thus, each step will overcome the motor’s natural tendency to want to “jump” towards the full step ON position.

www.linengineering.com

Universal Single & Dual Axis Drive Modules for EtherCAT Networks from ACS Motion Control

Eden Prairie, Minn. – ACS Motion Control announces an EtherCAT slave Universal Drive Module that directly drives one or two axes.  Designated the SPiiPlus UDMnt, the Universal Drive Module operates as an EtherCAT slave device to any SPiiPlus EtherCAT master controller. The SPiiPlus UDMnt supports AC servo, DC brushless, DC brush, closed and open loop 2- and 5-phase step motors. In addition, many UDMnt devices can be linked together on a network, allowing up to 32 axes of fully coordinated control.

The SPiiPlus UDMnt is available in a 5A, 10A, or 20A peak current rating at up to 60Vdc bus voltage, and has dedicated encoder and limit inputs as well as general purpose I/O and robust fault protection. The drive performs real-time control of position, velocity and current at a 20kHz update rate for each axis.

The SPiiPlus EtherCAT family of products offer advanced, high-level machine control with a small footprint and low cost. The universal drive technology provides a flexible solution for all motor topologies, helping to reduce costs by letting users run multiple axes from one drive module.

For more information about the SPiiPlus UDMnt and other ACS EtherCAT network control components, visit the ACS Motion Control website at www.acsmotioncontrol.com.

EtherCAT® Motion Box for Stepper Motor Control from Beckhoff

Minneapolis, Minn. – Beckhoff Automation has introduced the EP7041 EtherCAT® Motion Box, allowing for stepper motor control in a compact, machine-mountable device. Using the EP7041 stepper motor box, small EtherCAT motion applications can now be implemented directly in the field without a protective control cabinet.

Ideal for harsh environments, the compact EtherCAT module in protection class IP 67 allows the connection of Beckhoff stepper motors up to 50VDC and 5A. An integrated incremental encoder connection on the EP7041 permits the implementation of a single servo axis with the compact IP 67 module.

Within the housing, which measures 5-in. x 1.2-in. x 1-in. (126 x 30 x 26.5mm), the EP7041 contains an encoder connection, two digital inputs for limit switches and a digital output for a brake, ensuring that all signals from a motor are combined in one compact box. In addition to the modules designed for 5A, there is also a 1.5A version (EP7041-1002) for the control of lower power stepper motors. By entering just a few parameters, the EP7041 EtherCAT Box can be adapted to suit the motor and the application.

The stepper motor module is capable of 64-fold micro-stepping, which ensures a smooth and precise motor rotation. The stepper motor modules are particularly well-suited for use in the feed axes of handling and processing machines as well as in assembly technology. Beckhoff offers a corresponding range of stepper motors with standstill torques ranging from 0.38 to 5 Nm.

For more information, email beckhoff.usa@beckhoff.com or visit www.beckhoffautomation.com.

The Many Faces of Stepper Motor Drives

Drives for stepper motors continue to advance beyond the basic L/R type drives.

A typical linear motion control system has several basic components, including motors, actuators, controllers and drives. The drive type plays an important role in the overall system. Here’s a look at the most basic drive configurations, including the latest advancements in chopper drives.

The IDEA programmable actuator from Haydon Kerk is an example of cutting-edge intelligent chopper drive technology. IDEA consists of an advanced microstepping chopper drive with an intelligent programmable controller mounted to the rear section of a hybrid stepper motor linear actuator in one fully integrated package.

Defining the L/R Type Drive
An L/R type drive is a voltage source drive, where the L refers to electrical inductance and R stands for electrical resistance. Inductance is an electrical parameter relating mainly to inductors that are coils of wire wrapped around a core material that can be metallic, non-metallic, solid, liquid, or even air. Typical inductors are transformers, chokes, and motor coils (including the windings in stepper motors and stepper motor linear actuators). A related parameter called inductive reactance in an electrical circuit impedes the flow of current relative to the voltage frequency. It can be thought of as a “dynamic resistance,” increasing and impeding more of the current flow as the frequency increases. An analogy for inductance in the mechanical field would be the principle of inertia.

Resistance also impedes the flow of current in an electrical circuit but is a constant value and is not affected by the frequency value of the voltage or current. The stepper motor coil resistance remains essentially the same from standstill through maximum step frequency with only minor fluctuations due to temperature. A mechanical equivalent of electrical resistance would be the friction in a system.

Stepper motor manufacturers offer a variety of coil voltage ratings. With an L/R type of drive, you set the output voltage of the drive (measured at the motor leads) equal to the voltage rating of the stepper motor. The voltage level of the drive power supply will be set slightly higher due to voltage drops across the power transistors. The ratio of inductance to resistance (L/R) determines the current flow through the windings at a given step rate (or frequency) in steps per second. L/R = 1 time constant, which is equal to approximately 63% of the final steady-state current. At standstill, the maximum current flow into the windings is determined by the coil resistance alone. The impedance effect due to inductance is zero when the frequency is zero. This is the condition where the motor has maximum torque (holding torque) due to maximum ampere-turns, defined by:

T_H α N x I

Where:

T_H = the holding torque
N = the number of turns in the motor coil
I = the electrical current

As the step rate increases, the coil inductive reactance (X_L) also increases according to the formula:
X_L = 2πfL

Where:
X_L = the inductive reactance
f = the frequency (step rate)
L = the inductance of the motor coil

With a constant voltage source L/R type driver, the motor current decreases as the total impedance (X_L + R) increases.

Because torque, both static and dynamic, depends on ampere-turns, the output performance of the stepper motor or stepper motor linear actuator drops off as the speed increases. Another factor affecting motor performance is the back-EMF (electro-motive force) produced by the rotor rotating in a magnetic field. Motors also behave as generators. High step rates may produce peak back-EMF levels approaching or exceeding the L/R drive output voltage level. One method used to partially compensate for these effects is to improve the inductance to resistance (L/R) ratio by adding external series resistors and increasing the power supply voltage. Some common configurations are the L/2R and the L/4R drivers. Because the respective voltage sources would have to be doubled or quadrupled, the efficiency drops significantly and much more of the power is wasted as heat in the external resistors.

Categories of L/R Drives: Unipolar and Bipolar
Unipolar drives have simple output configurations and are used infrequently due to the relatively low torque output and low efficiency. A unipolar drive contributes to a torque reduction of approximately 30% as compared to a bipolar drive at the same electrical power. In a unipolar drive, only half the phase winding is energized at one time, whereas in a bipolar drive, the entire phase winding is energized.

A unipolar drive configuration. Notice that the motor phase winding is center-tapped, thus allowing current to flow through only half the phase winding at a time.

A bipolar drive configuration.

Bipolar drives have more complex output stages. Many of the new specialized integrated circuits have come down in cost, making bipolar drives more affordable. The output configuration is an “H-Bridge” which allows the reversal of the phase currents. Instead of the phase currents being switched on and off in just half of the windings like in a unipolar configuration, the currents flowing through the entire motor windings are reversed in bipolar drives. At equal electrical power into a given frame size stepper motor, the bipolar driver/motor configuration can produce greater static and dynamic torque than that of a unipolar driver/motor combination.

Chopper Drives
The term chopper refers to the method of rapidly switching a relatively high voltage to the windings on and off. This technique of switching the output voltage on and off controls the average current per phase.

There are several steps involved in selecting a chopper drive. First, choose a power supply that has a high output voltage relative to the voltage rating of the stepper motor to be driven. The high available voltage compensates for the increasing coil impedance due to rising inductive reactance as the motor speed increases. A power supply to motor coil voltage ratio of 8:1 or higher will provide the best performance at the higher motor speeds. Second, low-voltage steppers, with correspondingly lower inductance coils, are recommended. Linear type motor power supplies work well with these drives. Third, virtually all chopper-type drivers are a bipolar configuration, making use of the entire motor windings, which yields improved torque. Even unipolar stepper motors can be driven with these bipolar choppers as long as their rated coil voltage is not too high. Six-lead unipolar motors would be connected as a four-lead type by leaving the center-tap leads unconnected. With eight-lead steppers, you can connect the two coils of each phase in series (especially low-voltage coils) or in parallel. Because inductance changes as the square of the number of turns, putting two coils in series yields four times the inductance. Stepper motor performance improves at the higher speeds, as compared to an L/R type drive, due to the chopper drive’s method of monitoring and controlling motor current throughout the usable speed range.

To control the average current through the phase windings, this type of drive technology “chops” the high output voltage on and off. Most choppers use a fixed chopping frequency of approximately 20 kHz or higher. This helps keep system noise low, since the chopping frequency is above audible range. Based on this constant fixed chopping frequency, the average output current is controlled by varying the pulse width of these repetitive output pulses, a technique known as pulse width modulation (PWM).

The output current is monitored by comparing the voltage level across a small ohmic value series sense resistor with a set voltage that represents the rated motor current. During each cycle of the typical 20-kHz waveform, the voltage across the sense resistor begins to rise as the current increases through the motor winding. An electronic comparator continuously monitors this voltage level; when it equals the set reference voltage it turns off the output voltage until the start of the next 20-kHz cycle. The current in each motor winding builds and decays as the voltage source switches on and off during each cycle, yielding the proper average current per phase.

As the motor step rate, or speed, increases or decreases, so does the corresponding winding impedance and the chopper drive electronics help to compensate for this effect. At slow speeds (lower winding impedance) the on time of the voltage source is relatively short per cycle (small pulse width). At higher speeds (higher winding impedance) the on time is longer per cycle to allow the current to increase to the proper level (large pulse width); thus the term pulse width modulation.

Advances in Chopper Drives
Chopper drives are now selected for most new stepper motor linear actuator applications and there has been ongoing progress in this drive technology. For instance, the use of low on-resistance Field Effect Transistors (FETs) in the output power stage increases system efficiency and reduces power dissipation within the drive, which also reduces the required heatsink area and physical size of the drive package. Also, new power stage circuitry can provide the higher phase currents required from low-voltage, low-inductance motors, which can yield improved performance over a wider speed range. Enhanced phase current control increases motor performance such as automatically providing boosted current levels during acceleration and deceleration ramping, or shaping to reduce overall resonance of the system.

Other advances include multiple levels of microstepping (electronically splitting a full step into smaller increments) to increase motor resolution, reduce motor resonance, and lower the motor’s audible sound level during operation. Also, the integration of smart controllers, by use of on-board microprocessors, which allows for execution of real-time motion functions such as indexing with or without ramping, and creating complete interactive motion profile programs. These programs can be downloaded into non-volatile memory on the controller and then run independently and un-tethered from any host computer.

In the realm of I/O, interactive optically isolated inputs and outputs now allow the driver/controller to fully communicate with other devices and equipment in a motion control system. And smart controllers can accept encoder feedback, which can be used for motor positional verification or speed control.

Discuss this on the Engineering Exchange:

Haydon Kerk Motion Solutions
www.haydonkerk.com

::Design World::

Fully Integrated Stepper Motor/Driver from Johnson Electric

Vandalia, Oh. – Johnson Electric introduces the Saia Compact Driver, a fully integrated step driver/motor solution that reduces design and integration time, and improves device performance compared with traditional stepper solutions by virtue of reduced parts count and greater immunity to electromagnetic interference.   Where space and power is at a premium, the Compact Driver’s low power consumption and small footprint make it a particularly attractive motion solution for battery powered portable devices.

The Compact Driver provides 3-wire operation of 28mm Saia motors, including UCL and UCE linear step motors and UCD and UCB rotary stepper motors. The linear Compact Driver solution provides forces from 0.1 to 50N with a step resolution down to 0.021mm and distances up to 150mm. The rotary Compact Driver solution can be combined with an Saia UGA, UGD or UGM gearbox to obtain higher torque and RPM outputs, and increase step resolution, all from the same integrated driver board.

The Compact Driver’s algorithm is programmed to detect the end of the motor’s stroke. This automated end stop detection eliminates noise, reduces mechanical stress, and compensates for transverse distance tolerances, helping decrease system hysteresis and maximizing operating life.

Additionally, the Compact Driver is available with three different types of control interfaces that can be used for any number of applications where on/off or proportional functions are desired, making it simple to integrate into new and existing device designs. The ON/OFF mode is operated by an external switch where the proportional function is controlled by a 0-10V or pulse width modulation (PMW) signal.

For more information, contact Johnson Electric at (937) 454-2345 or by fax at (937) 898-8624.

www.saia-motor-usa.com

AMCI Stepper Drives UL Listed

AMCI has expanded their selection of UL Listed stepper drives in response to increased safety and performance requirements for machine builders and OEMs. The SD17040, SD31045, and SD17060 series stepper drives are now certified by Underwriters Laboratories® (UL) as UL Listed products. The UL Listing mark on AMCI stepper drives indicates that the drives have been tested by UL to recognized safety standards. These newly approved drives are rated for operation in ambient temperatures ranging from 0°C to 50°C, and are compatible with AMCI’s complete line of motion controllers and high torque stepper motors.

AMCI’s stepper drives provide a wide range of features including network connectivity, onboard indexers, encoder feedback, compact design, and simplified set-up. All of AMCI’s UL-Listed drives are self-contained with their own power supplies, and range from 4.0 Arms – 9.8 Arms (Amps RMS) of output current. Additionally, a high voltage version is now available from AMCI to meet European standards that require 230Vac input. All of the units can be installed into tight spaces without thermal issues, and offer panel or side mounting for increased flexibility.

“Most machine builders and OEMs require UL approved control products because their equipment must meet safety and performance standards around the world. AMCI’s UL listed stepper drives achieve this level of excellence as verified by Underwriters Laboratories’ rigorous testing & certification”, explained Stan Mantchev, AMCI Engineer. Many stepper drives with UL approval are only recognized, whereas AMCI’s stepper drives are UL listed to ensure hassle free compliance in any installation.

Underwriters Laboratories® (UL) is a company that has developed standards and testing systems to ensure products are safe. A UL Listing mark on a product is always composed of four elements including the UL in a circle mark (logo), and the word LISTED in capital letters. UL Listed products represent products that are found to be free from reasonably foreseeable risk of fire, electric shock, and related hazards, and that the product was manufactured under UL’s follow-up service program.

Advanced Micro Controls Inc.
www.amci.com

Applied Motion Products Expands Stepper Drive Lineup

WATSONVILLE, CA – Applied Motion Products announces the addition of a new product in the ST Stepper Drive lineup. The ST-Plus is similar in specification to the ST-S base model but adds the full functionality of Applied Motions “Q” programming language.

The ST-Plus is available in two models, the ST5-Plus and the ST10-Plus delivering 5A and 10A respectively. The ST-Plus drive measures just 3” x 3.65” x 1.75” and has 3 digital inputs, 1 digital output and an analog input accepting 0-5VDC.

The Q software allows users to create sophisticated and functional programs that Q drives can run stand-alone. The commands available in the Q software environment consist of instructions for controlling motion, inputs & outputs, drive configuration and status, as well as math operations, register manipulation and multi-tasking.

ST-Plus drives are ideally suited to applications needing full motion control capability but only require a small I/O count.

Applied Motion Products
www.applied-motion.com

Compact Stepper Drive from AMCI

Terryville, CT – Advanced Micro Controls, Inc. (AMCI) introduces a space saving, powerful, 170V bus, 4.0 Amp microstepping driver. The SD17040C requires no additional power supply and can drive 4, 6, or 8 lead step motors, NEMA sizes 23 to 42. Standard features include switch selectable microstep resolutions, automatic idle current reduction, anti-resonance, short circuit protection, and over-temperature circuitry.

The SD17040C is designed to withstand demanding applications, with board-level components rated to 105^oC (221^oF). Panel or side mounting options allow the SD17040C to be installed in tight spaces without supplemental fans or cooling aids. The use of DSP (digital signal processor) technology in combination with high quality transistors has enabled AMCI to customize the drive’s performance for most applications, while also reducing space within the unit. The drive’s exceptional power combined with anti-resonance circuitry delivers the smoothest, most reliable performance possible in a stepper motor system.

AMCI’s SD17040C microstepping driver offers several standard features from safety, to performance, to customization. Features include:

• Compact Size (2.1”W x 4.0”D x 6.2”H)
• 170V Bus, AC Line-Powered (No Additional Power Supply Required)
• Switch Selectable Motor Current, 1.0-4.0 Amps
• (16) Switch Selectable Microstep Resolutions, up to 50,800 steps/rev.
• Selectable Self-Test Feature
• Interlock Safety Feature and Short Circuit Protection
• Automatic Idle Current Reduction, Fully Programmable
• Anti-Resonance

AMCI’s SD17040C stepper drive is 100% compatible with all of AMCI’s stepper controllers and motors.

Phone: (860)-585-1254
Fax: (860) 584-1973
http://www.amci.com

Lin Engineering’s R525 Microstepping Step Motor Driver

Santa Clara, CA— Lin Engineering announces the release of their new R525 microstepping step motor driver. The R525 is designed to help reduce overall design time and system cost for a wide array of step motor applications needing high torque, power, and smooth motion.

The R525 measures just over 3.3” in length and 1.3” in height making it very easy to accommodate in most systems. The R525 has been extremely competitively priced coming in at almost 20-30% less than similar products. With the R525, you get a lot more than you pay for.

The R525 is capable of outputting up to 5 amps peak current and handling up to 75 volts DC. Not only can it be used with all NEMA 8, 11, and 17 motor motors, it is compatible with the majority of NEMA 23 motors and many NEMA 34 motors as well.

Configuring the R525 unit is simple as well. With built-in RS485 communication, the unit can be easily connected to a computer and configured via Lin Engineering’s graphical user interface (GUI), LinDriver. Configurable settings include, but are not limited to:

1. Step resolution
2. Run current
3. Hold current
4. Damping modes for smoother motion
5. Selection of sensing the step pulses on the rising edge or falling edge

Lin Engineering
www.linengineering.com

Mechatronic Stepper Motor Drives with CANopen

Hamburg, Germany – TRINAMIC announces new members of the PANdrive™ family. The latest members of the family are the types PD-140-42-SE and PD-116-60-SE. Both feature TRINAMIC’s integrated absolute sensOstep™ encoder which detects and corrects missed stepper-motor turns by examining the absolute posi-tion. This insures correct shaft motion even under heavy motor loads. Reliable high-speed motor operation is assured by TRINAMIC’s patented chopSync™ function which eliminates resonance problems.

The new mechatronic units from TRINAMIC have an integrated absolute sensOstep™ encoder. CANopen firmware lets the PANdrives™ be used in large networks.

Optional CANopen firmware makes it easy to use the PD-140 and PD-116 in large net-worked applications, even with components from various vendors. The advantages of such distributed designs include greater flexibility, reduced wiring expenditure and main-tenance-friendly service.

TRINAMIC also offers its TRINAMIC Motion Control Language (TMCL) which lets engi-neers develop programs easily. Complete programs can be downloaded and run inde-pendently on the PANdrive, or specific commands can be sent to the drive. A selection of different interfaces such as RS-232, RS-485, CAN and USB are supported and a com-plete PC-based Integrated Development Environment (IDE) is available for free.

The new PANdrive™ PD-140-42-SE from TRINAMIC has sensOstep™, which offers recognition and correction of step losses, and allows exact positioning and ‘step loss correction’.

Both models have general purpose inputs and outputs as well as additional inputs for limit switches or reference switches. The supply voltage is typically 24V.

The PD-140-42-SE is based on a 42 mm NEMA17-flange stepper motor. There are sev-eral variants, with retaining torque from 0.22 Nm to 0.47 Nm. The larger PD-116-60-SE has a 60 mm NEMA24 flange and retaining torque options from 1.1 Nm to 3.1 Nm. An impact-resistant cover protects the electronics module.

An integrated encoder for position maintenance increases the system reliability at low cost. This is especially important in applications such as laboratory automation, biotech-nology, wafer-handling and chip testers.

www.trinamic.com

Applied Motion Adds CANopen Option to ST Step Motor Drives

WATSONVILLE, CA – Applied Motion Products announces the addition of CANopen communications to the ST series Step Motor Drives.

The addition of a CANopen option card to the range of communication options allows the drives to be controlled by a CANopen master utilizing the DS301 and DSP402 communications protocols and the CAN 2.0b Passive physical layer. Using these standard protocols the drive can be commanded to execute point to point moves, homing routines or run at a set velocity. ST CANopen Drives are available in 5A and 10A versions. Each has eight digital inputs, four digital outputs and two analog inputs. ST drives are configured using ST Configurator software.

CANopen is utilized by OEM machine builders to integrate many devices of different types on a single field bus connection. Drives such as the ST can be put on the same network as sensors and interfaces. The user then has a single learning curve to develop programs that can communicate to all compatible devices. Up to 132 devices can be connected on a single CANopen Network.

Free printed literature and a price quote are available to aid product selection efforts. Full product CAD drawings are also available.

www.applied-motion.com