CVD Stepper Motor Drivers Explained

CVD stepper motor drivers are the recommended drivers for PKP Series high torque stepper motors for its ability to lower vibration and improve torque performance throughout its entire speed range.  The latest update includes the addition of RS-485 communication and MEXE02 software support.

One reason why engineers should consider the same manufacturer for motors and drivers is for the manufacturer's unique knowledge of both products, which can be used to improve performance.  An example is the CVD driver's current compensation control.  This function pairs actual motor winding data with unique driving algorithms to lower vibration.

• Lowest Vibration and Noise with advanced Microstepping control
• Significantly improves positional accuracy when microstepping
• Highest torque with Bipolar configuration (4 lead wire)
• Small, thin microstepping drive with space saving FETs
• 24 VDC Input / 0.5A to 4.5A

In part I, I will be briefly explaining some of these unique benefits of the CVK Series.  In part II, I will introduce the four main types of CVD drivers and the product variations offered in each type.

The CVK Series was originally introduced in 2014 as a stepper motor and bipolar microstepping driver package model, which included both PKP Series stepper motors and CVD drivers.  The compact, board level CVD drivers were specifically designed to improve both the torque and accuracy of the PKP Series stepper motors, but at the same time, minimize different types of vibration and improve accuracy.  The CVD drivers also work well with other 4 lead wire stepper motors.

Lowest Vibration Performance

What sets the CVD drivers apart is that they offer multiple functions to minimize different types of vibration.  The way it classifies vibration is by speed range.  In the speed-torque curve below, you can observe the vibration level (measured as voltage) on the Y axis and the speed range on the X axis.  The black line represents the performance of a conventional stepper motor and driver system (like our discontinued CMK Series or CSK Series stepper motors and drivers).  The green line represents the performance of a PKP Series stepper motor and a CVD driver.

With Oriental Motor's unique Smooth Drive algorithm, the driver automatically microsteps at 2048 steps per full step (1.8° for 2-phase; 0.72° for 5-phase) over the entire speed range.  The benefit of this function is that the controller pulse output resolution can stay at full step while the motor operates with smooth, microstepping performance.  This is an updated Smooth Drive function (it used to be only 16 microsteps per full step). 

The Smooth Drive function effectively minimizes vibration at 50 RPM or below, which are caused by step movements.  In addition, the Current Phase Correction minimizes the vibrations from 50~200 RPM, which are caused by resonance frequencies and torque ripples.  Furthermore, the Vibration Suppression Control minimizes vibrations from 500 RPM and above, which are caused by back EMF.

As indicated in the image above, the CVD drivers also utilize a full-time digital current controller for easier current setting and improved current waveform control.  In past driver designs, one current detector was used for all phases of the motor.  In the CVD driver, each phase has its own current detector.  This improves current uniformity in all motor phases.  By outputting an uniform, sinusoidal current waveform (sine wave drive), accuracy is improved when compared to trapezoidal wave drive.

The vibration characteristics do not change; even when step angles are changed.  This is the result of Oriental Motor's unique current control capabilities.  The graph below shows the 3 types of resonance/vibrations exhibited by stepper motors, and how much they are lowered when all vibration suppression functions are active.

For higher positioning accuracy especially when microstepping, 5-phase 0.72°/0.36° stepper motors are recommended.  If even better accuracy is desired, high resolution type stepper motors are recommended.

The stop accuracy specification is +/-0.05° for standard 1.8° and 0.72° PKP Series standard stepper motors and +/-0.034° for high resolution stepper motors.  The higher toothed rotor from the high resolution stepper motors actually makes the motors more accurate.

The CVD drivers are available for both 2-phase and 5-phase stepper motors.  2-phase stepper motors are the most common while 5-phase stepper motors are designed for applications demanding less noise and vibration.  For the same frame size and stack length, a 2-phase stepper motor with a CVD driver would offer more low speed torque, while a 5-phase stepper motor with a CVD driver would offer more high speed torque.

With the CVD drivers, it's easy to upgrade from 2-phase to 5-phase since the driver size is the same.

The CVD drivers have also improved their power efficiency.  The highest power efficiency occurs at about 175 RPM.  At this point, the power loss is  75% less than past designs.

Due to all of the CVD driver's compactness, available variations, Smooth Drive, vibration suppressing functions, and the fact that it's able to reference motor data, Oriental Motor considers the CVD drivers to be the industry's top performance driver for PKP Series stepper motors.

Resolution Selection

There's also another dip switch to select from 32 resolution settings (16 for 2-phase; 16 for 5-phase).

Heat Sink is Optional

One unique advantage that is prevalent on the CVD drivers is that the heat sink is optional.  The metal mounting plate is actually for installation; not for heat sink.  The CVD drivers utilize low-loss FETs and optimized tracing on the PCB for better heat dissipation.  I'll explain a bit more later.

When we originally released the CVD drivers, only one type of drivers was offered - the pulse input type.  Over the years, we have expanded its product breadth to include four types total and various variations within.  For the most updated CVD drivers lineup, please refer our website.

• Pulse Input Type
  
  • Board only
  • Mounting plate
  • Right-angle
• RS-485 Communication Type
  
  • Mounting plate
• SC Type (Speed Control Type)
  • Built-in pulse generator
• S Type (Board Mounting Type)
  • I/O setting or SPI communication

1. Pulse Input Type

Aside from being compact, the CVD pulse input type driver is the most traditional type of stepper motor drivers.  The driver's I/O includes "pulse" and "direction" input designations in 1-pulse mode, and the same inputs switch to "CW" and "CCW" input designations for 2-pulse mode.  A controller is typically connected to these inputs and provides the command signals for the motor.  While the number of pulses commands the motor exactly how far and how fast to run, the frequency of the pulses (Hz) control its speed.

• Selectable step angle and microstepping filter control
• 2 mounting types and connector configuration
• Alarms
• 24 VDC Input / 0.5A to 4.5A

Two variations are offered for the CVD pulse input type driver: board only and mounting plate.  These variations are more about installation and mounting.  There is no critical functional difference between pulse input driver variations.

Board Only

This is the variation of the pulse input type driver that mounts directly with the 4 bolt holes and does not require a heat sink.  The utilization of efficient components (low-loss FETs) and better heat dissipation properties (optimized tracing) helped make this possible.

Mounting Plate

There are two differences between this one and the board only.  First, the obvious difference is the addition of a mounting plate to easier installation.  Second,  the connectors now are oriented horizontally instead of vertically.

Here's a video of the CVD drivers (original CVK Series) if you haven't seen it yet.

2. RS-485 Communication Type

This is the newest type of CVD driver, which was released in 2021.  The critical functional differences from the pulse input type driver are listed below.

• Built-in stored data controller
• 256 motion profiles can be stored
• RS-485 Communication - up to 31 drivers can be connected in an RS-485 network
• MEXE02 software - easier data, parameter setting with GUI software
• Built-in stored data functions - help make programming easier
• More I/O - satisfies more application requirements

The major updates include the obvious RS-485 communication and compatibility with the universal MEXE02 support software.  

With an RS-485 network, up to 31 drivers can be connected together.  Wiring is minimized just communication instead of the I/O, and communication between the host controller and driver can be improved.

With the MEXE02 software, it's like hitting the easy button.  this means the driver now includes a built-in controller.  This means no external pulse generator is necessary.  With Oriental Motor's stored data operations, such as jog, continuous, positioning, automatic sequential operations as well as its AREA outputs, advanced motion sequences can be programmed in minutes (seconds if you're familiar).

For example, automatic sequential operation allows the user to "link" up to 256 motion profile sequences with just one START signal.

The RS-485 communication type driver satisfies our most recent update for the CVD drivers, which was improved operation with network connectivity and GUI software.  If you have a suggestion to improve our products, please comment below.

There are two types of the RS-485 communication type.  Please see below.

Mounting Plate

The mounting plate variation has the motor, power, and I/O connectors facing vertically.

Mounting Plate (Right-Angle)

The mounting plate (right-angle) variation has the motor, power, and I/O connectors facing horizontally.

3. SC Type

The "SC" in "SC Type" means "speed control".  This is actually a simplified version of the CVD Series drivers that is designed to run a stepper motor in a speed control application.  At this time, the SC type driver is only available for 5-phase motors.  

• No pulse generator needed
• 2 speed settings are possible
• Compact and high torque stepper motor
• Improved stop position repeatability
• Maintains torque even when stopped
• Continuous duty is possible
• *Motor cables required (sold separately)

This driver is designed for only one or two-speed operations, so it may be best suited for applications that only require two stored speed settings.  The benefits of this driver are reduced cost and minimized footprint.  Although continuous operation is possible, the heat generated from the stepper motors may not be ideal when placed in close proximity to materials that can be adversely affected by heat, such as biological samples for research.

Here's a short video showing how to operate the SC type driver.

4. S Type

The S type CVD driver is different than the rest.  The S type is the smallest of the CVD drivers and offers a short cut for engineers who design their own drivers.  These drivers can be easily mounted on a bigger board for multi-axis control.  Similar to other CVD drivers, the I/O pins can be oriented vertically or horizontally to fit different driver designs.  

• Current Setting Range: 0.5 A ~ 2.8 A
• 32 Motor Resolution Settings (16 for 2-phase and 16 for 5-phase)
• All functions required to drive a motor are equipped in the driver
• Simply add an aluminum electrolytic capacitor on a mother board
• The basic performance is the same as the CVK Series
• Contact Sales for Pricing and Lead Times

Since this product is designed for advanced users who design their own driver board, they are not available for sale online.  A product consultation with our technical support engineers is recommended before purchase.

Board Mounting Type Driver Module - Horizontal Mount

This variation includes horizontal pins, which are oriented at a right angle from the board.

Board Mounting Type Driver Module - Vertical Mount

This variation includes vertical pins, which are oriented in the same direction as the board.

The table below describes how the "H" and "V" driver variations differ.

For the two product variations above, users can also select either I/O setting or SPI communication.  The I/O setting driver is for users who simply want to use I/O to operate the driver.  The SPI communication driver is for users who want to use board-level communication for setting certain parameters. 

To learn more about SPI, here's a link to Wikipedia.

If you'd like to learn more about the S-type drivers, here's a white paper explaining its development.

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PKP Series 1.8°/0.9° Stepper Motors	CVD 2-Phase Stepper Motor Drivers

CVD Stepper Motor Drivers Brochure