Engineering Notes by Oriental Motor

CVD Stepper Motor Drivers Explained

[fa icon="calendar"] Apr 1, 2021 9:35:17 PM / by Johann Tang

Johann Tang

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.

2-Phase Bipolar Stepper Motor Drivers

  • 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
  • Selectable step angle and microstepping filter control
  • 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.

Part I: Introduction

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 movementsIn addition, the Current Phase Correction minimizes the vibrations from 50~200 RPM, which are caused by resonance frequencies and torque ripplesFurthermore, the Vibration Suppression Control minimizes vibrations from 500 RPM and above, which are caused by back EMF.

CVD drivers reduce stepper motor vibration and improve accuracy

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.

1.  Low speed vibration occurs between 0~50 RPM (cause: step movements)
2.  Mid speed vibration 50~200 RPM (causes: resonance and torque ripples)
3.  500 RPM and above (cause: back EMF)

CVD driver vibration comparison

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.

CVD drivers: high positioning accuracy

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.

CVK series vs CMK series: stop position accuracy

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.

CVK series: 2-phase vs 5-phase speed and torque characteristics

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

 

CVK efficiency

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.

CVD compact driver dimensions

Resolution Selection

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

CVD pulse input type drivers - resolution settings

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.

CVD drivers - high efficiency design

Part II: 4 CVD Driver Types + Product Variations

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.

  • Lowest Vibration and Noise with advanced Microstepping control
  • Pulse Input or RS-485 Communications Type
  • Significantly improves positional accuracy when microstepping
  • Highest torque with Bipolar configuration (4 lead wire)
  • Small, thin microstepping drive with space saving FETs
  • Selectable step angle and microstepping filter control
  • 2 mounting types and connector configuration
  • Alarms
  • 24 VDC Input / 0.5A to 4.5A

CVD pulse input driver for stepper motors

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

CVD pulse input type driver

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

CVD pulse input type driver

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.

Improve Your 2-Phase Stepper Motor Performance

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.  

CVD RS-485 drivers for stepper motors

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.

MEXE02 universal software

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.

CVD drivers - automatic sequential operation

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. 

Mounting Plate

CVD RS-485 driver

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

Mounting Plate (Right-Angle)

CVD mounting plate type driver - right angle connectors

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)

CVD-SC speed control driver for stepper motors

This driver is designed for only one or two-speed operations, so it may not be suited for applications requiring many different speeds.  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.

CVD SC type driver for stepper motors

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

04_CVK SC_US_0420

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

CVD and CVD-S Board Sizes

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

CVD board mounting type driver module

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

Board Mounting Type Driver Module - Vertical Mount

CVD board mounting type driver module

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.

CVD-S Installation Address

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.

 

Thanks for making it to the bottom of this post.  Please comment if there's another function you wish the CVD drivers had, or subscribe for new posts.

 

For more info, please refer to these two related blog posts below.

Minimizing Stepper Motor Vibration

Improve Stepper Motor Performance Further with Advanced Driver Features

 

Topics: Stepper Motors, Smooth Drive, VIDEOS

Johann Tang

Written by Johann Tang

Johann Tang is a Product Specialist at Oriental Motor USA Corp. with over 15 years of knowledge and experience supporting applications of various types of electric motors, gearheads, actuators, drivers, and controllers.

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