With this encoder kit the AX2550 can easily be upgraded to support optical encoders.

This upgrade kit consists of an encoder module that plugs onto the controller's main circuit board. A new faceplate with an opening for the extra connector is supplied with the kit.

AX2850 = AX2550 + Optical Encoder Inputs

The AX2850 is Roboteq's AX2550 controller with the addition of a built-in Optical Encoder module. Physically, the AX2550 and AX2850 differ only by the addition of an extra 8-pin connector on the controller's faceplate. The AX2850 shares all the electrical, mechanical and software features of the AX2550.

Enabled Features & Capabilities

• Support up to two quadrature optical encoders
• 250kHz Max frequency per encoder
• Support 4 optional limit switches
• Two 32-bit up/down counters
• Automatic speed computation
• Dedicated MCU for Encoder functionality
• Encoder information accessible via controller's RS232
• Easy setup, test and calibration using PC utility
• Field upgradeable module software

Roboteq Optical Encoder Kit

Existing AX2550 users may easily upgrade their existing controller to support optical encoders. The upgrade kit is composed of a module that plugs onto headers located on the controller's main board. A new faceplate with an opening for the extra connector is shipped with the kit.

Encoder Operation & Benefits

Optical incremental encoders are a means for capturing speed and traveled distance on a motor.
Counting the pulses tells the application how many revolutions, or fractions of, the motor has turned. Rotation velocity can be determined from the time interval between pulses, or by the number of pulses within a given time period. Because they are digital devices, incremental encoders will measure distance and speed with perfect accuracy.

Since motors can move in forward and reverse direction, it is necessary to differentiate the manner that pulses are counted, so that they can increment or decrement a position counter in the application. Quadrature encoders have dual channels, A and B, which are electrically phased 90 apart. Thus, direction of rotation can be determined by monitoring the phase relationship between the two channels.

The encoder's speed measurement makes it possible to use the controller in closed loop speed mode without the need for calibration and drifting problems that can occur using analog tachometer.

The pulse count feature is very useful to measure the actual traveled distance by the robot. It can also be used to perform sophisticated and high precision positioning algorithms.

Connector Types & Recommended Encoders

The module may be used with most incremental encoder module as long as they include the following features:

• Two quadrature outputs (Ch A, Ch B), single ended signal
• 2V minimum swing between 0 & 1 Level on quadrature output. TTL levels are acceptable
• 5VDC operation. 50mA or less current consumption per encoder

More sophisticated incremental, encoders with differential outputs, index, and other features may be used but these additional capabilities will be ignored. The choice of encoder resolution is very wide and is constrained by the module's maximum pulse count at the high end, and measurement resolution for speed at the low end. Connecting Optional Limit Switches

The Encoder module's 4 input lines (ChA, ChB for each of the two encoders) can be shared with optional limit switches using multilevel signaling. Using simple resistors, the output of the encoder can be "shifted up" so as to create the signal shown in the figure below. The encoder module looks for signals at different cut-off threshold to distinguish switch activation from a regular quadrature signal.

Easy Setup & Diagnostic with PC Utility

Extensive diagnostic, calibration, setting and testing support is provided in the Roborun PC utility.

With this utility, the following actions can be accomplished:

• Set and program the encoder module's parameters in EEPROM
• Activate the motors in each direction at variable speed
• View the measured encoder counts
• View the measured encoder speed
• View the status of the Limit Switches

Downloads

Optical Encoder User Manual (Revision 1.0) (.pdf 1.14 Mb)
Roboteq AX2550 Quick Start Manual (Version 1.5) (.pdf 732 Kb)
Roboteq AX2550 Overview Brochure (.pdf 1.33 Mb)
Roboteq Users Referance Manual (Version 1.5) (.pdf 2.06 Mb)
PC Configuration and Updating Utility (Version 1.5) (.zip 4.495 Mb)
Controller Software Update (Version 1.5a) (.zip 9 Kb)

Useful RoboteQ links and resourses