Arcus

This is an EPICS IOC for the Arcus stepper motor controller and driver:

• single-axis ACE-SDE and
• two-axis PMX-2ED-SA

Required

Modules

• asyn
• stream
• calc
• base 3.15.6

Hardwares

• single-axis ACE-SDE and
• two-axis PMX-2ED-SA
• 12V or 24V power supply
• USB to RS485/422 cable
• TM-STPP-23 Hybrid Stepper Motor (NEMA 23)
• IDC 50 pin Cable Connector
• IDC50 2x25 Pins 0.1" Male Header Breakout Board

Parameters Configuration

1. PPMM

Pulses Per MilliMeter, used to convert the number of pulses in the controller to the unit of mm (or degree if rotation stage), need to be characterized for specified stepper and linear guide.

• set PPMM to 1, and move the stepper motor by a number of pulses,
  e.g. 10000 pulses;
• measure the distance of motion L (in the required engineering unit, e.g. mm);
• the value of PPMM should be set as 10000/L.

2. LCA

Limit Correction Amount, in the unit of Pulses. When press the home limit button, the motor moves to the specified direction. After hitting the switch button, it moves in the reversed direction by the number of steps defined by the LCA.

3. Ratio

Ratio between motor pulses and encoder counts. This ratio depends on the motor type, microstepping, encoder resolution and decoding multiplier. Value must be in the range [0.001 , 999.999].

Reference

Refer to the manual:

• Arcus ACE-SDE Single Axis Controller-Driver Manual Rev 1.24.pdf
• PMX-2ED-SA-Manual-Rev-1.18.pdf

Trouble shooting

Here is a list of the issues that occurred while testing the stepper motor.

Stepper motor alternates its direction during/between motions

If the stepper motor alternates its direction during moving while it's expected to move in the same direction, the current pulses are not circulating as expected, the reason could be:

• The internal wire of the motor is broken
  => one of the wires might be disconnected;
• The connection cable is broken
  => one or two wires might be disconnected;
• The driver does not send the pulse sequence as expected
  => one pair of outputs might fail.

Need to check with a multimeter:

• Measure the resistance between A-/A and B-/B to see if it's close to zero (usually $\le 1 ~\Omega$). If it goes to infinity, it's disconnected somewhere;
• The same diagnostic can be applied to the connection cable;
• Use the multimeter to measure the voltage of the outputs, if the voltage difference bwtween a pair of output is always zero, that driver chip might have failed.

Encoder Ratio

To use a stepper motor with encoders, one should properly set up the parameter Ratio. The procedures is as follows:

• properly connect the encoder cable from the stepper motor to the controller;
• turn off the encoder power switch, move the stepper motor by a number of steps N1, and read the encoder position N2, the ratio is R=N1/N2;
• the value R should be a positive value in the range 0.001-999.99, if R is negative, one should try to switch the outputs of A <==> B and /A <==> /B.

Control Pannel with MEDM