ML1400 - Can I use a 1762-OB8 for PWM, PTO

[Chris12345]

Hi all, I have a Micrologix 1400 BWAA and the correct software for it. I would like to learn to program PWM to control a stepper. I am currently building an H bridge circuit for the motor. The BWAA only has relay outputs and, if I'm reading the manual correctly, I need a controller with "Fast DC" output for PWM and PTO. (1) is this correct? (2) If so then can I do it by adding a 1762-OB8 24V DC Source output expansion module? Would that module or another one provide a Fast DC output? Thank you for any help on this.

 

[Ken Roach]

Welcome to the PLCTalk Forum !

The high-speed input (HSC) counter functions and the high-speed output (PTO and PWM) functions of the MicroLogix controllers are implemented in an embedded microcontroller that runs specific points on the built-in I/O only.

Only the DC I/O models of MicroLogix have them, and they aren't present in the expansion I/O.

There are some special stepper control modules made for the MicroLogix 1100/1400 family by AMCI, but if you're just in a learning mode, those probably aren't appropriate.

 

[BlueAltezza]

Yeah, you're better off getting the BXB models that have the embedded fast DC outputs instead of figuring out the AMCI stuff.

Plus it depends on the details of your application. Stepper drives are getting "smarter" and have more capabilities, so it may be possible that you can select a drive that can do most of the work instead of the PLC.

 

[Chris12345]

Bummer, I guess I'll have to hold off with learning those features for now. That's OK though, I'll just design some extra sub-circuits to my stepper motor controller circuit design and do it that way for now.

Thanks for the quick replies.