Always update your software (and be cautious of new components)

When I used to do service computers for a few customers I always made a point of telling everyone to update their computers. Under Windows there are many advantages especially with the introduction of SP3 for XP including performance, security, and stability. ¬†Since I’m no longer doing PC support I might as well let you know why it’s also important to update your control software, especially if it’s the software directly running the system as in Beckhoff’s TwinCAT.

During our first Beckhoff trial I downloaded a demo version of TwinCAT to try things out. This was in September of ’09. A project came to our plate that required the use of a few stepper motors to position a table to align some fiducials. To try this out I purchased the stepper components (EL7041) and a coupler (EK1100). The EL7041’s are a brand new terminal from Beckhoff that can handle up to 5 Amp/Phase Steppers with encoders for a very reasonable cost. Once I received the stepper drives I plugged everything in and lo and behold, the steppers were completely disabled!

I tried everything I could think of and nothing would work. I tried uninstalling TwinCAT and reinstalling, and surprisingly, after that everything worked! Brilliant, I thought, all is good. The configuration I was using only called for steppers without encoders, nice and easy. I got it fired up, setup all my motion parameters and got the motor moving. Next thing I noticed is that while positioning, the steppers were oscillating! They wouldn’t settle down and stop in a final position.

Considering that the steppers are positioning a table that is being viewed by cameras at a high magnification, any oscillation will be clearly visible. So I called our local Beckhoff motion guy and setup a meeting. We started playing around with our setup and found out that he couldn’t get the motors to enable either! We played around for a little while trying to figure things out and as it turns out, because the modules are so new, you need the latest TwinCAT to get them to move.

As to why the oscillation occurs on a stepper motor without an encoder, you’ll have to wait for the next post. However, the moral of the story is, 1. Make sure you use the latest software 2. Be cautious of using the latest components out there, you may need to do a little bit of beta testing yourself!