adccommunitymod (AutomationDirect) asked a question.
Writing to and Reading from Memory Locations
Created Date: January 19,2005
Created By: Sam
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I am using a DL 205 PLC. Has anyone ever ran into issues with scan times affecting writing or reading memory locations or is this an anomaly that only I am experiencing? Later, Confused http://forum1.automationdirect.com/board/smile.gif
Created Date: January 19,2005
Created by: Sam
I am using a DL 205 PLC. Has anyone ever ran into issues with scan times affecting writing or reading memory locations or is this an anomaly that only I am experiencing?
Later,
Confused http://forum1.automationdirect.com/board/smile.gif
Created Date: January 19,2005
Created by: franji1
PLC scan times definitely affect the SPEED at which you can read or write memory locations.
Please give more detail on what you mean by "affect " - both reading and writing.
Created Date: January 19,2005
Created by: Sam
My application is a knife-off using a CTRIO Card and an encoder. I run a profile of my cut length in the CTRIO and then read the encoder position from the top idler roller to see how much the material has slipped on the bottom drive roller. Then I subtract that position from the target of where I wish to be. Then I tell the drive to move that distance to make up for the slippage before cutting the piece. (This is poor attempt to make a closed loop system out of an open loop!)
The issue seems to be reading the encoder position register and subtracting it from the target memory location and writing the move position registers fast enough to keep up material line speed.
Have anyone else attempted such an animal?
Any help would be appreciated! http://forum1.automationdirect.com/board/smile.gif
Created Date: January 20,2005
Created by: clasentech
Yeah I have a similar problem. And believe it or not when I bogged down my ECOM (via wonderware and DSData) it gets worse. How are you talking to your drive? I have been living with this for sometime. I currently use the high speed pulses to tell the drive what to do. I am going to try communicating via ASCII and let the drive do most of the work instead of the PLC. I have a lot to learn first though.
DL260/CTRIO
Created Date: January 20,2005
Created by: Sam
I talk to the drive with pulses also. I'm going to attempt putting a color sensor on the web to try and stop the drive on a registation mark later today. I still wish to kept the encoder out there for now but if the color sensor works, then I'll have an encoder to play with on my next project!
Created Date: January 20,2005
Created by: Rday
I had a similar problem using the WinPLC and H2-CTRIO. I finally had to give up and just send the move profiles to the Baldor servo drive via ASCII. I used discrete I/O to flag the drive to start the move profile and look for the drives move completed flag. This is method proved to be far more accurate than I ever could have hoped for.
Classentech what brand of drive are you using?
Created Date: January 21,2005
Created by: clasentech
Rday you are the man.
I am stuck using Baldor. I have to upgrade to Flex+ for the ASCII. Right now I just have regular Flex. If I was not stuck with it I would probably use Yaskawa; they have MODBUS TCP/IP. I think I'd like to talk to you. Is this possible?
Created Date: January 21,2005
Created by: Sam
Using the color sensor works wonderfully. I should have perused this earlier! Now I run my profile with the cut-length I want and then run a homing profile to make up for slippage at the end to get me exactly at my registration point before I cut the piece. Quicker and more accurate plus I don't have to deal with reading and writing memory locations for the encoder!
Thanks for all the replies to my questions hope you all have a GREAT DAY ! http://forum1.automationdirect.com/board/smile.gif
Created Date: January 21,2005
Created by: Rday
clasentech,
Exactly what I am using. I started out with Flex too and had to upgrade to Flex +. You are in for some fun.
Sure I would be glad to talk with you and help any way I can. Email me at rday@pmaf.com and I will give you phone number.
Created Date: January 24,2005
Created by: clasentech
Yeah it looks quite cryptic. I'll be sure to get in touch with you. Thanks.