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About macg

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  1. Thank you BobLfoot & Joe E.  I know I posted this back in December.  Christmas shutdowns had us all very busy.  There is only one Control Logix processor.  The various other components that may or may not be attached to the system will all be blocks of remote I/O.  We are mimicking the old PLC-5 setup for the customer.  
  2. I'm sure many of you remember AB's DH+ communications.  I have a system that is variable or configurable.  I have a customer that paints large parts automatically.  The coating process dictates what type of auxiliary equipment is required.  I wrote a program years ago that would determine what subroutines to run depending on what DH+ stations that reported in when the processor was powered up.  The program new by what was attached the type of system it was and controlled that particular process.  Thank goodness DH+ is for the most part in the past. This same customer wants to upgrade many of the PLC-5's running this code to a ControlLogix.  I'm struggling how to create the same type of setup of determining what equipment is attached be looking for the IP address.  Has anyone done this or have ideas on how to find a known IP address on a network?  The IP addresses are all fixed.
  3. I'm look for some suggestions for two problems.  1. I'm working on an environmental chamber that I only need to control the temperature.  It's range is -50C to 200C.  Cooling is accomplished with CO2 on a single valve.  Heating is made up of 3 heat levels; high, med and low.  I'm using a ControlLogix processor with a PIDE and SRTP instructions.  I originally monitored the output percentage of the heating portion of the SRTP instruction to determine which level of heat to use.  However that confuses the gains of the PIDE when switching between the heating levels.  Any suggestions on how to determine which heating level and how to tune the PIDE? 2. A second issue with the PIDE instruction is that the temperature input is not very stable while operating.  A blast of CO2 into the chamber of course drops the temperature quickly which the sensor reflects however when the valve is off the temperature is warming back up.  So the D portion of the PID instruction is going crazy.  I've tried averaging to try to smooth it out and that wasn't helpful. Ideas???  Quit my job and be a Walmart greeter?
  4. Logix5000 PIDE Heat/Cool Tuning

    Thanks dFx.  I had thought of your item 3 last night while trying to sleep!  Yes, my typical method for tuning a closed loop system would be as your last few sentences stated.  This PIDE instruction for its autotune uses open loop.  I have one more trick up my sleeve to try this morning.  If that fails I'm going back to the standard PID instruction and do something similar to your item 3.  Thanks for the help.
  5. I'm looking for advice.  I have an application requiring control of an environmental chamber that requires both heating and cooling.  My temperature range is -60C to 200C.  Cooling is provided by CO2 and heat is a high wattage heater and a low wattage heater.  I've read through about every tech document Rockwell has to offer on heat/cool PIDE.  So I have the CV to start off at 50, 50 and up is heating, 50 and lower is cooling.  In general, that seems to work.  The issue is the tuning.  I have finally got it to run through the tuning process.  However the results where outrageous numbers.  For example P=15, I=1.6 and D = .07.  The CV oscillates wildly.  After 5 minutes,  it kind of settled on the setpoint but it was poor control.  I tried playing around with the instruction like I'd tune a regular PID control and that didn't work well either.  One more piece of information, loop update is 1 sec (1000ms).  I tried 2 and that made it worse. Any suggestions?  Should I just run back to the old PID?  Tuning seems to be my biggest issue.
  6. ASCII !@#$!@#(*&^

    Thanks VDS.... most helpful post of response.   I'm sure you older guys understand my frustration.   This stuff was supposed to go away with our youth.
  7. ASCII !@#$!@#(*&^

    Hi Guys, I need help/advice.  First, I'm not new to PLC programming and design. I've been doing this for 30 yrs.  OK that said, 30yrs ago I cared about things like PLC5 serial communications sending ASCII characters as it was a common thing.  Well, I've slept and drank a whole hell of a lot in 30yrs so I really don't care now but I need to do it again. I'm working on a PLC5 to Control Logix conversion.  The company will not update this ancient chamber environmental control.  So, the ASCII coms need to stay.  The old PLC5 took the command string to change the temperature and did a AWA command and out port 0 the new temp setting went.  Logix however, it is not that pretty.  I'm using a Prosoft Technology PLX31 Ethernet to ASCII.  My problem is, the Prosoft device data table in the Logix is data type SINT.  How do I get the command string "L1S"+temperature value, example 27C, so the command would be "L1S27" into the data type array of SINT.   The header is constant.  The only thing that changes is the digits.  So would you guess I convert the L & 1and put those in the first address, S and the first digit of the temperature in next address and the remaining digits in the 3rd word?   Perhaps I'm making it all too difficult.  From what this old memory is telling me, I need to convert each character into the ASCII Hex or Decimal equivalent.  So anybody out there still familiar with this s....tuff? 
  8. Rockwell 1756-IRT8I

    Thanks Ken.
  9. Rockwell 1756-IRT8I

    I'm using three 1756-IRT8I's.  This is a test application.  Of the possible 24 TC inputs, they may use any one of the inputs or only 1.  One TC is required on the first card input 0.  The reset of the points may or may not be used.  I do not see a built in bit that indicates whether or not a TC is connected.  Should I just look at the under range bit?
  10. PF755 Cip Motion

    I have just been handed a horrible task. I am to program a control logix processor for 5 PF755's such that 5 hoists raise and lower together. The hook height can not vary more than 1" between all five as they are moving. For most lifts, all of the hooks are at the same level. For some lifts the hooks will be at different levels but must move maintaining the shape. Two types of motions are required. One motion is operator jog. The second is an automatic lift or lower to a predetermined location. Any suggestions other than just saying CIP motion????