jmalter

We just tried powering up a PLC5/80E that has sat unpowered for who knows how long.  The processor battery light and PROC light are on solid. Does anyone know any tricks for getting this processor running again? fyi, its not for production.  We are doing some migrations and wanted to use this to test some DH+ communications. thanks in advance, Joe Malter Grantek      

Russell, Thanks for the quick reply.  You gave us new hope and it worked.  The challenge was getting a serial connection to the processor.  Our USB to serial (and throw in through a VM for complexity) failed to connect.  We were able to get RSLinx to connect once we switched to a docking station with a hard serial port. All good. thanks, Joe

Is it possible to limit the tags an extrnal client can read/write in a Controllogix processor? We have a situation where a DCS needs to read and write data to a L71 based system and I would like to protect all other tags from possible manipulation. The DCS vendors preference is to use Ethernet/IP (CIP). We could use a Prosoft card using Modbus and only map what they need however I don't want the extra programming or using a slot.

We are looking for a recommendation for a label engraver for our panel shop. We've always gone out to some suppliers for this service but have a large panel project that requires thousands of labels and we know it will be cheaper and more flexible for us to make them ourselves. I saw a Roland EGX-350 recently at a trade show and it looked good. Does anyone have experience with this unit or company? I look forward to your reply. Joe Malter PSI Control Systems

Thanks for the input. Someone else recommended the GravoTech M40. All our tags are plastic. I'm looking for something that can engrave a sheet of labels like a spreadsheet that we would break a part into individual labels. Can the unit you recommend do that?

We experiencing some unexpected starting of motors that are controlled by E3+ overload relays. We are using one of the inputs of the relay for a start signal from a hand switch in the field and I suspect there is an induced signal on the control wires when another motor starts. The 120 VAC control wiring is in the same cable tray as the 480 VAC motor leads and some of the runs are a couple of hundred feet long. I don't know how close the cables are in the tray. The E3+ as an EIMD interface to convert from 120VA to 24VDC. We tried installing a 33k ohm resistor from the input to common but this did not help. Our next option is to install a interposing relay. The buckets are crowded and it will take some time and skill to install. There are about 20 starters with this configuration although not all have experienced this problem. We couldn't measure the voltage as the signal is probably too fast. The problem is intermittent. Does anyone have any recommendations or suggestions? Rockwell was not very helpful.

Thanks. You saved me a bunch of trial and error. Worked like a charm!

I'm trying to setup a MicroLogix 1100 PLC to Write ASCII strings out to a display. I'm not sure how to deal with control characters. The following is the format of the string: Format: <SOH>1<STX>65;reason ID number<ETX> Example: <SOH>1<STX>65;11<ETX> The value 11 is the only variable I need to change. <SOH> = Start of Header control code 01Hex <STX> = Start of Text control code 02Hex <ETX> = End of Text control code 03Hex Any suggestions? - Joe

Excellent point. We are using the input to the PLC. Assuming the cross talk is short duration we can add a timer in the PLC to make sure the start push button is held in for say one second. Anything shorter will be treated as noise. The operators may need to hold the switch a bit longer but the motor is right there so they can hold it until the pump starts.

Thanks for the reply. I'm not sure how to size an inline resistor. We can try measuring the current but I'm not sure a standard Fluke meter will catch the signal.

Thanks, that should do the trick.

We are using Controllogix with Enternet/IP communications to remote I/O using ENBT modules. We want to keep the CPU running even if one of the remote chassis fail or we take the panel out of service. I figured out how to override the processor and allow it to run witht the rack off but I don't know how to find out if the rack is failed(off) through programming. we wnat to display and alarm on our HMI. Any ideas?

This is news to me. Do you have any more information on the problem? I have a number of WW systems with that configuration on a job site in China with WW newbies starting them up. They have not reported any problem. We staged the system for several weeks but did not have any continuous operation of the application.

I'm developing some standards for some of our projects and I'd like some feedback on recommendations and ideas. I'm somewhat new to Logix but have a lot of experience with 5's and SLC's. It was suggested, for analog inputs, to scale on the card to engineering units. What are the advantages/disadvantages? It looks pretty straight forward but I seem to recall some limitatiions. There are many ways to handle analog alarming including ladder, function block, and at the HMI. I plan to make the PLC routine generic therefore requiring Low, Low Low, High, High High alarming and the ability to enable/disable the point. The function block item appears workable but we have to consider conditional alarms; such as ignore low suction pressure until the pump has ran for 5 seconds. I'm not sure how to handle these types of conditions with the function blocks. I'm intersted to hear what the PLC experts out there think. regards, Joe

I've have link thousands if not tens of thousands of points between WW and AB plc's without seeing this type of problem. I'm pretty confident Wonderware is not the issue. (although I think there is a way to tag browse with DASABTCP server. I've haven't had a lot of luck or much time to look into it.) The problem appears to go away if I enable the 4 AI JSR's in the sample code. I think my original assumption is correct. With so little logic the processor is spending a lot of time in the Alarm scaling and alarming subroutine.

I used your basic concept and made some adjustments to meet our requirements. I am experiencing one problem with our HMI interface where I sometimes have a hard time writing a value to the PLC. My guess is the subroutine resets the controller tag with the data returned from the subroutine. The values "take" when the program is not in the subroutine for that item. The HMI is Wonderware Intouch and we are reading the controller tags such as PI-101. We make the alarm alarm limits available to the operator (password protected). I sometimes have to enter it 3-4 times before it takes. Any suggestions? AI_ScaleAlarm.ACD

Thanks for your advice. I found a good document called Logix5000 Controllers Design Considerations, Publication 1756-RM094A-EN-P, that has a lot of good information specific to logics. There is a good section on programming methods covering Inline duplication, Indexed routine, and Buffered routine. I'm all for fail safe logic hardwired inputs but once it's in the PLC you can handle the logic anyway you prefer. We prefer using a normal closed (XIO) PLC internal to a coil that goes high (1) in alarm.

1. Not if you call it from another routine multiple times, unless I'm missing something. The logic enabling and resetting the timer changes each time you call the subroutine with different variables. For example if you first call it for PIT-101 and PIT-101 is above the High setpoint then the high setpoint delay timer should start timing. Then the program leaves the subroutine, back to main, and then back to the subroutine with PIT-102. If PIT-102 is below it's High setpoint the timer will reset. Your logic is slightly different using the TOF timer but the concept is the same. 2. I'm talking about the GRT, LES type functions. It makes more sense to me that when the PV is greater the setpoint then it's in alarm. Your logic is if the PV is less the setpoint then it is NOT in alarm. It works the same but not as clear.

Thanks for the example program. I like the use of subroutines and gerneral program structure. I have a few comments/questions: 1. Don't you have problems using timers in subroutines? It seems like the timers would not work independantly for each run through the subroutine. 2. I'm not crazy about the negative logic used is comparing the PV to the setpoints. It's less intuitive but works. Did you need to do this for a reason?