Upgarding from PLC-5 to ControlLogix

[Steve Cav]

Hi,

I'm looking to upgrade a machine from PLC-5 to ControlLogix.

Unfotunately the rack contains a number of 1771-NIV (8 Input High Resolution Analogue Input Cards). Which is the equivalent card in ControlLogix?

Also there are IMC121's which I can presumably replace with Sercos. The rest of the I/O are 1771-IBD, 1771-OBD and 1771-OFE, which shouldn't be to hard to find a direct replacement.

Processors are PLC5/86 & PLC5/66 which I'll replace with 1756-L61

As the machine will be down for several months for repair there should be no problem in moving the I/O to the controlLogix

Any Help Appreciated
Steve

 

[Ken Roach]

You'll want to do a little homework on the 1771 "N-Series" Analog modules and determine exactly what mode (current or voltage), range, and polarity are being used.

There's no precise equivalent of the 1771-NIV in the 1756 family but several modules overlap in capability.

1771-NIV was an 8 channel isolated +/- 5V or +/- 20 mA bipolar analog input module with 15 bit resolution. In current mode, the precision was 0.70 uA per bit.

The standard 6-channel isolated input module for ControlLogix is the 1756-IF6I.
It's resolution is 16 bits, with 0.34 uA per bit in current mode, so it's roughly twice as precise as the 1771 module.

But you'll see that the 1756-IF6I is unipolar in current mode; if you happen to be using the bipolar current mode of the 1771-NIV then you'll need a different input module for ControlLogix or you'll have to change the sensor.

If you run into very precise or unusual voltage ranges, the Spectrum Controls modules for the 1756 chassis can often handle them.

It sounds like an interesting project. I'd read about the PLC-5 "x6" secure controllers but never actually saw one in the wild.

 

[Honga]

I suppose another route would be to keep your PLC-5 Rack and use a RIO card in the ControlLogix, if it's a hassle to replace the analog.

 

[Steve Cav]

Thought about keeping the PLC-5 rack and using a RIO card in the ControlLogix but I think I'd have a problem with the IMC121 cards. Also the machine will be down for months so it's a good time to replace the lot as the IMCs are obsolete. It would also free up PLC-5 spares for other machines

 

[Steve Cav]

Thanks for the info Ken,

Done a little digging around and the 1756-IF6I should be an adequate replacment.

 

[bobbuilder]

We did a PLC5-Ctrlgx conversion a couple months ago. Too many remotes to change so used a RIO card, most racks used a combination of standard isolated digital & both 1771-NIS inputs & 1771-NOC outputs. No issues with the anal inputs but the output cards caused some problems. Apparently with the Control Logix they won't take their scaling & revert to default scaling values. For example almost all outputs used to be scaled in the PLC5 so that 4-20mA = 0-4095 for PID etc...Now they must be scaled 4000-20000 (which after much digging I found out is the default for those cards) No matter what scale you tell it to use, it doesn't change. Not that big a deal but it would have been nice to know this sooner. I had researched the knowledgebase at the beginning because I wasn't too familiar with the N-series cards, but this issue never came up.

 

[LadderLogic]

No issues with the anal inputs

That's good.

 

[daba]

.... but the output cards caused some problems. Apparently with the Control Logix they won't take their scaling & revert to default scaling values. ...

I have used 1771-NOC with ControlLogix and can confirm they will accept whatever scaling you require (within their constraints).

All thats needed is to poke the right values into the BTW array and fire that at the module, which incidentally won't know or care the identity of who sent the configuration BTW.