Remote IO nodes using Flex IO or CLX?

flyers

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Sep 2006
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Guys,

I'd like to ask what is the advantage of using Controllogix modules (1756-CN2R) at the remote IO nodes compare to Flex IO modules (1794-ACNR15).

I only see Flex IO is cheaper in cost, is there any features CLX can do, but Flex IO couldn't?

My redundant CPU is CLX architecture.

Hope to hear from you guys. Thanks.
 
The advantages to Flex are obviously the smaller size and the fact that it is less expensive.

The biggest advantage really to the CLX chassis would be the ability to add modules on the fly without having to reschedule the ControlNet network.

Of course you also get all the features of the 1756 style I/O such as diagnostic digital modules and scalable analog.

Those are off the top of my head. I'm sure others will pitch in with other recommendations.

OG
 
The advantages to Flex are obviously the smaller size and the fact that it is less expensive.

The biggest advantage really to the CLX chassis would be the ability to add modules on the fly without having to reschedule the ControlNet network.

Of course you also get all the features of the 1756 style I/O such as diagnostic digital modules and scalable analog.

Those are off the top of my head. I'm sure others will pitch in with other recommendations.

OG

OG,

Thanks for your input, I din know we have to reschedule the ControlNet network if adding one module to the Flex IO. By rescheduling the CNET, meaning we'll have a down time on the system? Our system is a monitoring system, even tho there is no fast process involved, but the up time is very-very critical. That's why the redundant CPU, power supply, media comes in the picture.

Can't we assigned 8 IO modules for each Flex IO adapter at the beginning of the project? Or we must specified what type of Flex IO modules we'll be adding in?

I taught the adding IO modules is the same as CLX & Flex IO.

There is not Devicenet involved in this architecture.
 
You must specify what modules are in the system whether it is CLX or Flex. Adding modules that don't exist yet can be done but they would need to be inhibited to avoid being identified as errors.

If you use CLX you can add new modules online and in Remote Run mode without having to re-schedule the ControlNet. The new modules operate in the unscheduled bandwidth on ControlNet. But the benefit here is that the PLC can continue to run and the network is unaffected.

For Flex I/O you must go offline to add the modules and then download it when done. This of course requires the PLC to switch to Program. Then you must reschedule the ControlNet.

It sounds like you need the CLX style for your remote.

OG

Controlnet.jpg
 
Why you guys saying that flex I/O is cheap compare to ControlLogix?
Here is an example fo analog input.
I understand that you still need chassis and power supply for logix, but bottom line will be very close once you add all modules.
17 slot chassis takes about the same panel space as 8 flex modules with adapter.
Since Logix modules have much better functionality and support online edit, I would think twice when selecting flex I/O

Don't get me wrong, if you have few modules only, Flex is probably more cost efficient.

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a1756.jpg a1794.jpg
 
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17 slot chassis takes about the same panel space as 8 flex modules with adapter.

Flex has the advantage of having a nice terminal strip already in place for landing field wires. With a CLX/SLC chassis you really need to have dedicated terminal blocks for landing field wiring to make start up/troublshooing/future mods easier. Throw in terminal blocks for that 17 slot chasis and that format's footprint expands substantually. Remote flex blocks allow for smaller control panels in mulitple locations rather then one extremely large control panel in a single loction. That single location will cost more in wiring/conduit/labor then a remote flex setup will.
 
While I agree that Logix needs terminal blocks, I still believe that 17slot chassis with terminal blocks will take about the same space as two 8-module banks of Flex I/O (that needs some terminals too).

The most important that "low cost" Flex I/o in most of cases will cost about the same as logix I/O

As for true remotely located I/O, I would recommend to look at Point I/O instead as a better (not chaper) option than Flex
 
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Somewhat skewing the topic of IO, but the FlexIO processors are in silver series. My inclination is that the flex IO would be moving in that direction to be replaced by PointIO?

For low density remote locations, I use the PointIO modules - lower cost and works fine. Otherwise I use the 1756 series IO.
 
I would also suggest Point in stead of Flex.
I am bit surprised that the price advantage isnt better with point i/o.
You certainly save a bunch on the point adapter compared to 1756 Rack+CPU+adapter. But the i/o cost almost same.

How about Beckhoff ?
Similar to Point IO, works with DeviceNet and Ethernet/IP, and costs 1/3 of Point I/O.

edit: Oh, I see that we are talking about Controlnet here.
I think that Beckhoff is the only 3rd party supplier of Controlnet adapters:
http://www.beckhoff.de/german/bus_terminal/bk7000.htm?id=201533526245
 
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Somewhat skewing the topic of IO, but the FlexIO processors are in silver series. My inclination is that the flex IO would be moving in that direction to be replaced by PointIO?

For low density remote locations, I use the PointIO modules - lower cost and works fine. Otherwise I use the 1756 series IO.

I've moved off of FlexIO completely, and on to the PointIO platform. Smaller, more intelligent, pretty inexpensive, and very configurable.
 
Guys, thanks a lot for all the feedback. the Flex IO must go offline to add IO is really a big turn off in the critical (monitoring) system which require up time.

I think I'll redesign my system in CLX platform instead of Flex IO, yes I do notice there is not much cost impact between Flex IO and CLX IO, but our panels normally has redundant 24V DC power supply for the PLC. For flex IO, we can use 3rd party 24V DC power supply which we can share with other devices in the panel. If CLX IO is used, we must have 1756-PB75R, which cost around USD 2000 each set.
 

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