I/O Hardware

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Thread Starter

Guy H. Looney

I have an application involving a SLC505. I will need to drop some I/O in remote locations & will be using Device Net. I need some advice in regards to selecting the hardware for the remote I/O locations. Specifically, please compare Flex I/O versus Remote I/O in terms of pricing, form factor, ease of use, & anything else that is relevant in regards to making a decision with which hardware to select. Thanks in advance, Guy H. Looney Motion Control Engineer A.C.E. Systems, LLC work: (615) 754-2378 fax: (425) 944-5017 cell: (615) 330-0044 website: www.acesystemsllc.com
 
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Steve Myres, PE

I don't think standard 1746 SLC I/O is an option if you are committed to DeviceNet, as I don't believe there is a remote rack adaptor available (like the 1747-ASB for the Remote I/O protocol). In my opinion, Flex I/O is overly expensive and the density is very low. AutomationDirect.com has DeviceNet adaptors for the 205 Series I/O racks as well as a new line of terminal block I/O which I believe is now shipping (as well as Profibus, SDS, etc.) In my experience, though, DeviceNet may be a poor choice as a remote I/O platform as it is designed with the capability to be an actual device (sensor / actuator) bus. 24VDC power is included in the bus cable, for example. You might want to consider Profibus or some other control level bus. I've found these to start up a little easier than DeviceNet (although admittedly, I'm newer at DN) Steve Myres, PE [email protected]erealtime.com
 
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ALVARO A. RODRIGUEZ Z.

You should also take a look at the VersaMax I/O from GE Fanuc. It does what you need, and is very price competitive. Regards, Alvaro Rodriguez REDES ELECTRICAS S.A. Bogota - Colombia
 
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Curt Wuollet

Hi I've used the Beckhoff(same as Wago) Bus terminal setup with devicenet. They have an "economy" bus coupler and IO is added in increments of 4 inputs or outputs. Seems to work well. These are distributed over a fairly short distance, 100m so your mileage may vary. Regards cww
 
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Larry Lawver

Steve--- From a given SLC 5/05, Guy wanted to add DeviceNet I/O. From a clean sheet of paper, I wouldn't choose this architecture today, but from the given 5/05, it's a way of moving forward. Profibus is not an option from this starting point, though. The Allen-Bradley Profibus Scanner product will be found in the same alternative universe as the Siemens Remote I/O Scanner, but not in the one we are conversing in. FLEX I/O is high-density and low-cost unless it is applied incorrectly. In the DeviceNet world, I would use FLEX profitably if my I/O count was more than forty I/O points at the node. For lower counts, I would consider CompactBlock or ArmorBlock distributed I/O systems. For I/O counts higher than sixty, FLEX is remarkably effective in reducing wiring labor, box sizes, and life cycle costs, especially at the machine builder. The advantage of FLEX I/O has always been that the field terminal blocks and the I/O system are integrated. This advantage is only important if field terminal blocks were needed in the first place. If space is more important, A-B offers the Compact I/O system off of the 1769-ADN adaptor and the Point I/O system off of the 1734-ADN adaptor. Ease of use is going to be a problem from the SLC 5/05 starting point. The SLC500 series was intended simply to migrate the SLC-100 series 12 years ago, but the market and advances in electronics have driven this product into the world of networked I/O. The SLC500 processor is limited to a relationship with distributed I/O through the memory map of a scanner, instead of a direct connection. This limitation applies both to open DeviceNet and proprietary Remote I/O. The configuration software helps to manage this, but ease of use can only be improved by moving up to a network-oriented architecture such as CompactLogix. Hope this helps! Larry Lawver Rexel / Central Florida
 
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Guy H. Looney

Larry, Thank you for the information. It is by far the most useful piece of information I have received to date. That surprises me a little, based on the number of AB installations & users there are out there. One thing you didn't mention was how Flex I/O hardware compares in cost to Remote I/O hardware (either way, we'll be using DeviceNet). I've heard that Flex I/O is much more expensive than Remote I/O. Is it your position that Remote I/O plus the cost of terminal blocks would be less than or equal to the cost of Flex I/O? Is there a difference in "ease of use" between Remote I/O & Flex I/O? The person that I'm speaking with has had good experience w/ Remote I/O & no experience with Flex I/O. Would the learning curve of using Flex I/O prove to be difficult based on his experience w/ Remote I/O; i.e. opportunity cost of switching? My application has between 100 and 150 points per distribution point. Each point would be contained in a cabinet & would need some sort of terminal blocks to wire the field I/O. Please advise. Thanks again, Guy H. Looney Motion Control Engineer A.C.E. Systems, LLC work: (615) 754-2378 fax: (425) 944-5017 cell: (615) 330-0044 website: www.acesystemsllc.com
 
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Larry Lawver

Guy- Ooops. I thought someone had already answered your original question while I was off helping a customer push a machine out the door! I do recommend using DeviceNet and FLEX in the situation you describe below. However, I want to clarify some things. Remote I/O and DeviceNet are networks and architectures. RIO is proprietary to Allen-Bradley and supported by a few dozen vendors; DeviceNet is open and supported by hundreds of vendors. RIO is classic Master/Slave; DNet is Producer/Consumer, which includes Master/Slave as a subset of its capabilities. RIO supports backwards compatibility to the early seventies; DNet looks forward from the mid-nineties. RIO only supports relatively complex objects; DNet can support a single point of I/O. Meanwhile, FLEX is an Allen-Bradley I/O product line introduced in 1994 that originally supported Remote I/O, but now supports most of the best-known industrial networks, including DeviceNet. Thus, FLEX vs. RIO is not really a comparison at all. They can be the same thing. (And at that level, RIO vs. DeviceNet costs about the same!) In your application, FLEX is a good choice, and DNet vs. RIO is an option. I recommend DeviceNet because it positions you cost-effectively for future enhancements to the machine. FLEX is costly. It only makes sense to use it when the cost of wiring, conduit, terminal blocks, and marshalling is significantly reduced. In my experience, I get there when field terminal blocks are required and the I/O count at the node is more than forty; at sixty I/O points, FLEX drops installation cost dramatically. Yet, with DeviceNet, a lot of choices from a lot of vendors are possible. Keep the dialog going by rephrasing your questions... Larry Lawver Rexel / Central Florida
 
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