need advice regarding pros and cons of devicenet-

Hi Everybody,

I need your advice regarding pros and cons of using DeviceNet. We have an application with 17 VFDs and 33 fixed speed devices and need to decide whether to use DeviceNet or not. On one hand some people claim that DeviceNet system eliminates up to 90% of motor control centers traditional control wiring. On the other hand, it is said that analog data transmission over DeviceNet consumes a lot of bandwidth and if analog I/Os count for more than 5% of a total I/O count, it can be tricky to set up the connection in a in an organized and predictable fashion. Will the cost savings in wiring be offset by the increased cost of programming and maintenance? While I can understand DeviceNet usage in applications with several hundreds motors (like paper mills, for examle) I am not quite convinced about my application which is a relatively small environment cleanup plant. I want to avoid using of DeviceNet just for the sake of using it. Please advice. Thanks!

Wesley,

It sounds like you made up your mind already. But here are my pros and cons:

Pros:
Available monitoring data i.e. fault codes, at speed, etc can be displayed on a HMI.
A lot less wiring and mistakes from wiring.
Automatic Device Recovery (ADR) - when a device fails hook the new one up; power up, down, and back up; and the line is running again. Don't have to re-program parameters (very helpful with VFD's)

Cons:
Learning curve. If you have time to learn it DNet is the way to go.
Another network to maintain. Although with the 7 or so networks in my plant that are about the size as yours, I never had any "network related" trouble.

The PLC programming either way is pretty much the same. As is cost of components/wiring. And if you are worried about network size; I just setup a network with only seven nodes on it. Be careful about the upper limit though, only 30-35 devices on a 125K network (especially if the majority of the network is VFD's). And follow the recommendations for power and grounding requirements from your manufacturer/supplier.

Other than that it's a piece of cake!

Patrick