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Who Keeps RS-485 and RJ45 Apart?

May 14, 2009
It Feels Like Suppliers Are Holding Machine Builders Hostage
About the Author

Jim Montague is the executive editor for Control. Email him at [email protected].

There ought to be a law. Unfortunately, many times there isn’t.

Sometimes there are criminal, prosecutable conspiracies that can be revealed and punished. Unfortunately, there also are conspiracies of convenience, inertia and neglect. These are less well-hidden, and so their outlines are more visible overall, but they’re devilishly persistent—like endless, low-grade fevers or a flu bug that hangs on and on.

For instance, you’d think it would be easy to get a certain type of cable made with a certain type of connector, especially if you and your friends were willing to order and pay for a lot of it. Well, not so fast, buddy. M&R Printing Equipment in Glen Ellyn, Ill., has been wrestling with a very frustrating problem for a long time. M&R builds several kinds of textile printing presses, which helps many T-shirt manufacturers stay nimble enough to deliver championship shirts to teams and fans seemingly within minutes of their victories.  

Bo Biel, M&R’s chief electrical engineer, says his persistent headache is seeking, but failing to find, suitable RS-485 cabling combined with RJ-45 connectors for basic communication on his presses. “In 2005, we started looking at the cost of communications between different components on our machines, such as temperature sensors, AC drives, servos and vision sensors. However, we wanted to avoid using one of the more costly fieldbus protocols. What we found was that suppliers have been focusing so much on Ethernet that they seem to have stopped developing RS-485 and that left us in limbo.”

Biel explains that Ethernet’s two main challenges have been developing its common-English TCP/IP protocol and disseminating wiring with clickable RJ45 connectors among its many users. Likewise, to be able to use TCP/IP, M&R settled on using Modbus TCP/IP and continuing to use Modbus RTUs via RS-485, says Biel. However, M&R found it couldn’t use pure TCP/IP because it’s a character-based language that can send numerical symbols but can’t send data values, and so it needs programming to translate and reassign values as needed. Consequently, three years ago, M&R began building its machines with Modbus communication cards, but service technicians began complaining that fieldbus wiring was difficult to install and troubleshoot because its connections needed precise torque or the network would be prone to communication problems.

“We needed clickable connections that would be quick and precise, so we could put together multiple devices fast like IT people using Ethernet,” says Biel. “Unfortunately, from 1995 until now, we still can’t find RS-485 cable that terminates in RJ45 connectors for industrial control and automation. There are clickable connectors for Ethernet wire, but no one seems to offer this for RS-485.”

Biel adds that Ethernet Cat. 5e cable with the right connectors is close to RS-485 and that many users can rig patch cables between RS-485 nodes, but these still pose communication, troubleshooting and cost problems. “We don’t have any lab-tested and approved RS-485 cable that’s clickable at regular prices,” says Biel. “Right now, it feels like the suppliers are holding machine builders hostage.”

Sadly, there are still suppliers who do what’s financially convenient for them at the expense of their customers. Usually, this is done so a few bad apples can make some extra quick cash in the short-term. This replaces traditions of behaving ethically, responding to and nurturing clients and patiently growing and profiting in the long-term. So, what’s to be done about these guys? Well, there are several possible steps.

  • First, do your best to make sure that you don’t buy any of their products.
  • Second, make certain that applicable consumer protection laws are applied to the full extent that local prosecutors can enforce them.
  • Third, organize yourself and your fellow consumers into a purchasing block that can shout out your demands more loudly and widely to the suppliers who should be making the products you need, and then reward those do it.
  • Fourth, if there’s no other way, explore the possibility of making a much-needed product yourself. If demand and a willingness to pay are great enough, then some development effort and a bank loan might  be all you need to carve out a new market niche for your company.

Of course, the snag these days is that a decent loan can be as hard to get as a good product. Maybe some of the responsible folks left should start a bank? Just asking.

About the Author

Jim Montague | Executive Editor, Control

Jim Montague is executive editor of Control. He can be contacted at [email protected].

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