Control.com - Nerds in Control

Hi,

We are a small company integrating vision and robotic systems into customer production lines.

We have a query from a customer, who wants a PC-based vision system to communicate with his A-B CompactLogix series 1768 with 1768-ENBT Module.

The communication requirements are very simple, about 10 digital I/O lines.

What is the cheapest and most simple option regarding communication interface on the PC (.NET)?

Ethernet/IP based communication?

OPC server on the PC?

I've looked at the .NET controls from automated solutions, but cannot decide whether they are completely overkill for my purpose or there exist some simpler means.

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Best regards,
Jakob Kirkegaard

You have two requirements here. One is the customer wants the connection through an AB Ethernet/IP PLC module. That implies AB's proprietary Ethernet/IP protocol. The PC software drivers available for that seem to be OPC servers from a couple of companies, AB itself, Matrikon and Kepware. These drivers are usually a lot more expensive than you would guess, so be sure to get a quote on the cost before you commit yourself to the customer.

The other requirement is that you have to interface to whatever vision software you are planning to use. What is that capable of? If the capabilities of this software don't include being able to interface to an OPC style AB Ethernet/IP driver, then you have a design conflict that will have get resolved one way or the other.

To address your question more directly, you raised three points as if they were different options (Dot-Net, Ethernet/IP, and OPC). They actually cover different parts of the problem.

Dot-Net is just Microsoft's brand and marketing name for a set of some of their proprietary programming languages and accompanying libraries. Ethernet/IP is AB's proprietary Ethernet network protocol. OPC is a set of libraries from a vendor association which lets two proprietary vendors connect their products while releasing the minimum of information about how their system works. These different things can connect together, but they are not substitutes for each other.

For handshaking between a PC application and a robot or PLC that doesn't have an open interface, the cheapest solution in many cases is to use conventional discrete digital wiring between the PLC (or robot) and an Ethernet I/O module. You can get I/O modules from companies such as Advantech (ADAM 6000 series) or a few others whose names escape me at the moment. These would connect the PC's Ethernet port so you can control it from your PC program. Modbus/TCP is an open protocol, and you can get drivers for free from a number of sources. You would link the drivers directly into your PC application without needing any OPC stuff in between. That is assuming of course that you have the source code for the PC program. If not, then you are probably out of luck when it comes to this option.

This may seem like going the long way around to connect two things together, but often it is a lot cheaper and simpler than gluing bits of proprietary software together. In many cases, its the only way to connect two things together.

The above gives you some options. I can't however recommend a particular approach without being more familiar with the overall application.

Checkout Acromag's Model 989EN Ethernet I/O Module. See below.

Model 989EN-4C16, 16 ch DIO (any mix of ins/outs), Ethernet Modbus TCP/IP communications, low cost. Here's the link:

http://www.acromag.com/parts.cfm?Model_ID=375&Product_Func tion_ID=27&Category_ID=22&Group_ID=2

For .net communications, there are several good software companies with Modbus TCP/IP drivers. Try http://www.automatedsolutions.com,
http://www.modbusdriver.com, http://www.sapia-inc.com, among others.

Donald Lupo
dlupo@acromag.com

Hi Jakob,

Automated Solutions .NET driver for Logix family is available with two license options:

1. Full Development, which allows for a single development PC and runtime deployment to multiple target PCs.

2. Single Machine, which allows for development and runtime on same PC.

If the Full Development license at $899 is overkill or doesn't make economic sense, consider the Single Machine license at $249.