Start Learning OPC

Good for you! Of course, when I hear "skill set", I think, "bow-hunting skills, nunchuk skills, computer hacking skills", the outcome of having had teenage kids when the Napolean Dynamite movie was popular.

For conventional OPC DA (Data Acquisition), you need more than PC/laptops, you need some kind of field device from which to read data that an OPC server can fetch data from. Any box that's a Modbus slave will do, like a temperature controller, or a PLC with data communications capability. If you don't have access to a field device that need the services of OPC (PLCs, controllers, whatever), one alternative might be to find and install Modbus slave simulator software (Modbus TCP over ethernet will be easier to implement than Modbus RTU over RS-485) on one of the PC/laptops, so that an OPC server has some device to connect to and read its data.

To my knowledge there are no freeware OPC servers. (An OPC server runs low-level drivers for the field device communication and the effort to produce and maintain such drivers is generally seen to warrant a profit.) But it's a big world and there might be a freebie out there.

For self-teaching, experimentation and test purposes, the 2 hour run time of a commercial OPC server can't be beat. Most of the OPC server vendors offer a free download and some free trial period. I know Kepware's OPC server has a 2 hour run time limit, then it has to be closed and restarted. There is no calendar limit on Kepware's package (it doesn't lock out after a month or whatever). If you save your work, nothing's lost when the 2 hours times out and the OPC server and test client can be restarted and run at full capability. I use Kepware to 'prove' that devices I deal with can be read by an OPC server.

Most of the OPC server vendors also offer a limited function OPC test client, which when launched, finds the OPC server and displays the data that it's been configured to read from the slave device.

HMI/SCADA software packages nowadays are OPC clients, or have an optional module/component that makes them OPC clients. The client is configured to request data (OPC DA is inherently report-on-exception, but can be re-configured if need be) from the field device(s) through an OPC server.

The OPC Foundations' web site has a document on configuring DCOM (a Windows component) which is a necessity for OPC DA. Be sure to find it and go through it item by item, or your efforts will come to naught because DCOM defaults to a disabled condition in Windows.

Matrikon offers a tunneling package as an alternative to DCOM, but reports from users warrant wariness.

The latest version of OPC, OPC UA, is now out there but I'm still dealing with people who run DA and AE (Alarms and Events). If you run it, let us know how it works.