chrgibson

Our tags are very simple: Events(10) INT eg. Machine Faults, Power, Safety Guards Data(7) INT eg. Cycle Times, Force Measurements, Pass/Fail Acknowledgements(5) INT eg. Handshaking between applications and PLC/OPC I'm not sure how I can even detect the crash in VB, let alone restart it.

Hi all, just wondering where I can get the specification/documentation for the OPCDAAuto.dll? We've noticed over the last week a couple of show stopping OPC crashes (the actual OPC server not our applications), once this happens we don't receive any data arrival events for the group that crashed. I'm using the OPCItem.write syntax to allow me to write arrays back to the PLC. The syncwrite method was allowing me to write an array but was only writing the first value (without errors).

Thanks guys! I think the best way forward is to further group our data into arrays of data. This should leave us with 3-4 bits/arrays of data per process. Since we are not heavily reliant on speed, it shouldn't cause us any issues.

Well I don't get any data change events in Visual Basic/OPC until the PLC writes to the parts of the data table I'm monitoring. This means our 'end of cycle' data (the majority of all data) will only come in once per 30 seconds. What I've done is setup a group in the OPC server that contains all the 'end of cycle' data, and another group that has all the safety and line stop bits. What this means is I only have to run through all the end of cycle data once. The safety/line stop group simply logs the on/off states of the bits, and this can happen any time, but 99.9% of the time there will be no changes to these bits and therefore no data events to handle.

Well we've got it setup now with two test processes with around 10-15 tags in each, we dont envisage any more tags, but I'm a little unsure what is meant by: If we use a WORD or DWORD then the OPC server seems to constantly poll, but if its an INT or LONG then the values are not visibly polled. Does OPC poll the data internally? Or a more relevant question is do you mean we'll be ok as long as the VB app isnt polling?I'll be setting up a test including counters that will be logged, three cells is our maximum test at the moment.

The PLC will only be used to fire the scanner, everything else will be handled externally. It must get a good read to validate the part and continue in the process, which means the process will wait until the part has a good scan. There will be no chance we will miss a barcode scan.Thanks Jesper!

We will be scanning around 3 per minute per process, and we have around 25-30 processes. The Keyence scanners will be daisy chained, the PLC will fire the scanner and I will simply receive the result through the com port. I'm not worried about the scanning and validation, because I will be using MSMQ to make sure the application is always responsive. I'd prefer not to go down this route until we've exhausted all our streamlining ideas!Thanks again for the help.

Hi all, very informative forum from what I can see, so hopefully this will be the place I can get some support. I have been tasked with a full traceability system on three production lines using Allen Bradley PLCs. There is already a DH+ network and we will be using Keyence barcode scanners. Myself and my colleague have been looking at PLC to DH+ to VB6 communication and seem to have settled upon using the OPCDAAuto.dll along with an OPC server to map the data we require. Each line will have around 40 nodes and its own PC to collect the data. There will be around 20 tags or so for each machine. These tags will be grouped into 3+ groups so I can receive events separately and reduce processing. We will struggle to create enough of load test to be 100% confident this solution will cope with amount of data flowing around. First tests seem positive, but will this prototype scale up to full production size? I've little to no experience in OPC or DH+ and have only just noticed the syncread method so I can pull data from DH+ myself (from a single 'data ready' bit tag possibly). Would this be a better method? Also, I'm looking for the documentation for the automation DLL, does anyone have a link? Thanks in advance!