I am building a Microsoft Access database to log scale weights in a batch mixing application. I am using RSLinx and a PLC 5/20. I know how to use the DDE link to link to the scale values but I don't know how to set up a trigger to log the weight just before the batch dumps. I have a batch ready bit that goes high just before the batch dumps but I am unsure how to use the bit in Access as a trigger. Thanks

 

Assuming that your Access can talk to the PLC via DDE. You than need to use the VBA in Access to respond your high bit as an Event. In the Event Procedure you can then do what ever you want to do, calling another procedure etc.

 

Use the batch ready bit (leading edge, one-shot) to move the scale weights to another set of registers (N or F files). Call them Previous weights. The batch ready bit will trigger the database to collect the information from the previous weights registers. They will not change until the next batch, so you should have plenty of time to collect them.

The batch ready bit may need to be stretched by using a timer so the database will have time to see it. Or you could use a handshaking scheme.

Let me know if you need more help.

Lewis Bodden
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