How can I send the latest DB entries of a column to a PLC if the DB table is a historical table?
A little about the process…
This involves an annealing furnace that can hold 12 boats. A boat is just a metal tray that the parts are stacked on. The operator uses a PC to give the boat an ID number. Each new boat ID is logged in the database along with other info. I need to send the ID number to the PLC as it shows up in the DB (Oper PC to DB then to PLC). The boat ID will then be saved in a shift registry in the PLC in the order it showed up in the database. The ID will be used to track and display the boat through the furnace and cooling areas.
I’ve been watching the videos and reading the forum. I am using a standard transaction group and Bi-directional mode with the table action set to update/select. The only time I can get it to update the item value of the OPC item is when its the very first entry of the table. I have tried setting the update/select mode to first and last but it doesn’t update the item value after the first entry. I have read one forum entry that says to use the custom setting with the where clause but I don’t know what the boat ID will be when it shows up in the database. My SQL instruction knowledge is weak and I don’t know if there’s a way to use the where clause to get the data I need.
Thanks in advance