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The next step is to add two new states: "Add Chemical" and "Settle." First, click add new state and name the state "Add Chemical." For this state, we need a rule. There are many rules we could create, but for simplicity's sake, let's say that if the time in the Add Chemical state exceeds 1000 s that we should switch to "Settle."
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You can see that in the figure above that the next state to proceed to is set to OFF. Set this instead to "Settle".
Step Four: Create Set Point for Rule
Next we need to create a set point so that the computer has a value for the 1000 s time interval which it will spend in the Add Chemical State. Click on set points and click "Add Set Point" after the last set point you just added. Title the set point "Time for Add Chemical" and enter a value of 1000 (as the time in Process Controller is measured in seconds).
As a quick exercise, make a rule for the "Settle" state that if the time exceeds 300 seconds then switch back to the "Add Chemical" state.
Step Five: Edit State to Correspond with Stamp Box Controls
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For the "Settle" state, we wish to turn off the pump and turn off the valve that releases chemical, and we wish to turn on the "Drain Valve." Do this and then confirm that your edited state looks like the one in the figure below.
Step Six: Check the Stamp Box
If you have not already done so, plug in the appropriate valves and pump to the appropriate location in the stamp box. Remember to check that the stamp box is communicating with the computer and that your code makes logical sense for what you are going to run.
Exercise for Completion
We're not done yet! Your next task is to add another state "Drain" to drain the experiment. Set the time for the drain state not to exceed 10 s. You should then set the order of processes to be "Add Chemical" state switching to the "Settle" state switching to the "Drain" state. The "Drain" state should then switch back to "Add Chemical" state. In this sense, we are creating a cyclical process that could run indefinitely. In the "Drain" state set the "Drain Valve" to ON.
Click here to see if you have set up the process appropriately.