Productivity PID Loop - Part 8 - Programming Miscellaneous Logic
(VID-P3-0041)
Part 8 of 11
Programming Miscellaneous Logic. Productivity3000
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In this video I’ll cover some miscellaneous ladder logic that is used to control our Stack Light Tower indicators and audible alarm, and also make the overflow shutdown circuit functional. We can program our signal from the high level alarm float switch relay to give us both an indication on the C-more Touch Panel that there is a problem, and also sound the audible alarm horn on our Stack Light. Referring back to our schematic diagrams, the float switch is wired so the overflow shutdown relay is normally energized if conditions are OK, and a normally open contact is wired into the Master Control power circuit to allow it to be energized. Another normally opened contact from the overflow shutdown relay is wired to input 2 on our P3-08ND3S DC input module that allows us to monitor the status of the overflow shutdown circuit. Back to our ladder logic, we see the symbol for a normally closed contact with the Tagname ‘Overflow’ is used to control the Stack Light audible horn that has been named ‘Horn’, and is physically wired to the first output of our P3-08TD1S DC output module. Bottom line, if the float switch is actuated, indicating a too high water level in our Process Tank, then the overflow shutdown relay is de-energized, the Power On and Emergency Stop circuit is dropped which kills power to the Diaphragm Pump. Also, the Stack Light horn is sounded and there is also an indication on the C-more Touch Panel that the float switch has been actuated. Also shown on our miscellaneous logic are a couple of Math Instructions that are used to calculate a high alarm value and a low alarm value. A volume of two hundredths of a gallon is added to the current Tank Volume Set Point for the high alarm, and subtracted from the Set Point for the low alarm. The results are used to control the three Stack Light indicators, as seen in the next ladder logic explanation, to let us know if the Process Tank’s current volume is within plus or minus two hundredths of a gallon of the Set Point, or if it is above or below this narrow range. With some additional simple ladder logic programming using the Productivity 3000’s Compare Contacts, we can have the three colored Stack Lights indicating our Process Tank’s volume status. The Red indicator is lit when the actual ‘Tank underscore Volume’ value is ‘greater than’ the Tagname ‘High_Indicator’, and the Amber indicator is lit when the actual ‘Tank underscore Volume’ is ‘less than’ the Tagname ‘Low_Indicator’. Finally, the Green indicator is lit whenever the volume is neither greater than nor less than the actual ‘Tank underscore Volume’. A normally open contact using the ‘Power underscore On’ Tagname is used in each indicator rung to turn off the corresponding indicator if the Power On/E-Stop circuit is powered off. In Part 9, I will cover the use of the C-more Touch Panel’s built-in PID Faceplate Bar Graph Meter that will make setting up and using our PID Loop a lot easier.
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