First head to the outputs table and configure the first stage cooling. At Tab1 we give the item a long 20 character name which is used in the graphics displays and floorplans. At Tab3 we give the output a short label which is used in the programming. At Tab2 you click in the ‘Range’ column to bring up the dialog with various ranges and select off-on.
Next head to the inputs table to configure the room temperature sensor. The sensor inside the Tstat10 case is at input #9 but any of the inputs could be used. Configure the range at Tab5, in this example we’ll use DegF and a 10k type3 thermistor.
Now set up a variable to hold the setpoint for the room101. We’ll use DegF here to match the temperature sensor range
Next configure the PID loop by clicking on the PID icon as shown below. The PID is what tells the system to go into cooling or not. First specify at Tab6 which sensor to use for the PID feedback. You can input either IN9 or the user name of TEMP101. You could also use any of the other inputs in the system, its completely up to you and the application which sensor will be used as feedback for the PID loop.
Next specify the setpoint for the PID loop at Tab7, this will be the variable we previously configured for the setpoint. At Tab8 we set the PID loop action to a ‘+’ for cooling. The plus sign means as the setpoint exceeds the setpoint the action of the PID loop becomes larger.
The P term at Tab9 is set to 2 which means we want the PID to go from 0-100% when the temperature exceeds the setpoint by two DegF. This is quite a sensitive PID setting which will be suitable for a larger room, increase it for a smaller room to avoid short cycling. Leave the other terms like Int(egral) and Der(ivative) terms at zero to get started, most applications work very well with them left at the default of zero.
The output of the PID loop is shown at Tab10, the example is prepared offline but in a normal online system the output will be at 0% when the setpoint is satisfied and increase up to 100% as the room temperature goes above the setpoint.
Now that the PID is set up we need to use it to turn the cooling on and off, this is a very simple program to get us started. Click on the programming icon and hit the button at Tab11 to bring up the editor, then cut & paste the simple program below at Tab12. Hit the send program at Tab13 to check the syntax and send the program to the controller:
10 REM ****** ROOM101 COOLING **********
20 IF PID1 > 50 THEN START COOL101
30 IF PID1 < 30 THEN STOP COOL101
Assuming all went well you will get the ‘Success’ dialog as shown. Make sure the program is running at Tab4 by setting the program to ‘On’. When you are connected to a live system you can see the execution time of the program, the output will go on and off as the temperature and setpoint change.
You can debug the program by setting the temperature at input9 to manual mode where you will be in charge of the reading. Enter some high and low temperatures in the ‘Value’ column to see the PID and the output responding. It can take several seconds for the program and PID action to kick in. If its not responding check that the program is in fact running, check that the PID is responding as expected, if the I term is non-zero for example it will take some time for the integrate term to wind down.