Nuts and Volts - April 2017

the functions you want to incorporate.

There will be problems when you try to duplicate anyone’s complicated LabVIEW VI. Even having an electronic copy of a VI does not guarantee that it will operate on another MyRIO or PC without some troubleshooting taking place.

There are many files associated with any VI, and they can be located in different folders, directories, etc., on different computers. I realize that this system is not a cost-effective replacement for a $20 household thermostat. This is just a way of providing a universally understood control system, and using LabVIEW and the MyRIO to solve the task while learning how to use them.

The file view, front panel, and block diagram for this VI can be seen in Figures 4, 5, and 6. Figure 6 is an overall view of the complete diagram which will be broken down into individual boxes in the sections that follow. When explaining how the VI operates, most of the time will be spent going over how the block diagram works. It should be fairly straightforward to recreate the front panel and place the same controls and indicators as well as the iPad data dashboard. To make the block diagram explanations easier to follow, decorative frames were placed around most of the areas. Numbers were placed in the upper left corner of each decorative frame. These frames are for documentation purposes only and do not affect how the VI operates.

The Initialize frame on the left simply makes sure that the heat and cool outputs to the MyRIO D I/O lines are off. It also initializes who sets control to the front panel; this might be necessary in the event someone using an iPad had set itself as the temperature controller and did not return this control back over to the front panel. The Close frame on the right makes sure that the heat and cool MyRIO outputs are off. The explanations will be listed in order frame by frame. However, we’ll call it box by box here so as not to be confused with the sequential frames.

First, a word about the wireless “network published” variables you will find located throughout the block diagram. They are only necessary if you want to include the wireless control and display features through an iPad data dashboard. For example, in box #5 is the green MODE_CON rectangle with an arrow pointing out of its right side. There is a corresponding MODE_CON on the project view window under the DDASH_TEMP.lvlib label. This icon was placed in box #5 by dragging it from the project view window down onto the block diagram. The arrow on its right side is pointing out; this means that it is in the READ mode and will be wirelessly receiving data from the iPad data dashboard control linked to MODE_CON. It will receive this data from the iPad control and pass that data into the VI. The green color signifies that it is a BOOLEAN type of data — either a T or F. Notice on the block diagram in box #10 there are two orange boxes with the words “temp” and “set” in them. FIGURE 5.