Nuts and Volts - April 2017

Their arrows are on their left sides and are pointing in. This indicates that they are in the WRITE mode and are receiving data from the VI, wirelessly transmitting or “publishing” that data out of the MyRIO unit. The iPad data dashboard will have indicators linked to these and display their values. The orange color indicates that their data type is a DBL (double precision 64-bit number). You will also see pink rectangles for string data types; refer to box #12.

Box #1:

A one second time delay. This slows the while loop down so that the LCD is not constantly fluctuating. If you are not using an external LCD display, this could probably be eliminated.

Box #2:

This is the main while loop terminator. By clicking on the front panel stop button or on the BUTTON0 on the MyRIO itself, the while loop will terminate.

The BUTTON0 feature allows the user to stop the VI when it is running in real time and a front panel is not present.

Box #3:

This turns on external physical LEDs located on a breadboard connected to the MyRIO unit. The red LED indicates that you are in the heat mode; the green LED indicates the cool mode. These are the two top LEDs in Photo 2. Box #4:

This box allows three different ways to manually turn the heat output on, overriding the automatic temperature controlling function of the VI.

You can either turn the heater on from the iPad, click on the front panel HEAT ON manual control, or from the physical DIP switch #3 located on the breadboard.

You probably do not want to leave any of these controls on all of the time. They are really only there for troubleshooting purposes.

Box #5:

This box does the same thing as box #4 except it is for a manual override for the MyRIO cool output, which is DIP switch #2 on the breadboard.

Box #6:

This box acquires the analog voltage from a physical 10K ohm potentiometer located on a breadboard. It converts its 0V to 5V range into a 60 to 80 degree temperature range; 4 x 5 = 20, 20 + 60 = 80 for the maximum temperature that this pot can set.

Box #7:

This box acquires the analog voltage coming from the LM34 temperature sensor. It displays its raw or unaltered voltage on the front panel, then multiplies it by 100 to convert it to degrees F and displays the actual temperature. The “= to within tolerance” icon determines within + or – one degree when the heater or cooler should turn on or off. This makes it so that when the actual temperature equals the set temperature, the heat or cool output does not rapidly turn on and off attempting to maintain an exact temperature match but allows the system to be adjusted within a range.

Box #8:

This box turns the heater on in the heat mode or the cooler output on in the cool mode. LED indicators were added to the front panel to show when the TEMP < SET, TEMP = SET, or TEMP > SET. There are two physical LEDs on the breadboard as well (see the lower two LEDs in Photo 2). The green LED comes on when the cooler output is on and the red LED when the heater output is on. SSR’s positive control pins can be connected to the anodes of each of these LEDs to control actual higher voltage and current AC or DC loads.

Box #9 True and Box #9 False:

This box determines who is actually controlling the set temperature: either the front panel control; the physical 10K pot on the breadboard; or the slider control on the iPad. At the bottom of this box is a true/false case