if the temperature drops more than two degrees below
the set temperature. The upper LED is turned off and the
lower LED is turned on.
Hopefully readers will be able to duplicate this VI
and system hardware. The system is not perfect and
other features and enhancements to the hardware and
software could be added. For one thing, the cycle times
could begin after the chamber has reached the desired
temperature rather than including the heating up and
cooling off times in the cycles. LabVIEW is also capable
of PID (proportional integral derivative) control which
was not used. It’s possible for LabVIEW to store the
results of the chart into a spreadsheet or other types of
files, as well. The acrylic box may not the greatest
material to be heating up; it seems to hold up well at up
to 130°F. Most of the electronics are inside of the
chamber and are going through the thermal cycles
themselves which probably isn’t the best thing for them
either. The system built here is more of a demonstration
unit and a way for the author’s students to learn how to
use NI’s hardware and LabVIEW software.
NI’s LabVIEW software is a very powerful
programming tool. Readers interested in gaining more
proficiency in LabVIEW should spend some time
exploring National Instrument’s website at
www.ni.com. SV
FIGURE 9
FIGURE 10
SPECIAL THANKS
Thank you to Garth Black for his help with this article. Garth is a field systems engineer with
National Instruments for Utah, Idaho, Montana, and Wyoming.
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SERVO 07.2009
53
