Greenhouse Automationx - VTC

healthyapricotMechanics

Nov 5, 2013 (3 years and 9 months ago)

66 views

Greenhouse Automation

Silas Harris

Tsjellum van der Stok

Problem Statement


The VTC greenhouse has two individual
climates, each contain fans, heaters, and vents
that are controlled by an obsolete Wadsworth
microSTEP

greenhouse controller.


VTC has requested a new control system that
will interface seamlessly with the greenhouse,
allowing full manual override when necessary

System Configuration

2
20V AC motor opens and closes
roof and wall vents. (4) total
motors

Potentiometers will be
mechanically fastened
to the roof and wall
vents, relaying precise
position feedback

120V exhaust fans
lower interior
temperatures in
conjunction with the
vents

Thermocouples placed
throughout the zones will
precisely measure temperature

System Configuration (continued)

Two humidity sensors
will measure relative
humidity in each
climate, relaying this
information to the
controller

Preexisting relay
panel consists of
(40) 5 amp relays,
connected to each
load, i.e. heaters,
fans, vent motors,
etc.

Reznor

heaters
contain 2
-
speed
fans.

1
nd

Solution

The first possible solution
includes a Click PLC, and an
analog user interface. Downsides
include the archaic UI, and
relatively high cost. Expansion
modules may be required to
interface with further
accessories. Benefits include the
simple programming (ladder
logic), and seamless relay
integration.

2
rd

Solution

The second possible solution is
the usage of a microcontroller,
such as an Arduino or a
Freescale

8 or 16 bit MCU.
Advantages of this solution are
the flexible programming (C
language) and very low cost.
The UI would be similar to that
of the PLC, analog gauges and
lights to indicate output
conditions. Disadvantages
would be the UI and the
potential issues found in
CodeWarrior.

3
st

Solution

The third solution is to utilize a
National Instruments USB
-
6212
and a laptop computer to
interface with the sensors and
relay panel, as well as offer a
professional user interface.
Potential issues are the required
computer to display the GUI, as
well as high cost. Benefits include
simple programming (
LabView
),
as well as GUI.

Conclusion


To conclude, we have chosen option three. We
feel that using
LabView

in conjunction with a
DAQ would offer the best end user interface
and provide a relatively simple programming
method.