Specifications

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delivered to the array driver when the I/O pin goes to its “high” state. This range
of current is within the range accepted by the array driver to switch the
corresponding internal transistor to the “on” state. The pin will hold its “high”
state while the corresponding HVAC component needs to be running and the
transistor will stay in its “on” state, keeping the corresponding resistor‟s contacts
touching providing the control voltage (24V AC) to the power relay that will allow
the HVAC system component to run.
4.6 Demonstration
The final step in the prototyping process is the demonstration of the HVAC
control system. We will be required to make the system portable so that it can fit
into a room to be tested in front of a panel of professors. Because the system is
designed to be installed into an existing building, there are obvious modifications
that must be made in order to demonstrate the system works to a group of
people in a room. Actually installing the system into the building where the
demonstration will take place is not an option as there is already and HVAC
control system in place. Also, installing it into one of the homes of the group
members is not possible because the group is required to have the LCD touch
screen interface in the room where the presentation will take place.
Main Control Unit and User Interface
The main control unit and the user interface will be mounted to a surface, such
as a sheet of plywood that will allow them to be fastened as if they were installed
on a wall in a building, but at the same time be portable enough for the group to
carry the system into the room where the demonstration will take place. The
main control unit and user interface will be well secured to the backing surface
using a method such as screws. The group will wait on the arrival of the LCD
screen to see if it comes with any mounting hardware and if it does not they will
shop for hardware suitable for mounting a 7” LCD to the wall of a building.
During the demonstration all functions of the LCD touch screen will be shown
and the group plans on letting a person not in the group operate the touch screen
to show that it is easy to use.
Remote Sensing Unit
The remote sensing unit is designed to be mounted on the outside of a building.
It is designed to be powered by a battery, and therefore will require no external
power supply. This unit will be small in size and easily transportable. It is also
designed to communicate with the main control unit wirelessly. Since it does not
require external wires for power or for communication, the remote sensing unit is
completely self contained. The internal components of the remote sensing unit
will all be mounted on a printed circuit board. There will be a sensor, a
microcontroller, a wireless chip, and a battery mounted to the board. Since this
unit is designed to be placed outdoors, the printed circuit board will be mounted
inside of a housing to protect from the harsh elements that outdoor electronic