Specifications

96
transmission. The ZigBee chip then transmits the information to the ZigBee chip
on the Main Control Unit.
The Main Control Unit is the most complex part of the Efficient HVAC Control and
Feedback System. The Main Control Unit is composed of a main microcontroller,
a ZigBee wireless transceiver, an 802.11b RF transceiver, control relays and a
temperature and relative humidity sensor. Our main control unit deals with two
types of interfacing conditions that communicate with the main microcontroller
and two types of connections. They are SPI (Serial - Peripheral) and I
2
C (Inter-
Integrated) interfacing as well as the serial connection between the main
microcontroller and the LCD Touch Screen Display. This serial interface will
consume one of the two UART connections. Figure 48 shown below illustrates
the main control unit‟s interfacing structure for the Efficient HVAC Control
System.
Figure 48 - Main Control Unit Interfacing
The main microcontroller is then required to accept inputs from multiple sources.
First, it must accept the information that has been transferred from the Remote
Sensing Unit using the Zigbee chips. Second, it must accept another
temperature and relative humidity reading from the on - board sensor. Third, it
must accept user inputted settings from the LCD touch screen interface controller
board. Fourth, it must accept inputs from the web server through the 802.11b