Specifications
101
4.1.3 Sensirion
Sensirion is an engineering firm that is located in the municipality in the Canton
of Zürich, Switzerland. This company consists of more than 180 employees that
manufacturer sensor parts primarily for OEM applications. Sensirion was created
in 1998 by Felix Mayer and Moritz Lechner. The products developed at Sensirion
are applied in the medical field, automotive industry, and HVAC systems. The
technology for the sensors integrates CMOS circuitry. Noticing that these
products are used in the HVAC systems, we ordered humidity and temperature
sensors from their company‟s website. This company played a big role for our
project because of the need for our HVAC control panel to read the inside and
outside temperature and humidity settings. When looking at which part would
best work in our system, we had to make sure that these sensors would meet the
conditions that the sponsors wanted. In order to meet the conditions, the
component that would do that is the SHT21 temperature / relative humidity
sensor.
4.2 Printed Circuit Board
The most important issue that comes into constructing our HVAC control system
is the printed circuit board design. Printed circuit boards are necessary because
it allows all of our IC chips (for Temperature and Humidity) as well as the LED‟s,
resistors, capacitors, memory devices and other electronic circuits to be soldered
by surface mount technology directly to the PCB. Without the surface mounting
process, we would have to manually connect everything to the board by a
soldering iron and the process would take too much time. Nowadays PCB‟s are
assembled step by step using computer based programs. The software used for
these computer programs are nice to utilize because they allow for flexibility in
board design layout as well as editing in case you make a mistake.
To start the printed circuit board process, our group went onto the website:
<http://www.pcb123.com/>. From there, we downloaded the free PCB Design
Software. When comparing this software to other existing software available out
there, this one best suited our needs. The software acts as a prototype for our
HVAC control system so we can refer to it often in case for help. Once we fill in
all of the detailed design specifications for our PCB we can directly order it from
the PCB software.
Procedure for designing a new printed circuit board using the PCB123 software
for our HVAC control system:
1) Call the board any name that you want.
2) Make a netlist file for your printed circuit board. A netlist file will tell the
manufacturer in an organized fashion all of the listed individual
components, their numbered terminal ports, and where they should be
placed on the board.
3) Next step is to define your board size in terms of width and height of the
printed circuit board. Make sure to choose a good width and height so that