Demand Controlled Ventilation using CO2 Sensors in a Wireless Sensor Network
Dave Parsons, Lewisville ISD, Georgette Jordan, Dallas ISD
RET Program- Summer 2013
Faculty Advisor: Dr. Xinrong Li, Dr. Rudi Thompson
Graduate Student: Sherin Abraham
Department of Electrical Engineering, College of Engineering
University of North Texas
INTRODUCTION
Abstract: The focus of this research project was to investigate Indoor Air Quality (IAQ) monitoring technologies, government regulations and policies, and
best practices to improve IAQ. The goal being to minimize the adverse effect of poor IAQ in direct relation to CO2, specifically in the classroom environment
and test demand controlled ventilation applications. The investigation involved: development of a cost effective indoor air quality prototype sensor unit for
CO2 levels; the testing of the unit in a simulated room environment; and collection of data from testing. The data from the simulations was then compiled and
analyzed. Additionally, literature research was instrumental in determining testing parameters and conducting experiments. This provided valuable
experiences which will be shared with the educational community.
In recent decades much research has gone into the concept of improving
indoor air quality, specifically its importance as a public health issue.
Research has shown that both short term and long term health conditions
can be linked to the indoor characteristics of buildings. According to
ASHRAE, “providing superior IAQ can improve health, work
performance and school performance, as well as reduce health care costs,
and consequently be a source of substantial economic benefit.”
Indoor Air Quality Sensor Setup
Project Goals
o Build experimental IAQ CO2 monitoring system with “Demand
Controlled Ventilation” capabilities using Arduino technology
o Compare the performance of the prototype with the professional grade
Gray Wolf IAQ measurement system
o Test IAQ CO2 wireless sensors in simulated room environments to
collect IAQ data
o Analyze effects of building materials on CO2 levels
o Develop a lesson plan and prepare hardware and software for
inclusion in a high school classroom
Wireless Sensor Network
Receiver/Fan Control
Results
CO2 Sensor/Transmitter
This project uses an Arduino board in combination with an XBEE shield
which allows the Arduino to communicate wirelessly using Zigbee for
our wireless sensor network (WSN). The WSN consists of three
components: gateway, node, and software. The node interfaces with an
indoor air quality (IAQ) sensor board that was specifically designed to
mount on and interface through Arduino. This IAQ board is capable of
monitoring carbon dioxide (CO2) levels and triggering a “Demand
Controlled Ventilation Fan” to evacuate excess CO2. The IAQ monitor
node transmits CO2 levels wirelessly through Zigbee to the host. The
IAQ sensor assembly and wireless transmission is based on the
compatibility of the Arduino with the XBEE modules either from Max
Stream or Digi, depending on which shield you incorporate into the
design. Possibilities for usage include using it as a serial/USB
replacement or put it into a command mode and configure it for a variety
of broadcast and mesh networking options.
Comparison of Prototype Unit and GrayWolf Sensor
Indoor Air Quality Room Simulation Project
.
To be able to use the CO2 Arduino prototype, a calibration
had to be done by use of a professional IAQ sensor, the
GrayWolf. The ppm from the GrayWolf were correlated with
the voltage output from the prototype. Voltage
measurements from the CO2 sensor readings correspond to
levels of CO2 as the graph on the left shows. Getting the
Arduino to turn on a fan at a minimum threshold level and
ramp up its speed with more CO2 was accomplished with
programming skill and panache.
Prototype Design
Readings were taken from 6 simulations:
Simulation 1: Dry Wall, unpainted (2 pcs. 5” x 26”)
Simulation 2: Cinder Block, unpainted (16”x 7.5” x 3.5”)
Simulation 3: Bricks (3 ea. 7.5” x 3.5” x 2”)
Simulation 4: Ceiling Tile (2 ea. - 1 sq. ft. each)
Simulation 5: Linoleum Floor Tile (1 sq. ft.)
Simulation 6: Plants (1 Fern & 1 Caladium)
Fan vs. Gravity Driven Ventilation
With a 20 second response time, the fan driven exhaust
system evacuated the CO2 at a far greater rate than that of
gravity and kinetic motion alone, bringing the enclosure from
a ridiculously high CO2 level to a safe one in under 2
minutes.
o Each simulation was monitored using our IAQ
prototype, the Gray Wolf, and a Dell computer.
o Each simulation was tested to see if the building
materials had any effect on the CO2 level
o We then analyzed the data to identify certain trends
based upon each simulation
Amusing Discovery
One peculiarity the group uncovered was the fact that cinder
blocks absorb CO2. Much more time and effort could be
expended in investigating this phenomena, but time and
budget excluded the group from further pursuit.
This work was supported by the RET program through the
UNT Engineering School and staff.
We appreciate the opportunity to participate in this research
project and look forward to sharing what we have learned
with both district teachers and students.
Research Experiences for Teachers
Our “On Demand” CO2 Sensor and Ventilation prototype incorporates
two distinct designs using Arduino and Zigbee technology. The first is a
CO2 sensing unit that has an additional filter/amplifier board. This
assembly wirelessly sends CO2 levels to the second assembly which
turns on a ventilation fan when the CO2 reaches predetermined levels.
The fan speed is determined by the CO2 levels. Higher levels require
faster fan speeds to evacuate CO2 from the room to improve IAQ.
RET (Research Experiences for Teachers), on Sensor Networks, Electrical
Engineering Department, and Institute of Applied Sciences, UNT, Denton,
Texas. This material is based upon work supported by the National Science
Foundation under Grant No. 1132585 and by the IEEE Control Systems
Society (CSS). Any opinions, findings, and conclusions or
recommendations expressed in this material are those of the author(s) and
do not necessarily reflect the views of the National Science Foundation or
IEEE CSS.