Demand Controlled Ventilation using CO2 Sensors in a Wireless Sensor NetworkDave Parsons, Lewisville ISD, Georgette Jordan, Dallas ISD

RET Program- Summer 2013Faculty Advisor: Dr. Xinrong Li, Dr. Rudi Thompson

Graduate Student: Sherin AbrahamDepartment of Electrical Engineering, College of Engineering

University of North Texas

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)

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 levelo We then analyzed the data to identify certain trends

based upon each simulation

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.

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.

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 improvingindoor air quality, specifically its importance as a public health issue.Research has shown that both short term and long term health conditionscan be linked to the indoor characteristics of buildings. According toASHRAE, “providing superior IAQ can improve health, workperformance and school performance, as well as reduce health care costs,and consequently be a source of substantial economic benefit.”

Indoor Air Quality Room Simulation Project

Indoor Air Quality Sensor Setup

Research Experiences for Teachers

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.

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Wireless Sensor Network

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.

INTRODUCTION

Project Goalso Build experimental IAQ CO2 monitoring system with “Demand

Controlled Ventilation” capabilities using Arduino technologyo Compare the performance of the prototype with the professional grade

Gray Wolf IAQ measurement systemo Test IAQ CO2 wireless sensors in simulated room environments to

collect IAQ datao Analyze effects of building materials on CO2 levelso Develop a lesson plan and prepare hardware and software for

inclusion in a high school classroom

Prototype Design

Results

Comparison of Prototype Unit and GrayWolf Sensor

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.

Receiver/Fan Control CO2 Sensor/Transmitter

Fan vs. Gravity Driven VentilationWith 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.

Amusing DiscoveryOne 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.