Project Motivation, Needs and Goals
My name is Albert Hagan and I am a graduate mechanical engineering student.
My interest lying in energy led me to do this project because its application involves the conservation of energy.
In this experiment, I am going to create a temperature-controlled system called Envivovent. This control system uses temperature sensors such as the DHT, thermocouple and the temperature resistor sensor to measure the temperature at different locations within the Envivovent. The goal of the project is to be able to control and study the temperature within different locations in the Envivovent using fans to cool the system via a relay channel and an Arduino control board.
Applications of this system include greenhouses, industrial rooms and in in projects which apply temperature-controlled environments.
In order to model a system which is temperature controlled, we adopt a mathematical model form the zero dimensional energy balance equation.
Project Background
The principles of first law of thermodynamics is applied to understand the energy changes in the system. Next, we apply the zero-dimensional energy balance equation. The zero-dimensional energy balance equation enables us to come up with the parameters of the equation to analyze the system. The equations developed can be shown below:
Next, we also study the principles of the Psychrometric chart and incorporate that into the project. The psychrometric chart is a graph that employs the principle of using the humidity ratio and the dry bulb temperature to determine to determine the properties of air at a specific temperature.
Equations for studying the system.
The above equation can then be converted to a first order ODE. This can then be solved using numerical methods.
Project Schematic and Sequence
The electrical connections ar
Materials Used
The materials used in this experiment are:
This is a basic lowcost temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and output a digital signal.
THERMOCOUPLE MAX 31855
The thermocouple is a temperature measuring device which measures resistance using voltage difference across its wires.
This contains 4 5v relays which interfaces microcontrollers and sensors. It can be used to switch multiple loads at the same time.
Learning Objectives
The project is designed to enable to student gain knowledge in the following areas:
- Arduino Programming
- 3D printing and CAD Modelling
- A strong understanding of psychrometry and heating ventilation.
- Electrical circuit connections and Electrical Schematics
- Using PID controls to stabilize and optmize an HVAC system.
Project Vision and Narrative
The ultimate vision of this project is to enable the student to understand psychrometry, heating and ventilation to be able to control characteristic factors of a system. This will then be used in modelling a building system to minimize energy loss.
Arduino learning
- In this part the student will learn how to read data from a sensor. The sensors used are the DHT 11 sensor and the MAX 31855 thermocouple. This will be done using arduino. The arduino will serve as the main control unit of the system and it will communicate with the sensors to record data from the surroundings.
- This part can be performed by students in their sophomore year as it will help improve their knowledge on basic electrical circuit connections.
Calibration
- Learning to calibrate the sensors.
- The ice bath method involves inserting one end of a K-type thermocouple wire in an ice bath with a pre-measured temperature of 0C by a dry thermometer. The temperature of the end of the other K-type thermouple is measured. The temperature difference creates a voltage difference which helps to measure the temperature of the ice bath. A graph linear of voltage vs temperature in degree celcius is generated and checked against the readings provided by the thermocouple manufacturer. If they are similar , then it is calibrated.
This is found in modern thermocouples where the cold junction compensation is inbuilt. It adjusts the voltage in the sensor compensating as if the cold end is an ice bath.
- This part will involve connecting the relay channel to the arduino to and making the electrical connections on the perforated board. This is the current phase of the project and the image below shows the electrical connections. This part can be done by students in their junior year and will help improve knowledge in basic electrical connections and reading schematics.
An autonomous system that is able to read data on its own and use PID control to keep the system stable. The PID(Proportional Inetgral Derivative) is a control loop mechanism which uses feedback to improve stability and optimize the system control.
Tuning system control characteristic factors such as temperature
Instructional Lecture 1: Project Overview
This video shows an overview of the project. It walks us through the various stages, stating the current phase of the project and also the future directions in the next phase.
Instructional Lecture 2: Thermocouple Calibration
This video explains the calibration methods used for thermocouples.
About the Author
My name is Albert Hagan and I am a first year master of science student in the MEMS department. My interest lies in the area of controls and energy. I had my undegraduate education at Temple University and I studied mechanical engineering. Prior to being a student at Duke University I worked as a project engineer, modelling land development plans for a civil engineering consulting firm.
Last updated May 2021
