1.1 Engineering Problem
In Singapore, because of the humid and warm weather, water heaters are not used for heating water. Rather, aquarium chillers that use either refrigerants or thermoelectric effect are deployed to cool and maintain the temperature of the water sufficiently for the fish to survive. Currently, the market only has aquarium chillers that chills the water continuously, unless the power source is turned off. This results in a great waste of electricity, as during cooler periods of the night, the water is cool enough and need not be chilled anymore. Permanent powering of the aquarium chiller often results in high electrical bills for the aquarium owner.
1.2 Engineering goal
The goals for this project are to build a Temperature Control System that is able to monitor the temperature and maintain water temperature by switching the aquarium chiller on at required periods of time, so as to allow a minimum operational cost of the chiller. In this first phase of the project, due to safety reasons, we are substituting the aquarium chiller with a 5 volt DC motor, until we can successfully build the entire system excluding the aquarium chiller. Since the aquarium chiller is only being substituted by a DC motor, the rest of the system will still be the same and will remain the basis for the second phase of our project.
1.3 Literature Review
Fish-keeping has been becoming a popular hobby for everyone around the world. The popularity of keeping fishes as a pet has been rising, be it on a small scale in a small aquarium or on a large scale with schools of fishes in an enormous aquarium. We have recognized that the number of people who have been directly engaged in fish-capture and aquaculture has reached 44.9 million as of 2008. Thus, we have embarked to create an aquarium which is able to control the temperature and requires minimal manpower.
Fishes are affected by the temperature they live in. Finding the optimum temperature for the fishes to survive and breed in is essential to any fish-keeper. Pankhurst and King; & Pankhurst and Van Der Kraak’s study (As cited in Chiu, 2010) both highlighted that “Temperature plays an essential role in fish reproduction, particularly in cueing the precise time of gamete maturation and spawning and providing the capacity for reproductive cycles to be locally tuned to shorter terms with less predictable variations in thermal conditions.”. Thus, identifying and maintaining the optimum temperature is very important. The acceptable range for tropical freshwater fishes is 76° to 80°F (25° to 27°C).
To be able to detect temperature, one would have to utilize a temperature probe. The temperature probes one may find on the market often consists of a long cable connected to a metal rod of about a span long. The metal rod contains and a small-sized temperature sensor. One of the most common temperature sensors used for multidisciplinary projects are the TMP-36GZ temperature sensor and the LM-35DZ temperature sensor. The LM35 series, manufactured by Texas Instruments are precision integrated-circuit temperature sensors, with an output voltage linearly proportional to the Centigrade temperature (Texas Instruments, 1999). The LM-35 temperature sensor are able to measure a temperature range from -55ºC to 150ºC, making it a versatile sensor for many applications. The cost of the LM35 sensors are also significantly lower than other temperature sensors, due to trimming and calibration at the wafer level. TMP-36 temperature sensors, which are manufactured by Analog Devices Inc. are similar to the LM35 sensors, except for a few variations. While it also sends an output voltage linearly proportional to the Celsius/Centigrade, the TMP-36 can only handle a temperature range from -40ºC to 125ºC. (Analog Devices, 2010). Thus, after comparing the advantage and disadvantage of both sensors, it would appear the LM-35 temperature sensor is a much better choice for use.
1.4 Specific Requirements
- It must be a freshwater aquarium, as this project is designed for tropical freshwater temperatures.
- Must be operated through an electrical supply.
For our project, we have found 3 plausible systems that could be used to achieve the engineering goal of a temperature control system. We had to ensure that the systems we are going to evaluate for our use is capable of being programmed, which is needed so that the relay board can switch on a chiller at a particular value of temperature. This means that any datalogger-only system has to be rejected, as they can only log data but not execute any functions. Our online research narrowed down the list to three different kinds of systems - the Arduino-based system , the PC-based system and the LEGO Mindstorms NXT-based system.
An Arduino-based system, as it suggests, is mostly based on the Arduino Uno board, which is the most commonly used version of the Arduino. Arduino is a single-board microcontroller designed to make accessible the use of electronics in multidisciplinary projects. The basic hardware consists of a simple open-source prototyping board designed around an 8-bit Atmel AVR microcontroller or a 32-bit Atmel ARM ("Arduino", 2013). The software consists of a Arduino Integrated Development Environment programming language compiler and a bootloader that executes the programming on the microcontroller. It can also receive inputs and log the raw data from multiple sensors, serving as a datalogger when connected to the computer. The Arduino Integrated Development Environment (IDE) software can be run on Microsoft Windows, Macintosh, and Linux operating systems.
The second system that we are considering is the PC-based system, which works by using a computer application or programming to execute the required functions. It can allow electronic devices such as microcontrollers, relays or sensors to communicate with the computer for data analysis and processing, after which further operations can be executed accordingly. Such a system allows for the real-time display of host computer, so that users are able to monitor and view the measurement systematically and easily (Mohd Adam bin Mohd Razali, 2007). Mohd Adam bin Mohd Razali (2007) also stated that more advanced features for data analysis such as plotting graphs allows users to be informed of the processes and status of the system.
Lego Mindstorms NXT-based system is the third system that is under evaluation. The Lego Mindstorms NXT 2.0 is a programmable robotics kit released by LEGO. It comes with NXT-G programming software, or optionally LabView for LEGO Mindstorms. The main component of the Mindstorms NXT kit is a open-source brick-shaped computer called the NXT intelligent brick. While the NXT intelligent brick can run basic programs on its own, complicated programs can be uploaded to the intelligent brick via a USB cable to the computer. The NXT software can run on both Macintosh and Microsoft Windows operating systems. The software provides a visual programming language for writing simple programs and downloading them to the NXT Brick. This means that rather than requiring users to write lines of code, the programming software instead uses flowchart like "blocks" to design their program (“Lego Mindstorms NXT”, 2013), allowing an easier and more functional programming experience.
1.5.1 Final Solution:
After comparing the 3 types of systems, we decided on making an Arduino-based Temperature Control System. The Arduino is an open-source electronics prototyping platform. It has a powerful microprocessor on the Arduino board that can execute actions or operations in connected devices according to its programming in Arduino language. It is also capable of recording data from multiple sensors when it is connected to a computer. Therefore, it is suitable for use for our Temperature Monitoring System, where the chiller has to be activated according to a certain temperature. It is also comparatively cheaper as compared to the other two options - computer-based system and NXT-based system. The other options are not selected: The computer-based system is not feasible as it would be a very complicated and lengthy process to connect analog outputs (temperature sensor) and wires to a non-Arduino microcontroller before connecting it to a computer. Also, constant use of the computer is very energy-consuming ; The NXT based system is not used because it would be similarly complicated, since there are no slots for separate electrical components to be connected.