Aquarium Monitoring System

Devin Bonnie

Summary:

The main goal of this design project was produce a device that would measure temperature, pH, and oxygen levels in a fish tank and display this relevant data on a LCD screen. This data would be updated based on the real time input from the sensors, thus the screen would constantly be updating the values displayed. A major goal of this project was easy setup to place the sensors within the fish tank and then have the user power the device. One important feature was to have sensors that did not need calibration, as this makes it easier for the user. Another important goal was to have accurate measurements of temperature, pH, and oxygen levels.
The many ideas that were considered for this design ranged from setups both inside and outside of the fish tank. The setup inside the tank would have the sensors built into the casing and have a waterproof seal for the electronics and LCD (which would be able to be seen from outside the tank). The setup outside the tank would house the electronics and LCD and the cables would run from the tank to this housing unit.
The final design completed was a housing unit that would hold the Onset TFX-11v2 microcontroller, Scott Edwards LCD, and 9V batteries and sit outside of the tank. The sensors attached to this housing unit are connected to the microcontroller and then are run to the tank to take the data measurements. Once power is applied to the system data is recorded to the LCD screen almost instantly, but first the microcontroller runs internal tests and prints a “please wait” message. After a period of about 3 seconds the LCD screen displays the relevant temperature, pH, and oxygen data. The temperature is in degrees Fahrenheit, the pH is simply levels 6-8 (if it is too acidic A!! is printed and if it is too basic B!! is printed), and the oxygen levels are in mg/liter (standard concentration measurement). The temperature sensor (analog thermistor) and the oxygen sensor both work perfectly with a high accuracy and quick response time (4 second response time, 10 degrees for each measurement max). However, the pH sensor is not as accurate as desired, with a +/- 10%, but will perform well in this setting. The plastic case used for the housing unit has worked out well in that the plastic is durable and fire resistant yet could be cut in order to make holes for the power/signal connections. The LCD screen fits in a hole made in the front of the box and fits well. All of these results fulfill the requirements the project set out to complete.