Our current setup has a GSM shield, SD shield, Arduino Mega, Proto board, RTC, conductivity sensor, pressure sensor, and two thermistor’s. Let’s work from the ground up; since this project brings together many different components, a lot of libraries and memory storage are needed by our device, so the best option for us was the Arduino Mega 2560 microprocessor. The GSM shield transmits the data wirelessly to a Google Docs spreadsheet, so that we can get the data in real time. We found a great tutorial on connecting the arduino to a Google Docs spreadsheet here, http://www.open-electronics.org/how-send-data-from-arduino-to-google-docs-spreadsheet/. For the GSM shield we are using the Arduino GSM shield. We also wanted to store the data on the device, just in case we cannot connect to a wireless network, so we used the Sparkfun sd shield. Since there are many additional components that we are using for power management, such as the Real Time Clock (RTC,) relay, transistors, and resistors, we bought a pro to-board to solder all of them together. We used the PCF 8563 RTC as a way to save power; the RTC, in combination with a relay, allows the Arduino Mega and GSM shield to be on only when it is taking and transmitting data.
For sensor’s, we used the Atlas k10 Conductivity Sensor to take salinity and conductivity readings of the water, we chose the k10 series because it is the only one that can measure the salinity of salt water. We also purchased a conductivity circuit from Atlas, so that we could get the data from the sensor. For our pressure sensor (which allows us to calculate the depth) we chose the AST 4500 vented pressure gauge with a 1-5v output, which allows the Arduino to measure it directly through the onboard analog digital convertor. To measure the temperature of the water we used a 10k ohm thermistor with threaded mounting fitting from Omega and to measure the temperature of the air in the pvc pipe (to see if the electronics were overheating) we used a glass encapsulated 10k ohm thermistor. Other parts that we needed were two 10k ohm resistors (used in series with the thermistors,) a few feet of different colors of wire for soldering, solder (60/40,) and a soldering iron. FInally, I used a transistor (PNP?) to sink current, and a switching relay to save power.
Links to all of the different parts below:
Arduino Mega 2560 – http://arduino.cc/en/Main/arduinoBoardMega
Sparkfun SD shield — https://www.sparkfun.com/products/9802
Arduino GSM shield – http://arduino.cc/en/Main/ArduinoGSMShield
RTC PCF 8563 – http://www.wvshare.com/product/PCF8563-RTC-Board.htm
Conductivity Sensor – https://www.atlas-scientific.com/product_pages/sensors/ec-sensor.html
AST 4500 Vented Pressure Gauge (1-5V) – http://www.astsensors.com/submersible_level_sensors/AST4500__AST4510
10k Thermistor for Measuring Water Temperature – http://www.omega.com/pptst/ON-910_ON-970.html
10k Thermistor for Measuring Electronics Temperature – http://www.omega.com/pptst/55000.html