Introduction: Mapping the Mangroves Wireless ORP Sensor

In aqueous solutions, the reduction potential is a measure of the tendency of the solution to either gain or lose electrons when it is subject to change by introduction of a new species. A solution with a higher (more positive) reduction potential than the new species will have a tendency to gain electrons from the new species (i.e. to be reduced by oxidizing the new species) and a solution with a lower (more negative) reduction potential will have a tendency to lose electrons to the new species (i.e. to be oxidized by reducing the new species). Because the absolute potentials are difficult to accurately measure, reduction potentials are defined relative to a reference electrode. Reduction potentials of aqueous solutions are determined by measuring the potential difference between an inert sensing electrode in contact with the solution and a stable reference electrode connected to the solution by a salt bridge.

< Needs attention from a chemist! >

The sensor you're building is designed to measure the Oxygen Reduction Potential and Temperature of seawater. It will transmit data back to the Gateway (link to gateway instructions) Node for later upload to the Internet.


Step 1: Materials Required

This project requires the following:
  • Solar Panel
  • Arduino Sensor Shield
  • ENV-TMP Temperature Sensor
  • ORP Sensor Probe
  • Saboten Sensor Node
  • 2.4 GhZ Antenna
  • ORP Calibration Solution
You will also need the case (not shown) and a #2 Philips Screwdriver.

Step 2: Install the Arduino Shield

The Arduino Sensor Shield will only work properly if it's installed the right way around. Its pins must align with those of the Saboten board (pictured with red outlines).

Place the Arduino Sensor Shield on top of the Saboten board and make sure the pins are aligned on each side. Then gently push down until the two boards are attached to one another.

Step 3: Install the ENV-TMP Temperature Sensor

The ENV-TMP has 3 colored wires (Red, Black, White) on one end, and a silver probe on the other. The probe is what senses the temperature. The wires need to be attached to the blue screw terminals on the Arduino Sensor Shield in the right way.

Looking at the shield, you will see that three of the blue screw terminals are under the heading "TEMP" and have "W B R" written across from them. These letters correspond to the color of the wire that needs to be inserted.

Place one wire into the silver area of each screw terminal and tighten it down gently. You don't want to screw it down so hard that you break the wire, but you do want to make sure that the wire is securely fastened.

Step 4: Install the ORP Circuit Board

The ORP sensor consists of a small circuit board and a probe. The circuit board interprets the information from the probe in a way that the processor on the Saboten board can understand. The circuit board is installed on top of the Arduino Sensor Shield. The probe is attached to the white "BNC" connector on the Arduino Sensor Shield.

To install the circuit board, you need to make sure that it is the right way around first. The board has markings on the edge. Find the side that says "ORP 4.0 VCC PRB GND" on it. Make sure that these three pins are on the same side as the white "BNC" connector.

Place the circuit on the pins and ensure that things line up. Push gently until the board is seated.

Step 5: Install Battery and Solar Panel

The Saboten board has a Solar battery charger built-in. There are two connectors along the edge of the board labeled "Solar" and "Battery". These connectors mate with the connectors on the wires from the solar panel and battery. They will only go in one way around, do not try to force them into the connectors.

Step 6: Assembly Complete

Please refer to the code tutorial <HERE> for instructions on how to install the code onto your ORP sensor.