Underwater camera housing rarely leak, but if this event occurs the results are normally catastrophic causing irreparable damage to the camera body and lens.
SparkFun published a water detector project in 2013, where the original design was intended as a replacement for a NautiCam leak sensor. This project adapts the SparkFun design to an AdaFruit Trinket. The resulting implementation is sufficiently small as to fit within an Olympus PT-EP14 housing (e.g. for the Olympus OM-D E-M1 Mark II body).
Step 1: Cut Vero Board and Attach Ribbon Cable
A section of Vero board is used to create a sensor that sits at the bottom of the underwater camera housing. Vero board has parallel strips of copper, where normally one creates segments for individual circuit nodes.
The Vero board can be cut with a number of tools, but the cleanest solution is to use a diamond saw blade (e.g. normally used for cutting tile), where water is not required for the blade. The width of the sensor is two copper strips wide and the length is whatever is suitable for the housing in question.
Olympus housings normally have two grooves in the bottom center of the housing which are used to trap a desiccant pouch. The sensor is fit between the grooves, as shown in the picture.
Attach ribbon cable (two conductors wide) to one end of the Vero board and optionally add heat shrink tubing over the end of the board, covering the solder joints.
Step 2: Attach LED, Piezo Transducer and Battery Holder
Attach LED, piezo transducer and battery holder to the AdaFruit Trinket circuit card. Any light gauge hook up wire can be used between the Trinket and battery holder.
Step 3: Flash Software
Using the Arduino IDE, flash the firmware to the Trinket using a USB cable.
Note: For this project version 1.8.2 was employed, though there is nothing special about this version of the Arduino IDE.
Step 4: Install Into Housing
The battery holder and Trinket are attached to the underwater housing using a Velcro dots (e.g. ~1 inch diameter). The piezo transducer has a self adhesive ring, where the transducer is attached to the wall of the housing near the Trinket. The sensor is a friction fit into the lower portion of an Olympus housing. Other housings might require special accommodations. Picture hanging putty has been used to secure a sensor when no suitable housing features are available.
Note: The piezo transducer must be mounted to a surface, otherwise the volume of its output is a faction of what is achieved when the circumference is constrained.
Step 5: Test
Wet your fingers and touch the Vero boards strips. The LED should flash and the piezo transducer produce an audible warble.
Step 6: Circuit Diagram
A 47k ohm current limiting resistor is used in series with an LED. Given that the Trinket is running off of a battery, the voltage available to the LED is such that colors other than red cannot be driven.
A piezo transducer was chosen given its very low drive current.
Step 7: Bill of Material
- AdaFruit Trinket (3.3V version)
- Red LED
- 47K ohm resistor
- Piezo transducer (TDK PS1550L40N)
- CR2032 battery holder (Memory Protection Devices P/N BA2032SM)
- CR2032 battery
Added updated firmware, where instead of polling once per second polling only occurs ever four seconds until triggered. Then once per second polling occurs for two weeks. The idea is that if you leave the battery in the sensor the battery life should be a year. Go on travel and trigger the sensor to test its function. Then if your trip is two weeks you will have a fast response time. After two weeks the sensor goes back to its lower power saving state.