4m Hull Compartment Water Sensors

Shop Made Options
An option to build water sensors is to bend a piece of plastic into a 90 degree bracket and attach two wires a certain distance apart. When the compartment fills with water the circuit would be completed and this would signify that a compartment has water in it.

To do this a known voltage will be applied across it and the current will be measured to find a separation distance of the two wires that completes the circuit. The salintiy of ocean water is 35g/kg. Therefore to mix salt water 35g of salt needs to be dissolved in every litre of water. The temperature of the water should be between 15 and 20˚ C to best simulate the surface conditions of the atlantic ocean in the summer months when the boat will be operating.

Pre-Fabricated Options
Discusses fiberoptic sensing of water level.

http://www.youtube.com/watch?v=_q2TIU_PfYg&feature=autoplay&list=UL8RpKEPHJyHk&playnext=7

-seems overly complicated for our application

Can also use conductivity of water as a switch?

http://www.snapi.org.uk/info/devices/liquid_level.htm

Decided on Shop Made Option
Need to ask hardware people what kind of voltage and amperage they want to use for the sensons 5V or 12V (when tested 12V seemed to high so 5V will be used)

Need to figure out how to fabricate the brackets and what material should be used 

bend in shop; can ask machinists to help and use any clear plastic. Or purchase pre-made and cut into sections

Need to figure out the best method to attach the exposed ends of the wire to the plastic bracket for long term use and durability

wrap wire under a bolt and tighten to pin the wire between the bolt head and plate. Doubles as a terminal

To the right is the prototype of the water sensor. The two terminals are 2.5in apart. When submerged in the salt water and 5V was applied a current was read thus completing the circuit. One problem that arose during testing was bubbling around one of the terminals. After some research it was found that this problim is actually a corrosive process. When two different metals are in contact in the presence of water they have a current that passes through them causing corrosion. The metal that corrodes is based on the galvanic series of metals. The metal with the lower number will be the one that corrodes. The presence of the current speeds up this process.

The problem with bubbling has been solved by adding an extra resistor to the circuit to reduce the current.

The final design will be made of sections of angled plastic brackets with two terminals similar to the photo. With the use of digital logic gates the sensors will be wired in a way that if water is detected in any of the compartments the program will know.