Plumbing the Depths

Amidst the 3D Printer repairs following the transportation accident during the AggieSTEM Summer Camps, our workshop participants continue to work on their Sea Perch ROV designs. Several very elaborate and relatively successful designs were proven for pressure vessels able to provide a watertight operating environment around car backup cameras and security video cameras, both of which are relatively inexpensive with the 12V rechargeable battery pack, LCD monitor, cable and camera under $45 USD all together.


Attempts are still underway to develop a Raspberry Pi-based system that can handle more complex signals (video and sensor data feeds + thruster and navigation controls) over a simpler TCP/IP connection via amplified Ethernet signals. That will be next year’s ROV project, but the new enhanced Raspberry Pi B+ model has captured my student’s interest, so they are making A/V streaming systems and a range of other designs (including our Octopi controllers for the 3D Printers) using the same inexpensive platform (roughly $35 USD each).


When examining the over-engineered pressure vessels and discussing the depths we are operating within (~100ft of the Surface due to limitations of the design), I asked them to identify the least expensive pressure vessel that could be manufactured using no more than local resources. So far, connecting a solvent-fit PVC plumbing fitting with a screw-together open fitting seems the best combination, with a total cost well under $10 USD (the acrylic 1-3/4″ disc remains to be cut out so is currently an estimate only).


The volume of the 1-1/2″ plumbing fittings is sufficient to contain either of the test cameras and our wire connections, using epoxy for potting the transit passage through which the cable passes out of the vessel. The entire body of the case can then be equipped so as to be easily movable from one student’s ROV to another, while the battery pack remains with the external controls out of the water.

We are having the acrylic disks laser cut from a sheet, as the only source for 1-3/4″ discs has a minimum order volume of 200 pieces, while we need perhaps 8-10 to have a few spares on hand. Due to the summer break, the only local laser cutter is offline until student’s return, so I am talking with several hackerspaces within a few hours’ drive to see if we can find time to cut out the clear “windows”.


I hope to ultimately see the camera monitors completed for less than $50 overall, which was already the target cost per ROV (without the camera) and a good constraint for educators under tight classroom expenditure controls.

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