Building Pressure Tolerant Electronics (PTE) for deep ocean vehicle applications

At HDDG20, Nic Bingham discusses creating electronics that can withstand the pressure of the deepest oceans in the world.

Supplyframe’s mission is to create more access to information about electronics design and manufacturing. As such, we do a meetup in San Francisco called, Hardware Developers Didactic Galactic. These events include talks by industry experts in hardware and software. The speakers are often building hardware for recreation or as part of their employment. The common thread is that they want to give a view “under the hood”.

At HDDG20, held April 20th 2017 at the Supplyframe office in San Francisco, both talks covered electronics that would be used underwater. In this talk, it was about electronics going deep underwater…in fact, to some of the deepest parts of the ocean.

Our speaker was Nic Bingham, who is lead EE at at the Schmidt Ocean Institute. He has spent months at sea supporting ambient-pressure electronics in the deepest trenches of the world ocean, and conducted three missions to service autonomous solar-diesel power plants operating at the high domes of the Antarctic plateau.

Pressure Tolerant Electronics (PTE) have a wide range of unusual challenges. The components used must be able to withstand external pressures, and yet this is never a specification on a datasheet. For example, things like capacitors (discussed at length in at a past HDDG talk) require extra analysis. It is not possible to use aluminum electrolytic caps because of the internal liquids in the devices. Ceramic must be used instead, which can be troublesome for applications where a large amount of capacitance is needed, especially in a constrained amount of volume. Any component that has air space inside (relays, ICs, diodes) also needs similar consideration and testing.

Unique component usage introduces challenges around sourcing. Nic mentions high lead times for things like the hose couplings and external components (not contained within a pressure tolerant vessel) that will be subjected to additional pressures. On the circuit board, the parts being used are sometimes older technology components, which risks obsolescence. This is driven by pressure tolerance compliance that only certain package types will allow.

This talk was interesting because Nic is an expert in a particularly narrow field, with rather high stakes. His expertise is so niche that he was contracted to work with James Cameron for his journey to the bottom of the Marianas trench in the Deepsea Challenger. This included the power distribution systems, vehicle control networks and an 11,000m pressure-tolerant motor controller used to drive all thrusters and hydraulics on the vehicle. Seeing the forces imposed upon the electronics sets the human accomplishment even further apart.

Nic has written about this subject more in a whitepaper found on his company’s site, Unmanned Underwater Technology. If you’re planning any deep sea missions in the future, he can be contacted via that site for further inquiries.