Rebreather HUD

The Brief

Rebreathers for SCUBA diving have many advantages including silence and lack of bubbles to scare fish away, reduced decompression times and extended dive times. However, they do come with their own problems. One potentially lethal issue is losing regulation of the amount of oxygen in the breathing circuit.

Commercially available rebreathers all come with O2 monitoring systems, however, many divers prefer to have a redundant, independent monitor. These are available, however, they generally involve bulky battery packs and awkward access to controls. The heads-up versions also have the issue of taking up too much of the diver’s field of view.

Nudi’s brief – create a small, low profile HUD unit for monitoring three O2 cells with inbuilt power/calibration button and AAA battery.

How Nudi Helped

We looked at the current options available and settled on the widely adopted Smithers Code method of indicating concentration with flashes of one LED per cell.

Extending this research, we learned that modern capacitative switch sensors cannot tell the difference between a human finger or being immersed in water – which provided an auto-on function and allowed sensing of when the unit leaves the water for an auto-off function if the diver forgets to turn the unit off. This saves battery life.

Nudi has run this project from start to prototype including the research, design of case, electronic and firmware design and prototyping, 3D printing of case prototypes, CNC milling the aluminium moulds for resin injection prototyping, test diving and refinement of the prototype.

The “whistle” profile allows the bulk of the unit to rest behind the mouthpiece, out of sight, whilst the thin rectangular bar containing the LEDs sits comfortably within view.

The entire case is potted around the PCB and cable in solid polyurethane, meaning the only area susceptible to water penetration or airspace for crush damage is the battery compartment – which in turn is sealed via a low profile O-ring cap.

The device has been through prototyping and field testing and is ready for tooling and manufacture.