To describe the working principle of our product, we first go over each of the important components in our product and their functions.
Compressor
We use an oil-less, diving air compressor. This means that oil is not used for the lubrication or fuel of the compressor, to keep the air output safe for breathing and free of oil-related contaminants.
This is a small compressor that outputs air at a low 1.85 bars and a constant flow of 65L/min, which suffices for water pressure up to 3m underwater. This output air translates into different flow rates at lower pressures, as shown in the chart above. at 3m depth where ambient pressure is 1.3 bar, flow rate is approximately 93L/min, which is more than enough for the average or even beginner diver.
Filter
A filter is attached to the compressor, which filters out all particles over 5 microns in diameter from entering the air supply tube. This keeps the air free of contaminants, water or others.
Battery
A 12V lithium ion battery, with an impressive 9ah capacity, allows divers to stay underwater for 2-3 hours continuously.
Electrical Components
1. Buck Converter
Buck input: 12V, 0.5A
Buck output: 5V, 0.08A
This device is used to step down voltage of the battery from 12V to 5V, so that the current flowing into the micro switch near our mask is low. This acts as a safety feature, so that no major injuries will occur shall an electrical fault arises.
2. Relay
The relay is a current activated switch, allowing a small current from the NCC and IN terminals to complete the circuit at the NO and COM terminals.
Float and Box
Four styrofoam floats are velcroed to the box, which holds the battery, compressor and the electrical circuitry. The floats, being placed on all four sides, ensures stability on every side even when exposed to tides and wave currents.
Our box is delicately crafted with materials such as Polypropylene (PP) and Tritan™ to provide a sturdy and waterproof storage for our electrical and high energy devices. This will withstand the strong currents usually faced when diving in the ocean.
Mask
Connection to hose by 3D printed piece
The mask we are using has a soft nose, allowing the user to release some pressure on their ears while deep underwater. Air comes from the compressor above via a tube, which connects to the mask through a custom 3D printed adapter piece. Do not worry, our tube is fully waterproof and of medical grade. The 3D printed adapter is 3D printed from a mosfed hotbed, with waterproofing measures placed such as a thin layer of acrylic paint, spread around the adapter.
From the mask, air is exhaled through a one-way valve into the surroundings. The mask is equipped with a silicone padding around the face, allowing air supplied from the compressor to always be at ambient pressure.
How it works
These about sums up the functions of each our product. So, how do these components synergise together so well to provide us the beauty and comfort of the SASS?
From the box on the surface, wires, properly insulated with 2 layers of heatshrink, is gently attached to the tube. The wires goes down into the mask, where an insulated, small lever switch is fixed right under the padding. When the user breathes in, they will experience a “suction” effect. This effect squeezes the silicone padding in the mask, toggling the switch. By the way, this “suction” also occurs when the user is underwater, where ambient pressure is higher than the air pressure in the mask.
This switch will send an electrical signal up to the float, activating the compressor to pump air until the air pressure in the mask equalizes with whatever the ambient pressure in the surrounding is. The switch is reopened once the pressures have balanced, and the padding no longer pushes the switch lever down. At this stage, the user will not experience this “suction” effect.
Now you may think, this is just a simple concept of closing a switch through our breathing. Well, actually, you are right! We, the creators of the SASS, pride ourselves in putting in the thought to maximizing efficiency and elegance in design. A famous idea in engineering, coined The KISS principle, states that most systems work best if they are kept simple rather than made complicated; therefore, simplicity should be a key goal in design, and unnecessary complexity should be avoided. Keep it simple, stupid!
Next, this is where the electrical components become vital. With wires going up to the user’s face, we need to step down the voltage and current of the circuit leading up to the switch. The buck converter steps down the voltage to just 5V, while the relay module has an electromagnet that only activates when the buck converter correctly steps down the voltage. These two work hand in hand to keep the user safe even if any dire situation arises.
Even assuming the air for scuba was pressurized under ideal conditions, for a scuba tank of a standard volume and pressure, energy consumption at 3m is still 1240kJ/hr, whereas for the SASS, with the inefficiencies of our compressor it only consumes 118kJ/hr.
In a single charge of the SASS, it would be able to dive continuously for 198mins at the depth of 3m, with a flow rate of 30L/min (the average flow rate of an amateur diver), whereas with a standard scuba tank, a diver can only stay for 119mins.
This shows the SASS’s superiority compared to the scuba at our intended depth.