Electrical Safety:
The first learning point was more of a technical aspect that we will definitely remember for any future projects.
After letting the lab advisors look at our product, they pointed out a key issue that we overlooked. The power going into the microswitch was too high. The microswitch was rated 5A 250V, so it was not an issue with the switch itself, but the energy loss occurring travelling through 6m of wiring at that current, as well as the hazard of having 12 watts (12V, 1A) travelling through a switch that’s very close to touching your forehead, which may not sound like a real and immediate danger as the switch we used is supposedly waterproof, but will later learn that we have indeed dodged a bullet.
Buck Converter:
This lead to the addition of the relay and buck circuitry. The buck itself was a component that steps down and up voltage, and was placed between the battery and the microswitch. The voltage was stepped down from 12V from the battery to 5 volts to the microswitch.
Buck input: 12V, 0.5A
Buck output: 5V, 0.08A
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. When the microswitch closes, the parallel component to the circuit with the battery, compressor and relay is closed by the small current in the side with the microswitch, causing 12V and 8.33A to run into the compressor to turn it on, solving the problem of having a relatively high power having to run through the microswitch.
Thankfully, this was a lesson well learnt. Before Making & Tinkering, none of us had even known of the existences of buck converters that can step down voltage/current. This certainly has opened up to us one of the most important components out there to ensure that we can step down high voltages and currents for more sensitive components.
Untrustworthy Labelling:
As foreshadowed above, the ‘waterproof’ switch had short-circuited during the pool testing, despite the waterproof labelling. We had thoroughly sealed the contact points of the switch and wires with marine-grade silicone sealant, narrowing the fault down to the quality of manufacturing. Luckily the total power going through the switch was XX watts, lowered greatly due to the new circuitry. To fix the issue would be rather straightforward; for a temporary solution on the day itself was to grab a spare (thankfully the switch we ended up using came in a pack of 10) and wrap a small plastic bag over it and tape it up. For a more lasting and professional solution, the switch itself would merely be replaced with one that actually lives up to the waterproof characteristic it boasts of.
A similar occurrence happened when buying pneumatic adapters to fit various components together. As the convention for these fittings may be confusing, suppliers online often mix up one type for another (mislabeling 1/4″ NPT adapters with 1/4″ G adapters and vice versa). This has led us to make several wrong purchases that on paper should have been correct.
Technical Skills:
Throughout this M&T journey, each of us has picked up many useful skills that we definitely plan on using in the future, even as we diverge into our different disciplines. 3d modelling through apps like Fusion360 allow us to visualize and properly assess the ideas in our head, as well as using 3D printers to turn them into reality. Lab skills like soldering and learning the basics of different electrical components and how they should be used is also something we will take with us for future projects.
Design Thinking and Creativity:
This whole endeavor has also let us practice thinking in a more innovative way, constantly thinking up solutions to our own problems, critically assessing our ideas and being creative. Not to say we made up most of this project on the fly, but we kind of did. Our end result was far different from what we would have ever imagined it from the start, and we daresay it’s turned out surprisingly much more elegant and out-of-the box than we taught. We got lots of advice to just do things the ‘safe and obvious’ way, using extra electrical components and coding to do all the work for us, but we managed to get by simplifying everything into a simple mechanical solution, by using basic physics, and that may have been the most satisfying learning outcome of all.