Thinking about usability

Since last time I’ve thought a lot about usability. The main discussion point is how to implement two different power-settings, where one is variable. Should I have a knob? Should it not be variable during the dive, but merely accept switching settings? How much should the diver be able to do during a dive? What is an acceptable cognitive loading? I’ve talked a lot about this with Mikael, with different approaches pros and cons discussed. Today I went past Oceanic Tech and talked to them in regards to the cognitive loading. He said that the proposed variants I had posed no problem at all and stressed that robustness of the torch was the important aspect of doing something more advanced (electronically at least) than the ones available on the market (that I know of or at least). For this reason I have considered doing a redundant system, but I feel that it would be overkill. Most sane people have at least one extra torch while diving in murky water or night diving.

So much for the cognitive loading. The diver is allowed to configure the torch while diving. So what about usability? Do I want an extra knob to configure the variable power? How do I in that case switch between 100% and the variable? I decided that I want it to work as some dimmers work. The idea is:

  • Press once for switch on or off
  • Hold to increase power
  • Release and hold again to decrease power
  • Rinse and repeat

I plan to implement this with the same type of switch that are already in use, but a sibling which has a off-on-(on) 2P setup instead. I have yet to find a model, but I’m quite confident that there should be one available that could do what I want it to do.The switch would thus have a off mode in one end and a on-mode in the middle and past that would be the switch. If you want to start it you simply flip the switch and if it flexes, it will just return to the middle setting and be turned on.

One of the big drawbacks of the idea of having the switch on the canister is that the cable between the canister and torch can no longer just be two poles, it needs a third for the signalling. I still haven’t looked much at cables, so we’ll see how this affects it.

On another note, I looked at reflectors yesterday and found one I really liked from Ledil. I could however not find it in stock at Farnell and sent them an email about where to find them and they offered to send two samples free of charge! Thanks!

The reflector has a drop-off that I think will be perfect for my project, in that it has a spot of 18° and then a quite soft falloff. It will illuminate surroundings as well, but softly. The drop in the middle is not visible by the human eye.

minnieAll in all I’m very happy with the prospects of this reflector!

One cool thing that Mikael suggested yesterday was the prospect of using the diode as a photo diode. Having a capacitance to keep the MCU alive and then pulsing a computer screen in a binary form would allow for setting the permanent 100 % setting to something else, for example 80 % (it may turn out that 100 % is to strong). This could probably easily be implemented on smart phones as well, so you could change it while on a boat without lugging a computer around. The cool thing is that this allows complete customisation without opening the casing of the torch after pressure testing it.

Big shout-out to Ledil, Mikael and Kalle (Oceanic Tech) for all the help! You guys rock.

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