We've gone through a couple iterations of the preliminary design; we had to accommodate the button action, as we had conceived it, as well as the battery bracket. We also had to tweak the design a couple times to account for the relative imprecision of 3D printing. And now we really are almost there.
Our focus has been to produce two rough-n-ready prototypes that I can put in people's hands – or rather, on their wrists – and run tests on (how much power these things use is a major concern). As far as I'm concerned, these things can shoot sparks after a week's use. They don't need to be shock- or water-resistant yet – we just need to work out major kinks and learn a thing or two before delving into some of the finer points. I've been thinking of this as Phase 1 of prototyping. Phase 2 will consist of taking what we've learned and moving forward on a watch that isn't over-large (the rough-n-ready prototypes are), is shock- and water-resistant, and whose power draw is known to us.
I met with Don (the electrical engineer), Jenna (the industrial designer), and Mat (the mechanical engineer) on Sunday to review the “rough-n-ready” prototypes. (Kentaro lives in Pittsburgh, so he missed out on sipping beer in The West's outdoor seating area as the temperature dropped. Brrr.) These prototypes are much bulkier than Jenna's original design concept, so the biggest visible change visible when we hit Phase 2 is that the design will be slimmed back down.
Mat, the mechanical engineer, walks the rest of the team through the rough-n-ready prototypes that he's been working on.
Jenna, the industrial designer, pointing out the back plate, which had to be expanded out to fit the internals. Her mockups are on the table.
With the buttons where they are now on the printed circuit board (PCB), the actuators – or what the user sees as the buttons, on the body of the watch – activate the buttons in a mechanically inefficient way, at an angle. In other words, this is too rough-n-ready (!), and we have to go through another tweak. For these rough prototypes, Don will put new buttons the side and return the components to Mat to assemble. Mat will redesign the actuators as part of this assembly, and then return the units to Don so that he can load the program onto them.
"That car in the distance fits between my thumb and finger. I'm CRUSHING it. I'm CRUSHING it!" Jenna and Don, the electrical engineer, look on in amazement.
Once these two prototypes are complete, Don will redesign the PCB and Mat will rework the overall design and mechanics in consultation with Don and Jenna. This redesign will be a departure from the current prototype, and while we’ll go through a few iterations moving forward, those iterations will presumably not be that different one from the other. The team will explore the following in this new phase:
- Changing the button action such that the actuators directly make contact with a plated surface on the side of the PCB
- Using a 500mAH rechargeable battery instead of a coin cell; this is longer lasting than a coin cell, and would be physically easier to fit. The battery would be recharged via either induction or USB. Induction charging would guarantee a perfect seal, while USB charging would introduce a set of issues to solve. This is a big departure for me – having the unit run on a coin cell has been one of the hills I was ready to die on – but Don makes a compelling case. A rechargeable battery will require:
- A different connector
- A different micro processor
- Battery charge circuitry
- Reducing the height of the unit, mostly on the back plate. We’ll try to reduce the height even further, to make it smaller than Jenna’s original design, if possible.
- Designing for shock and water resistance
Stay tuned!