If there are just few buttons, they could be attached directly to Raspi’s GPIO header. That would save quite some space and a little of power.
Depending on the power supplies in the devices themselves, the thing could run from a bare 3.7V battery without needs for losses at the boost converter. Raspi B+ has a switching buck converter for its chips, and the 5V rail is used just for the USB port powering. We can disconnect the internal converter and feed 3.3V directly to its power rail.
These modifications above are however requiring some expertise above clipping together off-the-shelf modules, so may be somewhat restrictive for general adoption.
For field deployment, some good housing may be necessary. The exposed circuitboards are susceptible to mechanical damage and moisture. (Some materials soak water readily along the circuitboard edges. Once inside, it causes current leakages and corrosion - thin conductors in electrolyte, when exposed to voltage, form an electrolytic cell and the anode dissolves annoyingly fast.) A conformal coating of the boards is generally an advisable idea. Protect connectors before dipping in it, or brush it on carefully, though.
The projector is the cornerstone of the device. We need more of such small miniature high-res projectors, for as low cost as possible, and, if possible, DLP-based. They have myriads of uses, from stereolithography through structured light 3d scanning to projection to surfaces as a form of shareable augmented reality. With DLPs the light source can be swapped and way more uses can be achieved with relative ease.
What’s the state of the art of these little projectors? What are the costs at the cheap end? Teardowns to see how they can be modded to e.g. higher brightness?
Wear this around and you’ll be tackled or shot, because anything that looks more complicated than a mobile phone or tv remote is half a bomb and therefore a problem, and there is no problem guns cannot solve.
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