frankly, we've been living on witchcraft and dubious looking datasheets for far too long. empiricism is required for us to proceed. this thread is to discuss the bits that are required for such a device, as well as a rough idea of what their tolerances and dfm (design for manufacturing) requirements (3d printable parts, off-the-shelf micros, etc.) should be.
note that i am aware that some have built nice one-offs of such devices before. imsto at one point posted some pretty sweet pictures of one based on a mouse optical sensor and basic jeweler's scale. iirc limmy had an analog version he designed. however, my feeling is that we have the expertise on the forum now to come together and design a kittable device that is reproducible, can be calibrated, and can be manufactured with a minimum of salvaging for a reasonable cost.
but, why? the variety of switch designs, variants, mounting configurations, and so on and so forth has become dizzying. just think, 5 years ago, there wasn't even a forum to discuss keyboards on the english internet. yet we now live in a world where logitech, one of the largest input device vendors in the world has made the mechanical-ness of their flagship keyboard its primary selling point (ironically monopolizing the switch output of an entire company for half a year, BUT ANYWAY). this is fantastic, as its attracted more attention to the hobby than ever before. however, as lampson might say, it's become a bit of a success disaster; we now have more opinions than ever on what keyboards feel like and which ones we like best (or we're on our way to becoming opinionated curmudgeons there). however, we have incredible trouble quantifying the metrics and intervals along those metrics that contribute to our like or dislike of a keyboard.
this is a problem for a few reasons. first, it makes it difficult for us as a community to express to manufacturers what we want more/less of. second, it makes it difficult to direct ourselves in what to push the envelope on. people have recently been going crazy over the korean-manufactured drop-in springs for cherry switches. however, no one can quite express exactly how they're different from the OEM springs in cherry switches, nor in what way they want replacement springs to be different from the springs provided by cherry (is it that we actually want progressive springs? different behaviors over a specific frequency bandwidth? !?!?!? no one knows, frankly). finally, i have noticed many complaints recently about defective switches. how can we determine when a switch is defective if we don't even know what the average operating parameters are supposed to be? we have many many samples of these devices (a hundred per board!) and yet we still don't know what the reasonable manufacturing variation is or should be.
what i suggest let's build open source plans for a device that can used to reliably measure the relevant properties of a keyboard switch. this holds value to us for two reasons as well. not only will we get a reproducible device out of it that can help us quantify our tastes, but it's also a great project for us to work on as a community that is both practically realizable, and yet not just another revision of a keyboard with an incrementally new feature-set.