It seems there are three general possibilities:
- Somehow integrate a TON of diodes throughout the existing membrane matrix
- Produce a custom flexible PCB for the model m
- Somehow convert the existing membrane matrix to capacitive operation
Producing a flexible PCB seems the cleanest option, but cost is then the issue for this option. Even via dirtypcbs, the cost quickly becomes excessive, especially if you need to do a few design iterations.
So, I am considering the third option (re the title) wherein I 'somehow' convert the existing membrane, hammers, or whatever with the result being that the model m can then somehow operate with a solution akin to xwhatsit's solution.
Undertaking said conversion, I would want to assure that the existing mechanical operation (movement, force patterns, general 'feel', etc) of the model m remains as close to 'natural' as possible. I would of course not want the model m to feel 'worse' (somewhat subjective) in anyway, sure it could end up feeling more like a model f, that is a consideration, but not 'worse'.
So, I just wanted to come here and ask if anyone had considered such modifications before and also if anyone had any input or feedback to offer.
In terms of the 'easiest' way to convert the model m to full capacitive key operation, I thought that the integration of a VERY thin poly sheet just above the lowest membrane (that nearest the steel plate) would be perhaps the easiest option.
The layout would be:
Steel plate -> existing model m membrane with conductive traces -> thin poly sheet with no holes -> existing model m spacer membrane with existing holes -> second existing model m membrane with conductive traces
The addition of the very thin poly sheet would act to never allow the conductive membrane layers to ever touch each other. Ideally, this poly sheet would be as thin as possible.
Now, for the operation. Basically, when the buckling spring actuates and the hammer depresses upon the membrane stack, this then modifies the capacitance between the two existing membranes with conductive traces. The reason the existing model m's spacer membrane with existing holes is kept is to allow for a greater 'change in capacitance' before and after the hammer depresses the membrane stack. The greater the change in capacitance, obviously, the easier it is to 'detect' when a given key has been pressed or not. This is where the thin poly sheet comes into play also, the thinner the better, as the capacitance change increases per the thinness of the poly sheet. So, it is the combination of the slight air gap provided by the existing spacer membrane and the poly sheet that both contribute to the resultant change in capacitance possible per key per press. Given sufficient change in capacitance, I think this seems a via option.
I hope the above is clear and makes sense what it is I am trying to achieve and how. Any suggestions, thoughts, considerations?
I have the means of producing the above myself, in terms of test equipment and the like, GHz scopes, etc, but, I figured, why not seek some alt suggestions before I embark on a huge project via a defined path when I can may integrate a few paths into one or something?
Thanks all.
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