Can't keep any secrets here. You guys are too smart. So yes, I am trying to do a type of probe. It only needs to indicate in one dimension. If fact, it should be strictly limited to one dimension.
Some of you are concerned about my accuracy numbers. I don't know what is possible. I am trying to find that out. Naturally I want the best accuracy possible. And the REPEATABILITY of the switch mechanism is a major factor in that. Thermal expansion is definitely in the mix. Surface electrostatic effects? I must look that one up. Is it a fancy way of saying capacitance? If what I have is just a DC circuit, does that matter?
As for all the talk about active sensors and sleep and wake-up times, this is a FLASHLIGHT circuit: battery, switch, and LED. That's it. I am not even sure I need a current limiting resistor as the internal resistance of the CR2023 seems to limit the current flowing in the low current LEDs I have found. And when the switch is OFF, zero current flows. I guess you could call that "sleep mode". I am not worried about those details. At the present I just need to build a repeatable switch. And one with a long life, if possible.
In spite of all that, I seem to have stumbled into a way of building that circuit that allows it to operate in multiple ways or modes while other, similar devices are limited to just one. That should provide a competitive advantage over the others, at least for a time.
Those contact pads look interesting. I had hoped they might come with a dome shape, but it looks like they are all dead flat. So I am back to the stainless steel balls. The pogo pins would be good except the radius at the tip (0.5mm) is relatively short. So, after a number of cycles against a gold pad, the gold on the pad would be indented quickly and I don't know what effect that would have. This seems to be validated by the fact that the gold plating on the pins is twice as thick as that on the pads.
As for those Renishaw probes, that is a WHOLE 'NOTHER LEAGUE. And their prices definitely reflect it. But then, in about 15 minutes of looking, I could not find even a single specification on them. If I had a product that was worth those prices, I think I would be shouting the specs from the rooftops.
Anyway I do appreciate the help. And perhaps I/we can come up with something that fills a different nitch.
I am not aware of the contact pads. They sound interesting. Can you provide any further details: who makes them, what is a good search term for them, etc?
They're often listed alongside pogo pins and other spring-loaded contacts, since they're meant to be used together. Hopefully this search link will work: https://www.digikey.com/en/products/filter/contacts/contacts-spring-loaded-pogo-pins-and-pressure/311?s=N4IgjCBcoKxgTFUBjKAzAhgGwM4FMAaEAeygG0QBma%2BANgAYQBdIgBwBcoQBldgJwCWAOwDmIAL6SgA
Pairing one of those with a solid domed pin (example) may provide a better-defined contact point vs two flat pads, at the expense of more deflection of the contact due to higher contact pressure.
Looking back at the first post, .0076mm is getting into the world of surface electrostatic effects, thermal expansion etc. I can't see physical electrical contact working for this except maybe in combination with some kind of lever to amplify the movement.
Those and several other challenges have to be factored into the mechanism, materials, and manufacturing choices for sure. OP had a previous thread about a CNC toolsetter where some of this was discussed. But it is doable with a well-designed and well-made mechanism -- commercially made CNC probe systems (eg Renishaw) claim repeatability down to <1μm for mechanical contact systems.