-------------------------------------------------- From: "RussellMc" Sent: Monday, July 12, 2010 3:20 PM To: "Microcontroller discussion list - Public." Subject: Re: [TECH]:: Auto stop table saw - demo with real finger > I think I'd have a fair prospect of making something now which comes > close to all that. (Read prior posts for some of that). > SawStop are going to have to have extremely broad and insightful > patents if they want to keep asking 8% royalties. Yes, I thinking the same :-) That was why I asked about the standard weight of a blade etc, but you would have to take the blade mounting into consideration too of course. Just trying to do some rough calculations to work out what forces are needed for decent acceleration/decceleration out of the way of finger in worst case scenarios - does look like there will be a fair bit of energy required quickly. Also how to go about the capacitive sensing, ideally without user having to wear anything. Or as you say below pretty thoroughly, maybe camera, optical etc etc. Or some combination of. A system that is usable with other similar machines (as you also mention below) would be great. Be interesting to make a test model for proof of concept anyway, if I have time between various projects I might have a little go at it, if for no other reason than it interests me. Were you thinking of doing similar? Or just thinking out loud.. > For following, all rights reserved. > :-) - what rights those are vary with administration. NZ = none. US = > much AFAIK. > > Some mix of some of: > > - Pop back blade to withdraw from user at a velocity which rapidly > exceeds some design feed rate. > - Cover/guard which shrouds blade - with blade having withdrawn far > enough that finger is not impacted by closing guard. > - Rapid but non damaging braking. > - Non contact proximity sensing. "Those skilled in the art" [tm] will > easily envisage many methods by which this may be achieved. > Examples only include capacitance, optical (& electromagnetic in > general) (eg camera hand position tracking, beam blocking, > reflective, doppler, TOF ranging, ...) , acoustic (much of as for > light), etc. > - Adding a signal to machine or user to enhance operation both in > isolation and wrt conductive materials. eg em signal capacitively > coupled from user to blade system. Increasing frequency allows > decreasing capacity coupling requirement until substantial non contact > proximity viable. > - Glove / hand / finger piece or mark or ring etc fir highly positive > tracking. More applicable in professional systems allowing very great > freedom of movement relative to open blade etc in exchange for > discipline of utilising the system. > - Extension to many or any other systems - saws, rotating and linear > action machinery, presses, stampers, guillotines and anything that > moves. Non contact proximity vvv desirable in some of these - eg > large press - ir pressing your fingertips is unwise AND a hand in the > air may be well inside "maw" of machine when closing action starts. > Active hand etc (limb, head, body ...) tracking allows extremely good > control. Two or more systems can track and vote to give near failsafe > operation. This is getting well away from SS ideas but is even more > useful. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist