Look at how inkjet printers work. They need to trip a home switch so that each line of sprayed ink lines on to better then 1/1000th of an inch. They use a low cost optical device. There is a slot cut in a plastic block. One one side is a LED on the other a light detector. The look at each other through a pin hole. They are very reputable and you can get then for free from salvaged printers. One trick is to modulate he LED's light at about 30KHz and use an RC filter on the detector so as to be insensitive to absent light. The plastic block the interrupts the beam is just a simple square, no slot or hole. If you have to buy a new one the cost is about $1.
On Tue, Feb 16, 2016 at 6:46 AM, Roland Jollivet <[email protected]> wrote: > On 16 February 2016 at 14:46, Bertho Stultiens <[email protected]> > wrote: > > > On 02/16/2016 01:38 PM, Nicklas Karlsson wrote: > > >>>> It seems that the micro-switches are well suited for the purpose, > but > > I > > >>>> guess some hard (unbiased) data has yet to be gathered (outside of a > > mill). > > >>> The alternatives seem to have the same problems of repeatability. > Using > > >>> a hall sensor or optical one will give the same problems. > > Micro-switches > > >>> are at least inherently mechanically constrained. > > >> Indeed, unless you can crush them. There must be a run-into-the-wall > > >> protection, as mentioned earlier, to prevent killing your switch. > > > > > > Pass over the switch might be possible? > > > > No. The datasheets I've read all say the same that you must activate the > > plunger straigt on. Any angle will give you bad performance. Any > > sideways stress on the plunger can kill the plunger assembly. > > > > The only alternative is to use a level-based micro-switch. That, > > however, will probably make it less accurate. Especially when you move > > over it side-ways. The angle of attack is too small with respect to the > > travel distance. > > > > -- > > Greetings Bertho > > > > > > > That's not true. Use a switch like this > < > http://uk.rs-online.com/web/p/microswitches/1031645/?searchTerm=103-1645&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3130332D3136343526 > >, > where the roller is almost directly over the plunger. > Then, use a wiper with an edge set at about 70deg. When this approaches the > switch, the angled edge will cause full travel over less than 1mm. After > that, overtravel will have no effect. > > I've never seen a travel limit switch used head-on in a machine. It's a > ticket to disaster. > > Regards > Roland > > ------------------------------------------------------------------------------ > Site24x7 APM Insight: Get Deep Visibility into Application Performance > APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month > Monitor end-to-end web transactions and take corrective actions now > Troubleshoot faster and improve end-user experience. Signup Now! > http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
