OK could be the optical switch sonly used for self-calibration when the printer is first powered up. Still the little things are very accurate. I bought some a while back, I think a bag of them for $5 on eBay.
Does the printer need to do a SLOW home one each line? I thought the advantage of an optical switch was that there was not physical contact and you can blow through them at any speed. Simply note the encoder count as you pass. This would mean it self corrects for any missed steps. We would need the firmware source code to really know for sure and even then different printers might be different. I've used these to build a motor shaft encoder, you need two per shaft for quadrature. With a mother spinning at a couple thousand RPM and over a dozen slots on the disk you get a decently fast pulse rate. The device would handle a very high speed, certainly no need to slow down and bump. In fact I wonder if the slow pass the printer makes is not for some kind of backup mechanical switch? In any case anyone with a machine tool and a dial indicator could rig up a test and determine for themselves the specs for a mechanical or optical switch. Just watch on the dial where the switch trips and repeat a few dozen times. On Tue, Feb 16, 2016 at 8:40 PM, John Dammeyer <jo...@autoartisans.com> wrote: > I believe they only use the home switch to figure out where the end of the > printer is. Once established for page of printing it's not used to > reference until perhaps the next page and probably not even then. From > then > on the positioning is based on the motor steps. Just think if they had to > do a slow homing operation on every line. > > John Dammeyer > > > > -----Original Message----- > > From: Chris Albertson [mailto:albertson.ch...@gmail.com] > > Sent: February-16-16 6:34 PM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] Micro-switch repeatability > > > > > > 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 > <roland.jolli...@gmail.com> > > wrote: > > > > > On 16 February 2016 at 14:46, Bertho Stultiens <ber...@vagrearg.org> > > > 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=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C > > 753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F2 > > 55C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F5354 > > 4F434B5F4E554D4245522677633D4E4F4E45267573743D3130332D3136343526 > > > >, > > > 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 > > > Emc-users@lists.sourceforge.net > > > 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 > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > ------------------------------------------------------------------------------ > 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 > Emc-users@lists.sourceforge.net > 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
