Yes, that is entirely non-intuitive. Years ago someone at work had the optical components from an anti-tank weapon system on his desk and the lens looked to be made of a shiny black stone. You could not see through the lens at all. Then he told me it was an infrared telescope. My knowledge of such devices starts at the point where the data is digitized. I'd never seen the mechanical parts.
On Tue, Aug 25, 2020 at 12:19 AM John Dammeyer <[email protected]> wrote: > The black PLA was transparent to IR. Painted with metalized paint fixed > that. The grey PLA I started with blocked the IR. > > In both cases the scope waveforms were nice. > > John > > > > -----Original Message----- > > From: Chris Albertson [mailto:[email protected]] > > Sent: August-24-20 10:04 PM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] Spindle Speed sensing. > > > > Being "black" is not enough. It should be black in IR wavelengths. > > > > But really, if you use one of the "C" shape sensors that have the > > emitter and receiver built into one housing the beam is 10X smaller than > > your slots reflections and such don't matter. What will mess you up is > > if the IR beam is so broad that it illuminates three slots at the same > > time. Then you get "multi-path" but that is easy to fix. > > > > I have this little mobile robot chassis with motors that use slotted > white > > plastic disks and IR optical sensors to measure and control wheel speed. > > It is not even shielded from ambient light and the $1 "C" shape sensors > > give clean signals. > > > > On Mon, Aug 24, 2020 at 4:33 PM jrmitchellj <[email protected]> > wrote: > > > > > Since your tacho disk still has some thickness to it, you may get > > > reflections off the inside edges that could make the transitions > "unclean". > > > > > > --J. Ray Mitchell Jr. > > > [email protected] > > > > > > > > > > > > "Good enough is the enemy of excellence"author unknown > > > > > > > > > On Mon, Aug 24, 2020 at 12:38 PM John Dammeyer <[email protected] > > > > > wrote: > > > > > > > > From: jrmitchellj [mailto:[email protected]] > > > > > Have you considered blacking the part? Either anodizing or flat > black > > > > > paint? > > > > > > > > > > --J. Ray Mitchell Jr. > > > > > [email protected] > > > > > > > > Why would I want to do that? > > > > > > > > The bottom that you cannot see is actually already black since it > was the > > > > outside part of the TEC86 computer front panel. The back surface is > > > > actually clear anodized by the looks of it. > > > > > > > > John > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > Emc-users mailing list > > > > [email protected] > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > > _______________________________________________ > > > Emc-users mailing list > > > [email protected] > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > -- > > > > Chris Albertson > > Redondo Beach, California > > > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
