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
