I believe that gizmo is the same device I linked to in one of my earlier posts. It’s fairly inexpensive, which raises some concerns about its potential to fail and damage my TouchDRO adapter unless protected, as you mentioned. Hopefully, Yuriy will stop by and weigh in with some advice.I do believe the transmission is a great invention and so against my beliefs to aid and abet the full range VFD scheme...but if you insist, have a look at a gizmo such as this V -> F converter board. Would require some electronic knowledge as these cheap Chinese modules have little to no useful documentation and since this one runs off a 15-24V supply, incorrect configuration could damage your TouchDRO interface. (You'd want to configure it to grounded-emitter, open-collector type output and let the TouchDRO input pull-up resistor take care of the positive logic level or better yet use an opt-isolator device to protect the TouchDRO board from the big, nasty VFD - if this language doesn't make sense - this is probably a bad idea). Don't know the upper frequency limit of your particular TouchDRO interface but if 10Khz is to high the module does claim to have some full-scale adjustment or just attenuate the analog output of the VFD for a suitable max frequency.
My plan (no yet implemented) uses four small Nb bar magnets held to the spindle with adhesive lined shrink tubing and a hall sensor attached to the nose piece. I plan to blind thread the nose piece for a small fastener to hold a small surface mount sensor module. Turns out that old style Sonicare toothbrush heads (with the threaded locking nut) use two perfectly sized (2.5 x 5 x 10mm) Nb magnets which are pretty easy to remove without cracking. Otherwise I imagine suitable magnets are pretty easy to find. Sharp Mill has a magic-belt style variable-speed transmission head so the VFD runs at full speed (except for jog and threading).
Did something similar on my VFD enabled lathe - works like a charm. Hardest part was finding the large diameter adhesive shrink tubing in affordable quantity (only need an inch or so).
Cheers, Louis
@mksj’s application looks promising—I might take a closer look to see if it’s compatible with my mill.
