[sdiy] Very cheap SPI pressure sensors.. anybody ??

[John P Shea]

https://github.com/nai-kon/PlaySK-Piano-Roll-Reader


On Sat, 20 Mar 2021 at 10:35 pm, Ben Stuyts via Synth-diy <
synth-diy at synth-diy.org> wrote:

> Has anybody ever tried pointing a video camera at the piano roll and do
> some real-time machine vision type of recognition? Would the resolution
> (i.e. timing) be good enough?
>
> Ben
>
>
> > On 19 Mar 2021, at 23:06, Didrik Madheden <nitro2k01 at gmail.com> wrote:
> >
> > On Fri, 19 Mar 2021 at 22:29, Jean-Pierre Desrochers <jpdesroc at oricom.ca>
> wrote:
> >> An optic based reader would look about like this:
> >> [Image]
> >>
> >> Notice the big horizontal LEDs bar over the row of holes in reading..
> >>
> >> Not very nice..
> >
> > The cable management could be nicer, but I would personally not mind.
> > But I can see two problems:
> > 1) It doesn't look original.
> > 2) Even if you don't care about that, it obscures the currently played
> > line, which might be aesthetically important.
> >
> >> On the other hand a vacuum based reader would look like the original
> thing:
> >> [Image]
> >
> > Oh! That's something I didn't understand about the mechanism at first.
> > I thought the vacuum was transmitted through the paper, so that you
> > would have one "transmitting" side and one receiving side. Instead, it
> > has constant pressure and relieves the vacuum pressure when a hole
> > passes over.
> >
> > So that gives me a different idea for a working principle based on
> > light: reflection. No hole=light reflects back. Only one side of the
> > paper has electronics. This could be done with either a visible LED
> > (for an additional visualizer effect) or an IR LED (for
> > authentic-looking operation). This method might be susceptible to
> > light interference through the holes though... Probably not a good
> > idea, just throwing ideas out there.
> >
> > /Didrik
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