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

[Didrik Madheden]

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