<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><meta http-equiv="Content-Type" content="text/html; charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Ok, I thought I’d mention the PlaySK project in case you missed it.<div class=""><br class=""></div><div class="">About your plan with a matrix of phototransistors, how about this variation: You will <span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">basically</span> have 90 phototransistors in a long row. So you will need a long pcb anyway. Why not get some 8-bit or 16-bit shift registers (parallel -> serial) and put them on the pcb? That way you have easier routing, and you can latch every phototransistor at exactly the same time. So no timing/jitter worries. Another variation would be using a bunch of (cheap) microcontrollers, bus them through SPI bus, and connect each phototransistor to and ADC input. That would also be great for calibrating the response curve.</div><div class=""><br class=""></div><div class="">Ben</div><div class=""><br class=""></div><div class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On 16 Aug 2022, at 01:57, Jean-Pierre Desrochers <<a href="mailto:jpdesroc@oricom.ca" class="">jpdesroc@oricom.ca</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta charset="UTF-8" class=""><div class="WordSection1" style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class="">Yes I know that project..<br class="">But I want a self running unit (no PC needed).<br class="">Stuff that I’ll use:<o:p class=""></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span lang="EN-CA" class="">Microchip uPC<o:p class=""></o:p></span></b></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span lang="EN-CA" class="">MP3 player to play the paper roll notes (88 playable ‘Honkytonk piano’ wavefiles) on stereo audio outputs<o:p class=""></o:p></span></b></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span lang="EN-CA" class="">MIDI output for any external device.. like a synth for instance !</span></b><span lang="EN-CA" class=""><br class=""><br class=""><o:p class=""></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class="">I think so far the matrix way to read the notes could be the easiest way<br class="">with the less components used.<o:p class=""></o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class=""><o:p class=""> </o:p></span></div><div style="border-style: none none none solid; border-left-width: 1.5pt; border-left-color: blue; padding: 0cm 0cm 0cm 4pt;" class=""><div class=""><div style="border-style: solid none none; border-top-width: 1pt; border-top-color: rgb(225, 225, 225); padding: 3pt 0cm 0cm;" class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span lang="FR" class="">De :</span></b><span lang="FR" class=""><span class="Apple-converted-space"> </span>Ben Stuyts <<a href="mailto:ben@stuyts.nl" class="">ben@stuyts.nl</a>><span class="Apple-converted-space"> </span><br class=""><b class="">Envoyé :</b><span class="Apple-converted-space"> </span>15 août 2022 19:05<br class=""><b class="">À :</b><span class="Apple-converted-space"> </span>Jean-Pierre Desrochers <<a href="mailto:jpdesroc@oricom.ca" class="">jpdesroc@oricom.ca</a>><br class=""><b class="">Cc :</b><span class="Apple-converted-space"> </span><a href="mailto:Synth-diy@synth-diy.org" class="">Synth-diy@synth-diy.org</a><br class=""><b class="">Objet :</b><span class="Apple-converted-space"> </span>Re: [sdiy] Reading IR phototransistors in a 8X8 matrix<o:p class=""></o:p></span></div></div></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Have you seen this project? It uses a webcam to read the piano roll:<o:p class=""></o:p></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><a href="https://github.com/nai-kon/PlaySK-Piano-Roll-Reader" style="color: blue; text-decoration: underline;" class="">https://github.com/nai-kon/PlaySK-Piano-Roll-Reader</a><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><a href="https://www.youtube.com/watch?v=8lkMRsoG9cg" style="color: blue; text-decoration: underline;" class="">https://www.youtube.com/watch?v=8lkMRsoG9cg</a><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Ben<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><br class=""><br class=""><o:p class=""></o:p></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt;" class="" type="cite"><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class="">On 15 Aug 2022, at 21:00, Jean-Pierre Desrochers <<a href="mailto:jpdesroc@oricom.ca" style="color: blue; text-decoration: underline;" class="">jpdesroc@oricom.ca</a>> wrote:<o:p class=""></o:p></div></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div class=""><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class="">I'm designing a piano Roll reader/player (yes antique paper piano rolls !)<br class="">that will read holes on a scrolling paper and play the actual musical notes<br class="">using MIDI standards..<br class="">This has already been done in the past but with very few documentations left<br class="">for DIYers like me.</span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class="">So.. I'm thinking of using IR (940nm) LEDs, phototransistors and aligned short optical fibers<br class="">to read the actual scrolling holes. 90 phototransistors will be used as 'bit' readers.<br class="">I would use IR because paper is mostly opaque to 940nm wavelength<br class="">compared to visible light that could get through it.</span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class="">Because of that high quantity of PT’s to be read I was thinking of using<br class="">rows/columns matrix of switches like keyboards in synths like this:</span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class=""> </span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class=""><image004.png></span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class="">But instead of switches like in this circuit I would use 2 pins phototransistors like this one:<br class=""><image001.png><br class=""><br class=""><br class=""></span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class="">The resistors could be around 10K and this configuration would use only 2 x 8 bits ports.</span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class="">But I was wondering about using PT’s in a matrix like that would bring glitches or noise</span><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span lang="EN-CA" class="">In the CPU readings..<span class="apple-converted-space"> </span><br class="">Has anybody used PT’s in such a circuit ?</span><o:p class=""></o:p></div></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 10.5pt; font-family: Helvetica, sans-serif;" class="">_______________________________________________<br class="">Synth-diy mailing list<br class=""></span><a href="mailto:Synth-diy@synth-diy.org" style="color: blue; text-decoration: underline;" class=""><span style="font-size: 10.5pt; font-family: Helvetica, sans-serif;" class="">Synth-diy@synth-diy.org</span></a><span style="font-size: 10.5pt; font-family: Helvetica, sans-serif;" class=""><br class=""></span><a href="http://synth-diy.org/mailman/listinfo/synth-diy" style="color: blue; text-decoration: underline;" class=""><span style="font-size: 10.5pt; font-family: Helvetica, sans-serif;" class="">http://synth-diy.org/mailman/listinfo/synth-diy</span></a><span style="font-size: 10.5pt; font-family: Helvetica, sans-serif;" class=""><br class="">Selling or trading? 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