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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Hi Jean-Pierre!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">What about adding Schmitt Trigger Gates at the phototranistor board, This makes the signals digital and low impedance – crosstalk should then be no problem.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">74HC14 for example (inverting!)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">But be careful – strong digital signal and edges normally lead to more EMC problems!<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Ciao<br>
Peter<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="DE">Von:</span></b><span lang="DE"> Synth-diy <synth-diy-bounces@synth-diy.org>
<b>Im Auftrag von </b>Jean-Pierre Desrochers<br>
<b>Gesendet:</b> Donnerstag, 1. Dezember 2022 19:44<br>
<b>An:</b> Synth-diy@synth-diy.org<br>
<b>Betreff:</b> *EXT* [sdiy] Piano roll reader project.. using Photo-transistors to read holes.. Sensitivity wise... ??<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoPlainText"><span lang="EN-CA">So far my Piano roll reader project goes well..<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA">I’m now doing some experiments using T1 phototransistors (940nm IR wavelenght)<br>
that are each inserted in the small one inch long copper pipes that prolong the rear of<br>
each square holes of the main brass reading bar.<br>
I noticed that rising the PT’s collector resistor will in fact also rise the PT gain<br>
thus making it more sensitive. That’s good.. but there is a problem,<br>
rising these resistors too much will create possible crosstalk between<br>
the IR PT’s wirings (around 88 x 2 inches long wiring pairs) to the pcb that holds the readers IC’s (74HC165).<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA">There will be 11 x 74HC165 parallel to SPI interfaces mounted on the main board<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA">To read the 88 holes.. See one of the 11 SPI reader circuit here.<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA">One thing that encourages me is that the rate of holes changing on the scrolling paper<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA">Will never be higher than the humain hands that played the original song.. so not very fast for crosstalk..<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA"><br>
I tried 10k’s but this needed a too strong IR beam facing the PT’s..<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA">100k’s gave a much more sensitive result..<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA">I could select a final value from 47k to 100k for all these resistors..<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA"><o:p> </o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA">What do you think about the possible crosstalk at that read speed, and the value to use ?<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA">Thanks for your time !<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA">JP<o:p></o:p></span></p>
<p class="MsoPlainText"><span lang="EN-CA"><o:p> </o:p></span></p>
<p class="MsoPlainText"><span lang="FR-CA"><img width="956" height="727" style="width:9.9583in;height:7.5729in" id="Image_x0020_2" src="cid:image001.jpg@01D90625.6C35EBD0"></span><span lang="FR-CA"><o:p></o:p></span></p>
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