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</o:shapelayout></xml><![endif]--></head><body lang=FR-CA link=blue vlink=purple style='word-wrap:break-word'><div class=WordSection1><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><img width=956 height=727 style='width:9.9583in;height:7.5729in' id="Image_x0020_2" src="cid:image002.jpg@01D9058A.F6C45CF0"><o:p></o:p></p></div></body></html>