<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style>
</head>
<body dir="ltr">
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
If you look for them, there are quite a few 4 pin optoisolators which work fine, and two of them take less space and cost less than a single 137.</div>
<div id="appendonsend"></div>
<div style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<hr style="display: inline-block; width: 98%;">
<div id="divRplyFwdMsg" dir="ltr"><span style="font-family: Calibri, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);"><b>From:</b> Synth-diy <synth-diy-bounces@synth-diy.org> on behalf of René Schmitz <synth@schmitzbits.de><br>
<b>Sent:</b> 28 June 2024 10:50<br>
<b>To:</b> synth-diy@synth-diy.org <synth-diy@synth-diy.org><br>
<b>Subject:</b> Re: [sdiy] MIDI cable impedance and MIDI In ESD protection?</span>
<div> </div>
</div>
<p><br>
</p>
<p>If you have the space and budget, use two optocouplers: one for each direction, that allows you even to sense which direction it is. </p>
<p>(So you can change the output too...)</p>
<p><br>
</p>
<p>Where do I collect my prize? :)</p>
<p><br>
</p>
<p>Best,</p>
<p> René</p>
<p><br>
</p>
<div>Am 28.06.2024 um 00:06 schrieb Mattias Rickardsson:</div>
<blockquote>
<div style="direction: ltr;">On Thu, 27 Jun 2024 at 20:55, Andrei Kudryavtsev <<a href="mailto:andrei.kudryavtsev@gmail.com" id="OWA4637ac86-67f9-cb88-63d1-fa83e283d46a" class="x_moz-txt-link-freetext OWAAutoLink">andrei.kudryavtsev@gmail.com</a>> wrote:</div>
<blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left: 1px solid rgb(204, 204, 204);">
<div style="direction: ltr;">Speaking of TRS mess, found this one in the recent application list for MIDI innovations:</div>
<div style="direction: ltr;"><a href="https://midi.org/innovation-award/psimidi" id="OWA7b971e89-703c-2268-c73d-61d6dda19573" class="x_moz-txt-link-freetext OWAAutoLink" data-auth="NotApplicable">https://midi.org/innovation-award/psimidi</a></div>
</blockquote>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">Oops, that has been solved in commercial products for over 5 years. </div>
<div style="direction: ltr;">But without those extra diode voltage drops! </div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">(Assuming 1.9 V drop for the optocoupler and 2 x 0.3 V drop for the Schottkys, and the new 3.3 V (+/- 5 % on the lower side) logic level, there's 0.635 V left for the 220 ohm resistor. The current is then only 2.9 mA, far below
the required 5 mA. Oops2!)</div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">(It would need to have 127 ohms instead of 220. But with 5 V (+/- 10 % on the higher side) logic level, and 1.9 + 0.3 + 0.3 V voltage drops, you get 3 V over the resistor. 23.6 mA is above the specified Abs Max input current of
the 6N138 optocoupler suggested in the MIDI spec, even if the 6N137 used here will survive. Oops3!)</div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">I'm sure similar gender-agnostic TRS MIDI In jack solutions must have been implemented by several manufacturers by now? It was a bit weird to see different brands using different polarities when TRS MIDI emerged, and even more strange
to see MMA omit a solution for it in the new standard. :-) </div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">Thanks for the reading tip, Andrei!</div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">/mr</div>
<div style="direction: ltr;"><br>
</div>
<div style="direction: ltr;">PS: I wrote "TS" in my first message, mistake - should have been "TRS". Sorry.</div>
<br>
<fieldset class="x_moz-mime-attachment-header"></fieldset>
<pre><div>________________________________________________________
This is the Synth-diy mailing list
Submit email to: <a href="mailto:Synth-diy@synth-diy.org" id="OWA16aaa8e7-cd06-e9a2-8d5a-9c2c1e958ce3" class="x_moz-txt-link-abbreviated OWAAutoLink">Synth-diy@synth-diy.org</a>
View archive at: <a href="https://synth-diy.org/pipermail/synth-diy/" id="OWAf9de5dc8-be9c-9f0a-e330-cbb9161870de" class="x_moz-txt-link-freetext OWAAutoLink" data-auth="NotApplicable">https://synth-diy.org/pipermail/synth-diy/</a>
Check your settings at: <a href="https://synth-diy.org/mailman/listinfo/synth-diy" id="OWA5702556a-363b-8832-bfbc-ab756403bd0f" class="x_moz-txt-link-freetext OWAAutoLink" data-auth="NotApplicable">https://synth-diy.org/mailman/listinfo/synth-diy</a>
Selling or trading? Use <a href="mailto:marketplace@synth-diy.org" id="OWA18a12a4a-193e-9f29-e794-26d025f9a983" class="x_moz-txt-link-abbreviated OWAAutoLink">marketplace@synth-diy.org</a>
</div></pre>
</blockquote>
<pre><div>--
--
<a href="mailto:synth@schmitzbits.de" id="OWAc274b855-4688-f858-39cc-4bf12254b111" class="x_moz-txt-link-abbreviated OWAAutoLink">synth@schmitzbits.de</a>
<a href="http://schmitzbits.de" id="OWA9b37500e-ec84-b9e2-1767-db27d9d2bd98" class="x_moz-txt-link-freetext OWAAutoLink" data-auth="NotApplicable">http://schmitzbits.de</a></div></pre>
</body>
</html>