[sdiy] MIDI cable impedance and MIDI In ESD protection?

[grant musictechnologiesgroup.com]

The latest MIDI electrical spec CA33 shows "optional ferrite beads to  improve EMI/EMC performance (FBx 1K @100MHz)"as well as "optional small  capacitor (0.1 μF typical) to improve RF grounding", along with diagrams.

GB

------ Original Message ------
From "Mattias Rickardsson" <mr at analogue.org<mailto:mr at analogue.org>>
To "modular at go2.pl<mailto:modular at go2.pl>" <modular at go2.pl<mailto:modular at go2.pl>>
Cc "synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>" <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>
Date 6/26/2024 1:57:09 PM
Subject Re: [sdiy] MIDI cable impedance and MIDI In ESD protection?


Thanks all for the discussion and advice.
Also a good idea to peek in commercial schematics, I see Kurzweil's 1nF caps now. :-) A bit larger than the 330pF ESD caps I was simulating, and a bit smaller than the 3nF of the wurst-case MIDI cable in Roman's example - which barely passes the MIDI pulses with style.

/mr

Den ons 26 juni 2024 17:21Roman Sowa via Synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>> skrev:
yes, before the resistor, otherwise it made no sense - LED or resistor
would go poof before TVS start to conduct

Roman

W dniu 2024-06-26 o 17:00, Ingo Debus via Synth-diy pisze:
>
>
>> Am 26.06.2024 um 15:51 schrieb Roman Sowa via Synth-diy
>> <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org> <mailto:synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>>:
>>
>> Maybe better to use TVS across the LED
>
> Hmm, usually there’s already a standard silicon diode (1N914 etc)
> anti-parallel to the LED, for reverse-voltage protection. Would an
> additional TVS do any good here? The LED or the silicon diode would
> conduct at a much lower voltage than the TVS.
> If there’s a really nasty spike, the 220-ohms-resistor would have to
> absorb most of its energy, no matter which of the diodes/TVS conduct. Or
> do you mean to connect the TVS _before_ that resistor?
>
> Ingo (remembering endless discussions with colleagues on the use of TVS
> diodes and varistors…)
>
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