[sdiy] MIDI and ESD protection

[Julian]

Am 06.02.20 um 11:08 schrieb Tom Wiltshire:
> Have you got ten fried MIDI outputs on your bench yet? How much is
> this actually a problem and how much is it a theoretical problem?
I guess more of a theoretical problem. since I never fried a single
piece of electronic due to ESD, even when I used just an UART pin and a
resistor.
On the other hand I'm not sure how real world applicable the ESD tests
in an EMV lab are.

My real world guess would be that any ESD pulse is probably rather
discharging into the shielding or the enclosure rather than the signal pin.
But simulating the IEC6100-4-2 ESD generator in SPICE shows values
exceeding the limits when applied directly to the signal line.

Human body model is much more forgiving then the IEC standard.
>
> I wouldn't change the design to fix a problem unless I was sure I’d
> got a problem. The old “if it ain’t broke, don’t fix it” principle.
> That said, if you’re using 74HC14 for the output buffering, you could
> probably just run it on a 5V supply and it’d be done. I seem to
> remember the logic voltage levels are set up so it can convert from
> 3.3V input logic to 5V output.
But rather expensive if you fail compliance testing due to omitting a 10
cent part ;) (I know, compliance is not really DIY related)
Maybe if I feel adventurous I'll make some precompliance testings with
and without a TVS diode on the MIDI IO.
I just have a cheap piezzo ESD gun like the one recommended by Henry Ott.

Julian