[sdiy] MIDI phantom power...over 5 pin MIDI connector ?

[Ove Ridé]

You're right, it's a current loop protocol and there are different ways to
skin the cat. Nevertheless, I expect all reasonably designed MIDI gear to
have current limiting of one kind or the other, on both the inputs and the
outputs. Thus the claim I was responding to, that this hypothetical special
high power device will by default destroy ANY regular MIDI gear if
connected by mistake, is patently false.

On Thursday, 10 September 2015, Neil Johnson <neil.johnson71 at gmail.com>
wrote:

> What I find particularly funny/frustrsating/disappointing is how many
> people don't understand the MIDI spec.
> All this talk of "5V" and "220R resistors" completely misses the point.
>
> *sigh*
>
> Here's a clue: the text of the standard makes no mention of voltage.
> Chapter 2, page 1, "HARDWARE".  The circuit given on page 2 is an
> illustration of one implementation.  I've also discussed the wording
> in the standard with the MMA and their response to the vagueness in
> the standard is "well no-one's pointed this out before, and we don't
> quite understand why the spec was written in this way, so, umm, la la
> la la..."
>
>
> Neil
>
>
> On 10 September 2015 at 09:29, Ove Ridé <nitro2k01 at gmail.com
> <javascript:;>> wrote:
> > On 10 September 2015 at 09:40,  <eidorian at aladan.net <javascript:;>>
> wrote:
> >> I just re-read the original post, and it might be that JP isn't asking
> how
> >> he can get power from a MIDI cable, he might actually be asking a subtly
> >> different question: how can he *send* more power over the two MIDI pins
> >> (presumably without affecting the ability of those pins to transmit MIDI
> >> to
> >> older devices at the same time).
> >
> > The MIDI-DIN states that pin 2 should be connected, if nothing else,
> through
> > the shield. Are there really cables around that have pin 2 completely
> > unconnected?
> >
> >> But yeah, there's no fun to be had doing this.  Any device that requires
> >> your "high powered" MIDI-out ports for power is going to damage your
> >> "normal" gear if you ever plug it in accidentally :-(
> >
> > I don't see how. A compliant, regular output device should have 220 ohm
> > resistors in series on both pin 4 and 5 to limit the current and should
> > handle even being indefinitely shorted. Likewise, a regular input device
> > will have 220 ohm in series with the optocoupler. 5/220=23 mA and that's
> > being really pessimistic and ignoring the LED forward voltage drop.
> >
> > --
> > /Ove
> >
> > Blog: <http://blog.gg8.se/>
> >
> > "Here is Evergreen City. Evergreen is the color of green forever."
> >
> >
> > --
> > /Ove
> >
> > Blog: <http://blog.gg8.se/>
> >
> > "Here is Evergreen City. Evergreen is the color of green forever."
> >
> >
> > _______________________________________________
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> >
>
>
>
> --
> --
> http://www.njohnson.co.uk
>


-- 
/Ove

Blog: <http://blog.gg8.se/>

"Here is Evergreen City. Evergreen is the color of green forever."
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