stealing power from Midi Data line

[rbairos]

Hello.
Im trying to build a simple midi circuit, but
is there any way to power it by stealing power
from the incoming midi-in cable thats plugged
into it?

Anyone have any circuits tips etc?

Thanks very much,

Rob.

 

[Nigel Goodwin]

Hello.
Im trying to build a simple midi circuit, but
is there any way to power it by stealing power
from the incoming midi-in cable thats plugged
into it?

A midi input is opto-isolated, so I wouldn't have thought it possible without destroying the isolation.

 

[grrr_arrghh]

midi input from what...?

if you are using a gameport-to-midi adapter cable plugged into a computer, some of the cheap ones arn't properly opto-isolated so you might be able to do it that way, because gameports have several 5v lines. Bear in mind, though, that midi data packets only last 200ns (or something like that).

However, if you're using standalone midi equipment, as Nigel says, its no-go.

I don't know what you're trying to do, but have a quick look at:

**broken link removed**
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[rbairos]

I wont be using the game-port adapter, but the 'midi out' cable
plugged into another device.
Ive built a midi circuit just fine which accepts analog inputs and spits out a digital midi-stream which can be read by my pc, or other midi devices with no problems.

The only thing I dont like is the fact the my circuit needs to be battery operated. Ive seen similar commercial products to the one Ive built which dont require any power but only require another midi device plugged into it.

I guess I would lose the opto-isolation, but I think I could grab +5v from 'pin 4' of an incoming midi cable ?

This violates the opto-isolation, but perhaps I could be careful by adding an extra 5.0v diode off that line ?