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

[Ullrich Peter]

Hi!

On a standard MIDI Interface you get the 5V voltage of the sourcing midi device via a 220 ohms resistor - so this is where you can get your power.
Of course the current is limited to a few milliamps as you can easily calculate.

What helps here is to use 3.3V microcontrollers (better: microcontroller with a voltage range from 2.7V to 5.5V) as these can work even with lower voltages. In this case it is recommended to use open collector/open drain drivers on the midi output so that they can drive the midi output better. As the midi inteface is only a current on/off interface the open drain is enough, and driving no high level on the midi out is better than driving it with 3V level as this could lead to problems on modern low current optocoupler in the devices connected after your device.

By using such a microcontroller it is useful to set the brownout level for the reset circuit to 2.7V or similar so that the device can really work down to these voltages.

Decoupling by an electrolythic condenstaor is useful, if you get dropouts due to the midi interface current then even a schottky diode in front of the electrolytix condensator can give you more decoupling but costs about 0.2 to 0.3V at these low currents.

Ciao
Peter

Http://www.ullrich.at.tt 

________________________________________
Von: synth-diy-bounces at dropmix.xs4all.nl [synth-diy-bounces at dropmix.xs4all.nl]" im Auftrag von "jpdesroc [jpdesroc at oricom.ca]
Gesendet: Donnerstag, 10. September 2015 02:13
An: synth-diy at dropmix.xs4all.nl
Betreff: [sdiy] MIDI phantom power...over 5 pin MIDI connector ?

Does anybody have schematics of an easy way to send
power using the 2 MIDI pins in a 5 pins cable ?
I don't want to use any of the 3 remaining wires of the cable
for universal use on ANY MIDI cables..
I know this company uses that technology:

http://www.midisolutions.com/prodmrg.htm

but I can't find any circuit ideas that uses it..
I know I'll need some kind of charge pump design to get something like 5
volts
out of the MIDI (idle or in use) signal.

Any clues ?

JP
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