[sdiy] MIDI Optocoupler

[harrybissell]

The 4N35 might be a little iffy in a MIDI application. Its a general
purpose
part more suited to control signals (industrial uses abound...) than
communications.
Most folks opt for the 6N137 / 138 for higher speed use.

Some of them will probably work OK...  Its just not a common choice for
MIDI.
If they worked well, no one would ever use the more expensive parts :^P

H^) harry

Tim Parkhurst wrote:

> Hi All, Just came across a whole bunch (like 2000) of a Philips 4N35
> optocoupler. I've seen these listed in some Sound Blaster to MIDI
> schematics, so it looks like they're okay for use in MIDI
> applications. What I'd like to know is, what is really the determining
> characteristic for a MIDI optocoupler? Speed? The 4N35 has a switching
> speed of about 3uS, so (1/.000003)/2 = a maximum switching speed of
> approx. 167kHz right? (divide by 2 because each cycle is two
> transitions, and 1/3uS to get frequency... right?) Anyway, if this is
> correct, then this part should be more than fast enough for MIDI. What
> about current capability? Any other factors to look at when picking an
> optocoupler? By the way, if these things are good for MIDI, I'll sell
> 'em real cheap since I have so darn many (something like $2 + shipping
> for a tube of twenty, I have to see how many are in a tube).Tim
> (right?) Servo
> --
> "Imagination is more important than knowledge." - Albert Einstein