[sdiy] MIDI Optocoupler

[Senso]

One of the most widely used is the PC900 (400kBit/s). You'll find it 
in lots and lots of synths and MIDI-interfaces and -processors. They 
are indeed more than a dime each, but I doubt you will need a couple 
of dozen in a design.
And they are cheaper than a TL084 or a CA3080. ;-)
Personally, I'd rather have two that work than 2 tubes of something 
that might work.

Senso

>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


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