opto couplers

[Colin Fraser]

I have used the CNY 17 too with success driving a 6402 receive input,
but not with a 6850. I suppose it comes down to a combination of
switching speed and the logic levels expected by the device after the
CNY 17.
Robert Penfolds 'Midi Projects' boot has a circuit that adds a tranny to
the output of a cheap opto-isolator (eg til111) to increase switching
speed - this works out a lot cheaper than say a 6N139, which cost me
about 3ukp.

Cf


>----------
>From: 	Rene Schmitz[SMTP:uzs159 at ibm.rhrz.uni-bonn.de]
>Sent: 	02 July 1997 12:57pm
>To: 	synth-diy at horus.sara.nl
>Subject: 	Re: opto couplers
>
>At 23:07 01.07.1997 +0200, you wrote:
>>Hi all,
>>
>>The last couple of weeks I'm busy making a midi interface with a
>>PIC16C73, for one of my analog synth projects.
>>The opto coupler I used in the first place was a CNY17-2 from QTC, which
>>didn't work properly. After measurements I found out that this one was
>>just to slow, because the rise and fall times at the transistor side
>>were too long.
>>After that I used the same type but from an other manufacturer (HP I
>>think). This opto worked well.
>>
>>My question is, which (low cost) opto is mostly used for midi
>>applications? Maybe the CNY17-2 isn't really suited for this kind of
>>stuff.
>
>I used the CNY 17-II and had (yet) no problem.
>But I had the idea to use the phototransistor along with an ordinary
>tranny in a cascode circuit, this should minimize the rise and fall times.
>(No there is nothing against a PC900 or something else to use here, 
>but I thought I might share this idea.)
>
>Bye 
> Rene
>
>