[GreenKeys] GreenKeys Digest, Vol 102, Issue 64

[epvgk at limpoc.com]

On Mon, Jul 23, 2012 at 08:42:00PM -0700, John Nagle wrote:
> On 7/23/2012 6:00 PM, greenkeys-request at mailman.qth.net wrote:
> > Message: 2
> > Date: Mon, 23 Jul 2012 19:36:25 -0500
> > From: "Jack"<wa2hwj at att.net>
> > Subject: [GreenKeys] Schematic
> > To:<greenkeys at mailman.qth.net>
> > Message-ID: <009001cd6934$5b823c10$1286b430$@net>
> > Content-Type: text/plain; charset="us-ascii"
> >
> > One correction on the schematic I sent out yesterday (fixed it
> > today): the opto-isolator is a H11D1, not HD11D1.
> 
>     An H11D1 seems undersized for a 60mA current loop.  Its
> absolute maximum rating is 60mA, but normal current transfer
> ratings for the device are 15 to 20mA, from figs 3 and 4
> of the data sheet.
> 
>     I used an HSR312L (now obsolete), and Steve Garrison used
> a G3VM-401B (pin-compatible, and better).  The G3VM-401B
> is good for 120mA as a recommended operating condition.
> Those are slower devices than an H11D1, but for any of
> the 60mA machines, a 1ms delay is tolerable.
> 
> 				John Nagle

I've been using PS7141E, which is pin-compatible with HSR312L but with
slightly better specs, and cheaper. These are what shipped in most of the
RTTY demod boards I sent out over the last year or so. 

Here is my brief analysis of the available options, from earlier this year. 

http://heepy.net/mediawiki/index.php/Optocouplers_for_teletype_current_loop



eric


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