[sdiy] optocouplers/Vactrols

[Tim Parkhurst]

> -----Original Message-----
> From: Paul Higgins [mailto:higg0008 at tc.umn.edu]
> Sent: Tuesday, October 19, 2004 10:49 AM
> To: Metrophage
> Cc: synth-DIY
> Subject: Re: [sdiy] optocouplers/Vactrols
> 
<snip>
> Well, that explains why I couldn't find any optocouplers on the
> Hamamatsu website, only LDRs.  And I have heard that Clairex has
> gaps.  I've also seen people use 35mm film canisters with holes punched
> in the bottom for the leads; kind of bulky, but it works.  With the
> right LDR and construction, you can get pretty good performance even
> from DIY "Vactrols".
> 
> -PRH
> 
> On Tuesday, October 19, 2004, at 08:51 AM, Metrophage wrote:
> 
> > I don't prefer any yet, I am just getting into them, like it sounds you
> > are. Each manufacturer makes units with various respective resistances
> > and response times.
> >
> > Clairex and Hamamatsu appear to be dropping their production of many,
> > if not all, analog photocouplers. There are still quite a few out
> > there. Compare specs for the values you need!
> >
> > CJ
> 
</snip>

So, what are the big variables in DIY optocouplers? As far as I can tell,
there are three main areas:

1) LED current vs. output. Manufacturers variation from one part to the
next.

2) Photocell illumination vs. resistance. Again, variation from one part to
the next.

3) "Manufacturing tolerances." I.e., variations in position, distance,
opacity, when the whole thing is being put together.

Okay, so #3 is at least under our control. Getting things positioned and put
together consistently just takes some care and practice. But how bad are the
variations in items 1 and 2? Could a simple trimming circuit (say a pot in
series with the LED) be used to get a fairly close min/max match between
several DIYOCs? (Note the new acronym. Remember where you saw it first ;) )



Tim (big variable) Servo

"Imagination is more important than knowledge." - Albert Einstein
 

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.776 / Virus Database: 523 - Release Date: 10/12/2004
 



***************************************************************************
This message is confidential.  The information contained in
this e-mail message is intended only for confidential use of the
recipient(s) named above. If the reader of this message is not the intended
recipient or an agent responsible for delivering it to the intended
recipient, you are hereby notified that you have received this document in
error and that any review, dissemination, distribution, or copying of this
message is strictly prohibited.  If you have received this communication in
error, please notify us immediately by e-mail, and delete the original
message.
***************************************************************************