[sdiy] what are these?

[Roy J. Tellason]

On Saturday 23 October 2004 10:46 pm, you wrote:
> on 10/23/04 7:08 PM, Roy J. Tellason at rtellason at blazenet.net wrote:
> > On Saturday 23 October 2004 05:37 pm, Roy J. Tellason wrote:
> >> I'm still sorting through parts...
> >>
> >> In this small bag labeled "optoisolators" I find these five things. 
> >> About an inch long more or less,  mayba a cm wide,  and irregular in
> >> contour -- there are two wires coming out of each end,  and the rest is
> >> covered by a layer of heatshrink.  Markings are "SIGMA 932" and
> >> "301T1-PC" and "26148". I'm not measuring anything with an ohmmeter
> >> between pairs of wires...
> >>
> >> Reminds me a little bit of those units that Fender used to use for
> >> "vibrato" except that these were obviously mounted on some board or
> >> other, wires are fairly short and all pointed in the same direction.
> >>
> >> Any of you guys have any ideas about these?
> >
> > Ok,  I opened one up,  since there only seemed to be 3 rather than 4
> > leads coming out of it.  And what do I find?  Another layer of
> > heatshrink,  this one thin and yellow.  I can see what looks like the tip
> > of a neon bulb peeking out of one end of the shrink,  and this yellow
> > stuff is apparently transmissive enough that this time when I put the
> > meter across the photocell I get readings that drop down to close to 100
> > ohms as I get closer to the lamp over my desk.
> >
> > Regular optos I can find a use for (and I have some,  and plans for
> > them), but not ones driven by a neon bulb.  Any of you guys have a use
> > for these?
>
> Could these be for detecting the presence of AC Mains?
>
> Cynthia

I suppose with the appropriate resistor (which is going to be rather different 
depending on whether that's an NE2 or an NE2H in there!) they could be used 
for such a thing...

The only thoughts I've had along those lines lately involve the building of a 
zero-crossing detector,  and this wouldn't work for that at all.