On Mon, 28 Nov 2005 20:03:56 +0000 (UTC), Frank Erskine
wrote:

On Mon, 28 Nov 2005 19:58:08 +0000, Palindr?me
wrote:

Andrew Gabriel wrote:
In article ,
Andy Hall writes:

Oh definitely. I even made phototransistors. You could do this
with an OC71 (which came encapsulated in black painted glass).
The procedure was to scrape off most of the black paint and then to
carefully scribe a line near the bottom of the case before carefully
breaking it away.
Inside was a bluish-white opaque paste which could be washed away with
alcohol of some kind. After that, the think could be put back together
and worked very well for optical sensing. I used it in a controller
to switch on lights when the sun went down.


Scraping the paint of an OC71 turned it into an OCP71 (yes
I did that too). However, you didn't need to take it out
of the glass tube or wash off the white heat sink compound;
it was translucent enough to work just as it was.

IIRC, the earlier ones were fine. Later they did put opaque compound in
that had to be removed. OC45s also worked, at much reduced sensitivity
to the '71..

I've used a centrifuge to drive the opaque stuff to the bottom of the
de-painted OC71.


Now that's just showing off :-)


--

..andy