On Sat, 31 Dec 2005 00:05:28 GMT, Paul VK3DIP wrote:
Hi all I recently purchased a bag of unmarked supposedly diodes and I am
trying to figure out what they are. The clues so far are normal diode
action on a multimeter (ie conducts one way but not the other) but the
forward voltage is high at about 1.4 - 1.5 volts. The packaging is a small
square black plastic box with flat axial leads one of which has a small
cross
piece on it. This packaging suggests small signal or at least low power.

If anyone wants to look at the mystery diode it is the top one
in this picture.
http://www.users.bigpond.com/pmcmahon/mysterydiode.jpg
The bottom one is a normal glass 1N914 just for scale.

There is nowhere for the light to come out (or in) so they are not LEDs
which is the only other diode like component I have come across with that
high a forward voltage. Could it be two silicon diodes in series?

Don't count it out as not being an LED. Some opaque-to-the-human-eye
packages are, in fact, quite clear in either the IR or UV range.
It could be an IR LED. (There's been many cases where light-sensitive,
'ordinary' diodes caused 'problems' in circuits on a well lit workbench.
The 'thing' would work one way in a buttoned-up case, and another way
under test.)

HTH
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
Pueblo, Colorado | @ | Jonesy | OS/2 __
38.24N 104.55W | config.com | DM78rf | SK

"Allodoxaphobia" wrote in message
...

Don't count it out as not being an LED. Some opaque-to-the-human-eye
packages are, in fact, quite clear in either the IR or UV range.
It could be an IR LED.

Other than being black, that thing looks suspiciously like an LED, so I
would go for an IR LED.

...

xpyttl wrote:
Other than being black, that thing looks suspiciously like an LED, so I
would go for an IR LED.

You could apply power it to as you would an LED (using a
current-limiting resistor), and take a look at it in a digital camera's
display. Digital cameras are somewhat sensitive to IR, even though they
usually have a built-in IR cut filter. Try it with an IR remote control
to see what I mean.

Dan, KB1RT

"Dan Halbert" bravely wrote to "All" (31 Dec 05 20:34:08)
--- on the heady topic of " Identifying a mystery diode"

DH From: Dan Halbert
DH Xref: core-easynews rec.radio.amateur.homebrew:90419

DH You could apply power it to as you would an LED (using a
DH current-limiting resistor), and take a look at it in a digital
DH camera's display. Digital cameras are somewhat sensitive to IR, even
DH though they usually have a built-in IR cut filter. Try it with an IR
DH remote control to see what I mean.

DH Dan, KB1RT

IR LED makes quite sensitive IR receiver. Just power up the mystery
diode near it and measure the voltage across the leads using a DMM.

A*s*i*m*o*v

.... Curiousity didn't kill the cat, I got him with the mower!

Hi, Thanks everyone for the suggestions.
I tried putting 5 mA through it ( approx 1.6v forward voltage) and examining
it closely with a camera that I tested as being good at seeing IR and
nothing showed. I am leaning towards the high voltage theory of two series
silicon diodes in the one package. Anybody know a manufacturer of these
sorts of things or even what the package type is called?

Paul.

"Allodoxaphobia" wrote in message
...
On Sat, 31 Dec 2005 00:05:28 GMT, Paul VK3DIP wrote:
Hi all I recently purchased a bag of unmarked supposedly diodes and I am
snip
it is the top one
in this picture.
http://www.users.bigpond.com/pmcmahon/mysterydiode.jpg



Don't count it out as not being an LED. Some opaque-to-the-human-eye
packages are, in fact, quite clear in either the IR or UV range.
It could be an IR LED. (There's been many cases where light-sensitive,
'ordinary' diodes caused 'problems' in circuits on a well lit workbench.
The 'thing' would work one way in a buttoned-up case, and another way
under test.)

HTH
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
Pueblo, Colorado | @ | Jonesy | OS/2 __
38.24N 104.55W | config.com | DM78rf | SK