Photosensitivity : Led and Neon

[harry bissell]

Ooohh I can answer that one....
Yes neons are photosensitive... In the presence of light they break over
at a lower voltage... because the photons are already beginning to
activate the gas...

Most neon bulbs have some radioisotope content (a miniscule amount) that
adds a constant amount of ionizing energy... this makes the light
sensitivity much less... Its like the light is "on" all the time. These
stabilized bulbs have the suffix "H" on the end of the part number...
like NE-2H. The stabilized bulbs are the most common type...

Try it yourself (I did as a child) make a simple relaxation oscillator
(OK so the batteries have been hard to get since I was a child...) and
take it in a dark room.
It will flash much slower. Use a bulb without the "H" such as the NE-2
and the effect is dramatic (if you are drama challenged like me...)

:^) Harry

Toby Paddock wrote:

> LEDs do generate juice when exposed to light.
> Not very efficient, but pretty fast.
> The only time I tried it was to look at the modulation of
> one of those cheap laser tag pistols.
> I connected it to a scope and shined the pistol at it.
> It did work after I added a load resistor to discharge
> the scope input capacitance. I think in general
> that they respond best to the same color that
> they emit. So I must have used an I.R. LED (?)
>
> Heading off-topic, I've wondered if shining light
> on a neon lamp would lower its trigger voltage.
>
>  - -- -  Toby Paddock
> http://www.seanet.com/~tpaddock
> I like using the word "juice" for the same reason
> my high-school electronics teacher hated it:
> It's vague.
>
> Harry Bissell wrote:
>
> >Does anyone have experience with LEDs as clipping devices.
> >These are not in a feedback loop here, they are just
> >forward biased or not...
>
> >Is there any effect of photosensitivity of the LEDs.
> >Do they form a detector that could photon couple
> >noise (ambient light etc) into the
> >circuit if they were exposed (like through a front panel...
>
> >OK I just like blinkey lights... allright ????