Alt-BEAM Archive

Message #01315



To: "Steven Bolt" sbolt@xs4all.nl, davidperry@mail.geocities.com
From: "Zulu 35" zulu35@singnet.com.sg
Date: Fri, 5 Mar 1999 18:20:37 +0800
Subject: [alt-beam] Re: photodiodes


hmmm..... in simple english?? what does that mean? cos i seem to have
trouble controlling my photopopper circuit using the photodiodes... boths
motors spin all the time.. and covering either one of the diodes never
seems to help.. :)

----------
> From: Steven Bolt
> To: davidperry@mail.geocities.com
> Cc: beam@corp.sgi.com
> Subject: Re: photodiodes
> Date: Friday, March 05, 1999 4:56 PM
>
> On Wed, 4 Mar 1992 davidperry@mail.geocities.com wrote:
>
> > maybe you should think of them as one way soalr cells, they generate
> > around 0.4 volts one way, and the other way it totally blocks the
> > electricity, thats the whole point of a diode. I don't know about
> > their resistance.
>
> It's not as simple as that...
>
> > > okay, quick question. as far as i know, photodiodes have resistance
> > > in only one direction. is the other direction blocking electricity or
> > > does it have no resistance?
>
> And there is probably no quick answer to this quick question. But
> how about this:
>
> Aach photon within the wavelength range of your photodiode creates an
> electron-hole pair. When reverse biased, this results in a current
> flow which is proportional to light flux. Meaning that "the other
> way," it does not totally block electricity, because it is a
> photodiode, not a diode. And you should not associate any of its
> properties with simple resistance; that is quite misleading.
>
> Best,
>
> Steve
>
> ----------------------------------------------------------------------
> # sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
> ----------------------------------------------------------------------
>

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