[Ronja] Pyroelectric receiver?

[Gullik Webjörn]

Hmm, What source of light would you be using?

Surely not LEDS, I read the datasheet, and as I understand it
that these devices are optimised for 5-15 uM wavelength,
i.e. far far infrared, whereas Ronja goes below 1 uM, i.e.
to 630 nM.

Gullik

-----Ursprungligt meddelande-----
Från: ronja-bounces+gullik.webjorn=flysta.net at lists.pointless.net
[mailto:ronja-bounces+gullik.webjorn=flysta.net at lists.pointless.net]För
alex dinovitser
Skickat: den 30 november 2007 07:32
Till: Twibright Ronja
Ämne: Re: [Ronja] Pyroelectric receiver?


There's no fundamental reason these devices should be so expensive... A lab
grade photodiode costs more!

A pyroelectric detector from Farnell costs about $10, but is slow.. for PIR
alarms etc.


Anyhow, here is a datasheet I just downloaded from Coherent scientific...

If someone finds a suitable low-cost device out there, please let me know!!!

One disadvantage of PIR is that the spectral response is extremely broad. If
this causes a problem (although I can't see why?), you may need an optical
bandpass filter.

Another advantage is that the preamplifier is always built-in to the
detector,
so you will not need the BF908 circuit.

Note that the smaller PIR detectors have a lower "Noise Equivalent Power",
and
hence may be more suitable for long-range.




best regards, and ciao for now.....


Alex Dinovitser.






--- Arun Krishnan <arunk at speedpost.net> wrote:

> Hi,
>
> $100? A whole RONJA kit costs less than that to make yo.
>
> Regards,
> Arun
>
>
> ----- Original message -----
> From: "alex dinovitser" <adinov at yahoo.com>
> To: "Twibright Ronja" <ronja at lists.pointless.net>
> Date: Thu, 29 Nov 2007 21:56:26 -0800 (PST)
> Subject: Re: [Ronja] Pyroelectric receiver?
>
> I also thought these detectors were slow, until a colleague of mine
> showed me a
> device (that he'd just blown up with a laser pulse!).
>
> There are probably many different manufacturers, probably cheaper than
> this
> ($100) laboratory device from "Molectron"
> Called the "P1-60" with a flat frequency response of 70MHz. The largest
> version, the P1-65 has an active diameter of 5mm or ~20mm^2, if you need
> that
> much!
>
>
> --- Gregory Maxwell <gmaxwell at gmail.com> wrote:
>
> > On Nov 29, 2007 9:38 PM, alex dinovitser <adinov at yahoo.com> wrote:
> > > I am surprised you are using a photodiade for this application because
of
> > the
> > > problems with ambient light and the possibility of DC saturation. Why
not
> > use a
> > > pyroelectric receiver? (which will only be sensitive to the AC
signal).
> > With a
> > > larger area device, you might be able to get *much* better range!!
> >
> > I can't comment on the Ronja design decisions but I'm puzzled by your
> > suggestion. I've never seen a pyroelectric detector that was very
> > past. Most that I've seen have a bandpass no more than 100kHz or so,
> > while ronja needs a bandpass of many mHz.
> >
> > Perhaps I just haven't been following pytoelectric detector science.
> > Could you suggest a part that you think might better fit ronja than
> > the current PIN diode?
> >
> > --
> > Twibright Ronja mailing list http://ronja.twibright.com
> > Ronja at lists.pointless.net
> > http://pointless.net/mailman/listinfo/ronja
> >
>
>
>
>
>
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