[Ronja] Pyroelectric receiver?

[alex dinovitser]

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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