Re: diy microwave alarm

[Jim <alarminex@xxxxxxx>]

On Saturday, May 3, 2014 8:40:12 AM UTC-4, joe hey wrote:
> On Sat, 03 May 2014 09:18:50 +0000, joe hey wrote:
>=20
>=20
>=20
> > On Sat, 03 May 2014 09:17:25 +0000, joe hey wrote:
>=20
> >=20
>=20
> >> On Sat, 03 May 2014 01:28:52 -0500, G. Morgan wrote:
>=20
> >>=20
>=20
> >>> joe hey Wrote:
>=20
> >>>=20
>=20
> >>>>On Fri, 02 May 2014 14:11:30 -0500, G. Morgan wrote:
>=20
> >>>>
>=20
> >>>>> joe hey Wrote:
>=20
> >>>>>=20
>=20
> >>>>>>(What is a 'PE beam'?)
>=20
> >>>>>=20
>=20
> >>>>> Photo-electric
>=20
> >>>>
>=20
> >>>>PE beams would be fine if they could span about 200 m in heavy rain.
>=20
> >>>=20
>=20
> >>>=20
>=20
> >>> You would need an array, and if CCTV breaks the budget than PE beams
>=20
> >>> are out of the question.
>=20
> >>=20
>=20
> >> oh, my bad, I thought CCTV would just be more expensive than PE.
>=20
> >> After all, I thought, PE is just an infrared emitting diode on the one=
,
>=20
> >> and a receiving photo diode on the other side.
>=20
> >>=20
>=20
> >> But maybe this is something useful?
>=20
> >> http://www.aliexpress.com/item/P92-Wired-250M-Alarm-Triple-Beam-
>=20
> >> Photoelectric-Infrared-LED-Detector-Tamper-Alarm-Output/1011069523.htm=
l
>=20
> >> It would only require 6 of those sets to cover al sides...
>=20
> >>=20
>=20
> >> Totalling about $380, wiring excluded!
>=20
> >=20
>=20
> > Oh, and solar panels for power, batteries for during the night.
>=20
> > And then have it all stolen one night...
>=20
>=20
>=20
> Forget the last remark. All units can be series-fed through one current=
=20
>=20
> source that's on a protected location and I'm sure an 'alarm voltage=20
>=20
> pulse' can be put on the feeding line which will be seen at the source=20
>=20
> which then would be able to ignite the alarm.
>=20
>=20
>=20
> I found this 'DIY' project.
>=20
>=20
>=20
> http://www.electroschematics.com/782/infrared-light-barrier/
>=20
>=20
>=20
> Double-modulated beam. With a bit of logic it can be made multi-beam,=20
>=20
> different frequencies, and such that the alarm goes off only when all=20
>=20
> beams are interrupted.
>=20
>=20
>=20
> I wonder if this can be equipped with laser pen-style laserdiodes, so=20
>=20
> that a high distance can be reached.

Laser pen diodes are in the visible light spectrum. You'd want something in=
 the infra red range.=20

But .... I still think you're going to spend a lot more money (and certainl=
y time)  developing this Rube Goldberg device than it would cost to just go=
 out and buy it. I know one thing that you haven't even considered and that=
 is alignment of the beams. You're thinking it's going to be easy ..... (HA=
!)  And don't kid yourself ..... there ARE going to be lots of false alarms=
 regardless ..... and MORE of them if you design it. You've got to guess th=
at the manufacturers of these devices didn't just think up the idea, put th=
e device together and it worked the first time. Outdoor sensors take years =
to develop and refine and even then they are prone to false alarms.

But ...... you sound like you're on a mission to prove something ....=20
so be it. Good luck.