Re: diy microwave alarm

[joe hey <joehey@xxxxxxxxxxxxxx>]

On Mon, 05 May 2014 11:26:59 -0700, Jim wrote:

> 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:
>>
>>
>>
>> > On Sat, 03 May 2014 09:17:25 +0000, joe hey wrote:
>>
>>
>> >
>> >> On Sat, 03 May 2014 01:28:52 -0500, G. Morgan wrote:
>>
>>
>> >>
>> >>> joe hey Wrote:
>>
>>
>> >>>
>> >>>>On Fri, 02 May 2014 14:11:30 -0500, G. Morgan wrote:
>>
>>
>> >>>>
>> >>>>> joe hey Wrote:
>>
>>
>> >>>>>
>> >>>>>>(What is a 'PE beam'?)
>>
>>
>> >>>>>
>> >>>>> Photo-electric
>>
>>
>> >>>>
>> >>>>PE beams would be fine if they could span about 200 m in heavy
>> >>>>rain.
>>
>>
>> >>>
>>
>> >>>
>> >>> You would need an array, and if CCTV breaks the budget than PE
>> >>> beams
>>
>> >>> are out of the question.
>>
>>
>> >>
>> >> oh, my bad, I thought CCTV would just be more expensive than PE.
>>
>> >> After all, I thought, PE is just an infrared emitting diode on the
>> >> one,
>>
>> >> and a receiving photo diode on the other side.
>>
>>
>> >>
>> >> But maybe this is something useful?
>>
>> >> http://www.aliexpress.com/item/P92-Wired-250M-Alarm-Triple-Beam-
>>
>> >> Photoelectric-Infrared-LED-Detector-Tamper-Alarm-
Output/1011069523.html
>>
>> >> It would only require 6 of those sets to cover al sides...
>>
>>
>> >>
>> >> Totalling about $380, wiring excluded!
>>
>>
>> >
>> > Oh, and solar panels for power, batteries for during the night.
>>
>> > And then have it all stolen one night...
>>
>>
>>
>> Forget the last remark. All units can be series-fed through one current
>>
>> source that's on a protected location and I'm sure an 'alarm voltage
>>
>> pulse' can be put on the feeding line which will be seen at the source
>>
>> which then would be able to ignite the alarm.
>>
>>
>>
>> I found this 'DIY' project.
>>
>>
>>
>> http://www.electroschematics.com/782/infrared-light-barrier/
>>
>>
>>
>> Double-modulated beam. With a bit of logic it can be made multi-beam,
>>
>> different frequencies, and such that the alarm goes off only when all
>>
>> beams are interrupted.
>>
>>
>>
>> I wonder if this can be equipped with laser pen-style laserdiodes, so
>>
>> 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.
>
> But .... I still think you're going to spend a lot more money (and
> certainly 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 that the manufacturers of these
> devices didn't just think up the idea, put the 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 ....
> so be it. Good luck.

Actually I'm not. I'm just trying to explore the options we have.
And yes, I did consider alignment of the beams of a laser pen and think
it's nearly impossible to do that right. Even if taking some very sturdy
concrete posts, put them 4 m deep in the soil for stability, attach
strong steel sockets around them holding the mirrors while using fine-
threaded screws to adjust them.
Keeping them aligned, or even clean after a rain without destroying the
adjustment, will certainly be near to impossible.

'Just go out and buy it'? : X6, that's the problem :)

thanks