Re: diy microwave alarm

[joe hey <joehey@xxxxxxxxxxxxxx>]

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.