Photo beam to trigger relay

[JimG]

Looking for recommendations on a simple photo-electric beam that works with a reflector which I can wire up to a relay. This would be for use in the f ront yard to detect intruders.

I currently use a Steinel and Redwall PIRs that trigger the relays and the relays in turn trigger the relevant CCTV cameras. These have worked well wi th the exception of one location where the PIR gets triggered (and eventual ly burned out)by direct sunlight or indirect sunlight reflected off windows . This is particularly bad early morning and late afternoon. Positioning ch oices are very limited for various reasons hence I am looking at going down the route of photo-electric beams. InfraRed ones appear expensive and need to be wired at both ends - hence my initial preference is for a combined transmitter/receiver in conjunction w ith a passive reflector.

Any input would be gratefully received.

[Peter Parry]

is a reflective IR system. However, neither visual nor reflective break beam systems can compete with the sun if it shines on the receiver or reflector.

The only break beam which can operate reliably in sunlight is a laser where the detector can be positioned at the end of a length of narrow tube (about the diameter of a drinking straw) which must be carefully aligned with the reflected beam.

[Brian Gaff]

Or those which work on modulated beams presumable, or are you saying the saturation from the sun is going to overwhelm it?

Brian

[Peter Parry]

The receivers saturate both in visual and IR and no trace of the modulation waveform makes it through.

[dennis]

They don't if the filter is dark enough. Then it depends on if the modulation can still be detected.

[Peter Parry]

If the filter is dark enough to attenuate full sunlight to manageable levels a non-laser light source of practical proportions has no chance of getting through. Hence the need for the tube and laser approach.

[Graham.]

When I was a kid I used torch bulbs, ORP12 LDRs, and 4in dia lenses to construct a pair of light beam telephones to communicate to the house across the street, it worked perfectly well in bright sunshine. The photocell (and lamp) were housed in an enclosure.

A properly designed modulated lightbeam alarm will work in bright sunlight. Trust me.

[Matty F]

th a reflector which I can wire up to a relay. This would be for use in the front yard to detect intruders.

e relays in turn trigger the relevant CCTV cameras.

Why not have the CCTV cameras recording all the time and use software to st art the recording when movement is detected? In the system I use I can sele ct the areas of screen where I want to detect movement, so I can avoid wavi ng trees. It also has a pre-record function for up to 30 seconds before the movement was detected. Only inferior systems don't do all of that.

[Mike Barnes]

Graham. :

I use a Takex twin-beam setup in full sunlight and it's never given any trouble in over ten years.

Previous to that I had a simpler setup with tubes to exclude stray light, but unfortunately they proved attractive to spiders.