advice reguarding beam detectors

[rssteve]

i have just purchased a set of beam detectors, they are marked as 300m indoor and 100m outdoor. Anyway i have them installed in my garden, approx 15m apart, and approx 700mm off the ground. anyway wired them up and aligned them all appears to be fine. i set the reaction speed right down to 1 which is the quickest. now the problem.

no false alarms so far, but, in the centre 5m between the trans and reciever i can walk through and even stop inbetween the sensors without the alarm going off. where as the 5m from each detector i can run through and the alarm picks me up. Its as if the beam is curving around me in the middle. Is this common or is the unit faulty?

 

[breezer]

i would say 2 things

1 its set wrong

2 you probably dont know how they work.


1) I cant speak for a reaction time option on a set of AIR beams, how ever i would ask what happens if you change it?

2) Unlike the movies a set of AIR beams such as you have do not emit a "laser like beam" The truth is its more of a cone. The centre of the cone being the brightest part.

As the beams are designed to work at 150m apart and you only have them 15m apart the light emited is very bright that close, and as you guessed you are not wide enough to block out all the light.

If you stand infront of the transmitter the cone is too small so you can not block all the light.
If you stand infront of the reciever you block all the incoming light.

I would take the beams back and get a pair with a shorther range.

There is however one other thing, if the beams are double, are you blocking both ?

Speaking of double, idealy for external use you should have 2 pairs of beams at least 50cm apart (as shown below)

T-------------------------------- R



R-------------------------------- T

Reason being so any falling leaves or wildlife can not set them off.
Wityh yours if something goes through the middle it will false alarm, a well installed pair of beams never false alarm

 

[bernardgreen]

It is possible to reduce the cone size by putting a plate with a hole in it in front of the transmitter. Then adjust the position of the plate until the receiver detects the beam.

Another way is to mis-align the transmitter so the centre of the cone is not pointed directly at the receiver.

One common reason for missing an object / person mid point is reflections of the infra-red from the ground. This can be prevented by narrowing the beam as above.

 

[Europlex]

i have just purchased a set of beam detectors, they are marked as 300m indoor and 100m outdoor. Anyway i have them installed in my garden, approx 15m apart, and approx 700mm off the ground. anyway wired them up and aligned them all appears to be fine. i set the reaction speed right down to 1 which is the quickest. now the problem.

no false alarms so far, but, in the centre 5m between the trans and reciever i can walk through and even stop inbetween the sensors without the alarm going off. where as the 5m from each detector i can run through and the alarm picks me up. Its as if the beam is curving around me in the middle. Is this common or is the unit faulty?

I get the impression from this that you have installed these beams (what make/model, by the way?) both in a horizontal plain, not vertical, one above the other as they should be?


By the way, I've beams across my drive, 50m beams covering a 3.5m wide drive, never a problem, always work.

 

[rssteve]

i've installed the beams to the manufactures instructions,. they are twin beam both built into the same unit approx 6" apart. im not worried about the odd false alarm they are only connected to a control panel which will log time and date so i can check cctv when im home. I did think about the beam going out like a cone, but even if it does and i stand in the middle, how is the light then going to bend back to the centre to go into the reciever, it aint as far as i can see.

reguarding the adjusted for time response, if i increase it to full i can cover the beams for almost a second before they go into alarm mode.

 

[breezer]

picture of your installation?

how to add a picture is in forum information.

the beam really does go in a cone shape, it is afterall just a light scource and light reciver, all be it the light is infra red, it still has to obey the laws of physics

 

[Atilla]

I did think about the beam going out like a cone, but even if it does and i stand in the middle, how is the light then going to bend back to the centre to go into the reciever, it aint as far as i can see.

Relativity Theory??

 

[bernardgreen]

Not relativity but reflectivity...

If the cones of radiation (from transmitter) and acceptance (into receiver) are wide angle then reflections from the ground, nearby objects etc etc will "link" the two cones round objects near the midpoint. The closer you stand to either transmitter or receiver the more of that cone you are blocking.

 

[coalpit]

i've installed the beams to the manufactures instructions,. they are twin beam both built into the same unit approx 6" apart. im not worried about the odd false alarm they are only connected to a control panel which will log time and date so i can check cctv when im home.

I've just read this old thread and am very interested in exactly how you are logging the time and date of the activations. I could do with a similar system to record when "visitors" pull into my yard.

Many thanks

Richard

 

[Europlex]

Have/get a control panel that will allow a circuit to be put 'on test', the activation/s will be recorded in the Log - simples

 

[coalpit]

Have/get a control panel that will allow a circuit to be put 'on test', the activation/s will be recorded in the Log - simples

Excellent, many thanks

Richard

 

[EightyTwo]

I got the impression that the OP had wired the beams to the alarm input on his DVR to record events. This is pretty straight forward too (on any half-decent DVR) and you wouldn't need to worry about 'translating' times from one system onto another!

 

[sparkymarka]

You can't tell em! but do they listen !

 

[Europlex]

Doesn't anyone look at the dates of posts?

 

[coalpit]

Doesn't anyone look at the dates of posts?

Surely the information in this thread is as relevant now as it was when the thread was started or have I missed something<G>

Cheers

Richard