Active IR beams for perimeter protection - experiences?

Hi folks,

I had planned to order some IR beams for my Christmas. Now already you might think. But when they need to arrive from Aliexpress, I need to start looking already :wink:

But got very recently feedback from a couple of people that they have removed their IR beam devices, due to a lot of false alarms. And although there are probably other kinds of surveillance devices available, I would like to keep the focus of this discussion on IR beams and how I can avoid false alarms.

Some thoughts to get started:

  • In contradiction to a PIR (passive which means it detects IR from a human body), those IR beams are generated by a transmitter and send to a receiver.


  • You can buy sets with 1, 2, 3, 4 (and in exceptional cases more than 4) beams. All beams should be interrupted at the same time to result in an alarm. So more beams (with enough distance between the beams) will result in less false alarms I assume?


  • You can buy devices for different distances (90m, 120m, 250m ...). It seems to me that it is better to buy a long range device, even for shorter distances? Because the beam is not a perfect line, but a rather large cone (with diameter of several meters if I'm not mistaken). I assume that long distance devices have a smaller cone diameter, so less false alerts?


  • If there is fog or the cover of the transmitter/receiver are dirty, then the beam will be diffused. As a result a weak IR beam will arrive at the receiver, so this might become a false alert.

  • Some devices have build-in amplifiers and DSP processing to solve some of these problems, but it is hard to see which devices are better than others ...

Here is an example of such a 3-beam device set:

Any thoughts or experiences?


I've seen them in professional building security arrangements but I think they went out of popularity I think, replaced with microwave, at least for outdoor use.

Hey Julian,
not really uplifting but thanks!
Do you mean something like this:

That is already more expensive...
Especially if you want to buy a set just to experiment whether it works good.

Hi Bart, apologies, I wrote that when a little distracted - might have been a little abrupt.

Didn't mean to put you off but I did want to make sure you are being practical. I think that you would need a clear path between them and, as you say, not have them too far apart.

They were certainly popular before the cost of radar/microwave sensors fell.

Oh no. Perhaps 'uplifting' isn't the correct word in this context (just found it via Google translate :joy:. No kidding ...).

When the beams don't work well, it is better that I know it before I buy them. But I hope that somebody has some tips that make those beams usable after all ...

1 Like

Haha, well it is true that it wasn't uplifting :slight_smile:

They were (maybe still are for all I know) popular for triggering gate opening so a 2m gap should be fine as an example. These are clearly a longer range though and presumably they do work just fine since it is a mature technology.

But if you were to use them round by us in the North of England in Autumn time, they might not be quite as reliable given the fog, rain and leaf litter we have this time of year :frowning: But you could probably allow for that in your flows.

I guess the real question is what do you fancy using them for - do you have something specific in mind? You need a clear line with suitable secure mounting at either end. So they need to be far enough away from a perimeter to reduce the likelihood of external interference (e.g. someone bashing it in or improvising a reflector) - not sure if they support a balanced circuit connection either (like alarm systems so that if the wiring is interfered with, an alarm is triggered).

Quite possibly a large glass of wine and a long day is clouding my judgement of course - you probably don't need government level security :rofl:

1 Like
  • They must be fitted to a (very) solid post so that they keep alignment. I've seen them fitted to fencing panel, which move in the wind. Metal or concrete posts are the best.
  • Avoid siting them near vegetation, which could obscure the IR beams.
  • Be mindful of white-light interference caused by sunlight or reflected sunlight off glass surfaces. This is a particular problem for cheaper detectors.

Yes I have already taking into acount that, when I have already been digging to install all the wires ...

Well very simple: when an indoor security system detects a burglar, they are already into your house. Would like to avoid that as much as possible, by already detect them on the outside (and take appropriate actions ...).

On most of those Aliexpress devices there are e.g. tamporing contacts. As soon as you open the case, a button is released. When that happens or when you cut (those tamporing) wires, you can detect that...

That is surely true!

That will indeed be a problem. Don't want to use the beams to alert me only that I need to start pruning my shrubs :rofl:

That is new to me. Pffff .... but thanks a lot!

I'm running a IR dual beam from Optex across my driveway about 50'. The unit I have is rated for 120' outdoors.
I tried microwave and ultrasonic with a large number of false triggers. The IR beam has been almost 99% reliable. It only falses during the few days of the year when the rising Sun shines directly into the receiver.
The only installation problem with this type of detector was trenching the power wire to the transmitter through my gravel driveway. My initial installation had both transmitter and receiver side by side with a passive reflector on the other side of the driveway. It worked fairly well except the received signal strength was boarder line and created false alarms. A more efficient reflector might have solved that problem.


Hi Bart,

I used an IR barrier successfully for some time.
As mentioned in previous posts the technology is mature and works pretty reliable if properly installed. Mine was a dual beam model able to reach 30 meters. I installed transmitter and receiver 20 meters apart, in clear sight, mounted on concrete walls. I did not spare time to select the perfect positioning and to calibrate the beams. While calibrating I found that my 8 years nephew was able to trespass the barrier using his highly trained military crawl (belly crawl). One final adjustment was required in the height of the assembly. Finally some time later I decided for the decommission of the old alarm central (not reliable communication and redundant given the others security devices I installed later on). It would be nice if I could find a way to integrate the IR beams with the raspberry PI that controls part of the security system (Node-RED + indoor zigbee sensors + Telegram). Anyway not in a hurry as the home has also surveillance cameras, an electronic dog, an aquarium with pirañas and a old lady next door that is always in the window of her attic watching what is going on with his neighbors.


Actually, I quite like the idea of a moat with electronic pirañas :rofl:


Or just put signs around the house with "BEWARE OF THE CROCODILES" :joy:


I'll bet you don't get much snow, hail or fog in Brazil?? :wink:

1 Like

Indeed Paul, no such inconveniences for the IR barrier , except maybe direct sunlight exposition (which i could avoid).

1 Like

Ok guys,
enough laughing, back to business :wink:

Hey Randy (@Randy),
That is indeed a good remark. I would have at least one device that will be fully exposed in the morning to sun shines:


Am I correct that I can minimalize this by putting my transmitter at location B, and putting my receiver at location A?

Ah yes, that is another approach. But my transmitter and receiver are both active powered devices. But yes as a result I have been digging lots of wires into the soil. But good that you mention it for others reading this!

Hi Paul (@Paul-Reed),
So I could run into this situation:


Am I incorrect that I could minimalize this with some kind of cover around the devices, so that they receive less environmental sun shines? E.g. something like this:


Hello Andrei (@Andrei),
What brand of beams are you using? Nice to hear that yours work quite well. Here in Belgium the wheather is better than in England but worse than in your garden. So not sure what the results would be if I would be if I would install exact the same stuff in my garden...
But avoiding direct sunlight seems to be a worldwide tip... :sun_with_face: + :dark_sunglasses: = :sunglasses:

1 Like

Yes, if you can build a shield around the device to block out stray light rays, that should help.

I recall being woke up 3 times in one week at precisely 5.15am due to alarm activations, but I couldn't understand why - I found not trace of a cause when I dashed downstairs in my PJ's... so the following morning I set my alarm clock for 5.00am and stood guard!!

At 5.15am I saw that as the sun rose above the horizon, it reflected sunlight from a pane of glass in a neighbour's greenhouse directly into the device sensor causing an alarm. But just 1 minute later - the reflected light had moved away as the sun got slightly higher.

1 Like

I use these little guys, really cheap and not to bad. The only issue is shorter range but I just use more sensors around my house.

1 Like

I have one in the kitchen to switch the under cupboard lights on when someone enters. One on each entrance coupled to a floodlight would be a great deterrent. They work through a plastic enclosure too!

£0.70 from AliExpress.

Added to my list of electronics to try one day :slight_smile:

1 Like

Just throwing in this idea I have had for a while to do some intelligent outside lighting control.

A small network of RCWL-0516 Radar sensors using a cheap 1-Wire cable with a DS2413 as a remote switch at each location, which could also be of interest to Bart as it could easily also be used as intruder detection: