Long distance trip wire?

So basically I am very new to Arduino and Electronics in general, however I am a software programmer so that side of things does not faze me.

However, I would like to build a basic setup where a beam is tripped, then a second beam is tripped further away. From my research this seems very straight forward in smaller applications, indoors etc however I need this to do something a bit more.

The situation is that this will be used outside with varying amounts of sunlight (based on weather) and possibly rain also.

So I need to know if there is a sensor that can be used with an Arduino board that would suit this situation? As I said I am new to all of this so scrolling through pages of maplin sensors just confuses me as I am not sure what I need, not sure of range, not sure of what type or sensor I need, power supply, etc etc.

Any hand to hold will be appreciated!

The theory is that a beam will be broken and a timer started, then when the second beam is broken then the timer will stop and result will be displayed.

What I need is advice on sensors / emiiters required to achieve this considering its application. They will need to be at least 10 meters apart and used outside.


Your description is rather vague.

Do you mean tha you want to measure the time that something passess two locations (A and B) which are 10 metres apart? If so how wide are the "trip wires"?

Or do you mean that the "tripwire" at A or B (or both) must be 10 metres long? If so, how far apart are A and B?

What is going to trip the "wire"? How fast will it be moving? How accurately do you want to time things? Can you arrange for a wired connection between A and B - so that a single Arduino can do all the timing?


This is a big ask, 10 Meters is a long way to send a beam in varying degrees of sunlight.

The TSOP4038 is designed for barrier operations, all the other sensors are not.

You might also have to play about with masking tubes and IR filters to get the range you are looking for. Otherwise you are going to have to especially engineer a system that works like the TSOP4038 but has greater sensitivity and greater DC ( sun light ) rejection.

You can use a red laser pointer to replace the typical IR LED for very long distances with the TSSP4038. 10 meters would not be a problem at all.

Rain could difuse any beam and IR needs to be pulsed or coded to avoid sunlight interference. I think even sonic devices would have a problem over a 10 metre distance.

huh ?

are the two trip wires 10 meters apart on the path ?

or is there 10 meters between the beam generator and the receiver ?

I have had many of day when the fog, the rain, the snow was too thick to see 3 meters.

this is a fair weather distance.

IR receivers like the recommended TSSP4038 won't have any problem with varying levels of sunlight, but direct, bright sunlight on the receiver can "flood" them and goof them up. The simple solution is to just enclose them in a tube or such to keep the direct sunlight off.

Regarding fog or rain, well, if you can't see anything through the fog then you're screwed, but these IR receivers are pretty sensitive and for 10m of fog I can't imagine fog thick enough to block a laser completely. With respect to rain drops causing nuisance trips, yes, I could imagine such, but you can easily program around that problem by ignoring very short trips; your granularity is 6/38000ths of a second so it shouldn't be a huge problem.

For the past two years I've been working on and off on a laser barrier. The distance between the laser and the sensor is about 8 m. The system is implemented indoors, and it is getting periodical upgrades, but remains offline for the majority of time. The main issue, the one that causes, by far, most troubles is the alignment. I find it very hard to devise fixed anchors that are not subject to bumps and get returned to the original position. Minute shifts of the laser result in significant offset of the laser dot at the sensor side, making the whole thing almost useless. I'm using visible light (red) lasers, but recently got some IR. My thinking is that with IR I can use less focused beams (bigger dots) that will be less susceptible to mechanical problems. I haven't had the time to see if it will function any better, but hopes are high.

Thanks guys for your help so far!

I thought I had made a good explanation, but shows how wrong you can be! haha OK so:

The distance between the sensor and receiver is likely to be around 10 meters.

The distance between the two gates is likely to be 3/400 meters. So would need to link one of them to the unit with a LONG cable.

When I say outside in weather, Its mainly going to be sunlight and the odd bit of rain it needs to cope with. I can program in some checking for rain so thats not a problem, but huge fog and snow we dont need to worry about.

One other thing is alignment - as it is outside I will need some kind of sensor that is large enough to take a large beam? Because it is outside, the risk of a break making subtle changes to the alignment is a real concern.

Now this question is very close to the one about using light communications, and in fact, the answers are much the same.

In case it isn't obvious (which it is if you read the datasheet), the TSOP4038 (or indeed, others similar) is a specialised receiver device to receive IR light modulated at 38 kHz, rejecting much visible light and constant illumination.

So for 10 metres outdoors, do not assume you can use it without a lens (recessed) in a black tube assembly to reject stray light.

Next, whilst it seems automatic to choose a laser for your light source, there are two things wrong with that choice. Possibly three.

One is that you need to modulate it at 38 kHz. You can do that with an Arduino, but in practice a CMOS 555 is more useful. You would have to use a laser with a current control circuit - which since you want a reasonable power, would be an active current control circuit rather than a single resistor - and this control circuit must operate "chopped" at 38 kHz which is a special demand on such circuits, not all are designed to be able to do this.

The second thing wrong with a laser, is that it can be too focused and too narrow. Particularly the latter, since it means that it can be blocked by a very small object such as an insect (or spider), and too easily affected by the atmosphere including heat haze. A narrow beam is also more of a danger to the eyes, particularly as IR beams are invisible.

So in fact, a plain LED of the desired power, which may even be more efficient than the laser, is probably a better choice, using a (large) lens to focus the broad beam. This will be blocked by large animals, vehicles or people and some birds, but not by common insects and spiders.

Of course, aiming an invisible beam can be tricky, but is readily done by using a common digital camera as a viewer.

many trail cameras and driveway cameras use multiple emitters and receives. cuts down on insects causing a trip.

if wireless is an option, is the moteino a candidate ?

RFM69HW @ 38.4kbps: 560m+:

should be within the 400m range.



RFM69HW @ 1.2bps with dipole: 1.5miles !

not sure how many meters in 1.5 miles, but I think it over 400.