# safety light curtains



## Ultrafault (Dec 16, 2012)

I have an application with a moving vehicle barrier. I am looking into installing safety light curtains to prevent the barier from rising under a vehicle. I have never installed these outdoors and think it may become an issue. I see there are enclosures that raise the rating to ip69 but that is not the same as being outdoor rated and I need 35 feet of barrier so I do not think my application would permit the attenuation. Do you guys have any good advice?

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## varmit (Apr 19, 2009)

You might look into magnetic sensors that embed in the concrete, similar to truck gates or a restaurant drive though. A light curtain is optical, so rain or snow would trip it. It would also be a challenge to keep in alignment outside in the elements. 

It sounds like you could buy a gate controller, saw cut the sensor(s) into the concrete, and be set.


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## gpop (May 14, 2018)

Depending on what the 35' looks like i would take varmit advice and look into a basic ground loop. You can link ground loops together with a number of different options including delayed timing and sensitivity.


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## splatz (May 23, 2015)

Take a look at these 

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/440l-um002_-en-p.pdf 

I thought that the purpose of a light curtain was to catch even small intrusions, these beam break type might be fine for something as big as a vehicle? 

They have a receiver rated for 70 meters (230 feet) so I have to believe it would make it even outdoors. 

It is IP 67 rated which I think would be fine in just about any parking lot or gate area.


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## gpop (May 14, 2018)

splatz said:


> Take a look at these
> 
> http://literature.rockwellautomation.com/idc/groups/literature/documents/um/440l-um002_-en-p.pdf
> 
> ...


Most gates and doors use a combination of diffrent sensors. Alot depends on what you would like the gate to open for and what you would like to protect when the gate is closing.

We might use ground loop or infa red sensors to detect a large item like a car while ignoring a person on foot. 
When the gate closes we may use a sender and reciever like the one you listed to protect a person in the path of the gate.


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## MDShunk (Jan 7, 2007)

For roller gates, they just use several emitter-receiver pairs, mounted at several levels (so they don't shine under a freight trailer, for instance, but can still catch a motorcycle or bicycle). I'd imagine the same thing would work just fine on your setup. Don't reinvent the wheel here. Use what has been proven to work. 

My experience with light curtains has been only in machines, and while they work just fine, they are very fickle on alignment and very sensitive. You'd be asking for trouble after trouble if you intended to use them in this application, I feel sure.


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## Ultrafault (Dec 16, 2012)

the important thing i need is the monitoring of the safety function. i am worried that the sensors will fail and the barrier will become unsafe. i cannot get maintenance to test these periodically. i know i can buy a saftey relay an light curtain combo that will accomplish this for me. but dont think i can achieve that with conventional methods.

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## gpop (May 14, 2018)

Ultrafault said:


> the important thing i need is the monitoring of the safety function. i am worried that the sensors will fail and the barrier will become unsafe. i cannot get maintenance to test these periodically. i know i can buy a saftey relay an light curtain combo that will accomplish this for me. but dont think i can achieve that with conventional methods.
> 
> Sent from my SM-N910P using Tapatalk


You wire sensors to fail safe. Now it just becomes a annoyances rather than a safety issue


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## splatz (May 23, 2015)

I have not used them for this application but the beam break sensors are very easy to make redundant and set at multiple levels.


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## Ultrafault (Dec 16, 2012)

The light curtain is extreme. I agree. However, I feel that if we are not monitoring the function of the saftey devices we risk a failure at some time in the future. I have found a photo eye that does have the potential for monitoring the emx irb-mon. however, i do not know of a way to integrate those with a saftey relay.

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## Ultrafault (Dec 16, 2012)

splatz said:


> Take a look at these
> 
> http://literature.rockwellautomation.com/idc/groups/literature/documents/um/440l-um002_-en-p.pdf
> 
> ...


i do not see that these are rated for 70m


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## splatz (May 23, 2015)

Ultrafault said:


> i do not see that these are rated for 70m


Look under "Ordering Information" on page 21, there are two receivers, one rated for 20m, one rated for 70m. 

Actually it's rated for 15 - 70m, looks like you'd want the one that's 0.5m-20m - 20m is 65 feet, that ought to do it.


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## Ultrafault (Dec 16, 2012)

splatz said:


> Look under "Ordering Information" on page 21, there are two receivers, one rated for 20m, one rated for 70m.
> 
> Actually it's rated for 15 - 70m, looks like you'd want the one that's 0.5m-20m - 20m is 65 feet, that ought to do it.


Those actually look pretty good. sorry i was looking at something different. 

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## JRaef (Mar 23, 2009)

The LEDs that put out the IR on light curtains are not as powerful as those separate through-beams. I've had trouble with light curtains getting washed out by direct sunlight. The single beam type have what's called "automatic gain control" that boosts the signal in response to high ambient. Some light curtains have that too, but it's not as good because there are sacrifices that must be made to cram all of those devices into that array tight enough to offer finger protection. It doesn't sound as though you really need that level of tight protection though. I've used several (3) through-beams for similar things to what you are doing, it's better that way. Actually depending on the nature of the application, a combo of loop detector and through-beam might be a good approach.


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## Jlarson (Jun 28, 2009)

Never had good luck with light curtains outside where direct sunlight can get them, even like the couple hundred mm access control curtains. The receivers just don't have that kinda light immunity. 



I use a lot of Eaton 50 Series sensors for gate an vehicle access detection. Other nice thing about separate through beam units is it's easier to shield them, think traffic light shroud.


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## paulengr (Oct 8, 2017)

Safety relays are often treated as some magic device, BUT...

First off safety and reliability are two different things. Redundancy can help improve one or the other or both. For instance with two sensors you can pick both in series which improves safety but more false trips happen or in parallel so you get the opposite. With three sensors you can do best 2 out of 3 and boost both.

A stock “ice cube” relay meets SIL 1 (worst case 10% chance of failure on demand based on getting tested every 3 years).

SIL 2 generally means 1% chance of failure. These days that’s a safety relay. These have two features. First the contacts are oversized to prevent contact welding. Second they have force guided contacts which means there is a redundant set in series so either all contacts work together or they don’t. So these changes improve safety.

SIL 3 requires no single points of failure and 0.1% failure on demand. Most light curtains output opposite logic where one output is 1 and one is 0 then they periodically flip or pulse outputs to detect wiring faults or jumpers. Need multiple relays at the end and multiple sensors.

The application sounds like SIL 1. Conventional equipment is fine.


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## MDShunk (Jan 7, 2007)

Ultrafault said:


> Those actually look pretty good. sorry i was looking at something different.
> 
> Sent from my SM-N910P using Tapatalk


I still think some of y'all are nuts for still thinking about light curtains. This is a solved problem, with the solution successfully deployed in zillions of places all over this continent. Stop reinventing the wheel. You'll only cause yourself aggravation.


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## John (Jan 22, 2007)

Nothing like overthinking a proplem.


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## Ultrafault (Dec 16, 2012)

paulengr said:


> Safety relays are often treated as some magic device, BUT...
> 
> First off safety and reliability are two different things. Redundancy can help improve one or the other or both. For instance with two sensors you can pick both in series which improves safety but more false trips happen or in parallel so you get the opposite. With three sensors you can do best 2 out of 3 and boost both.
> 
> ...


I cannot get into the specifics of the install or location. But the acceptable rate of unintended operation is 0. If I dont monitor the devices automatically it is possible the device would fail into an unsafe mode of operation. if this were a normal install of a sliding gate I would still be in violation for installing a unmonitored photo eye or inductive loop after 2016 changes to ul 325. I can appriciate the sentiment that I am over thinking this but that is exactly what I am supposed to do in this case.

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## MDShunk (Jan 7, 2007)

Ultrafault said:


> I can appriciate the sentiment that I am over thinking this but that is exactly what I am supposed to do in this case.
> 
> Sent from my SM-N910P using Tapatalk


Probably should have said so in the first place. This your first day here? :wink:

Is there any overhead structure to mount from? I feel like you'll have far better luck with a series of laser range sensors mounted from an overhead structure than you will a light curtain. Light curtains are just so fickle. Even water spots from dried water will fuss with their reliability. I have experience with sensors of every type and variety in washdown areas (not outdoors, mind you, but a similar environment nonetheless). I just think that if you do a light curtain you're going to regret it. If you mounted at least three laser range sensors from an overhead structure your reliability would be leaps and bounds over a light curtain. A light curtain keeps you from putting the tip of you pinky finger in a machine. Far greater resolution than you need for a car.


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## Ultrafault (Dec 16, 2012)

I should know better. I am open to anythng that has a monitored saftey function. I think overhead would not work in this case. I am currently looking into 4 beam sensors from banner engineering. we do need to cover a 4 foot range of heights but a spacing of up to 1.5 feet should not be an issue. I could not find anything fron AB that seems to fit my bill. I do want to use a saftey relay so i can stop two solenoids electricaly and send the signal to the plc.


MDShunk said:


> Probably should have said so in the first place. This your first day here? :wink:
> 
> Is there any overhead structure to mount from? I feel like you'll have far better luck with a series of laser range sensors mounted from an overhead structure than you will a light curtain. Light curtains are just so fickle. Even water spots from dried water will fuss with their reliability. I have experience with sensors of every type and variety in washdown areas (not outdoors, mind you, but a similar environment nonetheless). I just think that if you do a light curtain you're going to regret it. If you mounted at least three laser range sensors from an overhead structure your reliability would be leaps and bounds over a light curtain. A light curtain keeps you from putting the tip of you pinky finger in a machine. Far greater resolution than you need for a car.


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## MDShunk (Jan 7, 2007)

Yeah, the AB line is not very innovative. They only makes what sells, although their old-school Photoswitch line is quite popular for this particular application. I like IFM a whole lot better than anyone, but they just makes the staples. 

Banner, Keyence, and Sick would be who I'd be looking at first for something innovative. Probably in that order.


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## splatz (May 23, 2015)

MDShunk said:


> Yeah, the AB line is not very innovative. They only makes what sells, although their old-school Photoswitch line is quite popular for this particular application. I like IFM a whole lot better than anyone, but they just makes the staples.
> 
> Banner, Keyence, and Sick would be who I'd be looking at first for something innovative. Probably in that order.


If you like Sick, there's a bargain on a discontinued model: 

https://www.allelectronics.com/item/osu-1130/through-beam-photo-electric-sensor-pair/1.html 

I bought a couple to tinker around with, haven't opened them yet.


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