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> Outdoor Sensor Detecting People And Not Doors, outdoor sensor
fifi
Posted: December 05, 2011 05:56 pm
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Hi

I have an outdoor garage door that I consider to be a bit dangerous, specially for kids. It is iron built and it slides sideways.

I was thinking of installing an outdoor sensor that should trigger only when a person is close to the door, but obviously not when the door is moving.

Does anyone know if anything of this kind is commercially available?

Thanks for your help
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Jimthecopierwrench
Posted: December 05, 2011 06:50 pm
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Off the shelf PIR module could be interfaced to do it with a bit of tinkering to determine the best coverage and imunity to false triggering. For ultimate safety (depending somewhat on the physical layout and operation of the door) I might be inclined to go with an actual postive edge sensor - ie, a spring loaded bar that would contact an apropriate switch, or perhaps a sealed rubber tube or length of hose and an air "puff" switch - either connected to latch open a relay in series with the drive motor, or perhaps initaite the reverse function.


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tekwiz
Posted: December 05, 2011 10:20 pm
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If it's safety you're after, wouldn't you want the sensor to be active when the door IS moving? It can't harm anyone when it's not moving.
The very best protection comes from something known as a light curtain. These consists of multiple light beams close together, set up so they cover the entire danger area. The output is linked to the opener's emergency stop control.
These are widely used to protect workers from dangerous machinery in industry, & so are available off the shelf. Many come in modules so you can tailor the final coverage area to your exact requirements.
They are, however, not cheap. New cost of a system big enough to cover a garage door would be at least a couple of thousand dollars.
If this is for personal use, however, you may be able to get used equipment at a fraction of new price. The equipment isn't usually reused in industry because of liability issues. Therefore, there's lots of used stuff around, much of which can be found in industrial scrap yards, or from larger industrial control builders.


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Blue LED
Posted: December 05, 2011 11:49 pm
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QUOTE (tekwiz @ December 06, 2011 07:20 am)
If it's safety you're after, wouldn't you want the sensor to be active when the door IS moving?

I interrupted it as meaning triggered only by people, not by the movement of the door.

I agree that perhaps a PIR would suffice in the detection.


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fifi
Posted: December 06, 2011 10:30 am
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Thanks for your answers

Yes, the idea is to stop the door moving when someone is in the range of the sensors.
I also thought that PIR sensor would probably do the job, though i will probably have to install more an one to cover the dark spot caused by a pillar half way of the path of the door (i undrestand PIR needs direct vision to be triggered)
I have seen there are are some sensors used for alarms that combine both PIR and microwave. Would these be better for my purpose?
I took a look at the light curtains, and i think they are a bit expensive, even the used ones, as i understand i would need 2 pairs, one on the street side of the door, and the other on the house side. I have also some concerns around the installation of the stree side ones
Finally i am afraid Jim i did not understand what you said about the positive edge sensors (as you can tell i have just some basic knowledge on the subject)
Below is a drawing of the door
--| |--|
--| _________________________|--|............….....................
(pillar). Door when closed. (pillar). Door when open

Door opens --->
door closes <-----
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MacFromOK
Posted: December 06, 2011 10:56 am
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Jim was talking about a simple mechanical sensor on the edge of the door, so if it actually hit something, it would disengage or reverse the door. This is possibly the easiest and most effective method.

You might also consider a pressure switch on the drive mechanism, so it would disengage (or reverse) if the door encounters any physical resistance beyond normal. Snow/ice accumulation would play havoc with it, but any outdoor sensor has the potential to malfunction in bad weather. dunno.gif


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fifi
Posted: December 06, 2011 03:18 pm
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Covering just the edge is not enough, as i am worried that a kid might touch any part of the door while moving, and that would be dangerous too. Regarding the pressure switch, I think i would rather go for preventive measures, but thanks for your advice
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tekwiz
Posted: December 06, 2011 11:23 pm
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Your door mechanism likely already contains some form of overload clutch, or stopping the door with an obstruction would result in mechanical damage or a burned out motor every time it happens.

Also, nothing says you can't build your own light curtain(s). The use of cheap dollar store laser pointers as light sources would eliminate the necessity of special optics & special beam recognition circuitry. The only 'optics' necessary would be bits of black tubing to shield the detectors from ambient light.

If the operation of this door is always manually initiated, another option would be a video camera & monitor, so you can watch the door while it's moving.

Other than that, PIR detectors would likely be your best bet, as they are cheap, reliable, & can be set up to eliminate most false triggering. There wouldn't be much point in a combination PIR/µwave detector unless false triggering becomes a problem & cannot be relieved by repositioning the sensor(s).
The cheapest PIRs are likely those that come with cheap PIR equipped yard lights. These are already set up to run from the mains voltage, whereas security system detectors virtually all run from 12 volts DC.


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Trouble rather the tiger in his lair, than the sage among his books.
For to you, kings & armies are things mighty & enduring.
To him, mere toys of the moment, to be overturned at the flick of a finger.

Fortuna favet fortibus.
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GPG
Posted: December 07, 2011 02:45 am
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PIR detectors depend on movement from one sector to another so the lens/mirror zones need to be taken into account when selecting.
http://en.wikipedia.org/wiki/Passive_infrared_sensor
A search will turn up more.
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LARMGUY
Posted: December 07, 2011 07:17 am
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QUOTE (GPG @ December 07, 2011 02:45 am)
PIR detectors depend on movement from one sector to another so the lens/mirror zones need to be taken into account when selecting.
http://en.wikipedia.org/wiki/Passive_infrared_sensor
A search will turn up more.

Correct. PIR's require movement between elements and the best ones available have dual eneve triple technology and a brain for determining the actual validity of the alarm. Most PIR's are manufactured backwards from what yoiu w3ant There are touch sensors made by Ingersol Rand and others for unlocking doors just by the slightest touch. One of these could be used to operate a reversing relay in addition to any otheres involved in thr circuitry you may wish to add.
http://www.vonduprin.com/pdf/Chexit.pdf

Other devices are pressure switches. beam curtains, proximitycoils connected to loops embedded into the concrete or asphault. PIR's are manufactured in many ways to detune the actual alarm functions. They manufacture their PIR'S to keep from having false alarms so they tach multiple tecknowlogies then take the results from them and input them into a computer chip in which their is decided whether or not an alarm occurred.

Just going with the standard photo electric cell, adjustable slippage clutches, and training is good enough for most AHJ's in residential use.

Plese contact any security gate company and pick their brain a bit. It will be well worth it.
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fifi
Posted: December 07, 2011 10:03 am
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I have order a PIR with some brain to avoid too many false alarms, as there are some trees nearby, and with reduced detection angle to try to limit the operation just to the area around the gate.
http://www.securitywarehouse.co.uk/catalog...nge-p-2477.html
Thanks to all for your help
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MacFromOK
Posted: December 07, 2011 11:08 am
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Your moving gate itself may be a problem...


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tekwiz
Posted: December 07, 2011 08:42 pm
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QUOTE (MacFromOK @ December 07, 2011 02:08 am)
Your moving gate itself may be a problem...

It will be. However, careful positioning & adjustment of the PIR will minimize the effects.
You can also mask part of the PIR's lens with black tape to modify the pickup pattern.


BTW: Fifi, do you realize that the PIR you ordered requires 12 volts DC to operate? This may require the use of a separate power supply.
I also find that unit to be quite expensive...obtaining a mains voltage unit from a cheap yard light fixture shouldn't cost more than a quarter of that price.
You may also have to add another relay, because the one in the PIR is big enough for control loads only. It won't handle anything more than a small signal.


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Trouble rather the tiger in his lair, than the sage among his books.
For to you, kings & armies are things mighty & enduring.
To him, mere toys of the moment, to be overturned at the flick of a finger.

Fortuna favet fortibus.
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millwood
Posted: December 07, 2011 08:50 pm
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QUOTE
I have an outdoor garage door that I consider to be a bit dangerous, specially for kids. It is iron built and it slides sideways.


look into those auto reversal switches for car windows / garage doors.
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fifi
Posted: December 09, 2011 11:25 am
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hhmmm... A bit concerned to hear now that the moving gate may trigger a PIR, as this was really the reason for opening this thread. I just hope that placing it on the straight line of the movement of the door, and probably setting high the number of pulses to dectect before triggring will help to minimize it.

Tekwiz. Thanks for your note. Yes I did realize that I was requiring 12V and a relay, but that should not be an issue, as I have both of them available for a contact switch to cut the gate power when the 'people' garden door is open.
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tekwiz
Posted: December 10, 2011 02:30 am
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You should be able to mount the detector on the same plane of the door & have it fire along the length of it.
Careful positioning should enable you to put the edge of the detection cone adjacent to & alongside of the door. smile.gif


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Trouble rather the tiger in his lair, than the sage among his books.
For to you, kings & armies are things mighty & enduring.
To him, mere toys of the moment, to be overturned at the flick of a finger.

Fortuna favet fortibus.
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fifi
Posted: January 14, 2012 03:53 pm
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Just a note to let you know that this sensor is exactly what I was looking for. It is triggered by someone approaching the door, but not by the door itself of the trees nearby. The installation was not too difficult, in fact the part that took me longer was taking the cables to the sensor. Thanks to all for you opinions.
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