lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
 ·TekSavvy DSL
| reply to robbin
Re: Garage door problem said by robbin:We aren't debating whether it can do it in a single day, but whether at some point in the year it can affect a sensor on one side of the door and at another point in the year it can affect a sensor on the other side.
Try early morning on June 21 for one side and late afternoon on Dec 21 for other side. Or any other two date pairs when you think the worst case scenario might happen.
Make reasonable assumptions for the location of the sensor (like x=6 inches from garage opening ; y=1 inches towards the side wall ; and z = 6 inches from floor ) and sensor acceptance angle (like 11.25 degrees for a pathetic design).
said by robbin:You are of the opinion that it would be impossible and I think it is very possible. If this was just a matter of personal opinion, I would have stopped arguing long ago.  |
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
| reply to iLearn
I searched for US regulations re: garage doors because of another thread and found some rules regarding ambient light test.
»law.justia.com/cfr/title16/16-2.···0.1.1.11
Technically, all sensor installations must pass that test which means they can't be affected by early morning or late afternoon sun. Only potential problem for a compliant setup would be reflection from a really shiny floor when the sun is higher up in the sky. |
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robbinPremium,MVM
join:2000-09-21
Leander, TX
kudos:1 | No, technically the rules you are referring to apply to manufacturer certification of a product
"(a) Purpose. Section 14(a) of the Consumer Product Safety Act, 15 U.S.C. 2063(a), requires every manufacturer (including importers) and private labeler of a product which is subject to a consumer product safety standard to issue a certificate that the product conforms to the applicable standard, and to base that certificate either on a test of each product or on a “reasonable testing program.” The purpose of this subpart is to establish requirements that manufacturers and importers of automatic residential garage door operators subject to the Safety Standard for Automatic Residential Garage Door Operators"
»www.law.cornell.edu/cfr/text/16/1211.21 |
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
| said by robbin:No, technically the rules you are referring to apply to manufacturer certification of a product ... Since you are determined to be "technical" about this, such a certified sensor system should not fail when exposed to the same or lower intensity light interference in a garage. |
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garys_2kPremium
join:2004-05-07
Farmington, MI Reviews:
 ·callwithus
·Callcentric
| reply to robbin
said by robbin:said by lutful:You can verify from the shadow cast by the stick figure that it is quite impossible "for the sun to hit one sensor in the morning and the other in the afternoon" ... if you define "hit" as a reasonably small acute angle between sun-sensor-source We aren't debating whether it can do it in a single day, but whether at some point in the year it can affect a sensor on one side of the door and at another point in the year it can affect a sensor on the other side. You are of the opinion that it would be impossible and I think it is possible with the likelyhood greater as you move towards the equator but probably more likely towards the tropical latitudes and diminishing in the equatorial region. Actually, it's more likely the further from the equator you go. Think "midnight sun." A north-facing opening, with one inside wall facing east and the other west will have some days around the equinoxes where light will fall (at a low angle to perpindicular) on one wall in the morning and (on a different day) on the other in the evening. |
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
| said by garys_2k:... north-facing opening, with one inside wall facing east and the other west ... I understand what you are thinking, but the during the short time when the sun can hit an east-west oriented sensor at a narrow enough angle ... it will probably be blocked by trees and other homes.
Proper installations put the sensor about 6 inches from garage opening and at least 1 inch back towards the wall. That tiny offset will make the (maximum 15 degree wide) viewing cone stay completely within the garage. Properly designed sensors should reject sun-equivalent brightness between 15-20 degrees which also imply rejecting sun interference at higher angles.
The only problem left unconsidered is reflection from a very glossy floor or object coming into the sensor below 20 degrees. |
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| reply to lutful
Re: Garage door problem said by lutful:It is possible that some receivers were assembled with a wide angle lens by mistake. The receiver's acceptance angle can be easily checked. Garage door detectors have a wide angle for both the transmitter and the receiver to allow for fast aiming with large tolerances, conversely photo beams for security applications have very narrow beam widths, are IR filtered, highly selective and use a pulse modulated scheme to prevent or minimize interference from external sources of IR. |
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
1 edit | reply to MatrixHDV
Re: Garage door problem said by MatrixHDV:said by lutful:It is possible that some receivers were assembled with a wide angle lens by mistake. The receiver's acceptance angle can be easily checked. Garage door detectors have a wide angle for both the transmitter and the receiver to allow for fast aiming with large tolerances The transmitter side would create a "flood" instead of a "beam" if it used a wide angle lens in front of the IR emitting diode.
If the sensor side had a wide angle lens "by design" ... it would fail the mandatory compliance test which shines a 500W/3600K photo flood at placed at 15 degrees just 5 feet away. Check the diagram from US regulation ... just above the dead horse. |
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| said by lutful:The transmitter side would create a "flood" instead of a "beam" if it used a wide angle lens in front of the IR emitting diode. Try reading what I posted, I never said it has a wide angle lens, I stated garage door photo beams have a wider beam than security photo beams, which is why garage door photo beams can be swamped a lot easier then the ones designed for security. |
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
1 edit | said by MatrixHDV:Try reading what I posted, I never said it has a wide angle lens ... You wrote Garage door detectors have a wide angle for both the transmitter and the receiver ... and did not actually mention lens. So obviously it was wrong to make that connection.
The official US/Canada garage sensor compliance tests (which can only be met with a really narrow beam from transmitter and a really narrow angle lens on receiver) will probably be changed in the next revision to match your hunch. |
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1 edit | reply to lutful
Re: Garage door problem said by lutful:You wrote Garage door detectors have a wide angle for both the transmitter and the receiver ... and did not actually mention lens. So obviously it was wrong to make that connection. Again, you need to read what I posted, because I stated, " garage door photo beams have a wider beam than security photo beams, which is why garage door photo beams can be swamped a lot easier then the ones designed for security."
Quite easy to understand, that is unless you are taking comments out of context to prove a non-existant point.
Bottom line, garage door photo beams can be swamped by external sources of IR such as the sun, in which case they fail-safe holding the door open as if the path between the transmitter and receiver is blocked, furthermore if the source of the IR is the sun, there is enough scattered IR energy available the preclude the need for a direct shot into the receiver to swamp it and that is why reversing the transmitter with the receiver will not solve the problem.
The only real solution is and that is if there is room, would be to move the receiver further away from the edge of the overhead door. |
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garys_2kPremium
join:2004-05-07
Farmington, MI Reviews:
·callwithus
·Callcentric
| reply to lutful
Re: Garage door problem said by lutful:said by garys_2k:... north-facing opening, with one inside wall facing east and the other west ... I understand what you are thinking, but the during the short time when the sun can hit an east-west oriented sensor at a narrow enough angle ... it will probably be blocked by trees and other homes. Maybe, or maybe not. Remember that there's a big, wide driveway right outside that door and then a yard. Maybe plantings will block the sun but in a lot of cases that won't be the case.
said by lutful:Proper installations put the sensor about 6 inches from garage opening and at least 1 inch back towards the wall. That tiny offset will make the (maximum 15 degree wide) viewing cone stay completely within the garage. Properly designed sensors should reject sun-equivalent brightness between 15-20 degrees which also imply rejecting sun interference at higher angles.
So, we have a 16' wide door, that is 192" from side to side. We mount the sensor 6" inside the door and an inch further back, placing it 193" from the other side and 6" back. That means the tangent of the lowest possible angle that can cause sunlight to shine onto the eye is 6/193 = 0.0311, the arctangent being 1.78 degrees. That would be well within any reasonable acceptance cone for the receiver. |
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lutful... of ideasPremium
join:2005-06-16
Ottawa, ON Reviews:
·TekSavvy DSL
| said by garys_2k:lowest possible angle that can cause sunlight to shine onto the eye is 6/193 = 0.0311, the arctangent being 1.78 degrees. That would be well within any reasonable acceptance cone for the receiver. I drew a sensor located 6 inches in from garage opening and 1 inch back towards the wall. Imagine the sun is hitting those blue lines ... and they are NOT transparent.
The cylindrical pendulum used for the compliance test is less than 2 inches in diameter and placed 12 inches from sensor in beam path. If either the beam or the sensor angle was wider than certain values, and the transmitter was 200 inches away ... the pendulum test would fail because of diffraction. Any takers for those calculations? |
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