{"id":1875,"date":"2026-04-13T09:02:36","date_gmt":"2026-04-13T09:02:36","guid":{"rendered":"https:\/\/industrialsafetysensor.com\/?p=1875"},"modified":"2026-04-13T09:09:46","modified_gmt":"2026-04-13T09:09:46","slug":"elevator-light-curtain","status":"publish","type":"post","link":"https:\/\/industrialsafetysensor.com\/pt\/blog\/elevator-light-curtain\/","title":{"rendered":"Cortina de luz do elevador: o que todo engenheiro de eleva\u00e7\u00e3o e operador de constru\u00e7\u00e3o precisa saber"},"content":{"rendered":"
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Simply put, an elevator light curtain is an invisible safety barrier created between a closing elevator door and each individual rider passing it. With around 18 billion passenger trips on U.S. elevators annually–in just one year–a small leap in existing door safety standards translates to billions of passenger door crossings. Let this brochure show you how those infrared sensor systems operate, what the EN 81-20 and ASME A17.1 truly demand, and the most cost-effective way to specify, install, and service the unit that is right for your residential skyscraper, freight hub or hospital elevator bank.<\/p>\n

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Quick Specs: Elevator Light Curtain at a Glance<\/h3>\n\n\n\n\n\n\n\n\n\n\n
Technology<\/td>\nInfrared beam array (non-contact detection)<\/td>\n<\/tr>\n
Applicable Standards<\/td>\nEN 81-20 (Europe), ASME A17.1\/CSA B44 (North America)<\/td>\n<\/tr>\n
Required Detection Zone<\/td>\n25 mm \u2013 1,600 mm above car door sill<\/td>\n<\/tr>\n
Min. Detectable Object<\/td>\n14\u201350 mm (depending on beam configuration)<\/td>\n<\/tr>\n
Typical Response Time<\/td>\n6\u201331 ms<\/td>\n<\/tr>\n
Protection Rating<\/td>\nIP65 (typical)<\/td>\n<\/tr>\n
Safety Rating<\/td>\nUp to SIL 3 \/ Category 4 \/ Performance Level e<\/td>\n<\/tr>\n
Typical Lifespan<\/td>\n>5 million door cycles (~10+ years)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

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What Is an Elevator Light Curtain \u2014 And Why Has It Replaced the Mechanical Safety Edge?<\/h2>\n

\"What<\/p>\n

An elevator light curtain provides an optoelectronic safeguard to an elevator installation. It produces a solid line of infrared beams at the full height of the elevator door. Any obstructions such as a persons handbag hand or a childs hand will cause the beams to break and the door controller is informed to reverse or open the doors.<\/p>\n

This is the third designers have had to protect elevator doors. The first was a single-beam type of photocell (also sometimes called an elevator photocell) which saw only one point (namely at a people’s waist level), and thus left huge blind areas above and below. Mechanical safety edges were the next step; these were rubber-coated contact strips mounted on the protected edge of the door, which only reversed if physically pressed in by something attempting to obstruct the door.<\/p>\n

Both of these are still commonly seen in older elevators (not under compliance with current code).<\/p>\n

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What Is the Difference Between an Elevator Light Curtain and a Photocell?<\/h3>\n

A photocell usually employs 1 or 2 infra-red beams at a predetermined height and will only detect large objects at that height – anything above or below that point, and between the beams, will go undetected. A modern elevator light curtain uses anything from 32 to 159+ beams across the full width of the door aperture from 25mm to 1600mm, or even more, above the door sills. The device will detect an object down to approx 14mm – this compares with a legacy single-beam photocell which probably would have detected 100mm or more.<\/p>\n

That is the reason why the new standards such as EN 81-20 demand that the opening device detects objects down to 50mm. Photocells, mechanical edges or side-cues, simply cannot do this.<\/p>\n

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$441M<\/div>\n
Global Market (2024)<\/div>\n<\/div>\n
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68%+<\/div>\n
New Installs Using Light Curtains<\/div>\n<\/div>\n
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4.6% CAGR<\/div>\n
Projected Growth Through 2033<\/div>\n<\/div>\n<\/div>\n

Changing factors include the increasing stringency of safety standards internationally. As deadlines for modernization loom, the mechanical safety edge \u2013 with its rubber strips, springs and pivots is being taken out of service in preference to infra-red non-contact detection that complies with EN 81-20 and ASME A17.1 standards without the requirement for ongoing mechanical maintenance.<\/p>\n

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How Elevator Light Curtains Work \u2014 From Beam Physics to Door Reversal<\/h2>\n

\"How<\/p>\n

An elevator light curtain is comprised of two identical parts; a transmitter located on one side of the car door opening and a receiver located on the other side. The transmitter contains a cluster of infrared Light Emitting Diodes. These are pulsed on and off in a quick sequential pattern repeating in the kilohertz range and forming a maze of invisible beams across the doorway.<\/p>\n

The actual system, from detection to door reversal, is as follows:<\/p>\n

    \n
  1. Continuous scan: the transmitter switches each LED on and off in rapid succession. A complete scan of the door opening is generated every few milliseconds.<\/li>\n
  2. Beam interruption:
    \nObject entering the beams causes receiver photodiodes to shut off.<\/li>\n
  3. Signal processing: Front end microprocessor analyzes the interruption pattern, filters transient noise, and verifies obstruction.<\/li>\n
  4. Output signal: PNP or NPN output (swappable on modern units) instructs elevator door controller.<\/li>\n
  5. Door reversal: Controller halts the door motor and reverses the way.<\/li>\n<\/ol>\n

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    \ud83d\udcd0 Engineering Note: Response Time vs. Door Travel<\/strong><\/p>\n

    (0.5m\/s.) at 15mm extra door travel before reversal. At 6ms response (fastest units in the industry), the value drops to 3mm of potential equipment back lash; both figures are within safe, normal operating parameters; in fact, the relative size of the door’s kinetic energy at this travel is negligible.<\/p>\n<\/div>\n

    In multi-elevator single-shaft bank installations, door-opening cross-talk must be eliminated. State-of-the-art infrared curtains employ dual frequency (A and B channel) optical synchronizers to prevent cell signals from one elevator from interacting with the adjacent unit. Industry technicians have established that elevator door-light curtain cross-talk is among the most common novice diagnosis; the solution is to assign a different frequency to each elevator.<\/p>\n

    “When you’ve got two elevators in adjacent shafts and the curtains interfere with each other, nine times out of ten it’s a frequency mismatch problem. Assign the units to different channels and there is no interference any more.”<\/p>\n