CRITICAL REQUIREMENTS OF TODAY’S ELEVATOR LIGHT … · elevator decor. Lowest Applied Cost In the selection of elevator door controls, a system that incorporates low initial purchase

Educational Focus Compilation 67

EDUCATIONAL FOCUS: ELEVATOR DOOR PROTECTION SYSTEMS

Improved Immunity to Ambient LightToday’s elevators require light screens to be totally immune

to all ambient light sources. Many passenger elevators innew buildings use glass window panels that expose them todirect sunlight. In addition, many new buildings are utilizingthe newer fluorescent light fixtures that pulse at muchhigher frequencies. These situations can cause erratic perform-ance by elevator door light screens designed in the past.

In industrial and airport buildings, many forklift trucksand passenger vehicles use high-powered strobes that can alsointerfere with light-screen door-control performance. Thenewly introduced Leading Edge™ system is designed towithstand all ambient light sources found in these and othertough environments. It should also be noted that the newhigh-frequency fluorescent lights and high-powered strobescan also interfere with some of the original backup photoeyesmounted 5 inches and 29 inches above thresholds on manyelevators equipped with mechanical safety edges. Thiscan be an overlooked problem in some applications.Improved Immunity to Static Discharged and RF Transmitters

Even today, many elevator passengers reach out andplace their hands across the edge of doors, as they did onmechanical door edges in the past, to keep the doorsfrom closing on them. When this hand contact occurstoday, a high-voltage static discharge could go throughthe housing and circuitry of the electronic light screen ar-rays. These high-voltage discharges cause “unexplained”door-protection system failures that often occur in wintermonths when humidity is extremely low. An example

would be walk-ing across a car-pet and touchingthe edge. The newsystems are de-signed to with-stand interferencefrom static elec-tricity discharge,as well as fromh igh-poweredwalkie talkies,cell phones andstrong RF signalsradiating from air-port radar systems.

Improved Resistance to Water DamageMany elevators are exposed to the detrimental effects

of water. This is especially true with outdoor elevators,with parking garage elevators and during elevator lobbycleaning. The Tri-Tronics system was designed for theNational Aeronautics and Space Administration (NASA)to withstand the release of 320,000 gallons of water onthe launch-pad elevators during shuttle launches. Thereare no “O” rings or gaskets used; instead the system iscompletely epoxy filled. It will even resist leakage whencompletely submerged and will survive high vibrations.The Leading Edge is excellent for condos, hotels andother buildings located near saltwater, since it will resistcontamination and circuit-board corrosion. Improved Operation Under Brownout and Power-Up Conditions

The 120VAC power used for accessory control devicesfound in many elevators can sometimes vary to the pointwhere it can be quite low. To be safe during a brownoutcondition, the light-screen edge should operate at a voltageof 85 to 90VAC. The power supply/controller should alsobe capable of withstanding high voltages of 150 to 160VAC.After a power outage, when the power is restored, the systemmust also withstand erratic transients that in the past have“locked up” many microprocessors. These types of failuresusually require a service call. It is important to utilize asystem that can withstand these conditions.

CRITICAL REQUIREMENTS OF TODAY’S ELEVATOR LIGHT SCREEN DOOR CONTROLS

by Robert A. Warner, Tri-Tronics Co., Inc.

Eliminate water damage Compatibility with existing power supplies

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68 Educational Focus Compilation


The Need for Wide-Beam OpticsEarly light screen edge designs often made it difficult to

align the multiple transmitted light beams with the receivers.This is a problem on older unstable elevator doors. TheLeading Edge design allows the system to operate on doorsthat are misaligned by as much as ±30° at a distance offour feet between doors. This system has also been usedwith success on many round elevators that have a verytight turning radius.The Need for System Compatibility

Many systems are designed with the microprocessorand control logic built into the power supply/controller.This requires the purchase of all three components, thecontroller/power supply, the light source array and thereceiver array. A system that incorporates the micro-processor and logic necessary to function built into thearrays is a more effective setup. In some cases, only the lightsource and receiver arrays need to be purchased.

Simplifying InstallationLow-cost light-screen door controls are often the

most difficult to install. If they take longer to install, theinitial cost savings of the equipment can quickly disap-pear and additional costs could incur. The Tri-Tronicssystem is easier and quicker to install. Treaded studsand brackets are used on the doors. For mounting thearrays on difficult door jams, nylon adapters that screwonto the studs are provided. Push-in nylon fastenersthen make it easy to mount on the jam by simplydrilling holes.

The control board includes array connections thatare interchangeable and short-circuit protected. It alsoincludes a System Test button to simulate a beam breakfor a complete system test and a Control Relay Testbutton. As a result, Leading Edge installation can be

accomplished by a “single installer,” and the entiresystem can easily be tested from the top of the cab. Simplifying Diagnostics

Most light-screen door controls include a full complementof LED indicators on both the receiver and light sourcearrays that are useful for troubleshooting problems. Allthat is required to test The Leading Edge system is the useof the relay and system test buttons on the control boardwhile monitoring the response of the system.

Center-opening door installation

Easy push-in fastener array installation

Simple two-button diagnostics

Side-parting door installation

CONTROL RELAY TEST SWITCH

SYSTEM TEST SWITCH

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If the output control relay does not energize whendepressing the Control Relay Test button, the problemis most likely the control circuit board. If the relay en-ergizes and the door does not close, the problem couldbe faulty control relay contacts or failure of the dooroperating system itself.

If the system does not respond properly when depress-ing the System Test button, the problem is with one of thearrays. Monitoring the LEDs on the arrays will reveal whichone is faulty. Enhancing Appearance

The interior appearance of the elevator has become amore important issue with today’s new building and renova-tion designers. The Leading Edge offers arrays in a choice ofconventional black, brilliant silver or gold to enhance anyelevator decor.Lowest Applied Cost

In the selection of elevator door controls, a system thatincorporates low initial purchase price and installationcosts and high reliability is of paramount importance.

Robert A. Warner has been instrumental in thedesign, development and manufacture of photo-electric sensing devices since 1969. He served aspart owner and vice president of Unidyne during the1970s. When Tri-Tronics purchased Unidyne in 1976,Warner served as senior vice president of ProductDevelopment. He has continued in the innovativedevelopment of photoelectric elevator door productsfor the past 17 years.

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Memco Ltd. and its sister company in the U.S., JanusElevators, offer an extensive range of elevator door safetyproducts coupled with a wide range of fitting solutions tooffer maximum flexibility to customers.

At Memco, the research and development team worksclosely with input and feedback from the sales and serviceteams to ensure that new products are relevant to theneeds of customers. The products are also designed forease of installations, saving time for everyone. The Memco Detector FamiliesPana40 Plus

The Pana40 Plus family of detectors is programmedusing a Model 840 series controller to generate either a40-beam parallel light curtain or an optional 194-beamcrisscross pattern. Any interruption to the infrared beamsacross the lift door opening activates a relay which,through the door operator, can stop or reverse the closure ofthe lift doors. The detectors are available in a range ofwidths from 43.5mm down to 9mm and with a specialthin version for slampost mounting. The availability ofprofiles in these sizes simplifies fitting to the widest rangeof door types, both dynamically and statically.

The 840 controllers use micro-controller technologieswith software to:u Control the detectors u Perform self-test checks u Measure the received infrared signalu Update trigger thresholds u Make trigger decisions u Switch the system into “sleep mode” when not in use

The controller’s printed circuit board and metal housinghave been designed to allow easy access and installation.A pluggable terminal block is provided for easy wiring instal-lation. The main trigger relay has a socket, which is providedfor quick relay replacement if necessary.

LED displays are provided for status updates. The serviceengineer can easily locate these; there is a window in thecontroller housing that allows the display to be viewedwithout removing the lid. In Normal Mode, the display indi-cates whether the controller is scanning, triggered or inone of the timeout states shown in Figure 1. The controller can

Figure 1

also be switched to test mode, which allows the displayto show diagnostic information.

Other safety features, which service engineers can useto help with setting-up and checking, include: u A Tone Switch – When enabled, the controller emits anaudible tone if the unit is triggered, i.e., if either detectoris unplugged, or the cable severed. u System Self-Test – The controller’s software measuresthe regulated power supply voltage. If it senses that a detec-tor has become unplugged or the cables are cut, it willcause the lift doors to be held open. u Fail Safe Operation – The controller has been designedto fail-safe in the event of system fault or the loss of thesupply voltage. It will hold the lift doors open until thefault is cleared. u Light Curtain Timeout – This switch allows a partiallydamaged detector to continue working safely until it canbe replaced. It does this by ignoring a permanent triggeron up to five non-adjacent beams (e.g., due to vandalism).The timeout period is adjustable from 10 seconds to 70seconds. On 194-beam controllers, only four non-adjacentbeams are allowed to timeout.Pana40 Plus 3D

This is the Memco second generation detector family.Internationally patented, Pana40 Plus 3D is designed todeliver the optimum in passenger safety.

The 3D detection system holds the lift doors open whenit senses objects or people approaching in a detectionzone outside the landing doors. The system is designed sothat doors do not begin to close until the detection zoneis clear, thus reducing collisions and therefore damagebetween landing doors and wheelchairs, pushchairs, etc.In addition to the convenience to lift users, door damageis sharply reduced, often by 50% or more.

The latest generation system improves safety with twoindependent detection systems (see Figure 2):

ELEVATOR DOOR PROTECTION SYSTEMSby Jennifer Fenton, Marketing Manager, Memco Ltd.

Figure 2: The operating principle of the Pana40 Plus 3D showing the sensitivezone projected in the landing

Scanning State

TriggeredState

TimeoutState

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1. Light curtain – Infrared beams operating between thedoors. 2. 3D detection – Infrared proximity detection operatingin the landing zone.

Any object causing interruption of the direct beams orreflections within the 3D detection zone will trigger thesystem and re-open the lift doors.

The 3D detection is achieved by infrared light beamsreflecting from objects in the 3D zone. These beams operateupwards, downwards or straight out from the detectorsat an angle of approximately 45° to the plane of the door.The 3D detection range is approximately half the width ofthe car door opening.

The system can be configured for different operating modesto suit different installations, for example in an assisted-living facility the elderly and infirm may take some timeto pass safely in and out of the lift. Any object that inter-rupts the direct beams or reflections within the 3D detectionzone will trigger the system and reopen the lift doors.

The 3D detectors are suitable for both new and existinglifts and can be manufactured in various profiles (as thePana40 Plus system) to suit a wide variety of doors, includ-ing both center- and side-opening doors.Standard: Part No. 770 000

The Standard detectors are designed to fit on the sideof the door, flush with the door edge. They are fixed usingself-tapping screws, through height-adjustable brackets andcovered by a vandal-resistant finger guard (see Figure3). These detectors are particularly suitable for center-opening doors with a wide running clearance where thedetector also doubles as a sightguard. The cable may be

routed from the top ofthe detector or downinside the housingand out the middle ofthe back. The cablecan be secured withthe P-clips provided.Leading Edge: Part No. 770 010

The Leading Edgedetectors are designedto fit on the leadingedge of the door or onthe slampost. Thesedetectors are particu-larly suitable for side-opening doors, butcan be used on center-opening doors. Thedoor or slampost isdrilled in four places,Figure 4: Part No. 770 010

Figure 3: Part No. 770 000

and the detectors fitted by means of captive bolts, sliding ina track on the back of the detectors. Alternatively, the de-tectors may be secured through the detector housing onthe door edge, using the screws provided (see Figure 4).Fixings for both methods are included in the fixing kit. Mixed Set (Standard and Leading Edge): Part No. 770 020

The Mixed Set is convenient for side-opening doors,where it is desirable to have a Standard TX detector on thedoor and a Leading Edge RX detector on the slampost (seeFigure 5). If the door opens in the opposite direction, it willbe necessary to swap the plastic lenses so that the TX is kepton the left-hand side.

Slimline: Part No. 771 000

The Slimline detec-tors are 15.5mm wideand designed to fit onthe side of close-cou-pled doors. The detec-tors are mounted to theside of the car doorsusing the self-tappingscrews provided in thefixing kit. Optional PVCfinger guards (Part Nos.007 137 and 007 138)are available to fill the30mm gap found onsome door types (seeFigure 6).Ultraslim: Part No. 774 000

The Ultraslim detec-tors are 9.8mm wide,which allows them tobe fitted to virtually alllifts. They are particu-larly suited to lifts withnarrow running clear-ances. The detectors aremounted to the side ofthe car doors using self-tapping screws pro-vided in the fixing kit(see Figure 7).

The Pana40 Plus 3D Controllers operate the Pana40Plus 3D detectors. They are housed in a black steel box,which is normally fitted on top of the lift car using self-tapping screws. The controllers are available in severalversions to suit individual requirements.The Elite Range

This range is centered on the 632 and 633 models,which are designed for both new and existing installations.




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The detectors are fitted either dynamically on the doorsor statically on car-mounted brackets. They generate acrisscross curtain of 154 infrared beams.

Memco uses surface mount technology to build the EliteModel 632 detectors and improvements in optics nowallow diagonal beams to function to door close. The speciallenses are used with the surface mount transmit and receivediodes. Each detector is housed in a 9mm profile.

The Elite Model 633 consists of two 32mm-wide detectorsand shares the software features of the 632. For example,a timeout option is available. If this is enabled, then it willallow up to five non-adjacent infrared TX diodes to be ignoredif they are permanently obstructed. After a 10-seconddelay, beam scanning is then resumed – a useful servicefeature as the TX diodes can be ignored while arrange-ments are made to replace the unit.

New to Memco is the Elite 3D system – Model 674. Thislatest development complements the Pana40 Plus 3Dfamily and adds extra functionality to the Elite range.What Are the Main Differences Between thePana40 Plus 3D System and This Innovative Elite3D System – Model 674?

Model 674 has the same two independent detectionsystems as the Pana40 Plus 3D coupled with a light curtainof 154 crisscross beams. This has been designed for bothnew and existing installations with low power consumption.Each detector housed is in a profile 9.8mm wide. Thereare two orange LEDs positioned 29cm and 31cm from thetop of the TX detector to give the service engineer statusinformation when checking the installation.

Memco recommends installing the 674 system with aMemco 280 or 281 power supply. However, in many instal-lations, a separate controller is unnecessary, and the detec-tors can be connected directly to the door controller orlift operator, if it has a suitable power supply and “door-reopen” circuit (see Figure 8).

Memco offers after-sales support and service and a widerange of brackets, clamp plates, clips, coverstrips and sight-guards to cover as many installation options as possible.For dynamic installations, the Igus claim protects thedetector cable (see Figure 9).

There is also a fixed installation kit containing all fixingsneeded for installing a set of 9mm profile detectors in afixed position at either end of the lift car sill. See typicalinstallation in Figure 13.

Other elevator safety products from Memco includetwo new products:

Figure 8

Figure 9: Igus

Figure 10

Figure 11

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A) Memco Vision SystemThis is a new sensor for both landing doors and automatic

doors, providing video output, currently being launchedin Europe. The system is designed to be mounted abovethe door on the landing and to open the door accordingto the movements of people within the field of view of thecamera. The sensitive zone is fully variable over a span of0.5 to four meters from the door and three-meters widevia internal switches. There is no need for any further me-chanical adjustments.Main features of the Memco Vision Systemu Detects moving and stationary passengers right up todoor entrance. u Fast, easy fitting using single digital module with up totwo vision heads. u Eight different operating modes; flick a switch tomatch the system to the application. u Streamlined door operation; opens only when needed,ignoring passing traffic. u Provides video surveillance of the door area for securityof lift lobbies and landings. u Four-meter approach zone allowing no waiting fordoors to fully open.B) Chromaline

The Chromaline edges glow green as the lift doorsopen and glow red as the doors are about to close andwhile they are closing.

This full line of door protection systems will ensuresafe and reliable elevator operation on both new as wellas existing elevator installations. c

Figure 13: Fixed installation kit Chromaline showing green

Chromaline showing red

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harmful radiation. They are also immune to sunlight or anyother direct light sources, and most systems carry the ap-propriate approvals and certifications. The systems arenormally factory pre-wired and fully tested. Plug-in wiringkits and the necessary mounting hardware ensure trouble-free and simple installation.

The advantages of these infrared door protection systemsover earlier traditional mechanical systems are many butinclude additional protection provided by multi-beamcross-scanning features (up to 212 functional beams),which, if any one or more are broken or interrupted will, ifthe doors are closing, immediately signal the doors to reversewithout having to “make contact” with the obstructionand, if already open, will not attempt to close until the carentrance is clear and unobstructed. This is a major benefit insituations such as hospitals, retirement residences, hotelsand office buildings, where the intimidation of users bymoving doors is of concern. Where the elevator installationhas a slow-speed door-closing feature, a nudging featureand warning alarm can also be incorporated into this system.This is used to signal that after a predetermined time, thedoors close at a reduced speed and torque in accordancewith relevant elevator codes. A further advantage of theinfrared door protection systems’ “broken beam” principle ofthe doors not closing while an obstruction is present, isthe elimination of the large number of door-reversing cy-cles the door operator equipment is forced to performwith the mechanical-edge system until the obstructionhas been removed. A door system fitted with an infraredre-opening device will not attempt to close if open and doesnot have to repeatedly “make contact” with an obstructionin the entrance before re-opening. Over the lifetime of thedoor operator, this greatly reduces the wear and tear on thisexpensive piece of equipment, thus reducing maintenancecosts. Historical evidence has also revealed that elevatorsfitted with infrared “non-contact” door protection deviceshave significantly less door-related problems compared withthose fitted with mechanically operated “contact” devices.

Infrared door protection devices can also be seen as anexcellent device for “modernization” and “refurbishing”projects, providing an upgrade to the latest in doorprotection technology at a very reasonable cost making thisa very viable first step in a modernization program. Infrareddoor protection devices can also be configured to meetindividual OEM door-operator manufacturer’s specificationsand requirements and can be incorporated into their“door packages” shipped direct to the customer.

Modern elevators are generally fitted with a power-operated car and landing doors, which automaticallyopen and close on arrival and departure from the floorsthey serve. Relevant elevator codes worldwide call fordoor re-opening devices to be fitted to these power-operateddoors, which, in the event of an obstruction occurringduring the automatic door-closing sequence, operate tore-open the doors. In the past, these re-opening deviceswere in the form of a mechanical edge or shoe device,which when contact was made with an obstruction wouldoperate a mechanical switch to initiate the elevator dooroperator’s re-opening circuitry. While these devices weregenerally reliable and efficient, they relied on having tomake “physical contact” with the obstruction or personbefore operating and re-opening the car and landing doors.Development of “non-contact” door re-opening devices hasnow, in most cases, rendered the mechanical type safetyedges obsolete, these non-contact devices are generallyinfrared-based technology and consist of multi-beam trans-mitters and corresponding receivers, which interface withthe elevator door control circuitry via “dry or voltage-free” relay contacts.

These electronic microprocessor-based infrared devices,which are sometimes referred to as “light curtains” or“entrance detector screens” normally consist of three parts:a power supply, a receiver unit and a transmitter unit. Thereceiver and transmitter units are normally mounted onthe car doors adjacent to the leading edge, opposite eachother, providing dynamic coverage across the elevatorentrance. The power supply is mounted on top of the car orin the car-operating panel. The power supply also containsthe relay interface for connection to the elevator door operatorcircuitry. These systems are designed to be fail safe. If

power to the systems islost or a cable is broken,the output relay is de-energized resulting inthe re-opening of theelevator door, the sameevent would occur whenthere is an obstructionor “broken beam” in thedoor opening.

The systems aretested to ensure high im-munity to EMC electricalradiation and do not emit

INFRARED DOOR PROTECTION DEVICES INSTALLATION AND MAINTENANCE

by Peter Thomson, GM Engineering, and Ned Badis, Technical Manager, TL Jones (Microscan) Ltd.

CABLEKIT

TO DOORCONTROLLER

POWERSUPPLY

AC (DC) IN

1880 mm

1440 mm

1000 mm

560 mm

120 mm

Top beamat 1823 mm

2002 mm

Transmitter R

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InstallationMost infrared door protection systems consist of a receiver

unit, a transmitter unit and a power supply/controllerunit. These parts are connected to each other through cablesranging from specialized multi-wire cable looms to verysimple three-way cables. Although infrared systems aresupplied ready for center-opening doors installation, mostmanufacturers supply special kits for installation on side-opening doors (strike jamb kit).

During the installation of the infrared units, it is importantto pay extra attention to the following points:u It is recommended that the transmitter and the receiverunits be mounted slightly back from the leading edge ofthe door panels (e.g., 1/4 inch). This prevents repetitiveimpact damage to the transmitter and the receiver andtherefore prolongs the life of the door protection system. u Ensure that both transmitter and receiver are vertically

plumb and inline. Both transmitter and receiver should beplaced on a packer (e.g., 1/4-inch-thick wooden block) toensure that both units are installed to the same heightfrom the floor. Please note: it is important that the bottombeam height be within one inch of floor level as this providesfoot detection.

u Door-detection systems supplied with means for unitgrounding offer extra protection against electrical noise.Special care should be taken to ensure that the grounding isdone properly. It is also advisable to make sure that acontinuous ground connection between the elevatordoors and the elevator car is achieved. This could savethe installer unnecessary callouts for intermittent faultscaused by bad grounding.

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u As infrared-detection systems transmit beams from oneside of the entrance to the other, it is important to make surethat the receiver and transmitter units are properly aligned.

u For elevators with side-opening doors, make sure thatthe edge to be mounted on the door panel (receiver or trans-mitter) is installed first, and then use this side as a guideto align the edge installed on the strike jamb. Pay particularattention to alignment when the doors are fully closed. u The cables should be routed away from and not runparallel with other wiring to minimize the possibility ofelectrical interference. It is advisable to avoid any bendingover sharp radius, as this could cause damage to thecable over a period of time. The use of cable ties in theappropriate positioning helps minimize the risk of cabledamage, while the use of cable restraints prevents the ca-bles from swaying and catching on other elevator parts. u It is always a good practice to make sure that the doorprotection system is powered from a clean supply powersource, and that the system’s power supply unit is prop-erly grounded to the elevator car.

After the system has been initially installed, check that thepath of the beams between the transmitter and the receiveris not blocked by the door gear equipment (door vanepickups, couplers, etc.).

MaintenanceDuring routine elevator maintenance visits, it is rec-

ommended that the following procedures are carried out.u Use a clean, damp cloth of nonabrasive material towipe the receiver and transmitter lenses. Avoid vigorousrubbing as this can cause static buildup. Dust may accu-mulate on the lenses and can affect the operation of thesystem if left unattended.u Closely inspect the cables between the transmitter/receiverand the power supply/controller unit for any cuts and chaffingor rubbing. These could indicate potential cable failures.u Ensure that the cables are hanging freely and not likelyto snag or catch on other equipment. Check with the cardoors both fully open and closed.u Check connectors and terminations between transmitter,receiver and power supply for any loose fixings.u A routine check should also be carried out for damageand that the units are securely fixed to the car doors andstrike jam.u Finally, check that the system operates correctly by block-ing any of the beams and check that the doors re-open. Ifthe system has a nudging feature, check that this operatesafter the predetermined time delay and that, if fitted, thewarning alarm sounds. Troubleshooting

Most infrared door protection systems are equippedwith diagnostic indicators on the receiver/transmitter

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and/or power supply/controller unit to assist elevatorfield personnel with fault finding. Each manufacturer uses adifferent indicator combination to indicate a particularfailure scenario, such as “broken beam” conditions, butthe process of troubleshooting is generally very similar.The following are possible scenarios and correspond-ing steps to follow:

Elevator doors remain open without any obstructionbetween the doors. u Check lenses for dust, dirt or any other object thatmight be stuck to the lenses. u Check transmitter and receiver for alignment. u Check power supply for correct supply voltage andgood contact on output signals terminal blocks. u Check that both transmitter and receiver are pow-ered. (Using indicator lights or a multi-meter to verifysupply voltage). u Check cables for any cuts or breakages, and checkconnectors and terminations to ensure good contactis made.

u Check relay activity by turning power on and off to thepower supply unit. u Check for any source of excessive direct infrared lightto the receiver.

Elevator doors intermittently re-open during closingwithout any obstruction between the doors. u Check lenses for dust, dirt or any other object thatmight be stuck to the lenses (also check for excessivebuildup of floor wax on lower section of the lens, this canalso cause this problem). u Disable door operator and manually close doors tothe point where the unit false fires. At this point, checkfor misalignment between the transmitter and receiver.Also check for breaks in the cables which could causeintermittent faults. Conclusion

Electronic door-detector units have changed significantlyduring the last two decades. It is now a mature product,and the first choice in providing car door protection formost companies.

Major benefits include: u Longer life for the door operators due to lower numberof operations. u Compliance with the disablement codes. u Potentially less callbacks for door-related problems.

There has been a significant change in the initial cost forthese products and reliability has improved, so that now,most manufacturers are offering extended warranties.

Important issues to note when selecting electronicdoor-detector units are:

u Selecting a unit that is suitable for both side- and center-opening doors. This will keep inventory costs down andsave time at the site. u Consider the time it takes to install different units. Thesavings you may think is available with the initial pur-chase price may be lost at the installation time. u Check the cable used on the units. As these productsare installed on the leading edge of the car door, the cablewill be constantly moving. Look for simple plug-in cablesand the lower the number of cable conductors the better.u Water and dust will cause problems. It is better to lookfor a detector that has a high rating for this. Look for eitherNema 13 or IP65 as a minimum requirement. Most call-backs to detectors will be attributed to water and or dustentering the units.

This technology will continue to develop further. Currentlycombination 2D and 3D units are available. These productsprovide a degree of sensing into the landing area. Rightnow, this detection is limited to a triangular zone from thetransmitter and receiver units. The distance between the cardoors determines the area of 3D scanning. Combinationmechanical safety shoes with electronic detectors builtinto the nose of the shoe are also available. This type of unitcan provide the best of both technologies. In most cases,the safety shoe will be provided in the same mechanicaldesign as the proprietary product.

When choosing a sup-plier for electronic door-detection devices, look be-yond the initial unit cost.There are other areas ofpotential hidden costs.

Have a checklist:u Initial cost. u Installation time.u Reliability of cables.u Choose a unit that hasangled beams in operationat final door closure. Unitsthat switch to only parallelbeams as the doors closewill leave areas wherethere is no detection.u Units to suit both sideand center openings.u Availability of supply.u Delivery time.u Product support, bothbefore the purchase andafter.u Warranty period.u Cost of spare parts. c

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Documents

CRITICAL REQUIREMENTS OF TODAY’S ELEVATOR LIGHT … · elevator decor. Lowest Applied Cost In the selection of elevator door controls, a system that incorporates low initial purchase