Consider several features when choosing a sensor for your
wash
Just as car washes vary from self serve to rollover
to tunnel wash, there are many types of sensors being used to start,
stop, measure length, and control the wash and entry/exit doors.
However, all sensors are not created equal. There are early warning
signs to look for that might indicate a maintenance check-up is
in order.
Are the automatic doors operating properly? Are
the nozzles turning on and off as needed? Is soap being dispensed
after vehicles exit the wash instead of on time? Does snow and ice
cause false signals from the photo-eyes?
If your wash equipment and door systems are not
functioning correctly, the photo-eyes that signal the wash line's
computer system may not be operating properly. We will examine the
most common problems that photo-eyes face in the demanding wash
environment and the features that you should consider when selecting
sensors for your wash. Afterwards, we will review various types
of applications in each type of wash and give some "first-aid"
tips for your photo-eye sensors.
How many of you have ever experienced fog in your
bays so thick that you couldn't see someone standing 10 feet away?
This is a very common problem in locations where cooler temperatures
during the winter months combined with hot water put extreme demands
on your sensors. Most photo-eyes would fail under these circumstances.
To compound this problem, add soap, grease and dirty water and you
have the makings for a true disaster.
You know the picture. After a week of snow and
ice, the sun finally comes out and the temperature rises to create
a nice slushy, mud bath for your car. As cars line up at the wash,
the last thing the operator needs is for the equipment to stop working.
One single day of non-operation means lost profit that you can never
recover.
Keeping your car or truck wash equipment in top-notch
condition includes checking and replacing defective photo-eyes.
Sensors provide the critical signal to the wash computer. Therefore,
it is absolutely necessary they operate properly. As the old saying
goes, "junk in, junk out." A photo-eye could mean the
marginal difference between profit and loss for your wash.
Common Problems
The number one reason for photo-eye failure is
contamination. A car wash is ideally the best testing grounds for
a photo-eye because of contamination. Practically, no other industry
can compare to the wet, hostile environment of the car wash's dirt,
steam, ice, snow, soap, film, grease and everyone's "favorite",
fog. If a photo-eye can pass this test, you have a winner.
There are some sensor brands of this caliber on
the market. They are able to withstand this type of abuse because
they do not use a lens to magnify the light to the receiver eye.
Lens-less eyes are usually designed as modulated infrared sensors
(see figure 2).
The transmitter LED (light emitting diode) is turned
on and off, acting as a pulse of light, invisible to the naked eye.
The receiver is calibrated to the same frequency of modulation to
accept the transmittal signal.
Just as a lighthouse penetrates the fog to warn
an approaching ship of danger, the lens-less photo-eye cuts through
fog, steam, dirt and grime to ensure your car wash trouble-free
service. Relate the photo-eye made with a lens to a pair of glasses.
If you walk into the wash wearing glasses, they immediately become
fogged up. You must take the glasses off and clean them. This is
a perfect example of the wrong photo-eye to use in a car wash. By
removing the photo-eye made with a lens you eliminate the step of
continual lens cleaning.
Misalignment is another photo-eye problem common
to car wash facilities. In some cases, it is possible to judge visually
if the eyes are out of alignment at an angle or askew to one another.
When installing photo-eyes at a distance of eight
to twelve feet, it should be possible to pull a string between the
two to check positioning. If the viewing angle of the photo-eye
is eight degrees or greater, alignment should not be difficult.
The next common reason why so many photo-eyes fail
is vibration. Have you ever seen a car or truck wash facility devoid
of vibration? With arches turning on and off, and other assorted
wash components in constant motion, vibration is certain to occur.
If a photo-eye system is difficult to align when
installed, given the amount of on-site vibration, it is highly probable
that proper alignment will be difficult to maintain. With a wide
opening- angle, or "beam-spread", installation is not only simple,
but vibration won't knock the eyes out of alignment.
Mounting plays an important role in photo-eye alignment.
In the wash environment, eyes should always be mounted in a through-beam
manner (figure 2). Properly mounted eyes promote reliability for
the wash over the long haul.
A special word of warning: Do not use reflectors!!
(see Pix) In car and truck wash applications,
the use of reflectors is a bad idea. Condensation that forms on
reflector faces may cause significant problems and they are prone
to damage and mischief.
Last, but certainly not least, water leakage can
cause photo-eyes to perform intermittently at best, or fail altogether
at worst. As water leaks into the housing of the photo-eye, the
internal components become damaged and condensation begins to form
on the inside of the lens, fogging up glass and plastic lenses alike.
Check the rating on this eye to determine whether
it was designed to withstand wash-down or submersion. A rating of
IP67 means that a sensor will perform reliably in water. If the
photo-eyes in your car or truck wash are not performing up to standards,
replace them. Eliminating the problem sensor before it interferes
with the performance of the equipment will save you money on those
high volume days.
The Right Sensor
Selecting the right sensor for your application
can be tricky, and turning the pages of photo-electric sensor catalogs
may only add to the confusion.
The components for most infrared systems used in
the car wash industry include a transmitter, receiver, amplifier
and socket. Don't be tempted to purchase a photo-electric sensor
system based on price alone. The cost of installing quality sensor
eyes that are made specifically for the car or truck wash is more
than justifiable.
As an operator, you're looking for equipment that
will perform reliably, day in and day out, with the least amount
of maintenance. Remember, your best profit days are when you are
managing and the wash is working. Quality eyes will help put you
back in the driver's seat of your wash so you can do the important
things like servicing and delivering a quality wash.
Light immunity rating, sensing range, strain relief
and body style are other features to consider when selecting your
sensors; and often the application will help narrow down your choices.
For example, if you plan to mount photo-eyes at the entrance to
the car or truck wash, a compact body style will simplify installation
and service. These sensors should be fully encapsulated, resisting
water leakage. The entrance area also subjects the photo-eyes to
prolonged exposure to bright sunlight. To avoid intermittent interference,
opt for a sensor with a rating of 50,000 LUX or above.
Although operators only need to cover a distance
of approximately 10-50 feet, the sensing range of the photo-eye
is extremely crucial in carwash applications. Photo-eyes with ranges
of 120 feet or more are strongly recommended to ensure that you
will have enough power to penetrate the harsh environment caused
by dirt, water, soap, fog, etc.
Common applications
Now, let's take a look at some of the most common
types of car or truck wash applications.
Self Serve Washes
In self-serve washes, the most common usage is
on service-bay automatic doors. Photo-eyes are installed on entrance
and exit doors to prevent damage to a car or to the door if the
operator closes the door prematurely.
The sensors should be mounted on each side of the
door in a through-beam configuration with the transmitter placed
on one side and the receiver on the opposite side. (See
pix) The amplifier is placed in a watertight enclosure or in
the main control panel. As the car comes into or out of the wash,
it breaks the infrared beam and signals the door to reverse. Other
applications in self-serve washes include automatic entry systems,
exit signs, and "unlimited time" self-serve bays.
"Unlimited time" self-serve bays offer extra value
to your customers by allowing them plenty of time to clean their
vehicles. This may be achieved by installing two photo-electric
systems in the bay. One system is used to detect that a vehicle
is present in the bay. The second system is used to reset the timer
when that customer leaves to prevent the next customer from enjoying
a free wash.
Rollover washes
Rollover washes require the car or truck to be
driven into the wash and then the machine moves around the vehicle.
Photo-eyes are used to position the wash equipment, measure the
length of the vehicle and turn the equipment on and off as needed.
The entrance and exit doors generally use photo-eyes to signal the
PLC or industrial computer that the vehicle has entered or exited
the wash.
Tunnel wash
Tunnel wash applications are very similar to the
rollover wash except that a conveyor is used to move the vehicle
through the wash. Photo-eyes are used to start and stop equipment,
turn on soap or hot wax dispensers and start and stop rinse arches.
For those who are using old limit switches with
a wand that drags along the side of the vehicle, it's really time
to update your equipment. Wands are prone to failure in freezing
temperatures and are possibly damaging to the vehicle. If not adjusted
correctly, wands won't start the wash sequence correctly. Photo-eyes
are a no-touch alternative to wands.
Photo-eyes are also recommended in the tunnel wash
for entrance and exit doors. Most high-speed automatic doors are
equipped with a reversing edge or some type of sensor. The edges
become worn and cracked when exposed to a combination of continuous
cold weather and sunlight. If edges are kept in good repair they
can provide a backup system but photo-eyes are the ideal solution
for the doors because they offer a no-touch system.
Selecting the right sensor
for your application can be tricky.
Another common application in the wash environment
is the loop detector. Loops are generally found at the entrance
and exits of the wash. They are usually mounted in the pavement
by cutting into the concrete, inserting a loop of wire attached
to the controller and then some type of filler or potting is layered
on top to cover the wire.
If freezing rain, ice or snow seep down into the
loop area through a crack in the potting, the loop can malfunction
and cause invalid signals to the PLC or controller.
Also, with the large variation and size of cars
and trucks, loops often malfunction due to the height of a vehicle.
Faulty loop detectors can be easily replaced with photo-eyes mounted
at an angle with the transmitter approximately 12-15 inches above
the ground and the receiver 4-5 feet above the ground ensuring that
any size or shape vehicle will be detected.
We have looked at some of the various applications
found in the car or truck wash. You have been given the basics to
help you determine the type of sensor you will need for your wash.
Routine check-ups and maintenance will enable you to keep your wash
running this winter. If your equipment budget doesn't allow for
any changes at this time, check out the troubleshooting guide to
see a list of things you can do to keep your current equipment running.
Emily Finley is the President of Pantron Automation,
Inc., who offers quality photo-electric systems to the USA and Canada.
TROUBLESHOOTING
GUIDE
First-Aid for your sensors
If your equipment budget doesn't presently allow you to buy new
sensors to take advantage of the features listed in this article,
try the following. You may be able to inject some new life into
the old sensor and help keep your current equipment up and running.
Installation: Check
the mounting of the sensors. Are you using a reflective/eye combination
in the wash that requires constant maintenance? You may be able
to mount the sensors in a through-beam setup and totally eliminate
the need to use reflective/eye combinations. This will reduce the
maintenance time required to regularly clean the reflector and photo-eye
lens, or to realign the photo-eye itself.
Wiring: Look to see
if the wires of the photo-eye are pulled tight. Some manufacturers
of equipment pull the wiring tight and secure it in place for cosmetic
purposes. This can break down the seal on some photo-eyes and cause
leakage into the sensor. There should be some slack in the wire
coming out of the sensor. If it happens that the seal is broken,
apply a potting material to the back of the sensor to prevent any
more moisture from leaking into the sensor.
Maintenance: Have
the sensors cleaned during regular maintenance to remove soap, film,
grease and dirt from the front of the sensors. Also, check for proper
alignment at this time. Vibration can cause some sensors to be knocked
out of alignment very easily.
Sunlight: If you notice
that the sensors are malfunctioning when exposed to bright sunlight
check with the manufacturer of the sensor to see if a polarized
filter or shield is available.
Typical Parts
Wiring Diagram
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