How to Install and Maintain Photoeye Sensors for In-bay Automatic Car Washes

In-bay automatic car washes rely on sensors to control the car wash equipment. Without sensors, the wash computer would assume that every vehicle is the same length, height, and width. Applications for sensors include starting the wash, measuring vehicles, and controlling the opening and closing of doors. Photoelectric sensors have become a preferred method of detection due to their performance and ease of use. Proper installation and regular maintenance will ensure uninterrupted performance from the photoelectric sensors.

The first thing to consider when choosing a sensor for an automatic car wash is the type of application that the sensor will be used in. Photoelectric sensor systems typically consist of, at very least, an infrared transmitter, an infrared receiver, and in high-powered systems, an external amplifier. For the simple detection of a vehicle, the photo eyes are positioned on either side of the car wash. The transmitter photo eye emits an infrared beam of light across the bay that is detected by the receiver photo eye. When the infrared beam is interrupted by a vehicle, a signal is sent to the equipment to perform the desired application. This may be starting the equipment, measuring or profiling the vehicle, or simply opening and closing the doors. Usually, one sensor is mounted high, while the other is mounted low so that the sensors form a diagonal line to the ground. This causes the beam to pass through the area where the largest portion of the vehicle will pass and helps to reduce false signals. Mechanical treadle plates that are used to position the vehicle may be replaced by photoelectric sensing systems.

The body of the sensor should be durable and designed to withstand the harsh conditions of the wash. There are sensor bodies available in plastic, nickel-plated brass, and stainless-steel to meet the requirements of the car wash environment. A simple infrared sensor like the ones used in a residential garage door application are not designed to withstand the conditions in a car wash and should be avoided in this type of application because they lack the proper sealing. For the car wash environment select a sensor with an IP67 rating. This rating is used to inform the end-user that the sensor is sealed in a way that will not allow the internal circuits to be damaged by water spray or submersion. The range of the sensor is important for two reasons. It is much easier to mount the sensors in a place where they will not be hit if they have a long enough sensing distance. A strong infrared beam will also assist in penetrating the steam, mist, and soap that are present while the wash is running and will provide fewer false signals and the resulting down-time.

Required maintenance to photoelectric sensors is easy, and requires very little time. Check the alignment of the photo eyes using a length of string or wire long enough to pull in a line between the sensors. This line should be parallel with the sides of both sensors. If you are using a set of photoelectric sensors that uses an external amplifier, periodically check to be sure that the seal on the enclosure box is still intact and that no water has penetrated into the inside of the box.

If you have problems with the photoelectric controls, determine the nature of the problem. Are they giving an intermittent output that flickers? Do the sensors report an output all the time? Is it impossible to break the beam between the photo eyes? Once you determine the nature of the problem, it is then easier to isolate the cause. If there is a flickering output, check the alignment of the photo eyes. Next check to be sure the photoelectric system is turned high enough. (On amplified systems, this setting is located on the amplifier, inside the water-tight enclosure.) If both of these things appear normal, check for corrosion at any points where the cable has been cut and spliced. If you find corrosion, be sure to cut and reconnect the wires using a soldered connection and heat-shrink tubing. This will help seal out moisture from the connection. If you still see flickering from the output of the photo eyes, check to be sure all wires that should be grounded are connected to ground. The wires from the photoelectric controls should not share the same conduit as the wires from any motor controls.

If a constant output is the problem, check both photo eyes for obstructions. Be sure trash hasn't blown in front of the eyes and found a permanent home in the path of the beam. Alignment may also be an issue, but if they are out of alignment far enough to give a solid output signal, then this should be fairly obvious to the naked eye. Next, look closely at the face of the photo eyes. Check for visible cracks or bad abrasions. Even an IP67 sealed photo eye can be rendered useless if a large enough crack forms in the face of the sensor, thereby allowing moisture to breach the internal circuits of the photo eyes.

If it appears that the infrared beam between the eyes is impossible to break, the cause is one of several things. The first is simply that the intensity of the infrared beam is too strong and that it is literally not being blocked as the vehicle passes. Reflections on the wet walls contribute to this problem also. Try turning the strength of the system down a little. If this doesn't work, check the alignment of the photo eyes. Maybe the photo eyes see each other at an angle and when the vehicle passes through, the beam is not being broken at that angle.

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How to Automate a Haunted House Using Sensors

You've built a creepy haunted house and it's the scariest one around. How do you take it to the next level? Automate it using non-contact infrared photoelectric sensors to control electronic scare devices.

Haunted houses are designed to be very creepy and with enough volunteers, they may be loaded with frights around every corner. What if there are not enough volunteers available to haunt the house? Infrared photoelectric sensors are the perfect device to detect guests and to trigger electronic gadgets, such as noise makers or motorized animatronic characters, giving visitors a scare they won't soon forget.

Sensors are used every day in various industries ranging from food processing to automotive assembly lines. Some of the top commercial haunted houses in the country are now using the very same sensors to automate their haunted attractions, providing a far creepier presentation. Industrial sensors are available to the general public for less money than you might expect, giving the average Joe an opportunity to built a haunted house that rivals even the ones presented by major theme parks.

The easiest type of photoelectric sensor to use in a haunted house attraction is one that uses a mechanical relay switch. This type of sensor is as easy to wire and operate as a light switch. Also be sure that the photoelectric sensors use infrared light and do not display a visible light which would draw attention to them. Arrange the photoelectric sensors across from each other in a hallway or door jamb, or anywhere that a guest will pass between them. The guest will break the infrared beam of light, causing the mechanical relay switch in the photoelectric controller to close, which will provide power to a noise maker or animatronic device. Each time a guest passes the sensors, the same action will occur repeatedly without operator intervention. This allows volunteers in the haunted house to spend time mingling with the guests and not hiding behind walls, just making noise.

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How to Keep Trucks from Hitting or Becoming Stuck Under Overpasses

http://www.pantron.com/us/pantron-complete-set.htmlOperators of large trucks sometimes do not accurately measure the height of the vehicle or the extra height of the load that they are carrying. When they drive these trucks under a bridge or overpass that has a lower maximum height requirement, these trucks either strike the overpass or, in some cases, the vehicle becomes lodged beneath the overpass.

Excessive traffic congestion and the financial burden of removing lodged trucks and repairing overpasses is a good incentive to apply a relatively simple and inexpensive means of warning drivers if the load that they carry exceeds the maximum height for a bridge or overpass.

Purchase a set of industrial photoelectric sensors that use an amplifier with an internal manual relay.  These photoelectric sensors should be positioned in an opposed-mode configuration (or through-beam) so that the transmitting eye is located on one side of the lane and the receiver is on the opposing side.  The photo eyes should face one another so that the infrared beam projects across the roadway.  The infrared beam should be positioned so that it is horizontal to the road surface and at a height that is just below the maximum allowable vehicle height of the overpass.  When the beam is broken by a vehicle or by cargo, it will trigger a signal from the photoelectric amplifier.  These photoelectric sensors should be located far enough from the overpass, that they will detect the over-sized vehicle in time to warn the driver to exit the roadway.

Connect the relay from the photoelectric amplifier to a set of flashing lights and use the proper signage to alert the driver and provide them with simple instructions, for example, "WARNING MAXIMUM HEIGHT EXCEEDED - TAKE EXIT WHEN LIGHTS ARE FLASHING!"  Though, this solution is a simple one and very inexpensive, the benefits will be quickly realized.

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How to Test Whether a Sensor has a PNP or NPN Type Output Using a Multi meter

If you are replacing a 3 wire sensor which operates on DC voltage, it is important to know whether the sensor's output is a PNP or NPN type. Often this information is printed on the sensor itself, but it is not uncommon for it to be scratched off over a long period of time.

Set the multi meter to DC voltage. This is indicated by either the letters "VDC" or "DCV" or by a symbol which looks like 3 dashed lines over a solid line. There are usually several levels within the DC voltage setting. Choose the "600" level.

The power will need to be ON to perform this test, so use caution when attempting the following. Connect two of the sensor wires to the power supply. If the color combination of the wires is blue, black, and brown, then normally, the blue wire connects to 0v and the brown wire connects to positive volts. Touch the black meter probe to the 0V wire of the sensor. Connect the red meter probe to the signal output wire of the sensor. This wire is normally black. The meter should read "0."

Force the sensor to output. If it is a photoelectric sensor, block the photoelectric beam. If it is an inductive proximity switch, introduce a small piece of metal in front of the sensor. For an ultrasonic sensor or a capacitive sensor, you can just use your hand to make the sensor output. Be sure that the sensor is detecting the object. Many sensors have a small LED that illuminates when the sensor detects it's target.

Watch the meter display as you force the sensor to output. If the readout changes to a number between 10 and 30, then the sensor output is a PNP type, also known as "sourcing." If the meter display remains at "0", then the sensor output is an NPN type, also known as "sinking."

If you believe that the sensor is NPN, there is an additional test that may be done to confirm. Remove the meter probes from the wires. Now place the red meter probe on the positive voltage sensor wire, normally a brown wire. Touch the black meter probe to the signal output wire of the sensor, normally black. When the sensor does not detect it's target, the meter display should read between 10 and 30. When the sensor senses an object, the display should drop to "0." This will confirm that the sensor has an NPN type output.


How to Measure the Level of Material in a Large Bin or Hopper

Let's say you have a large bin or hopper and you regularly fill it with wood chips or powder or even liquid. How can you accurately measure the level in the bin?  In applications where it is necessary to measure the level of material in a large collection bin, there is not always an obvious way. This article will describe one method, using an ultrasonic sensor.

Purchase an industrial ultrasonic sensor (uses sound waves) with a range long enough to bounce from the top of the bin down to the lowest possible level of the material, or at least the lowest level that you care to measure. Be sure to select an ultrasonic sensor with an analog output.  Be aware that all ultrasonic sensors have a "blind zone" beginning at the face of the sensor and extending to various distances away. For this reason, the material to be measured should never be allowed to enter this "blind zone" because accurate measurement cannot take place in this range.  Also note that ultrasonic sensors are affected by drastic changes in temperature and may need to be re-calibrated occasionally.

Install the ultrasonic sensor in the top of the bin pointing downward so that it faces the material in the bin. The analog output from the sensor will need to interface with the PLC or computer so that the reading may be interpreted and any necessary functions may take place when the level reaches certain points.

Empty the bin and take note of the output from the sensor. Then, fill the bin to the maximum desired level and take another reading from the sensor. Now you have your high and low margins. You can program certain things to happen when the material hits a certain level, for instance, when the level of water in a bin reaches the top, the pump that supplies the water shuts off until the water is lowered again to another predetermined level.

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