Classic Smarteye Sensing Solutions

Photoelectric sensor used in a dusty environment

Challenge:

Photoelectric sensors offer distinct advantages/tradeoffs in industrial applications, including speed, narrow beam, shades of gray/color differentiation, and when using visible RED LED light source, the ability to sometimes see the light projected onto a specific location on a part.  What most users also associate with photoelectric sensors is their sensitivity to dusty/dirty/wet environments, sometimes to a fault.  Often, the selection of a photoelectric sensor is essential, but dust and dirt may prove an on-going challenge.  Frequent cleaning of the photoelectric sensor face/lens (and reflector, if used) are typical maintenance tasks that no-one enjoys.  Some users may suffer with alternative sensors for fear of the expected outcome of a photo eye in this environment.

Solution:

There are different modes of photoelectric sensing with their tradeoffs.  The through-beam/beam break mode of sensing, when appropriate, can offer some relief from dusty/dirty environments, if the application is appropriate for an IR/infrared LED source.  However, since some applications can not use a through beam mode, the alternative is generally the proximity/prox mode.  The prox mode is where the sensor bounces the light off the object itself, and back to the sensor for detection.  The prox mode is most challenging for dusty/dirty/wet environments, particularly when the application requires bifurcated, fiber-optic cables.  The glass fibers in a bifurcated fiber-optic are 50% randomly oriented, with the sender and the receiver strands of the glass fiber-optic at the sensing face end (closest to the target application), extremely close to one another.  Any dust, dirt, or water droplets on the sensing face of the bifurcated fiber-optic bridges/completes the path to some degree from sender to receiver strands, and either compromises the performance of the sensor to deal with this, or renders the sensor useless until the dust/dirt/or water droplets are wiped clear of the fiber’s sensing face.

Where physically feasible, if instead of a single, bifurcated fiber-optic in the prox mode, a pair of through-beam fiber optic cables can be used, and placed side by side with one another at the closest point to the target application, then high immunity to dust/dirt/moisture can be achieved.  This is enhanced further by using IR/infrared LED light source to burn through contaminants on the fiber’s sensing face.  The mere physical separation of the fibers, by having two separate fiber-optic through beam cables, provides sufficient separation to mitigate the impact caused by bridging of glass fiber strands from sender to receiver.  The Tri-Troncis F-C-36 or F-C-36P are optimal examples of this unique application, as they have through-holes in their flat surfaces, allowing bolting them together to make an compact, practical form factor.

These Tri-Tronics F-C-36 or F-C-36P fiber-optic cables provide nearly identical beam distribution, and distance as a single bifurcated cable, and yet mount in nearly the same physical space as the bifurcated fiber-optics.

Using these Tri-Tonics fiber-optic cables with a Tri-Tronics sensor with either an Action Alert or Auto-Track feature, may provide either advance notification of a gradually deteriorating signal due to dust/dirt, or may automatically correct the sensor to maintain optimum performance given the attenuation of the signal over time from that accumulation on the fiber-optic sensing face.  At Excel Automation, we have used this technique numerous times successfully, to retain the advantage of using a photoelectric sensor in that adverse environment.

Net Value to our Customers:

Whether you have an easy, or more challenging type application, give us a call.  Chances are we may have either the sensor and/or the experience to solve it.  Excel Automation, and Eagle Sensors & Controls, have years of experience, and are application-oriented Authorized Distributors of numerous products for Industrial Automation, and LED Lighting.