Photoelectric Sensors - Banner Engineering

In opposed-mode sensing, the sensor's emitter and receiver are housed in two separate units. The emitter is placed opposite the receiver, so that the light beam goes directly from the emitter to the receiver. An object is detected when it "breaks" or interrupts the working part of the light beam, known as the effective beam. Depending on the application, opposed mode sensing provides the highest reliability whenever it can be implemented. This is because light passes directly from the emitter to the receiver. Then, when an object breaks the beam, the output will switch.

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• Opposed-mode sensing offers the highest level of excess gain (sensing energy)
• Long sensing range
• Most robust for harsh environments
• Precise position sensing
• Small-part detection using lens apertures
• Impervious to surface reflectivity (the color or finish of the object)

A retroreflective sensor contains both the emitter and receiver elements in the same housing. It uses a reflector to bounce the emitted light back to the receiver. Similar to an opposed-mode sensor, it senses objects when they interrupt or "break" the effective beam. Because retroreflective sensing is a beam-break mode, it is generally not dependent upon the reflectivity of the object to be detected. 

However, it can be tricked by shiny objects. For those targets, a polarized retroreflective sensor should be used to prevent proxing. Proxing is when an object with a shiny surface returns enough light to the sensor to mimic the photoelectric beam coming back from the reflector and causes the object to not be detected. In a polarized retroreflective sensor, the emitter sends light waves through a filter that aligns them on the same plane. These light waves bounce off the reflector, and return to a vertically polarized filter on the receiver. When this polarized light reaches a shiny target, the light is reflected back to the sensor on the same plane as it was emitted and is blocked by the filter, signaling a broken beam. When the polarized light hits the reflector, however, it is scattered into unpolarized light with light waves on both the horizontal and vertical planes. Some of this light will pass through the receiver’s filter and the sensor will detect the reflector and know the beam is unbroken. 

A retroreflective-mode sensor offers a convenient alternative to opposed mode when space is limited, or if electrical connections are only possible one side of the installation. Retroreflective-mode sensors offer relatively long ranges. 

• Second-highest excess gain mode 
• Polarized model available to prevent the beam from proxing off shiny objects 
• Coaxial optics available for clear objects and precision 

Diffuse-mode sensors contain the emitter and receiver in the same housing but do not use a reflector. Instead, they detect an object when emitted light is reflected off a target and back to the sensor. With a diffuse-mode sensor, the object is detected when it "makes" the beam; that is, the object reflects the transmitted light energy back to the sensor. They are significantly affected by the reflectivity of the target objects, which can drastically shorten their range. These sensors should not be used in applications with very small parts that need to be detected, in parts-counting applications, or where a reflective background is close to the object to be sensed. Diffuse-mode sensors are very convenient and are often used when opposed or retroreflective-mode sensors aren't practical.

• Low installation effort
• Does not require a reflector

Excess gain is a measurement of the amount of light energy that the receiver element detects. A sensor needs an excess gain of one to cause the sensor's output to switch "on" or "off." However, contaminants in the sensing environment such as dirt, dust, smoke, and moisture can cause signal attenuation, so more excess gain will be required to receive a valid signal. Excess gain may be seen as the extra sensing energy available to overcome that attenuation.

An excess gain chart shows how much light energy is available at a given distance. The dirtier the environment, the more excess gain will be needed to overcome it. The graphs are logarithmic, which allows for a concise overview of data that varies by several orders of magnitude. Each minor tick increases by a factor of 1, and each major tick increases by a factor of 10. For example, starting at the origin and moving up the Y-axis, the graph's ticks represent 1, 2, 3, etc. Once the tick gets to 10, the ticks represent 10, 20, 30, etc. When the tick gets to 100, then the ticks represent 100, 200, 300, and so on.

I have access to a Banner engineering photoelectric sensor S18SN6FF100Q.

Originally it was my intent to take the wire from the sensor itself and wire the other end to a usb and plug it into my computer. Im a hobbyist programmer and so im still learning the basics so im not sure how to go about reading it that way so i had the epiphany that I could just use my arduino for the same effect. I just started my degree for computer science and I'm a complete novice with electronics so I'm not sure if my original usb idea would have even been possible. the above link is to banner electronics and that specific sensor and has all the data required hopefully.

my question is how would i wire this sensor to my arduino.

It looks like you require a power supply of 10-30 volts DC at up to 35mA.
So say 12 volts DC.

The 2 outputs of the device you have appears to be NPN transistor (open collector) outputs.
You need a voltage divider for each output to ensure that no more than the maximum voltage appears on the arduino pin (for a Uno, its 5 volts)

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Each voltage divider would be made of 2 resistors, say 12k and 8.2k (for a 5 volt arduino and 12 volt power supply for the device) :

  +12v ----- 12k resistor ----- device output ---- 8.2 k resistor ---- Ground ( common)

You'd connect the arduino pin to the point marked device output and the ground of the Arduino to the ground of the device.

Also look at an opto-coupler as an alternative (and possibly nicer) way of doing this.

Thank you, and the wiring diagram is EXTREEMLY helpful ,but whether its an appropriate sensor i wouldn't know. these are the sensors that trigger our glue computer that's all i know. since this is what my job uses and stocks its why im wanting to use it.

For my project, the sensor is just to count boxes. i also want to do something like a tachometer to read the speed of the machine. the arduino would have to log both the rate of boxes per hour and the speed of the machine so that the data could later be graphed. right now my plant has a system that simply counts boxes but doesn't keep track of the machine itself which got me thinking and i started throwing around ideas. I know that is redundant and probably stupid but its mainly just a learning opportunity since i havent really done anything interesting with my arduino and im still new to the world of electronics. i also want to do a windows forms app that would receive the data and then graph it and do all the fun stuff. Obviously the Arduino would have to be able to store all of the data until I could get it home and plug it into my computer and upload it to that. but i wanted to start with the sensor and see if it was even possible

OK. The diagram I supplied could even be simplified as @vwmarle pointed out in the case that you are using a sensor dedicated to your application. If, however, you are simply going to 'tap in' to a sensor which is currently also being used for something else, like the gluer machine, you have to be much more careful. My diagram also did not respect anything else using the sensor.

Maybe you'd be better of with a dedicated cheap infrared proximity sensor: example

To get data from the arduino so you can process it later on a PC, maybe look at an SD card module.

6v6gt:
If, however, you are simply going to 'tap in' to a sensor which is currently also being used for something else, like the gluer machine, you have to be much more careful.

I didn't think of that either.

If so, add a diode between the pull-up resistor and the sensor, anode to the arduino (so the arrow away from the Arduino). This way any higher voltage on the sensor pin can not reach the Arduino, but the sensor can still pull low the pin. Maybe best to add an additional resistor between the diode and the Arduino, to limit the current as the diode recovers (the first moment upon change of voltage a diode conducts in reverse).

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(hope the ASCII art is clear enough :-))

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