Off Topic - Edge Sensor

I'm looking to find sensors that can detect the edge of a running web and output a variable signal.

The sensors need to be immune to ambient lighting.

I need to track both edges of a running paper web, compare the sensor outputs, and drive a bi-directional motor amp running the motor either CW or CCW to achieve a Zero Error between the two sensors - or in other words web tracking.

Thanks in advance.

Michael

Is the web on a roll face somewhere? Depending on ambient conditions we routinely accomplish this two ways. For areas that aren't extremely dirty, dusty, just use two pinpoint reflective photosensors that reflect off the chrome roll face. Position the sensors close enough to represent your tolerance. As long as one sensor is seeing the roll and the other sensor is not (on the web), then all is good. If both sensors are seeing, drive the tracking one way. If neither sensor is seeing, drive the other way. No need for analog. The sensors are mounted to the tracking device so that they move with the adjustments.

If the area is dirty, then we use optical temp sensors instead. Again, same prinicple but the sensor is sensing the temp difference between the chilled roll face and the web.

Some other options are optical or contact paddles often seen on FIFE systems. Another product is SCAN-A-LINE which does output an analog signal based on coverage by the web. We used to use the SCAN-A-LINE products often, but found the optical temp sensors were more accurate and predictable.

Fife makes top notch stuff.

http://www.fife.com/fife_products_sensors.asp

Paul

If you are going to use it in a plc set-up VIA analog input, Look at the Banner Line of sensors they have one 0-5 volt out put. I used it many times on Fabric winding equipment. Let me know it you need a part number.

Also take a look at KEYENCE, they are a bit more expensive, but well worth the money! And their Sales and Techs are awesome at solving your engineering questions, and helping impliment the sensors to best suit your needs! www.keyence.com

Ive used web systems from erhardt leimer many times with no problems
http://www.erhardt-leimer.com/index/Kanada/CA+Position+sensors--2602.html

Derek

My choice for this application

I thought that I'd leave feedback on my final choice.

I went with the Banner D10UNFP LED ARRAY/IN 0-10vDC/OUT attached to the fiber optic cable sensors PIRS1X166UMPM.75
I purchased two sets - 1 for each side of the web and taught them to see maximum output when array fully covered. Using these two through a simple resistor bridge gives me the Plus/Minus output that I needed to control the Bi-Directional DC Motor Drive. The sensor range is +/- 0.75"

I found these Banner Sensors to be the most reasonably priced sensor for my application.

Thanks to everyone who commented.

Best Regards
Michael

MBHladilek said:

I thought that I'd leave feedback on my final choice.

I went with the Banner D10UNFP LED ARRAY/IN 0-10vDC/OUT attached to the fiber optic cable sensors PIRS1X166UMPM.75
I purchased two sets - 1 for each side of the web and taught them to see maximum output when array fully covered. Using these two through a simple resistor bridge gives me the Plus/Minus output that I needed to control the Bi-Directional DC Motor Drive. The sensor range is +/- 0.75"

I found these Banner Sensors to be the most reasonably priced sensor for my application.

Thanks to everyone who commented.

Best Regards
Michael

Click to expand...

So did you get fancy and make the response proportional to line speed? etc

What do you do for the extreme limits ?

Good point about the response proportional to speed - scaling output. Fortunately this machine runs between 30 and 60 fpm and the mechanical gear ratio driving the parallel rolls for web alignment is sized to give a fairly fast response time to position drive rpm ratio.

The parallel rolls have a +/- travel of 2". I use standard limit switches to prevent overrun (disable drive sound operator warning)