Light curtains

Hey guys,
I know this isn't direclty PLC related but I'm hoping someone here would be willing to help me.

I'm needing some type of "light curtain" that isn't safety rated. I need to detect a span of approx. 36" wide by about 20' long. I just need to know the presence or absence of something in this area. I know banner makes one up to 11" (I think), but that's not nearly wide enough.

Any help or ideas is greatly appreciated.

Jeff

What are you trying to detect?

Even safety light curtains have resolutions which leave 'dead areas' through which small items can pass undetected. (usually between 10-30mm)

Keyence do a safety curtain which they claim will span this area (1260mm x 7M - 20mm resolution), but I expect it will be very expensive.

Heres a link:
Expandible Safety Curtain

They also do a range of wide area laser sensors, though nothing which gets anywhere near the scope you need with one unit!

regards

Anthony

Thats a mighty tall and long order ya got there

If its not a safety issue and you just need to detect the object there are several ways to do this that may be cheaper than light curtains.

1. Maybe use photoreflective or similar to detect package in a "zone", should be easy to determine height and length. You can space the detectors as needed to get the resolution needed...ie if all you need is to KNOW that the package is exactly that hieght and length then space the sensors accordingly, use more sensors to detect too long too short etc.

2. The use of measuring sensors/devices, there are a variety on the market now.

3. A very simple aspect is using an encoder and 2 sensors..if you know the speed of the conveyance system then if sensor 1 is blocked at x time then sensor 2 is blocked at y time then and x sensor clears within z time then you can calculate lenght.....hieght would be just one sensor set at appropriate hieght.

I would have to play with it to see what could be done but this is in the area of where I would start.

It really depends, STI and AB sell light curtains ( the same ones I think and I think they are name branded by others as well...SICK maybe. May be possible to have some custom built.

As to what I'm trying to detect. I have a hoist and grippers that lower and clamp on bricks that have been spread apart. The bricks are two layers tall.

I need to detect if the grippers have left any brick after having picked off the table. Unfortunately, the grippers have no compliance. If a single brick is wider than the one next to, the narrower brick gets left behind.

I currently have two photocells looking diagonally across this area, but as wide and as long as it is, they will miss some remaining brick.

I realize I can build a photocell array myself, but I would need at least eight photocells to do this. I am hoping someone makes a light curtain that's not safety rated ($$) that would simply give a single output to the PLC if any one reciever cell was blocked.

Thanks for the replies.

Jeff

Check out the Banner 'Mini-Array' A-Gage systems. They're meant for measurement but the can span a large area.

a span of approx. 36" wide by about 20' long

Click to expand...

I'm trying to uderstand why you need a 20 foot range, should that be 20 inch?

In which case I would imagine you could use a long range through beam sensor with reflectors/mirrors to span the area.

Yeah, after thinking about it, 20' is a little out of the ball park. I believe 12' is closer to what I need.

Again, I was just wishing someone made a canned emitter/reciever array that's not for safety purposes. I've searched with google, and every hit I get, is for safety light curtains, ditto Global Spec.

Thanks,
Jeff

sti has non-safety light curtains
http://www.stiscanners.com/products/scan/index.html

I've just had a look at Banner's web site (following Bernies advice) and they do a range of inspection sensors which don't quite meet your requirements but maybe you could figure a way to use two or three to achieve your objective.

Banner Measurement & Inspection Sensors

Anthony

Oops
Posted link to wrong page!
try this one instead.

http://www.bannerengineering.com/products/measure_inspect/bmlv/

Could an ultrasonic sensor be used? I have only limited experience with them, used to detect whether paper is present in certain zones, or the height of plastic stacks.

http://info.bannersalesforce.com/xpedio/groups/public/documents/datasheet/48454.pdf

Page 6 has the detection zone specs.

Thanks all of you,

I've got plenty of research to do when I get back to work tommorrow.


Jeff

A COUPLE OF MANUFACTURERS TO RSEARCH. STI, KEYENCE, BANNER, BALLUFF, SCHMERSAL, AB. ALSO COST MAY BE AN ISSUE, BUT WITH A 3' X 12' AREA YOU MAY BE ABLE TO USE A SAFETY MAT. AB AND SCHMERSAL ARE GOOD OPTIONS.

Is it possible to move a photoeye across the field of view? A long strip of reflective tape could be placed on the other side. The eye could be moved by a linear slide arrangement and a servo or stepper motor.

IT IS POSSIBLE. A PNEUMATIC SLIDE MAY BE EVEN MORE COST EFFECTIVE. LOOK AT HOERBIGER ORIGA OR NEUMATICS PRODUCTS.