Cheap glue detection system

Hi,
I am trying to make a machine which glues two pieces of paper with liquid glue. I need a DIY and cheap way to detect the glue on the paper for reliability. The glue is clear like the one in the attached picture.

Thanks for any suggestion.

new-bottle-of-clear-glue-clear-glue-washable-dries-clear-adhesive-30b7359f600dcabd702fd6a70590e047.jpg

Hi, Is the glue water based, will it conduct electricity. You could some how check with two electrodes touching the paper, if the glue conducts you should be able to detect current flow.

Tom... :) Is the paper a long strip or just squares of paper?

Without knowing the glue's composition tricky, but you could experiment with different wavelengths of UV light to see if it shows up differently and detect the scattered light. Or perhaps try shining different visible or UV light through it and detect any increase or decrease in intensity.

Try adding some invisible ink from a UV security marker to the glue, then use an UV led to reveal its presence.

A couple ideas:

  • The glue coated paper should be more reflective than uncoated paper so you might be able to use a light source and photoresistor, something like the IR sensors commonly used in line followers.
  • Use a solenoid valve to blow a puff of compressed air at the papers in a way that will cause them to blow apart if not glued. Use a sensor to detect if the top paper lifts.

TomGeorge: Hi, Is the glue water based, will it conduct electricity. You could some how check with two electrodes touching the paper, if the glue conducts you should be able to detect current flow.

Tom... :) Is the paper a long strip or just squares of paper?

The glue is water based. So it should conduct electricity. But glue residues may stick to the electrodes and cause them to fail.

The paper is rectangle shaped.

theinlinaung2010: The glue is clear like the one in the attached picture.

If it was acceptable to colour the glue you could examine it with a camera and image processing software - but not with an Arduino.

Are you building the machine that applies the glue or are you using ready-glued paper? If your machine is applying the glue maybe it would be sufficient to test the last millimetre or so of application on the assumption that if that is correct all the earlier area is correct. Or can you test the machine after it has applied a layer of glue to make sure that glue is still issuing from all the nozzles? How is the glue being applied? Have you a diagram of the machine?

...R