Electronics > Projects, Designs, and Technical Stuff

Tricking Metal Sensor

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bostonman:
Long story short, I'm looking to trick a metal sensor on a machine to think it's detecting metal.

What could I use to do this?

I'm thinking maybe just sending voltage through a coil that's next to the sensor. Probably a simple circuit like a transistor, a pull up on the collector, driving a coil. I'm uncertain how metal sensors work, so I'm uncertain what would be affective.

minifloat:
Guess what you don't want to use is an actual piece of metal. SCNR

Do you have more info about the metal detector?
Which metal specific properties is it using?
Ferromagnetic
Eddy current
...

br mf

David Hess:
I suspect it detects eddy current.  I would try using an adjacent coil and shorting it.

bostonman:
This is for a friend who has a work related problem.

Tubing goes through a "metal detector" to detect metal, but the metal parts tend to get lodged, and they'd like to increase the size of the tube. Unfortunately larger sized tube will not fit through the "metal detector" (which is a ring and looks like a custom built module).

My idea was to bypass the entire thing, use a larger tube with a metal detector, and the output go to a coil (?) that will trick the real detector into thinking it has a piece of metal passing by it.

I thought of a metal detector that outputs a high when it detects (or some sort of pulse) feeding the base of a transistor, a pull up on the collector feeding a coil that sits in the actual metal detector, and obviously a snubber diode across the coil.

This way the metal triggers the metal detector, turns on the transistor, energizes the coil with the pulse, creates a magnetic field, and turns off.

duak:
If this is an industrial machine the existing metal detector may run on 24 VDC and provide a DC level back to the controller.  If you find a larger metal detector it may very well have a similar interface and it should be just a matter of working out connectors and wiring.

Here's a general introduction to the types of industrial sensors and how they can be used: http://www.ia.omron.com/support/guide/41/introduction.html

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