Just detect the presence with a microswitch to pull an arduino pin to ground

Vacuum/cup pickup eliminates any issues with magnets too..

I really want a solid state solution if possible.

 

Just to get back to the EM as the detector, am I using induction for this?

 

What about using a Honeywell SS400 series hall effect sensor, using a bi-polar latch version, the pickup cycle would latch it, and the demag cycle unlatch it.
Max.

 

Sorry to come to the party late, but how about driving the coil with AC and watching step decrease in average current when something magnetic contacts the two poles? Not only does it detect the presence of material in contact, but if you switch the current off at the correct phase or taper it off, you will avoid magnetizing the core.

(Edit: Changed "...step increase in current..." to "...step decrease in average current...")

 

What about using a Honeywell SS400 series hall effect sensor, using a bi-polar latch version, the pickup cycle would latch it, and the demag cycle unlatch it.
Max.

I think I follow you Max. But would this require the plate coming down to be magnetized?

 

Sorry to come to the party late, but how about driving the coil with AC and watching step decrease in average current when something magnetic contacts the two poles? Not only does it detect the presence of material in contact, but if you switch the current off at the correct phase or taper it off, you will avoid magnetizing the core.

(Edit: Changed "...step increase in current..." to "...step decrease in average current...")

Interesting. Would this detection also hold the magnetic material? I want to detect without actually holding it in one case, and hold it without detection in the other.

 

I think I follow you Max. But would this require the plate coming down to be magnetized?

If you want to detect a plate whether mag'd or not, then a regular ferrous metal hall effect switch will just tell the presence of steel plate.
Max.

 

If you want to detect a plate whether mag'd or not, then a regular ferrous metal hall effect switch will just tell the presence of steel plate.
Max.

That sounds like the most elegant solution! Let's say I embedded that in the potting of the electromagnet, would that interfere at all with the detection of the plate? It would be under no power for detection of course.

 

Interesting. Would this detection also hold the magnetic material? I want to detect without actually holding it in one case, and hold it without detection in the other.

If you don't run much current through it, it would not hold much of anything. Also, if you use is as the inductor in the resonant circuit of an oscillator you can just watch the frequency shift downward as the inductance increases. Measuring the current would probably be the easier of the two.

 

If you don't run much current through it, it would not hold much of anything. Also, if you use is as the inductor in the resonant circuit of an oscillator you can just watch the frequency shift downward as the inductance increases. Measuring the current would probably be the easier of the two.

Okay! Added to the test queue, thank you for the ideas!

 

That sounds like the most elegant solution! Let's say I embedded that in the potting of the electromagnet, would that interfere at all with the detection of the plate? It would be under no power for detection of course.

As long as you observe the sense distance, the typical sensitivity of the circular threaded type vary sense distance with dia.
As for potting there should be no problem and you would need to assure the set distance before potting.
Max.

 

As long as you observe the sense distance, the typical sensitivity of the circular threaded type vary sense distance with dia.
As for potting there should be no problem and you would need to assure the set distance before potting.
Max.

Excellent. Thanks again for the time!