Using a sensor to sense the presence of copper wire.

[A Former User]

what about when sliding the wire into the top hole you give it a + charge and the base a - charge with a circuit that will do when the 2 touch.

If the range of wire size was tighter, this would probably work well. But with the wide range of sizes, trying to make contact with the smallest sizes would be a real pain.

[Schlog]

@moparjay
how about an "S" shape input tube any size would have to touch the tube on the inside the "S" shape tube can be any size you like.

[executivul]

1. Optical detection: a light source on one side of the hole and a phototransistor on the other, read as analog values since the small wires won't completely cover the light source

2. Inductive sensor, a coil around the hole, and some form of detecting the change of inductance, start by making a small coil and test with a LCR meter

3. Capacitive sensor, open air dielectric, plates across the hole, the wire and operator (even holding the insulated wire) will change the capacitor response a lot, test with some capacitive/touch sensing circuitry.

[A Former User]

Thanks to all that have given input. I'm going to give in and simply use the momentary to open the cylinder (normally closed). It's just too easy. And going automated is not worth the added expense, as this single cylinder prototype will be duplicated to almost (100) cylinders....each completely independent from one another. Thank you!!!