# Coin Analyzer?

#### thatoneguy

Joined Feb 19, 2009
6,359
Magnetic field induces current in copper/silver, altering path of coin.

Not enough current induced in zinc to alter path.

Link for one not much for detail. These are in vending machines as well for finding slugs.

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#### gerty

Joined Aug 30, 2007
1,270
Zinc is lighter than copper. Maybe it weighs them ?

#### praondevou

Joined Jul 9, 2011
2,942
I read somewhere they recognize coins by the speed they are falling (with two light barriers. The speed is determined by the braking force through a magnetic field... much like this: http://www.youtube.com/watch?v=nrw-i5Ku0mI

Don't know if your specific device works like this too.

#### thatoneguy

Joined Feb 19, 2009
6,359
Zinc is lighter than copper. Maybe it weighs them ?
Some sorters work on this principle, but it is VERY slow compared to the magnetic test. 1 penny every other second since the scale/balance takes time to move/reset, vs several pennies per second by slightly altering path or measuring timing.

--ETA: European patent on sorting coins with magnetics.

#### tracecom

Joined Apr 16, 2010
3,944
I set up a Hall effect sensor and positioned a magnet where it just triggered the sensor. Then I placed a silver quarter between the magnet and the sensor, followed by a zinc quarter, in the hope that one would block the magnetic field more than the other. It didn't work.

#### thatoneguy

Joined Feb 19, 2009
6,359
Penny Sorting Describes a method using the speed difference in a aluminum channel with magnets to sort copper pennies from zinc.

Video Demo

The main limitation of this technique is the speed at which you can sort pennies. If you drop a copper penny down the shoot closely followed by a zinc penny there is a chance the zinc penny will bump into the copper penny. One way around this problem is to use an alternating magnetic field. An AC magnetic field will repel a conductor. If you attach a coil to a 60 Hz AC power supply the coil will push the conductor away from it. I have used this effect to levitate aluminum plates. I have not attempted this with pennies yet, but the idea is to simply drop pennies from a hopper above an AC electromagnet. As the pennies fall through the AC magnetic field they should be kicked away. Copper pennies would be pushed farther away than zinc pennies. A fence below the electromagnet can be used to direct copper and zinc pennies into different hoppers.