Silver coin finder

[interoth]

Saw this video


I don't live in the US but this tingled my interest.
He looks through dimes to find silver ones that are worth around $2 each.
First thing I thought is if that could be automated?
Would probably have to be detected with resistance if anything.

[chrome]

There are quite a number of things you can test:
Refraction, using an inductive sensor, resistance, weight(?)

[Rerouter]

hmm lets see whats difference ah the non silver ones are a high percentage of nickle, and nickle has a nice and high permeability (400) while silver and copper are all the way down near 1, so i would say, use a feild effect sensor to measure the starting feild strength, magnetise it one way, and then the other with the same amount of energy, e.g. constant current and constant time, and measure the remaining feild,

because the nickles permeability will make it not fall back to the same starting feild strength by a much greater margin, it should be very clear what material one is to the other,

and this will not be effected by tarnish or damage,

[Bored@Work]

What do you want to automate? He seems to be very fast and it would be hard to beat him. He spends most time opening the roles, and almost no time inspecting the coins. Your automated device would have to include a fast role opening mechanism to beat him. If it doesn't, and if your device requires manual opening you spend almost as much time as he does.

[digsys]

Why not just test the whole roll as is. Move it across the field while watching if the meter spikes !?
Do a control run as a reference.

[Rerouter]

well.. if it was using my method, he would be looking for the dip,.... either way i dont know how focused you can make a feild effect sensor for measuring coin against coin...

[digsys]

... either way i dont know how focused you can make a feild effect sensor for measuring coin against coin...

Wouldn't matter, you only need to know that THIS roll has an anomaly, unless every single roll has at least 1 silver ?

[G7PSK]

You could also use some form of optical system as well as the silver ones are a slightly different colour. But the cost of automating would be such that you would have to start sorting the coins by the ton rather than a few hundred dollars worth.
When the communists fell from power in Romania some Germans went there with bulk tipper truck and hauled out coins for the scrap value of the metal, having exchange German currency for them as the Romanian money was worth so little in exchange.   

[mikeselectricstuff]

As silver has very high conductivity, it should be possible to detect  it by differences in eddy current loss. Set up a thin coil driven with a few hundred KHz, run the rolls through it and look for increased loading - an easy way to do this is to make it into a tuned circuit, ping it with  a transient and measure the ring-down time. 

[Kevin.D]

As has already been said .Your  going to find it very hard to beat optical recognition by a person (or camera and laser reflection if you where doing millions),he's very fast you can scan hundreds of coins and see the silver ones almost instantaneously  .By far the slowest bit for him here is the unwrapping the coins, or  stacking them in piles if they arrived loose .

[mikeselectricstuff]

As has already been said .Your  going to find it very hard to beat optical recognition by a person (or camera and laser reflection if you where doing millions),he's very fast you can scan hundreds of coins and see the silver ones almost instantaneously  .By far the slowest bit for him here is the unwrapping the coins, or  stacking them in piles if they arrived loose .

..so an inductive solution, assuming you could get one to worth through the wrapping,  would potentially eliminate the slowest part of the process.

[Psi]

Personally I wouldn't be putting something like that on Youtube.

I dunno about where that guy lives but some countries still have serious fines for defacing money, which he would be guilty of if he melted them down for the metal.

[mikeselectricstuff]

He doesn't need to melt them - just sell them

[WhyMe]

A couple years ago I was searching half dollars for silver. I would buy $1000 dollars of halves each week and go through them. In a couple months I would end up with 1 or 2 rolls of silver halves, mostly 40% silver and a couple loose 90% halves. I was even starting to search dimes and nickels for silver. Nickels are hard because you have to look at the reverse side and look for the mint mark. Anyway I ended up almost tripling my money in 6 months. I even started looking at pennies for the old Wheaties and Indian head pennies which was very time consuming so I bought one of these:

http://www.pennysorter.com/

It compares the coins against a sample one held by the machine. It can then be dialed in to accept coins that match or reject them. This could probably be worked on to do dimes or nickels. I often thought of taking a coin mech from a vending machine and making my own coin sorter with it. Coin mechs in the US have a little switch on them that accept or reject Canadian coins. Any silver coin would be sent down the reject slot of the coin mech if the switch was set to reject Canadian coins. I've been out of this for a time, but this post might get me doing it again 

Here's a site that gives current melt values of coins:

http://www.coinflation.com/

[Sionyn]

ive wondered if you could fool those gold detector machines that identify the metal through resistance 

[Sionyn]

found some more info
http://shorinternational.com/TestGoldGXL24.php



i wonder if it infallible to any tricks ?