# Detecting amount of money in a area

I was wondering if my idea would work after my last one failed. Since dollar bills have slight traces of metal in them, I was wondering if you could detect the amount of bills in a certain area based on the strength of the pull. The area would be about 15cm x 7cm x 4 cm. Is there a sensor that can be this accurate? Is this idea possible?

I was thinking if there was any surrounding metal around the device (that would remain stationary) you could just zero out the measurement. I’m sorry if I’m being too broad, but the only thing that I found while doing research is something talking about drug money.

No.

Why not?

YoungsterSP: Why not?

How about, you post some links to the information that makes you think you can.

YoungsterSP: Why not?

Because magnetic attraction follows an inverse square law and anyway the metal band in money in not magnetic it is aluminum.

Okay, so my objective is to accurately tell how many bills are in my area. I'm planning on using a KY-035 analog magnetic sensor to detect the magnetic pull. So in essence it would be the more bills the higher the reading. I want to use the reading to calculate the amount of bills in the area. My question is would this be possible, because I do not want the small amount of magnetic ink on the bill to be so small that the sensor can't read it. Is there a better sensor I can get for less that \$10? Oh and there is magnetic ink on the bill itself it is not a band of aluminum.

YoungsterSP: My question is would this be possible

I believe that has been mostly answered. You never posted any links as requested. From a physics point of view you have multiple problems the greatest of which are: 1) sensitivity - the magnetic susceptibility of the bills is almost infinitesimal. 2) linearity - you are trying to measure a volume equally with sensors that by nature have a non-linear response.

YoungsterSP: I was wondering if my idea would work after my last one failed. Since dollar bills have slight traces of metal in them, I was wondering if you could detect the amount of bills in a certain area based on the strength of the pull. The area would be about 15cm x 7cm x 4 cm. Is there a sensor that can be this accurate? Is this idea possible?

I was thinking if there was any surrounding metal around the device (that would remain stationary) you could just zero out the measurement. I'm sorry if I'm being too broad, but the only thing that I found while doing research is something talking about drug money.

Might be easier to weigh the dollar bills using a nice set of scales.

If you reckon it is possible to do some magnetic measurement... then get a powerful electromagnet and see if it attracts the dollar bill.

Link proving money is magnetic: https://www.stevespanglerscience.com/lab/experiments/magnetic-money/ Link to the sensor that I'm not sure will pick up the bills:https://tkkrlab.nl/wiki/Arduino_KY-035_Class_Bihor_magnetic_sensor

I believe that every bill is printed with the same amount of magnetic ink so it is pretty linear unless you could explain why. Also in the link it explains that if you fold a bill and get a neodymium magnet it attracts. I don't think the magnetic force is infinitesimal, because I could attract a bill with my magnet. Do I need a better sensor to detect the bill and if so which one?

YoungsterSP: Link proving money is magnetic:

It certainly sticks to the fingers of shysters.

...R

If say a dollar bill weighs nearly 1 gram.... the ten of them would be around 10 gram.

YoungsterSP: Is there a better sensor I can get for less that \$10?

You're talking about picking up an infinitesimally small amount of magnetism. The sensor that can read that is not going to be in the bargain bin.

Why don't you take a few minutes to look at the numbers. What is the magnetic susceptibility of a dollar? What is the sensitivity of your sensor? Get the numbers and see. I think you'll see that while a dollar technically has some magnetic ink in it, a dollar is not really very magnetic.

YoungsterSP: I believe that every bill is printed with the same amount of magnetic ink so it is pretty linear unless you could explain why.

The relationship of magnetic field to distance is non-linear, as Grumpy Mike explained early on. You seem to think you can argue this project into existence. That's not how development works.

Gravity follows the inverse square law not magnetism which follows the inverse Cube law.

Why can't you stack the bills?

A number of years ago an equipment salesman was demonstrating a new check reader/sorter to some prospective clients. He was using out shop for the equipment and our check processing system.

While running a bunch of checks through the reader, one of the clients was asking what happened when ctual currency got mixed in with the checks. The sales man didn't know. So, I pulled a \$5 bill out and put it in witha bunch of checks. It was read, showing garbage where normal checks showed bank#, account# and amount.

All currency will show it has some magnetic ink just in case currency is included in a bank's check processing. Yes, it does really happen!

The way it works it the magnetic ink is magnetized by a magnet, obviously, and then a few milliseconds later, that area passes a magnetic sensor that digitizes the magnetic signal for the computer to process. A few milliseconds later, the magnetism has faded.

One of the problems the OP faces is determining which country the currency is from. The US gets Canadian currency, some times.

Paul

Ok so I understand now that it is better to go with weight instead of magnets. Thank you all very much!

Also, aarg I wasn’t trying to argue. I was simply trying to get more information. I was asking on the forum for a reason and that reason being I’m not the very brightest in arduino. When I asked you about a hole in the info you gave me you told me I was arguing with you... I wasn’t trying to argue and I apologize if you thought so, but next time please don’t shut someone’s idea down anymore without reason or not enough reason. It made me think that whatever solution I gave would be shut down and I would have to ask even more questions on why. I’m sure someone else in my position would feel the same way.

You seem reluctant to explain what you REALLY want to do.

Years ago, one of the grocery chains that is now part of the Kroger family brought all the currency and checks from all the stores to a central processing site. There many people worked in a locked room separating the checks form the currency and then segregating the currency by type of paper. 1\$ bills on one table, 5\$ on another, 10\$ on another, an so on.

Then the currency was bagged and weighed and the value estimated. Then all was sent to their bank for real counting and posting to the company account.

They had a real problem with \$ slipping into people's clothing, etc.

So your plan to weigh does have real, but not practical use.

Paul

I kind of had something different in mind that it would still be useful for, but thank you for your concern :)

what is it?