Coin Identification Using Eddy Currents

Team Members

Frank Lindauer Electrical Engineering

Mohammed Alhusainan Electrical Engineering

Momin Garrouch Electrical Engineering

Industry Advisor

Garrett Durland CSU BSEE 2005

Supervising Professor

Dr. George Collins

Project Team

Project Overview● Induce eddy currents by rolling US coins through a

stationary magnetic field

● Identify coins by measuring effect of induced current by timing coin roll using photointerrupters

● Faraday’s Law of Induction & Lenz’s Law:

Project Importance● Eddy currents are widely used in commercial applications

○ Non-destructive evaluation testing, proximity sensing, metal detection

○ Robust, inexpensive to design and produce

Project Objectives - Semester 1 ● Research & Design a system that uses eddy currents to

identify coins

● Build ramp display to demonstrate operation of system

● Integrate photointerrupter sensors with microcontroller

● Induce eddy currents in coins with permanent magnets

● Record & Analyze initial test data for all coin denominations

Current workPhase 1:

● ramp.

● Photo-interrupters communicate with the Arduino to provide us with readings.

Phase 2:

● Interrupt Service Routine programming.

Phase 3:

● Testing.

Why the Arduino Nano? (ATmega328)

● Size(0.73”x1.70”)

● Cost

Operating Voltage

5V

Input Voltage 7v-12v (20v)

Digital pins 14

Analog pins 8

Flash Memory 2KB

Clock speed 16MHz

Testing

● Foreign Currencies.

Penny Nickel Dime Quarter

Composition 2.5% CuBalance Zn

25% NiBalance Cu

8.33% NiBalance Cu

8.33% NiBalance Cu

Testing a Quarter

Testing a Penny

Data Analysis

● The way we intend to program the controller to detect rolled coin is by defining a unique time interval for each coin type

● Ran 10 different rolls for each coin type and recorded the max and min values observed for each coin type.

● Measured mean and standard deviation for each coin to better analyse the data

Data Analysis

Min = 2.24 secondsMax = 2.59 secondsMean = 2.398 secondsStandard Deviation = 0.12709

Min = 2.30 secondsMax = 2.81 secondsMean = 2.573 secondsStandard Deviation = 0.16391

Data Analysis

Min = 2.62 secondsMax = 2.94 secondsMean = 2.775 secondsStandard Deviation = 0.11385

Min = 1.99 secondsMax = 2.38 secondsMean = 2.17 secondsStandard Deviation = 0.10371

Data Analysis

Data AnalysisPossibly ways to decrease the Standard deviation for more accurate readings:

- Improve inner acrylic surface

- Use stronger magnetic field

- Change ramp angle

Budget

● Price vs Quality trade off

● Its all about finding the right balance between quality and Price.

$4

Plans For Next SemesterMust haves:

● Get unique time interval for each coin type

● Program Arduino board to display coin type and total roll down time

● Use an electromagnet and Integrate potentiometer to vary the magnetic field

● Integrate a Hall Effect sensor

● Program the microcontroller to display magnetic field strength on the LCD

Plans For Next SemesterNice to have:● Etch circuit on circuit board

● Mechanically sort coins into different bins

● Make system compatible with other foreign coins

● Involve a high proximity sensor to possibly detect coin composition