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This instructable demonstrates how to use an electromagnet, a simple amplifier circuit, and a personal music player to induce signals into a magnetic stripe card reader, causing it to think that you have swiped a card through it.
This instructable assumes that you have basic knowledge of electronics and a cursory understanding of C++.
NOTE: This device is useless unless you already know the contents of a particular magnetic stripe card that you want to emulate. Thus, you can't use this device to do Something You're Not Supposed To Do unless you've already done something naughty to obtain the data from a magnetic stripe card you're not supposed to have.
Don't do naughty things. Your mother wouldn't like it.
This instructable assumes that you have basic knowledge of electronics and a cursory understanding of C++.
NOTE: This device is useless unless you already know the contents of a particular magnetic stripe card that you want to emulate. Thus, you can't use this device to do Something You're Not Supposed To Do unless you've already done something naughty to obtain the data from a magnetic stripe card you're not supposed to have.
Don't do naughty things. Your mother wouldn't like it.
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Signing UpStep 1How it works
Before going any further, read the document I've attached to this step, "A Day in the Life of a Flux Reversal" by Count Zero. This document is pretty much the bible on how magnetic stripes work, and you need to understand how data is encoded on to them and the basic formatting of the tracks on a given magnetic stripe card. I'm going to go get a cup of coffee; have it read by the time I get back.
.......
Finished? Good.
As you will have learned from your reading, data is encoded on to magnetic stripes by means of magnetic flux reversal in the segments on the stripe. When the card is swiped past the card reader, the changing magnetic field of the passing flux reversals induce a current in the reader element, which is then decoded into binary bits, and the original data stored on the magnetic stripe is reconstructed.
So, in order to emulate a particular magnetic stripe, all we need to do is find a way to recreate the pattern of the way its magnetic field changes as it's being swiped past the reader. How are we going to do this? With an electromagnet!
As you may already know, an electromagnet is basically just a solenoid (coil of wire). When an electric current is passed through the coil, a magnetic field is created. By turning the electromagnet on and off rapidly, we can replicate the changing magnetic field of a magnetic stripe swipe.
The final piece of this puzzle is how to control the electromagnet. Well, we're trying to recreate a particular waveform of current through the solenoid in order to create a particular waveform of magnetism. What's a common way of storing waveforms and converting them to electric current? Sound files! So, all we have to do is encode the highs and lows representing the desired flux reversal pattern into a .wav file and play it back on an iPod or similar music player through the solenoid.
Music players designed to play sound through headphones do not produce enough current to drive the electromagnet in this project, so we will also have to construct a basic amplifier that the signal must be passed through before going to the electromagnet.
.......
Finished? Good.
As you will have learned from your reading, data is encoded on to magnetic stripes by means of magnetic flux reversal in the segments on the stripe. When the card is swiped past the card reader, the changing magnetic field of the passing flux reversals induce a current in the reader element, which is then decoded into binary bits, and the original data stored on the magnetic stripe is reconstructed.
So, in order to emulate a particular magnetic stripe, all we need to do is find a way to recreate the pattern of the way its magnetic field changes as it's being swiped past the reader. How are we going to do this? With an electromagnet!
As you may already know, an electromagnet is basically just a solenoid (coil of wire). When an electric current is passed through the coil, a magnetic field is created. By turning the electromagnet on and off rapidly, we can replicate the changing magnetic field of a magnetic stripe swipe.
The final piece of this puzzle is how to control the electromagnet. Well, we're trying to recreate a particular waveform of current through the solenoid in order to create a particular waveform of magnetism. What's a common way of storing waveforms and converting them to electric current? Sound files! So, all we have to do is encode the highs and lows representing the desired flux reversal pattern into a .wav file and play it back on an iPod or similar music player through the solenoid.
Music players designed to play sound through headphones do not produce enough current to drive the electromagnet in this project, so we will also have to construct a basic amplifier that the signal must be passed through before going to the electromagnet.
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THank you
For the amp stage, you could cut size *way* down by using surface mount ICs and draw the power you need straight from the card's power supply (just make sure you keep the current below 500mA or you'll overload the USB port!)
now if only i could find a girl who was hot AND as smart as me
I haven't had much time recently to work with this much more. The amp is essentially a simple "square wave" modulator. I'm not 100% certain that the wave files would even work without the amplifier though others have stated it does with the right miniaturized electromagnet.
Additional materials not included in the part list include some solid core wire to use for jumpers, copper clad, an audio jack which was wrenched from the end of a broken headphone, and an LED with resistor to display power state. The LED can be excluded.
http://pinouts.ru/Devices/ipod_pinout.shtml