Go Down

Topic: Using a video maghead to read cards? (Read 2174 times) previous topic - next topic

dubz

Feb 02, 2012, 11:25 am Last Edit: Feb 02, 2012, 11:59 am by dubz Reason: 1
Sorry for the bad title and sorry If I have placed this thread wrong.

Well I thinks it's hard to find information about the head that reads the magnet stripe back on cards. Either it's "maghead" or "magnetic card reader head". Does anyone here know a correct term to search for? I would also like to find some datasheets about magheads cuz I have some here at home which only have to pins and I don't know which is vcc and gnd.

Anyway here's my real question. Is it possible to take the maghead from a vhs player or old tape player and use that one to read the data stored on a magnetic stripe, back on a card?

Best regards!

Edit:
If you take a look at this image
http://desmond.imageshack.us/Himg641/scaled.php?server=641&filename=magheads.png&res=medium
The one to the right is from a tape recorder and the one to the right is a real one meant for reading cards.

cr0sh


Anyway here's my real question. Is it possible to take the maghead from a vhs player or old tape player and use that one to read the data stored on a magnetic stripe, back on a card?


Highly unlikely with the head from a VCR (you do know that a VCR head spins, right?) - and unlikely with the cassette tape head (but you'd have a better shot).

Basically, IIRC, there are more tracks on a magstripe, and they are spaced closer together than the 4 tracks on a cassette head; at best, you would probably get crosstalk from multiple tracks - but it might be worth experimenting with.

I would first do some more research on this topic, though; I'm sure if you care to brave the mess of various hacker forums you'll find a ton of information on card magstripe reading (and writing). Its not as easy as you think...

Finally (depending on where you are located), it might be better to look into obtaining a complete mag swipe unit (that has the head and slot at minimum; if you can get the amplifier circuitry, even better); I've seen such units on the surplus electronics markets every now and then (All Electronics used to carry them; not sure if they still do - also Electronic Goldmine). I've also found Verisign units being sold on occasion at local Goodwill stores; hit 'em up on 50 percent off day, and you can get a real bargain (hey, you'll also get a dot-matrix multi-character VFD in the mix to boot).
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

Grumpy_Mike

Quote
I have some here at home which only have to pins and I don't know which is vcc and gnd.

Basically read write heads are just a coil on a fancy former. As such there is no polarity. In fact most have an AC voltage applied to them in order to record magnetic information.

dubz

#3
Feb 02, 2012, 09:22 pm Last Edit: Feb 02, 2012, 09:54 pm by dubz Reason: 1
Thank you so much for the answers, will do some research now  :)

Highly unlikely with the head from a VCR (you do know that a VCR head spins, right?) - and unlikely with the cassette tape head (but you'd have a better shot).

Don't know about vhs but on a tape player the head doesn't spin, the tape itself spins against it. Just like the magnetstrip back on a card is swiped against a maghead.

Quote
Basically, IIRC, there are more tracks on a magstripe, and they are spaced closer together than the 4 tracks on a cassette head; at best, you would probably get crosstalk from multiple tracks - but it might be worth experimenting with.

There's 3 tracks on a card but track3 are almost never used.

Quote
I would first do some more research on this topic, though; I'm sure if you care to brave the mess of various hacker forums you'll find a ton of information on card magstripe reading (and writing). Its not as easy as you think...

Finally (depending on where you are located), it might be better to look into obtaining a complete mag swipe unit (that has the head and slot at minimum; if you can get the amplifier circuitry, even better); I've seen such units on the surplus electronics markets every now and then (All Electronics used to carry them; not sure if they still do - also Electronic Goldmine). I've also found Verisign units being sold on occasion at local Goodwill stores; hit 'em up on 50 percent off day, and you can get a real bargain (hey, you'll also get a dot-matrix multi-character VFD in the mix to boot).

I am well familiar with hacking forum since I have study computer security the last 8 years and I have several msr readers at home, both usb and portable and a msr writer. But yes you're right, I should do more research about the difference but it's very hard because I can't find a term to search for. But will begin researching about how vhs and tapes are read and then compare it to the information I know about magnetic stripes.


Basically read write heads are just a coil on a fancy former. As such there is no polarity. In fact most have an AC voltage applied to them in order to record magnetic information.

Could you please explain what you mean with the AC? From those magheads I have there's simple two pins (vcc and gnd) but then there's magheads for clock/data etc but never mind about those at the moment.

Do you mean that it doesn't matter if I have gnd connected? I have done some experimental with arduino uno and a simple maghead. It looks like a got a smother input when gnd is conected (whooaa) and a more stuttering (tic-tic-tic extremely fast) input when it's not connected.

Again thanks for the answers,
best regards!

Edit: Now I have done some simple research, took me a while finding it on wikipedia.
Here is magheads http://en.wikipedia.org/wiki/Disk_read-and-write_head
I have compared it to other articles on wikipedia and found out that there is no difference between readers/writers on card readers or in tape/vhs players. There all the same.

But final question is, connect or not connect gnd and what's the difference?
Regards!

Groove

Vhs is also helical scan, so usless for linear tracks
Per Arduino ad Astra

Grumpy_Mike

Look at
http://en.wikipedia.org/wiki/Vhs
I think you are confused by simple electronics. It dosn't matter which wire is connected to ground, if indeed any wire needs connecting to grain. It is AC, alternating current that feeds the head. That means the voltage polarity across the head is constantly and rapidly changing. This creates a magnetic field which in turn magnetises the tape.
A head can't read both clock and data, it only reads back a voltage proportional to the magnetic field. That data could contain a clock embedded in it or not depending on the encoding scheam but it only reads one signal. The electronics in the head can seprate these out and present them as two signals.

To use the word hacker in relationship with computer security is a very wrong and old fashion thing to do. A hacker is someone who repurposes equipment, not someone who fakes IDs.

Groove

If you still think vcr and linear tape heads are the same, you really need to do some more research
Per Arduino ad Astra

dubz


Vhs is also helical scan, so usless for linear tracks

I saw that now and now I also understood what cr0sh meant when he told me that the head spins. Sorry cr0sh  :)

Look at
http://en.wikipedia.org/wiki/Vhs
I think you are confused by simple electronics. It dosn't matter which wire is connected to ground, if indeed any wire needs connecting to grain. It is AC, alternating current that feeds the head. That means the voltage polarity across the head is constantly and rapidly changing. This creates a magnetic field which in turn magnetises the tape.
A head can't read both clock and data, it only reads back a voltage proportional to the magnetic field. That data could contain a clock embedded in it or not depending on the encoding scheam but it only reads one signal. The electronics in the head can seprate these out and present them as two signals.

To use the word hacker in relationship with computer security is a very wrong and old fashion thing to do. A hacker is someone who repurposes equipment, not someone who fakes IDs.

Thank you, but how does it work when the head writes to the magnetstrip? I have read that it writes when the head gets powered. But without power it can't read. So power when reading and power while writing, how does that work?
I am well aware about what a hacker is.

If you still think vcr and linear tape heads are the same, you really need to do some more research

No I do not, but I thought that if a tape player has a head then a vhs has similar, stupid me  :)

Grumpy_Mike

Quote
Thank you, but how does it work when the head writes to the magnetstrip?

I thought I said, it generates a magnetic field. That field then magnetises the materiel it is next to.

Quote
I have read that it writes when the head gets powered.

Yes the power creates a magnetic field like I said, the power is an AC signal.

Quote
But without power it can't read. So power when reading and power while writing, how does that work?

Reading can occur without power. But also you can do it with power. You provide a low level AC current to it, called a bias field. Then the magnetic material passing it modulates the AC current, so you then demodulate the bias current and recover the signal recorded on the magnetic materiel.
Early recorders used wire before tape was invented.

dubz

[...]

Thank you sir, and thanks everybody for very good and informative answers.
Best regards!

Edit: And again cr0sh, sorry!

terryking228

Quote
To use the word hacker in relationship with computer security is a very wrong and old fashion thing to do. A hacker is someone who repurposes equipment, not someone who fakes IDs.


Actually the use of "Hacker" as one who repurposes equipment and/or software and builds his/her own computer-related equipment is the OLD definition. Like 1978-79 pre-IBM-PC when a friend and I hacked (hardware changed) early Ohio Scientific systems to change Video output to 80 characters per line, and hacked (disassembled) the Operating System to add support for the display and even a line printer. We were recognized as "Hackers" by (unnamed) IBM executives who told us never to bring ANY of that stuff into work!

But the hacking success was used as one of the arguments that resulted in IBM releasing the BIOS  !!SOURCE CODE!! in the IBM PC Technical Reference Manual. We Won!
Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

Go Up