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'[ENG]: Mag Stripe Recording Head Drive Signal'
2007\05\22@151627 by PAUL James

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All,

I am wondering if anyone here knows anything about the amount of drivre
signal that needs to be fed to a Magnetic Stripe Recording Head to allow
it to record onto a magnetic substance similar in properties to the
magnetic stripe like on the back of credit cards or ID cards, etc.?

I want to use a mag card head because of the mounting mechanism on the
head itself.  I plan to record onto a piece of paper that has metallic
particles glued to it's surface.  If this works like I want it to, I can
put together a demonstration that will be interesting for all.

I've checked the web, and have found the ISO standards that are followed
by the Mag Card industry, but I don't see mention of the signal strength
to apply to the recording head anywhere in those documents.  Unless I
missed it, this info just isn't there.  

This is for a demonstration and possible utilization later, but in no
way do I have anything illegal planned for this unit.  It's mostly to
prove a point to myself,
and to a couple of skeptic brothers-in-law that think they have it
figured out that this won't work.  I plan to prove them wrong.

If anyone has this info, I would appreciate hearing it.     You can
reply offline to me at spam_OUTjimTakeThisOuTspamjpes.com.





Thanks and Regards,


Jim


2007\05\22@161552 by Robert Rolf

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PAUL James wrote:
{Quote hidden}

But the whole POINT of the piclist is to share such information.

The write current will be a function of the particular magnetic head.
Typically a few milliamps but you really should contact the manufacturer
to be certain.
5V drive is common for card heads, but you can always start with lower
current (it's inductive so current mode drive works better over a large frequency
range) and work your way up until you're erasing existing data (saturation recording).

Linear audio heads have 80V of 60kHz bias applied, but the audio drive is
only a few volts there as well (much higher head impedance).

There is a very old (1980s?) book called "Magnetic Recording" which has a huge
amount of information on this 'ancient' technology.

Robert

2007\05\22@173419 by PAUL James

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Thanks Robert,

I now have enough info to start working on this.  I'll let you know how
it all goes as soon as it's done.

TTYL,


       
Regards,

       
Jim

{Original Message removed}


'[ENG]: Mag Stripe Recording Head Drive Signal'
2007\06\08@042202 by David VanHorn
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ISO standards don't talk about that level, because it's not relevant
to the standard.

The standard is about the data, not the recording process.

To record today's hi-co cards, you'll need about 700 gauss to saturate the tape.
That is completely dependent on the head design, and you probably
won't have access to that data. So, one practical way to do it, is to
start with a square wave at roughly the correct BPI density (dependent
on card speed) and ramp up the drive current till the waveform when
you read the card, dosen't get any higher, indicating that the tape
has saturated.
Going more than that dosen't serve any purpose.



On 5/22/07, PAUL James <James.PaulspamKILLspamcolibrys.com> wrote:
{Quote hidden}

> {Original Message removed}

2007\06\08@042312 by David VanHorn

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Forgot to mention, Finn Jorgensen's "handbook of magnetic recording"
is a very good reference text, was recommended to me by Vikron, a head
manufacturer, when I was re-designing some heads with them.

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