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-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
Of Robert Rolf
Sent: Tuesday, May 22, 2007 3:16 PM
To: Microcontroller discussion list - Public.
Subject: Re: [ENG]: Mag Stripe Recording Head Drive Signal



PAUL James wrote:
> 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 jim@jpes.com.

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
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