Magnetic Head Circuit

[TechGladiator]

I am trying to create an access control device that will be able to
read magnetic tickets and/or credit cards. I have bought a couple
magnetic heads from world magnetics and I was wondering how to
communicate with these heads, Are there already made circuits that
will decode the information from the heads?

Thanks
Mike

 

[Dave VanHorn]

I am trying to create an access control device that will be able to
read magnetic tickets and/or credit cards. I have bought a couple
magnetic heads from world magnetics and I was wondering how to
communicate with these heads, Are there already made circuits that
will decode the information from the heads?

Magtek, and others, make F-2F decoder circuits, or you can decode it in
firmware.
You have a fair bit of work in front of you.

You'd be looking at a lot less work, to get a card reader mech that has
clock and data outputs.
That's pretty easy to read with a micro if you have an interrupt pin free.
[/QUOTE]

 

[Mike Gonzalez]

Magtek, and others, make F-2F decoder circuits, or you can decode it in
firmware.
You have a fair bit of work in front of you.

You'd be looking at a lot less work, to get a card reader mech that has
clock and data outputs.
That's pretty easy to read with a micro if you have an interrupt pin free.

It does seem like a lot of work.. Specially to somebody that doesnt know
muhc about circuit design. I am a programmer for 16 yrs but not much of a
circuit designer..
Have you done much with MSR heads/circuits?

 

[Dave VanHorn]

It does seem like a lot of work.. Specially to somebody that doesnt know

muhc about circuit design. I am a programmer for 16 yrs but not much of a
circuit designer..
Have you done much with MSR heads/circuits?

Yes. Ever hear of Verifone?

Finn Jorgensen's "Complete handbook of magnetic recording" is a good read,
if you can find it.

You have two options doing it in analog:
You can terminate the head with the proper impedance, and read the signal in
voltage mode, which means that the output will vary in amplitude according
to the read speed, and will require tricky filter design to help smooth the
response.
Or, you can amplify the head with a current to voltage circuit which works
nicely.

Or, buy a "decoded" reader with clock and data outputs.

At Verifone, we didn't want to pay the $12 for the readers, so we
charachterized some inexpensive far east heads, did our own amp (the first
method) and decoded the F-2F in firmware. It wasn't easy.

Later, I hit on the second approach. While you still have to decode it in
firmware, the analog part is a lot less interesting.

We also had to design proper geometry for the head mounting bracket, and
deal with the wiring coming off the back of the head dragging the head
around.

Later still, I solved all that by mounting the head direct to the PCB, and
routing away the PCB material to form a spring, cable, and mount for the
head at essentially zero cost. (patented)

If you have anything near the head that radiates a magnetic field, then
you're in for even more fun, with special steels and learning how to help
those fields go somewhere else. (assuming you can't avoid making them in the
first place, which is the far better solution)

Did I mention that I'm available for consulting or employment?

 

[Mike Gonzalez]

Yes. Ever hear of Verifone?

Finn Jorgensen's "Complete handbook of magnetic recording" is a good read,
if you can find it.

You have two options doing it in analog:
You can terminate the head with the proper impedance, and read the signal
in voltage mode, which means that the output will vary in amplitude
according to the read speed, and will require tricky filter design to help
smooth the response.
Or, you can amplify the head with a current to voltage circuit which works
nicely.

Or, buy a "decoded" reader with clock and data outputs.

At Verifone, we didn't want to pay the $12 for the readers, so we
charachterized some inexpensive far east heads, did our own amp (the first
method) and decoded the F-2F in firmware. It wasn't easy.

Later, I hit on the second approach. While you still have to decode it in
firmware, the analog part is a lot less interesting.

We also had to design proper geometry for the head mounting bracket, and
deal with the wiring coming off the back of the head dragging the head
around.

Later still, I solved all that by mounting the head direct to the PCB, and
routing away the PCB material to form a spring, cable, and mount for the
head at essentially zero cost. (patented)

If you have anything near the head that radiates a magnetic field, then
you're in for even more fun, with special steels and learning how to help
those fields go somewhere else. (assuming you can't avoid making them in
the first place, which is the far better solution)

Did I mention that I'm available for consulting or employment?

Ohhh yeah. I've heard of Verifone . I've worked with credit cards for a
very long time. I've developed software to emulate the Verifone on a PC.
Nothing much to it other then getting it certified with the different
networks.

I can understand what you are talking about with regards to design and all
but I would definetlly never be able to do it myself, I will definetly stick
with coding for now.

I was actually considering the consulting/employment part. I can give you a
call/e-mail you some of the details one this project and see what you can
do, maybe I can throw a few bucks your way.

 

[Dave VanHorn]

Ohhh yeah. I've heard of Verifone . I've worked with credit cards for a

very long time. I've developed software to emulate the Verifone on a PC.
Nothing much to it other then getting it certified with the different
networks.

And therein lies the fun
Kind of like getting equipment certed for australian telco used to be.
Some of their requirements were mutually exclusive, so it was actually
impossible to comply.
Makes it easy to keep foreign products out, if you want to.

I was actually considering the consulting/employment part. I can give you
a call/e-mail you some of the details one this project and see what you
can do, maybe I can throw a few bucks your way.

Sure, [email protected], or 765 287 1987