Magnetic Card Reader
The reader mechanism shown was purchased
from All Electronics for $1.50.
The unit provides the magnetic head on a spring mechanism along with low
level head signal amplifiers and data slicers. Three signal lines
comming from the unit provide card presence, clock, and data.
When actively reading a card, it draws about 50ma of current at 5 volts.
data from the unit appeared to be 'track-2' format. This is 4 bit
plus odd parity data. The data is readily converted to ASCII by
adding Hex-30 to each nibble.
The PIC12F675 looked like a good match for this project.
The pair of 10k resistors on GP0 and GP1 are to allow in-circuit programming
via a protoclip. RS-232 levels are generated by robbing the negative
voltage from the computers transmit line (which is not otherwise used
here), and creating usable signal levels from the device to the computer.
As it turns out, credit cards and many other type of comercial magnetic
strip cards use the track-2 data.
The Source and Object files