The Design Of Three Track Magnetic Readers Based On GMR Sensors

Magnetic card reader is a device that can convert magnetic card signal to digital signal, and it is widely used in many fields, such as financial industry, posts and telecommunications business, and traffic field. In order to meet the requirements of magnetic card reader in many fields, a novel design approach on three track readers based on Giant Magnetic Resistance(GMR) sensors is used, in which the bit error rate is low and it has solved problem of the difference brushing bard speed by users. The signal in magnetic stripe is read out, analyzed, filtering by GMR sensor and into the Micro Controller Unit(MCU) processing to restore the original input sequences.The core of this article is the design of GMR sensor magnetic head. Traditional magnetic head is thin film sensor head(TFI), and different brushing bard speed can cause different signal strength. We usually deal with the low bit error and solve problem of the different brushing bard speed by improve circuit. Compared the advantages and disadvantages of the TFI head with GMR sensor magnetic head, this article uses the design scheme as follows. Output signal frequency is only related on the magnetic card signal. In other words, different bushing speeds have no effect on the output frequency. Grant improving in performance area needs a new ampli-filter circuit. This article designs a read circuit, by means of output signal strength and regular from GMR magnetic head can read out the card signal.The tested results of GMR magnetic head demonstrate that this magnetic card reader have a stable performance, can output the previous card sequence. So it could be used to replace TFI head in the data reading application.