J M Davis & Associates

Some older projects

Magnetic Stripe Alignment

This may well be patented shortly so I can't go into much detail. The unit was developed to check that the encoded stripe on a (proprietary) magnetic card was correctly placed so that it would lie exactly under the read/write head. A production check rather than an accurate measurement, it resolves lateral alignment to about 50 microns on a 2.5mm track although the whole thing would scale down to smaller dimensions (and could doubtless be developed for much higher accuracy)

High Speed Magnetic Card decoding (1)

One of those "not rocket science" projects, this was a drop in replacement board for reading ISO stripe (bank type) magnetic cards on an automated line. The cards arrived over the read head in pairs, almost nose to tail, and the existing decoder simply couldn't keep up. A very simple new decoder board was produced with an ATMEL AVR microcontroller programmed in assembler for speed. The result was a doubling of line speed, from about 3500 pairs of cards per hour to over 7000.

High Speed Magnetic Card decoding (2)

A rewrite of some embedded software (C/8051) which decoded, decrypted, verified and measured every element of a proprietary Magnetic Stripe card. Along the way the software became somewhat smaller and a single version replaced three separate versions for different card formats. Maximum line speed was increased from 66 cards/minute to 100 cards/minute. A similar operation was carried out on the encrypt/encode/write software used for the same cards.

AC Motor Drive

A drive board to control three independent three phase ac motors. Produced to a detailed specification from an equipment manufacturer, this board uses a "six step" drive, which gives a reasonable range of output speeds but is not suitable for low speed operation. 240V mains is rectified to give a 350V rail which is then switched to produce the motor drive waveforms. Lots of optoisolation here, and filtering to prevent excessive EMI.

Details of more recent projects
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