By Martin Scherer, Plasticard

General description

This article deals with the new infrared card (IRCARD) technology. The system in question returns digital information when prompted by properly coded infrared transmission. It is self powered by the emission itself, througha system based on a principal similar to solar panels. In this way, no supply is required with clear advantages in terms of durability and reliability.

Infrared communication allows for interfacing with modern and commonly available serial optical communication gates, for example those meeting Infrared Data Association (IRDA) standards. Hence, no specially designed reception hardware is needed, with obvious advantages in terms of cost effectiveness and system spreadability.

The system can implement any communication protocol matching its technical features. Actually, it can replace all identification media currently in use (magnetic cards, microchips, transponders, etc.) whenever these are employed with a PC or with infrared interfaced peripherals. In other words, it operates like a transponder system using infrared rather than radiofrequency.

System analysis

The system mainly consists of four sections

1. Photoconductive diodes
For collecting light energy emitted by the host interface and turning it into electric energy (the number and type of photoconductive diodes may change depending on the power requirement of the following circuits).

2. D/C unit
For energy storage.

3. Processing Unit
Recognizes the input code and generates the response code (type and features may change depending on specific needs).

4. The Emitter Unit
Transforms the digital response code into light energy.

Prototype

The built prototype communicates with an IRDA interface, in RS232 emulation, at a 9600 Baud transmission rate.

It employs BPW34 photoconductive diodes, one BAT48 type diode, one 100 Nanofarad condenser, one Pic 12c508 microcontroller and one Sfh420 i.r. emitter with 470 ohm resistance. When powered, it emits ascii 'g' character.

With the industrial production of a single chip, consumptions as well as size can be optimized, thus allowing for top performance and its application on credit cards and on any other type of suitable medium. Interestingly enough, the system can be applied on standard credit cards, thus making them suitable for electronic money transactions, without having to change all the other standards.