Computer Output Interface

Circuit : Andy Collinson
Email : anc@mitedu.freeserve.co.uk

Description:
A universal output interface for any PC (based on Intel archietecture) that has a parallel port. The output data is buffered and can drive relays, LED's or other circuits and is controlled by software.

Notes:
Most PC's usually have a parallel printer port. Many printers these days use a USB connection and often the 25 way D type printer socket is available for use.

Any data sent to the parallel printer port is latched, it is therefore very easy to interface to the computer, just by including a buffer IC between the computer and external circuitry.

I have chosen the ULN2083A IC, pinout below, datasheet available here, to act as the buffer for the parallel port. The IC contains eight darlington buffers and capable of driving continuous loads of up to 500mA.

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