Hila Research Centre

Computer Engineering

Parallel Port Switch

The current available from the parallel port of a PC is enough to activate an opto-coupler. The circuit shown here uses an opto-coupler to close a relay. The relay is capable of carrying 2 amps of current , enough to run a small DC motor.

Caution! It is possible to damage your computer doing this type of experimenting. Proceed only if you have some knowledge of electronics and an inexpensive computer - a 286 is an excellent computer for doing this type of electronic interfacing.


This Qbasic program allows control of the parallel port. Enter "8" to turn pin 5 on, "0" to turn pin 5 off. To learn more about Qbasic, click here - Qbasic Information

Launching Model Rockets:

This circuit can also be used to launch model rockets. All safety procedures, including manual safety switches must be incorporated into the design of a computerized rocket launch system.

Examples of Rocket Launch Programs created by Hila campers.

More information about Parallel Ports

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