Linux and RTAI for Building Automation

This easy-to-deploy Web-based control system uses standard phone wiring and can manage any device that supports an infrared remote control.

Currently, nine air conditioners are controlled using the system described here; all of them are located in the same building. Another 15 will be added soon. The hardware cost of each microcontroller node is $60 US, and the central control computer costs about $500 US. The other costs are the deployment of the RS-485 network and, of course, the development and implementation of the system.


The implemented system fulfills the specifications of the actual user. Because of this project's success, every new air conditioner acquired by the university must be compatible with the system. The only condition that must be met to comply with the system is every new air conditioner must have an IR remote controller.

Thanks to RTAI, the system main control task is independent of the user interface tasks running in Linux. Even in the improbable situation that Linux goes down, the system would continue on with the programmed operations.

In the future, the system may be extended easily to control, for example, the building lights, alarms, access control to restricted areas and other systems.

Resources for this article: /article/7742.

Andres Benitez ( is working on his Electronic Engineering degree from the Catholic University in Asuncion, Paraguay. The work described in this article is the final project for that degree.

Vicente Gonzalez ( is a civil engineer with an MSc degree in Automation from the Polytechnic University of Madrid, Spain. Currently, he is an assistant professor in the department of Electronic and Computer Science Engineering, Catholic University in Asuncion.



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RS-485 driver availability in linux

Anonymous's picture

Please let me know how have you implemented the RS-485 functionalities in linux. Whether RS-485 driver is built-in driver of linux or we have write by our own?

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