【正文】 applications the PLC offers to much resources that are not even used to control the system, electropneumatic system is one of this kind of application. The use of PLC, especially for small size systems, can be very expensive for the automation project. An alternative in this case is to create a specific controller that can offer the exactly size and resources that the project needs [3, 4]. This can be made using microcontrollers as the base of this controller. The controller, based on microcontroller, can be very specific and adapted to only one kind of machine or it can work as a generic controller that can be programmed as a usual PLC and work with logic that can be changed. All these characteristics depend on what is needed and how much experience the designer has with developing an electronic circuit and firmware for microcontroller. But the main advantage of design the controller with the microcontroller is that the designer has the total knowledge of his controller, which makes it possible to control the size of the controller, change the plexity and the application of it. It means that the project gets more independence from other panies, but at the same time the responsibility of the control of the system stays at the designer hands 2. Electropneumatic system On automation system one can find three basic ponents mentioned before, plus a logic circuit that controls the system. An adequate technique is needed to project the logic circuit and integrate all the necessary ponents to execute the sequence of movements properly. For a simple direct sequence of movement an intuitive method can be used [1, 5], but for indirect or more plex sequences the intuition can generate a very plicated circuit and signal mistakes. It is necessary to use another method that can save time of the project, make a clean circuit, can eliminate occasional signal overlapping and redundant circuits. The presented method is called stepbystep or algorithmic [1, 5], it is valid for pneumatic and electropneumatic systems and it was used as a base in this work. The method consists of designing the systems based on standard circuits made for each change on the state of the actuators, these changes are called steps. The first part is to design those kinds of standard circuits for each step, the next task is to link the standard circuits and the last part is to connect the control elements that receive signals from sensors, switches and the previous movements, and give the air or electricity to the supply lines of each step. In Figs. 1 and 2 the standard circuits are drawn for pneumatic and electropneumatic system [8]. It is possible to see the relations with the previous and the next steps. 3. The method applied inside the controller The result of the method presented before is a sequence of movements of the actuator that is well defined by steps. It means that each change on the position of the actuators is a new state of the system and the transition between states is called step. The standard circuit described before helps the designer to define the states of the systems and to define the condition to each change between the states. In the end of the design, the system is defined by a sequence that never chances and states that have the inputs and the outputs well defined. The inputs are the condition for the transition and the outputs are the result of the transition. All the configuration of those steps stays inside of the microcontroller and is executed the same way it was designed. The sequences of strings are programmed inside the controller with 5 bytes。 5byte: value for the extra function. Table 5 shows how the user program is saved inside the controller, this is the program that describes the control of the example shown before. The sequence can be defined by 25 bytes. These bytes can be divided in five strings with 5 bytes each that define each step of the sequence (Figs. 9 and 10). 7. Conclusion The controller developed for this work (Fig. 11) shows that it is possible to create a very useful programmable controller based on microcontroller. External memories or external timers were not used in case to explore the resources that the microcontroller offers inside. Outside the microcontroller, there are only ponents to implement the outputs, inputs, analog input, display for the interface and the serial munication. Using only the internal memory, it is possible to control a pneumatic system that h