Spirometer testing is considered the most common method used to evaluate the pulmonary system. It diagnoses asthma, chronic obstructive pulmonary disease (COPD) and other conditions that affect breathing. Nowadays many pharmaceutical companies produce spirometer devices for patients with asthma, designed for home use. However, the machines are replaced annually due to the lack of control and results' reproducibility. Lacking a reliable mean of calibration leads to unnecessary replacement of expensive devices and/or inaccurate measurements. The objective of this work is designing and prototyping a controlled air flow machine, which will simulate the exhalation of a human based on correlations and predefined graphs found in medicine. This prototyped machine will be used to control and/or calibrate the spirometer device of the physician. The simulation of the human's exhalation was accomplished by varying the rotational speed of an AC single phase motor using a Variable Frequency Drive in addition of a hardware device. The motor is connected directly to a centrifugal fan with forward curved blades. Using the digital pitot tube anemometer/manometer, the flow rate was measured by taking an average value of 40 frequency samples in the range 0 Hz to 100 Hz. After obtaining a relationship between the flow rate and the frequency, the data were implemented in a hardware controller, to adequately control the motor. The control was made from an Android mobile application as follows: Manual and Automatic. The Manual feature enables the user to control the flow rate manually by choosing the required maximum peak flow values to run the test. By adding an air flow sensor, the automatic feature runs automatically and the results of the test shall be obtained as a feedback on the application's screen.