Most of devices used for controlling a system are composed of four main parts: a sensor that 'senses' the system, generally converting a physical quantity in electric signal, a control electronics that analyses this signal, an actuator that re-converts the electric signal to the physical quantity and finally a power supply unit that provides the general supplying of the device. The global effect is the control of the physical quantity through a feedback chain. In particular, for mechanical systems, the electronics and the power supply units make the device complex and expensive, increasing in many cases the time response. The device presented in this work, conceived for controlling a mechanical quantity (force, pressure, deformation, etc.), utilizes piezoelectric for both the actuator and sensor parts. The electrical signal generated by the sensor is directly supplied to the piezoelectric actuator without any additional intermediate electronics, realizing a fully self- supplied sensing-actuating device. Without control electronics and power supply unit the device becomes inexpensive, simple and fast no matter the distance in between the sensor and the actuator. An original configuration of the piezoelectric sensor-actuator control device is presented, together with a theoretical interpretation. Experimental trials, also illustrated, show clearly that the proposed solution can be a smart and inexpensive alternative to the traditional control devices.