This paper focuses on the development of a low-cost system, based on Arduino, for the active shielding of magnetic fields generated by power systems at industrial frequency. The modeling of the source, the design and the optimization of the shielding loop, and, finally, the hardware (microcontroller, sensors, driven voltage source, etc.) and the control algorithm of a prototype system are described. A number of tests, developed through an experimental setup, are performed to validate the prototype. The main results are also discussed highlighting the capabilities of the proposed active shielding.