The openEMSstim, a hardware board based on an Arduino Nano that modulates theamplitude of Electrical Muscle Stimulation (EMS) signals. These musclestimulation signals can be used for games, interactive art, etc. The approachis based on medical rehabilitation hardware and openEMSstim makes itapproachable for researchers to use it safely. The project aims at providing acomprehensible and open-source starting point to experiment with musclestimulation and learn how to keep it safe. openEMSstim provides not onlyhardware but also the software that communicates with the board and controlsit (for Unity3d, Python, Processing, Android and Node.Js). This board iscontrollable via Bluetooth and compatible with any BLE device (such as yoursmartphone) or controllable via USB. The openEMSstim has been created in collaboration between Pedro Lopes (atHasso Plattner Institute / University of Potsdam) and Max Pffeifer LeibnitzUniversity in Hannover (responsible for the original version). The openEMSstimhas been used in the ACM UIST'16 conference by 20 teams of students that usedit to create innovative prototypes. The openEMSstim, a hardware board based on an Arduino Nano that modulates theamplitude of Electrical Muscle Stimulation (EMS) signals. These musclestimulation signals can be used for games, interactive art, etc. The approachis based on medical rehabilitation hardware and openEMSstim makes itapproachable for researchers to use it safely. The project aims at providing acomprehensible and open-source starting point to experiment with musclestimulation and learn how to keep it safe. openEMSstim provides not onlyhardware but also the software that communicates with the board and controlsit (for Unity3d, Python, Processing, Android and Node.Js). This board iscontrollable via Bluetooth and compatible with any BLE device (such as yoursmartphone) or controllable via USB.