A mechatronics learning kit, based on the STEAM methodology, has been completely designed and developed at Burgos University. The learning system is focused to both primary and secondary school students. The kit is structured in three elements: a) a set of pieces which are employed to construct the main core of the proposed designs, versatile and adaptable to different projects; b) an electronic board which allows the connection of the different electronic components and sensors to the microcontroller system (a commercial Arduino), easily and without error possibility and c) a programming system tool based on block methodology, combined with child-friendly interface. All the mechanical pieces to build the projects and to adapt the electronic components and sensors have been designed and made by using 3D printing technology. The versatility of the kit has been shown by means of the design and development of different activities that allow us develop a large number of small design projects. Primary and secondary students can define the projects to be carried out by themselves, either starting from a proposed design problem or from their own imagination and curiosity. The kit presents as competitive advantages over existing products in the market its versatility and ability to adapt to different users and types of projects. The development of activities to be carried out using the kit in based project learning is endorsed by experts in the field of education. The market research done shows possibilities of commercialization through a start-up.