Virtual Circuits is an electrical network simulator implemented for mobile devices that uses Augmented Reality (AR) technology. This tool requires only a smartphone or tablet, a simple support, a fixed circuit configuration printed in a piece of paper, and a set of plastic tokens that represents electrical elements. These elements are shown in the following picture.
The project was developed at the Information Technology Center (Centro de Tecnologías de Información – CTI) at ESPOL university when I was working in there as researcher in 2017. I designed and implemented the system, also I conducted part of the testing with engineering students.
Design and Implementation.
The AR-based system is a low cost setup divided into two components: a digital environment with virtual objects (simulation engine, GUI); and a physical environment (sheet of paper, support, plastic tokens).
The previous image shows the physical environment. The virtual environment is a mobile application supported by an AR software implemented in the Unity 3D Game Engine using its Android plugin together with the Vuforia SDK. For the electrical circuit simulation, the source code from the library project SharpCircuit was integrated and combined with 3D models as electrical elements whose logic for the simulation is managed by this library.
The system is able to show measurements and graphs that are useful for studying electrical networks concepts. The next images are screenshots taken from a smartphone in which the augmentations can be identified in contrast with the physical objects.
Virtual and Physical objects in the AR system: screen capture of the AR interface on a mobile device 
Power vs. Resistance graph in the AR system: screen capture of an interactive visual component in the AR interface
The advantage over the traditional simulators is the chance to manipulate something physical and still visualize key values from a circuit before going to a real lab.
Results
Two laboratory experiments were designed based on electrical circuits’ concepts. These experiments were carried out by students registered in the Electrical Circuits Analysis II course at ESPOL university, they used Virtual Circuits to solve the tasks. Students were given a laboratory guide (with tasks and details about both experiments), they had to solve a test with questions about the experiments and a user experience survey.
Virtual Circuits was enthusiastically received by students and survey and test results pointed toward potential educational benefits. For more details, please refer to the conference paper below.