We have developed a project-based alternative approach to the traditional electronics laboratory course, incorporating a hands-on sequence of guided but open-ended activities. The Arduino microprocessor is incorporated from the beginning, which allows greatly enhanced scope and flexibility for projects and increases student motivation and agency. The course is designed for junior physics majors without significant experience in circuit design and construction. Students are given an orientation to the Arduino in the second week, and almost immediately begin constructing usable devices. As the projects grow more complex during the course, students are gradually introduced to the usual range of electronic components. The Arduino is particularly suited to measurement and control processes that are common in research environments, and the project themes emphasize signal production, detection, and analysis, including logging, filtering, and amplifying. By using the Arduino to control special-purpose ICs, students learn to read and interpret a datasheet. The course has now run once, with good learning outcomes and very positive student evaluations.