A low-cost system for experiments with digital circuits

The first digital circuits course becomes a lot more interesting for students when it involves practical experiments in the laboratory. Motivation is higher when students use old digital integrated circuits, such as the TTL7400 or CMOS4000 families, and construct circuits on solderless breadboards. The handling of these circuits containing logic gates is more motivating than using a digital circuit simulator software or an FPGA, which looks like a black box for beginner students. To verify the built circuit´s operation on the solderless breadboard, with a digital integrated circuit, it is necessary to generate input signals and display the output signals, as well as a probe in order to check the logic level at any point in the circuit. For this, there are two options: using didactic modules for experiments with digital circuits, or generating input signals with switches and showing the output signals with LEDs. The former has the disadvantage of relatively high cost. The latter has the drawback of inserting many other problems when building a digital circuit using breadboards. As a low-cost alternative, this paper presents a virtual instrument that consists of an Arduino and a software, which allows experiments using digital integrated circuits.