A simple and economical system that allows one to obtain the characteristic "I-V" curve in solar cells is presented. It is a computer-controlled system suitable as an instrumentation project for students who are learning about photovoltaic systems. This system is based on the use of an "R-3R" ladder circuit as a variable resistive load for a solar cell and is controlled by a microcontroller system connected to a PC. The system allows us to generate the "I-V" curve and calculates the parameters "I"[subscript sc], "V"[subscript oc], "P"[subscript max].