Fluorometers have become indispensable tools in the study of DNA-based nanomachines. The cost of such an instrument is usually outside the budget of a high school science department or that of an amateur scientist. This paper presents a low-cost fluorometer that can be assembled for the cost of approximately a hundred dollars. By monitoring Fluorescence Resonance Energy Transfer (FRET) from the donor dye TET to the acceptor dye TAMRA, this fluorometer has been successfully used to follow the repeated opening and closing of a DNA hairpin nanomachine. This instrument makes possible the investigation of DNA-based nanotechnology or the performance of FRET-based molecular biology experiments within a high school setting.