The centrifuge is an important piece of equipment for any biology lab, necessary for a wide variety of experiments. Cost, however, often prevents the use of centrifuges in many teaching labs, greatly limiting educational experiences for students. As a result, we describe how to construct a “homemade” single-speed mini-centrifuge using inexpensive parts easily acquired online or at hardware or other stores (e.g., a 4.7-quart plastic bowl and lid, standard computer cooling fan, AC/DC adapter, electrical wire, etc.). We further used this design and a commercial mini-centrifuge to pellet 1-mL samples of Tetrahymena thermophila, and we found that the two performed comparably. Finally, because our plans and the materials needed to build this device are all open source, we call our design the OPN Minifuge, and we hope that it will help to expand the scope of experiments that students can run in introductory and upper-level biology teaching labs.