The document discusses the development of a low-cost thermal cycler for polymerase chain reaction (PCR) applications, aimed at addressing the equipment shortages in low-income countries exacerbated by the COVID-19 pandemic. The thermal cycler utilizes a thermoelectric heating and cooling system and incorporates a PID control strategy, combined with feedforward and bang-bang controls, achieving high temperature stability with deviations less than 0.5 °C during continuous operation. The design is modular, leveraging available electronic components to streamline development and lower production costs.