Bang-Bang Temperature Control in Espresso Machines

Abstract

Consumer-grade espresso machines and bean-to-cup machines primarily regulate their brew temperature using on-off control, known in technical jargon as "bang-bang." Commercial and prosumer devices, on the other hand, are increasingly relying on PID control. From a product development perspective, this article explains how on-off control works in the key heating architectures—boiler, thermoblock, classic tube-type flow heater, and thick-film heater—why this results in the characteristic sawtooth curve with hysteresis, overshoot, and measurement dead time, and how PID-controlled temperature regulation differs under load. A patent- and manufacturer-supported case study on BSH's sensoFlow principle demonstrates how a lack of thermal mass is compensated for by sensors at the inlet and outlet, pulsed heating power, and flow rate measurement. It also highlights the new dependencies that arise in this process: the thermal saturation gap and scaling as a disturbance in the control loop. The analysis is based on published literature and patent sources, not on proprietary measurement data. The discussion covers the implications for extraction consistency, reproducibility, and long-term stability, as well as the underlying cost-benefit considerations. The core thesis is: the choice of control and heating architecture is a rational product decision that is, however, invisible to end consumers—and only its disclosure enables informed purchasing decisions.