Abstract: A circuit permits of monitoring the temperature and the color of coffee in the drums of roasting equipment, and controlling the flow of hot air with dampers operated in pairs by respective stepping motors. The dampers are moved through a succession of proportioning positions in a definite sequence of two stages; an initial, continuous movement that approximates to the thermal transition required, followed by a series of discrete steps producing a fine adjustment; thus it becomes possible to ensure that the set pre-roast and roast temperatures are reached in the drums at the prescribed moment in time.

Abstract: The device makes use of at least one photoemitter and at least one photodetector, operating in conjunction with the inspection glass of the oven against which the coffee beans tumble continually throughout the roast; the photodetector is located remotely, and receives its light input through an optic fiber link the transmitting end of which is supported, together with the photoemitters, by a block fitted to the discharge hatch of the oven directly over the inspection glass and invested with a coolant in order to maintain the temperature at the monitoring location within the preferred operating limits specified for the photoemitters and the optic fiber material.