Rancilio Silvia V3 is a mid-range coffee machine, therefore it has some disadvantages. For regulation it does not use any electronics. It uses a bimetallic thermostat for simple water temperature regulation. The thermostat controls a temperature of a single small 3 dcl brass boiler. The coffee machine has all the main features that a quality coffee machine needs: electromagnetic valve, adjustable OPV valve, professional group head, professional 58 mm porta filter. Rancilio Silvia V3 coffee machine has temperature controlled with three thermostats: thermostat for brewing temperature, thermostat for steam temperature, and one safety thermostat against overheating. The thermostats are not accurate and cause considerable water temperature instability. In the preparation or brewing coffee, one can never know whether the temperature is in the desired range.
The thesis encompasses the usage of PID controller for temperature regulation. It is used in many fields, mostly in industrial engineering. In this thesis, the PID controller is used on Rancilio Silvia V3 coffee machine. The main reason for using PID controllers is insufficiency of the existing regulation on certain products. The temperature is regulated with the bimetallic thermostat which has a large deviation of ΔT. This kind of regulation is especially problematic with higher temperatures or fast temperature changes. The thermostats cause major temperature changes or oscillations. But the thermostat is sufficient with the less precise systems e.g. room regulators. The temperature in coffee machine is constantly changing; therefore the PID controller is necessary or almost essential. Rancilio Silvia V3 has its thermostat on the top of the brass boiler. The brass changes its temperature (heating and cooling) with delay regarding the water temperature in boiler. The delay causes an extra ΔT to the thermostat. The bimetallic thermostat used in Rancilio Silvia V3 has fixed value of 100 ºC. But due to the PID controller the temperature can be set within the range of 1ºC and enables very responsive and accurate regulation.