Microprocessor circuit arrangement

摘要

In a drinks dispenser for carbonated drinks, a microprocessor is used in order to control the compressor and the ventilator of a cooling system as well as a stirring mechanism and a water supply pump of a carbon dioxide generator. The water levels in the carbon dioxide generator and the water supply thereto, and the size of the ice blocks which are constructed therein are monitored by interrogation signals which are applied to a group of sensors which are arranged in the carbon dioxide generator and the associated water supply container. The interrogation signals are controlled by the microprocessor and have a short duration with a low duty cycle in order to prevent galvanic precipitation on the sensors. The interrogation signals are derived from a low AC voltage which is required for supplying various components in the dispenser system. For this purpose, a rectifier and a filter capacitor are provided, in connection with a limiting diode and a bias resistor. The microprocessor causes repeated earthing of the resistor in order to generate a square-wave signal thereon. This square-wave signal is capacitively coupled to the sensors in order to avoid applying DC voltage components to them and in order to apply a balanced AC interrogation signal to the sensors.