Circuit for controlling electric motor e.g. fan motor, in fume extraction hood, during cooking, has safety switch deactivating control signal based on faulty operations when switching signal exhibits switch-off level

摘要

The circuit (100) has an input terminal (20) for connecting to a safety switch contact (30). A safety switching signal (US) with a switch-off level and an enable level depending on a switching state of the contact at the terminal. A motor control unit (40) e.g. microprocessor, is connected to the terminal. The control unit produces an activated control signal (UM) i.e. pulse width modulated signal, when the safety switching signal exhibits the enable level. A safety switch (50a) deactivates the control signal based on faulty operations when the switching signal exhibits the switch-off level.