Automatic control circuit for electric devices - has triac whose control electrode is connected to output of voltage divider with PTC resistor

摘要

The devices are e.g. electric motors whose speed is to be regulated or lamps whose brightness is to be controlled. The automatic control circuit comprises a phase shifting control with a power switch such as a triac which is controlled during each half-period of the applied A C voltage through a variable resistor, a capacitor and a diac. The control wire (7) of the electronic power switch (Tr) is connected to a point (6) between a resistor (R1) and a temp. sensitive resistor (+V1). The temp. sensitive resistor has a high positive temp. coefficient. These two resistors operate as a voltage divider.