Safety circuit for electrical device with electronic control - uses voltage limiting circuit and counter providing voltage protection for electronic control

摘要

The safety circuit detects the application of the network voltage before and after the main switch (1). A voltage limiting circuit (8) provides a clock signal for a counter (2) upon application of the voltage in front of the switch (1), with resetting of the counter (2) via a voltage monitor (9). An AND gate (10) delivers resetting pulses for the counter (2) until the latter reaches its end value with simultaneous detection of the voltage after the switch (1). The device is only operated via the electronic control (8) when the counter end position is reached. Pref. the voltage limiting circuit (8) is supplied via a series resistor (29) and diode (20), with a capacitor (21) between the diode (20) and the voltage line which is not connected to the resistor (19). USE - For electronically controlled electric drill or saw.