Long duration electronic delay - uses half wave rectified supply to charge capacitor to trigger transistor, with parallel circuit inhibiting trigger to provide long delay

摘要

The electronic delay circuit provides an output several minutes after triggering, and is intended to overcome problems associated with very high resistance and capacitance values normally required from delays of this order. The circuit uses the charging of a capacitor (30) through a chain of resistors (32-34) from an A.C. supply which is half wave rectified by a diode (31) in series with the chain. One section of the resistor chain limits the discharge current of the capacitor. The remaining resistors control the change time and provides a trigger level to a transistor (39). The trigger operation being inhibited by a parallel circuit across the same A.C. supply.