A Pilot Self-Sustaining Time Delay Safe Switch
We designed a type of pilot-operated self-sustaining time delay power on/off circuit which consists of a duplex switch, time delay circuit and a dual-coil, dual-contact electromagnetic logic control relay. We also depicted a dual-coil, dual-contact electromagnetic relay logic control circuit diagram dedicated to this design. Structures and specific couplings of the circuit were presented and analyzed. Functional analysis was also carried out for a variety of work processes performed on the circuit at static or dynamic state, and the results showed that the circuit, in addition to fulfilling its primary function for time delay shutdown of the main circuit, is also capable of automatically powering-off the control circuit and the control power supply when the device is left unattended. This design greatly meets the needs of current time delay control technology, and thus has a great commercial potential.