In the early elevator automatic con

In the early elevator automatic control system, the logic control of the signal was generally realized by the relay-contactor circuit. Since the relays and contactors are all electrical components with contacts, the volume is large, the arc discharge is serious, and the service life is limited. In the more complicated control system of the elevator, the reliability is not high, the wiring during the construction process is complicated, and the control requirements are changed. The hardware wiring must be changed to make the versatility and flexibility insufficient, and the production cycle is lengthened. In addition, the number of relays and contactors is limited, and the expandability is poor. The relay-contactor control system relies on the mechanical action of the contacts to achieve control. The operating frequency is low and the mechanical contacts are subject to jitter problems; the relay control logic generally does not have a counting function: at the same time, as the number of building layers increases, the relay-contactor control system is too large, which causes inconvenience to the design. Based on the above various reasons, the process control, operation reliability and safety of the elevator control system are reduced, so it has been gradually eliminated.