#Limitswitch as the name implies: an electrical switch used to determine or limit the direction of movement of an object; in elevator control circuits, it is often used to determine the position of the elevator car and door; if the car reaches the designated floor, (usually the car reaches the designated floor) , first contact the buffer limit, the buffer limit feedback signal to the PLC, the PLC sends a command to reduce and buffer the running speed of the car), after the #limitswitch is sensed, it feeds back the signal to the PLC in the control loop, and then the control loop ( PLC) according to the set program, perform actions such as opening the door; from the above point of view, the limit switch is a digital switch that can send 0 and 1, which sends instructions to the PLC, and then the PLC controls the acceleration and deceleration of the car, such as car acceleration and deceleration. , stop; the action of opening and closing the door.
Generally, a row of control switches are installed at the top and bottom ends of the elevator shaft to decelerate and control the elevator to stop. According to the running direction of the elevator, first encounter the forced deceleration switch——up (down) #limitswitch——limit switch. If the elevator deceleration switch with a higher speed is divided into a first-level deceleration switch and a second-level deceleration switch or even more. The elevator car performs deceleration action when it hits the deceleration switch. When the elevator car hits the upper (lower) limit switch, it will immediately stop running upwards (or downwards), but it can still run downwards (or upwards).
When the elevator car hits the #limitswitch, the control circuit will be cut off immediately and the car will stop running. Up and down can not run, only through the external force to move the car away, the elevator can run after the #limitswitch is reset. To control the speed of opening and closing the car door, a micro switch was used to control the series resistance to change the speed, and the terminal also used a micro switch to disconnect the power supply of the door machine. Most elevators now use variable frequency door machines to control the speed of opening and closing the car door and the limit of automatic door opening and closing. This is only a general principle, and the specific form will vary from manufacturer to manufacturer.
The #limitswitch and the limit switch of the elevator are two different things. The limit switch is divided into the upper limit and the lower limit. When the upper limit is activated, the elevator can go down. Similarly, the elevator can go up when the lower #limitswitch is activated; but the limit switch is connected in series. In the safety circuit, after the safety circuit is broken, the computer board of the elevator will stop all movements of the elevator, so the elevator cannot move. The switches they use are generally the same, and they can be reset automatically.
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