Almost everyone today knows and uses a Elevator in their daily life. But how many of us know how exactly it works?. Will you be able to design your own elevator if provided with necessary tools?. The idea of this article is to describe the Elevator system from a embedded systems designers point of view.
The below diagram shows how an elevator is installed in a building of 3 floors, Instead of naming them 1st, 2nd, 3rd floor, i have named them Top, Middle, Ground Floor. This is a simple elevator system with minimal sensors and can be designed using a basic 8051 microcontroller.
Elevator Car : Elevator car is the vehicle in which people travel, It has a door which opens and closes to let passengers inside and outside the car.
MOTOR : The elevator CAR is connected to a high power AC motor usually on the top of top floor. The motor controls the elevator car movement by pulling the car up or down using a steel cable pulley system.
UFC1, UFC2 : UFC1 and UFC2 are the safety switches to prevent the elevator car from moving upwards beyond the top floor. They are mounted on the top most floor to which the elevator service is provided. These are mechanical contact type switches activated by a contact rod mounted on top of the elevator car.
Landing Call Button : The Landing Call button is the button provided at each floor near the elevator door. Whenever a passenger wants to use the elevator service, he presses the landing call button. As soon as the elevator car finishes the current ongoing task, it arrives at the requested floor to pick up the person.
DFC1, DFC2 : DFC1 and DFC2 are the safety switches to prevent the elevator car from moving downwards beyond the Ground or lowest floor. They are mounted on the lowest floor to which the elevator service is provided. These are mechanical contact type switches activated by a contact rod mounted at the bottom of the elevator car.
UR : Up Reed is a magnetic reed switch which is used to sense whenever the elevator car passes by a floor while moving upwards. The UR signal is activated whenever the elevator car passes by the magnet attached at each floor.
DR : Down Reed is a magnetic reed switch which is used to sense whenever the elevator car passes by a floor while moving downwards. The DR signal is activated whenever the elevator car passes by the magnet attached at each floor.
UR, DR are used to count the number of floors passed and keep track of the elevator car's current floor status.
DRVSTOP : The Drive stop signal is used to stop and park the elevator car exactly aligned with the door of the elevator from where the passengers get inside the car.
CDP (Infrared sensor) : The CDP signal is generated by an infrared sensor fitted inside the elevator car doors. Whenever there is a obstacle in between the doors it remains open, preventing someone from getting hurt while the door being closed with a person in between. The elevator will not move until this signal is inactive and the door is properly closed.
CAR Control panel : The CAR control panel is a set of buttons inside the elevator car. The buttons include floor numbers like, 1, 2, 3 which when pressed requests the elevator to move to that particular floor. These buttons when pressed indicate requests to the elevator car and are called CAR calls.
The buttons DC(Door Close), DO(Door Open) are used to Close elevator door and Open elevator door respectively during manual operation.
The buttons FAN, STOP are used to turn on-off the fan inside the elevator and Stop the elevator car movement immediately.
These are the elevator signals we need to take care of and use them to properly control the elevator movements. My next article will be on designing your own elevator control panel and about the operations needed to be done whenever a particular signal is detected.
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