Project
A DC motor carry elevator top or bottom:
HARD WARE SETUP:
Elevator block diagram:
I would start this project by first: Consider what input and output devices you need. Example: at each floor you need a position switch to tell that the lift is there. A call button at each floor. An acknowledgement light at each floor to signal that the lift is coming. Motor forward (going up). Motor reverse (going down). I make that 6 inputs, 5 outputs. Might be more!
Then the important bit. Draw a "state diagram". Each state is a box. Each state has a fixed output condition which is shown inside the box.
How many states? 3 for the lift stationary at each floor. Probably another 6 for the lift travelling between floors - up and down. Draw arrows showing how the system moves between states. Note that, unlike the lift, the "states" move instantly.
Work out which inputs have to switch to cause the state to change to the next state. Mark these on the arrows. For example, when the lift is stationary at the middle floor (at-2 state), it could either go up (going-up-to-3 state) or go down (going-down-to-1 state). What inputs have to change for this to happen? Not all inputs have to be acted on in every state. Example: if it's at floor 1 then the call button at that floor has no effect.
Once you have got this right - and it might take some time! Then you can plan your control system. This is called a "systematic" method. I would draw your diagram on the computer in Visio or LibreOffice Draw so that you can change things until it's right.
The beauty of a PLC over relays is that these states can be created in a "state machine" (Google that!). Directly simulating your diagram. Could also be done with CMOS logic or a micro-controller.
How many states? 3 for the lift stationary at each floor. Probably another 6 for the lift travelling between floors - up and down. Draw arrows showing how the system moves between states. Note that, unlike the lift, the "states" move instantly.
Work out which inputs have to switch to cause the state to change to the next state. Mark these on the arrows. For example, when the lift is stationary at the middle floor (at-2 state), it could either go up (going-up-to-3 state) or go down (going-down-to-1 state). What inputs have to change for this to happen? Not all inputs have to be acted on in every state. Example: if it's at floor 1 then the call button at that floor has no effect.
Once you have got this right - and it might take some time! Then you can plan your control system. This is called a "systematic" method. I would draw your diagram on the computer in Visio or LibreOffice Draw so that you can change things until it's right.
The beauty of a PLC over relays is that these states can be created in a "state machine" (Google that!). Directly simulating your diagram. Could also be done with CMOS logic or a micro-controller.