Motor Control Design Problem (Control Ciruit for 2 Floor dumb-waiter)

Thread Starter

bfinskars

Joined Jun 8, 2018
5
Hello.

I have to draw a control circuit schematic and wiring diagram for a 2 stop dumb-weighter (food elevator). This is used when a restaurant has a kitchen below the actual floor where the guests are served. The elevator is used to transport food and dirty dishes up / down(not people). However this particular elevator has certain requirements.
Criteria:
-Elevator doors open and close manually.
-Pilot/Indicating lights, on both floors, indicate the direction of travel - up or down
-Door interlocks disable the elevator during unloading and loading (when doors are opened the elevator is disabled)
-Elevator stops automatically at floor
-Low voltage protection is required
-Provide up and down buttons on each floor
-Provide emergency stop on each floor.

Any help is greatly appreciated.
 
Last edited:

Thread Starter

bfinskars

Joined Jun 8, 2018
5
I drew up the schematic to the best of my ability, however I didnt meet all the reqs


How do I make the elevator stop automatically at each floor?
And how do I make the door interlocks disable the elevator whenever the doors are open?

Thanks
 

Thread Starter

bfinskars

Joined Jun 8, 2018
5
Show the schematic you have and we may help offering some advice!
Max.
Attached are the attempts I made and the assignment.

The first attempt is pretty basic, however I think i'm missing some things and didn't understand how to properly place the indicating lights for Up and Down directions (on both floors). The second picture I attempted adding lights but got kind of lost.

Any help is appreciated.
 

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Glenn Holland

Joined Dec 26, 2014
705
I used to work in the elevator business and I dealt with all the requirements you describe.

There may already be schematics for elevator controls on line, however I will scan a page from a handbook on elevators and post it on AAC.

So called "dumbwaiters" are usually powered from a single speed reversible AC motor and sometimes a DC motor if a larger speed (measured in feet/minute) is desired. One problem is how accurate do you want for the final stopping distance from the floor. If carts are used to carry the load, then you would want the floor of the dumbwaiter to stop +/- 1/4 inch from the floor of the building so the cart can be easily rolled on and off.

The stopping accuracy is influenced by the actual load on the car and it will vary from no load to full load. In that case, a DC motor (or an AC inverter) with some kind of tachometer feedback will be required and use dynamic braking instead of a purely mechanical brake.

For safety circuits, the power to the motor must be removed when the doors are open and unlocked and the doors must be closed and locked before the motor and brake can be energized. Also, the door cannot be opened when the car is away from the floor by a given distance. This requirement is met by installing a cam on the front of the car which pushes a roller on the door lock to release it.

Finally, is the design of the dumbwaiter control just a simple academic problem (like something you're doing for an engineering class) or something you're planning to actually build and install? If it's to be installed someplace, you must check the building code to make sure everything is in compliance.
 

Thread Starter

bfinskars

Joined Jun 8, 2018
5
I used to work in the elevator business and I dealt with all the requirements you describe.

There may already be schematics for elevator controls on line, however I will scan a page from a handbook on elevators and post it on AAC.

So called "dumbwaiters" are usually powered from a single speed reversible AC motor and sometimes a DC motor if a larger speed (measured in feet/minute) is desired. One problem is how accurate do you want for the final stopping distance from the floor. If carts are used to carry the load, then you would want the floor of the dumbwaiter to stop +/- 1/4 inch from the floor of the building so the cart can be easily rolled on and off.

The stopping accuracy is influenced by the actual load on the car and it will vary from no load to full load. In that case, a DC motor (or an AC inverter) with some kind of tachometer feedback will be required and use dynamic braking instead of a purely mechanical brake.

For safety circuits, the power to the motor must be removed when the doors are open and unlocked and the doors must be closed and locked before the motor and brake can be energized. Also, the door cannot be opened when the car is away from the floor by a given distance. This requirement is met by installing a cam on the front of the car which pushes a roller on the door lock to release it.

Finally, is the design of the dumbwaiter control just a simple academic problem (like something you're doing for an engineering class) or something you're planning to actually build and install? If it's to be installed someplace, you must check the building code to make sure everything is in compliance.
I need the dumbwaiter to stop level on the floor, there is no requirement, it just has to automatically stop at both floors.
The design for this dumbwaiter control is an academic homework problem.
I need to design a schematic (ladder) diagram and a wiring diagram.
Thank you for your reply.
 
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