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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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  #1  
Old 10-10-2012, 04:05 PM
NT01221 NT01221 is offline
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Question "Simple" 3 Floor Elevator "Relay" Diagram

I am looking to build a 3 floor working model elevator using relays and limit switches. Not worried about doors opening and closing or variable speed, just a simple 3 floor up/down operation. A 2 floor diagram is quite easy, however adding a 3rd floor makes it that much more challenging using relays. Does anyone have a simple relay diagram they could share? I'd like to have an "up" call button on the 1st floor, an "up" and "down" call button on the 2nd floor, and a "down" call button on the 3rd floor. There would be an external panel of three buttons to represent the panel inside the elevator car for floors 1, 2 & 3. Put your thinking caps on, and please.... keep it simple!!
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Old 10-10-2012, 05:11 PM
MrCarlos MrCarlos is offline
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Hello NT01221

You can start by analyzing the circuit in the attached image.
then:
Could change the switches shown in the image attached by magnetic sensors that activate the relays.

After:
Increase call buttons on the other floors

I hope this information will help you make your project

regards
at your service
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File Type: jpg So Easy.jpg (111.7 KB, 269 views)
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Old 10-10-2012, 11:58 PM
NT01221 NT01221 is offline
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Default Relay diagram

Thanks for your reply. I was hoping to get an actual relay diagram if someone could help me with that?
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Old 10-11-2012, 04:33 AM
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KJ6EAD KJ6EAD is offline
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This seems like a PLC programming assignment for school.
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Old 10-11-2012, 10:36 AM
NT01221 NT01221 is offline
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Default Nope, not school assignment!

A good friend has an Autistic child who is fascinated with elevators. I wanted to build a working model for him, however I never worked with PLCs, so I wanted to keep with the technology I know. Would love a relay diagram if someone could help!
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Old 10-11-2012, 11:33 AM
JDT JDT is offline
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Not simple - but interesting! I'm sure it can be done with relays - they must have done it that way back in the day. You will need latching relays to be able to "remember" things. Complicated! Get it wrong, you will have to re-wire.

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.

Last edited by JDT; 10-11-2012 at 11:49 AM.
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Old 10-11-2012, 02:07 PM
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williamj williamj is offline
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NTO1221,

Search this site for elevator and/or dumb waiter, there are several here already made out.

williamj
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Old 10-11-2012, 06:58 PM
NT01221 NT01221 is offline
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Well I guess by adding that third floor, things get complicated very quickly! I think I may go with just 2 floors and add a few extras like opening and closing doors, lights and a bell maybe. I never worked with a PLC before, but it sure sounds like the way to go. Looks like there are allot of used PLCs on EBay at great prices. Can anyone recommend a good type for me to look for as something to play around with? Maybe an Allen Bradley SLC100 or an Omron Sysmac Mini? Keep in mind, I need something simple to program. I assume you use some kind of ladder diagram software on a PCM and then load it into the PLC???
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Old 10-12-2012, 09:50 AM
JDT JDT is offline
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Yes, plenty of PLCs on Ebay. The problem is programming. Make sure you can get the programming software before you buy. Some PLC not only need expensive software but also need a programming device or dongle to connect the PC to the PLC.

Some more enlightened PLC manufacturers give away their programming software free, only charging for the actual PLC device (Omron and Matsushita - if I remember correctly).

Another way to do this is to use a PC as your control system. using Serial to I/O or USB to I/O modules. This is known as a "soft PLC".

Have a look at: http://www.audon.co.uk/cubloc_cpu/cb220.html
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Old 11-01-2012, 02:02 PM
NT01221 NT01221 is offline
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Thanks again! I had a look at the Cubloc and have one ordered along with the training board so I can play around with it!
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