# Model elevator HELP!!

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#### shashankhr

##### New Member
Hi,
I am in the 10th grade and am going to do a project for a science expo/competition. We have to build a model elevator with a minimum of 3 floors. There has to be a button for each floor(Not on each floor). The cabin has to stop only at whichever floor it is asked to go to, without stopping at the intermediate floors.
We have been given a DC micromotor rated 12 volts, a 1 inch pulley, 2 2inch pulleys and 3 shafts. We can use more pulleys if needed.
We are allowed to use ICs, but no PCBs. We can use sensors, microswitches, etc.
Please give me a circuit diagram so i can attempt to make this project a success.

ps: It's not homework. We have not learnt anything about electronics in such detail!

#### MikeMl

##### Well-Known Member
Is this right?

The elevator can initially be stopped be on any of three floors. If the button for the floor it is already on is pushed, nothing happens. If the button for either of the other two floors is pushed, the elevator goes to that floor in the correct direction and stops when it gets there. If it is at either end, it will only go in one direction.

What happens if another button is pushed while the elevator is moving?

Can you use relays?

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#### shashankhr

##### New Member
I don't think we have to worry about another button being pushed when the elevator is moving, but if anything can be done to ignore the push, or take it into account and move, it is good.
It is perfectly alright to use relays

Can anything be made so that it can handle more than 3 floors? More the number of floors, more the points.

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#### MikeMl

##### Well-Known Member
Here is a State Transition Diagram which I think implements your requirements. There are a total of six inputs, three Buttons B1,B2,B3, and three limit switches mounted at the parked position for each floor L1, L2, and L3.

There are seven states, where the elevator is stopped at FIRST, SECOND, and THIRD; is moving up during states UP2 and UP3, and is moving down during states DN2 and DN1.

It takes three flip-flops to represent seven states (with one possible state unused). I have assigned state values so as to make them easy to use to control the motor. Note the bit pattern 100 and 101 occurs when the elevator is moving up, while 011 and 010 occurs while the elevator is moving down. 000, 001, 111 occur while the elevator is stopped. If you look at the leftmost two of these bit patterns, they can be used to control the motor directly, where 10 means up, 01 means down, 00 or 11 means stop.

I'm out of time tonight. You have some reading to do. Read up on "State Transition Table or Diagram", State variables, Present state/Next State, etc.

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#### shashankhr

##### New Member
Thanks a lot!
I understand the logic, but I still don't know how I am to build it.
Can I have a circuit diagram please?

#### blueroomelectronics

##### Well-Known Member
Thanks a lot!
I understand the logic, but I still don't know how I am to build it.
Can I have a circuit diagram please?

Wouldn't someone doing your homework for you defeat the point of the assignment?

#### shashankhr

##### New Member
As i mentioned, this is NOT homework.
It is just a contest into which i was forced

#### blueroomelectronics

##### Well-Known Member
When's the contest?

August 8th

#### Hero999

##### Banned
Well if you've been forced to do it then do you really care if you win?

I remember being made to enter into contests at school and I never made much of an effort unless I was really interested in winning.

In this case I would be tempted to use a microcontroller but you may be forced down the path of logic gates. Heck if this was work, then I'd probably use a PLC.

8th August is a Saturday, what part of the world are you from?

Here in the UK the schools have closed for the summer and only private schools are open on Saturdays anyway.

#### shashankhr

##### New Member
We are not allowed to use any type of printed circuit boards
I would like to win it, if i make an effort to make the model
I am from India, where schools are open on saturdays

#### blueroomelectronics

##### Well-Known Member
Download an install the 30 day trial of Electronic Workbench. You can try out your design there for free. 8 days is not much time, how will you get the parts.

Wouldn't you think it's unfair to other contestants if we do the work for you?

#### Hero999

##### Banned
We are not allowed to use any type of printed circuit boards
That makes using ICs difficult but not impossible.

Is stripboard allowed? If not, use wire wrap, a pretty simple, old, tried and tested technology.

#### shashankhr

##### New Member
According to the rules, there is nothing about stripboards.
Although it says that breadboards can be used. I don't know if they are the same.

#### Hero999

##### Banned
A stripboard is a circuit board with copper strips and pre-drilled holes in a matrix pattern. Using a stripboard involves soldering but it's technically not a PCB because it's not Printed, although it is a Circuit Board but some might argue it's a PCB, so you're better off not using it
Stripboard - Wikipedia, the free encyclopedia

Wire wrap is just board with no tracks; the components are secured by wrapping wire around thier legs.
https://en.wikipedia.org/wiki/Wire_wrap

#### shashankhr

##### New Member
Let me see about the platform for construction of the circuit. I will think about it.

#### blueroomelectronics

##### Well-Known Member
Word of advice, waiting around for the forum members to do your contest entry is not a good idea.

#### shashankhr

##### New Member
I have no other resource!

#### trennonix

##### New Member
the buttons you use to specify which floor you need to go to are push-buttons or can they be switches?
if they can be switches you can use:
1-op-amps to determine if the level you're trying to reach is above or below you and it'll keep going till it reaches the desired level

2-or you can use a customised servo to move the whole thing, look up how servos work you'll get some ideas for your project (i think servos have builtin op-amps to see where they are)

#### trennonix

##### New Member
How do servos work?

do a more advanced search on the electronics behind it, or buy one, get the electronics out of it and mod it to suite your needs

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