Hi shashankhr,
Thank you for your appreciation, it took me three days.
And i realise it does not meet what you want, i put it forward as a possible basis for including extra circuitry.
You may not need flip-flops, you may only need bi-stables - which are easier to drive.
I assume that you would want them as 'memories' or just 'flags'.
A short 'wait' period would also be needed i think, so that the lift can then respond,
to a call from another floor, after completing the call in progress.
The arrangement i posted (# 45) uses simple 'make' press buttons for UP and DOWN,
these can be paralleled up and extended to the other floors. The thing i could not see an easy way to perform, is the operation of 'going past a floor' to answer a call more than one floor away. There might be an easy way to do this, but i havent seen it yet.
If you can see a way to do that, then i think that will meet your request.
With only three floors, such a call can only come from the top or the bottom.
It might be possible to include two relays specifically for those two eventualities.
The arrangement 'as-shown' is extendable over as many floors as you like, but as said- it would stop at each level.
It would no longer be extendable in that way if such special purpose relays were included for the middle floor of a three floor set-up.
I dont really see adding buttons for each floor as a problem.
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I have tried to see an arrangement using relays, because they are easier to understand for many people, but i cant see an easy way to meet your spec.
I think that your best way would be to sort out a micro-processor driving a motor, and fix up three sensors to drive the micro-processor.
Then ask nicely for someone to help with programming it.
Or maybe such small programs are aready downloadable from somewhere.
Given your limited time, and limited experience, i really think this is your most likely route to success.
Fixing up a small microprocessor and giving it a program to run from press buttons to call the lift, and sensors in the lift shaft is something that can be done in the time available.
I would be interested to hear from others, whether or not they agree with this approach.
Best of luck with your project,
John