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elevator system without microcontroller

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sam288

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Does anybody have an idea ,how can we design an elevator system without using micro controllers??
Can anybody please give me the names of related sites??
 
I have an idea, but I caution that I haven't checked it out thoroughly and could have a "gotcha" somewhere, which I am sure you or another poster will point out. :) Here goes.

Let a pushbutton request on each floor outside the elevator set a latch corresponding to its floor. Let's number those latches according to the corresponding floor. Let a press of a floor request button from inside the elevator also set the same latch corresponding to the floor requested. Let there be a indicator word whose length (number of bits) be equal to the number of floors. This indicator word will have only one bit set active at any time to indicate the position of the elevator. Let the outputs of all the latches also form a word of same length. Let us do a logic comparison of the latched word and the position word. The comparison will yield a result of "less than", "equal to", or "greater than". If "less than" the elevator will go in one direction, "greater than" it will go the other direction, "equal to" the elevator is stopped at the correct floor with nothing left to do. This is how the elevator will know what direction to go.

Let us also do an AND function of each pair of bits from the position word and the corresponding bit of the latched word. When this AND function yields a "yes" then the elevator has reach one of its destination floors and shall stop, open the door, and clear the latch for that floor, since its job is done for that floor. The elevator will proceed when the door closes.

The elevator will continue up and down serving the set latches, until all the latches are cleared.
 
By the time you mess around with all sorts of individual chips, it would be cheaper and simpler to use a micro.
With a micro you can adjust the timing, add additional features and get the design to work without having to change any of the hardware.

I have learnt a long time ago that a micro is the only way to go as the program can be kept from prying eyes and you have something you can sell.

You are simply wasting your time with discrete components if you want to sell your idea at some later date.
Here is the project I am currently working on:
It is a set of traffic lights that are all individually powered by a solar panel and communication is via an RF link with feedback to signify the lights are in sequence. This saves digging up the road and laying all those unnecessary cables.
The lights are LED based with adjustable brightness to suit the day or night. It is a million-dollar project with enormous cost-savings.
Even your elevator project is viable. I designed a small screen to show the floor and the numbers moved up the screen or down the screen to simulate the movement of the elevator.
 
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Actually i have no option but go for discrete components... Because its an assignment assigned to us and it says 'no microcontrollers'...
 
First you make a state table or state diagram (Google "state transition table" if you need to) of every state the elevator can have (at a particular floor, going to a particular floor, selection of a floor with a push-button, open door, close door, etc.). Then you generate the boolean logic to perform the state machine functions and to go from one state to the next. Finally, incorporate the logic using discrete IC logic gates or perhaps a programmable logic array.
 
I have made the state table....But the state table has only present and next states...should i add another variable 'output'...so that i can give this signal to the motor of the elevator....But i cannot exactly figure out how to go about this....Can anybody please help....
 
You are really going backwards, designing in logic.
I realise the teacher doesn't have a clue about microcontrollers but you should tell him that NOBODY designs around logic. In fact many of the suppliers don't even stock these old-fashioned chips.

Ask the teacher: What are you learning by using logic?

It reminds me of the days when I was a teacher and the girls learnt Pitman shorthand but all the employers required Dacomb.

Nothing has changed.
 
I have made the state table....But the state table has only present and next states...should i add another variable 'output'...so that i can give this signal to the motor of the elevator....But i cannot exactly figure out how to go about this....Can anybody please help....

Yes, you would add variables to command the motor's direction and whether the motor is ON or OFF.

If you can "cheat" a little, a crude form of microcontroller, called a state machine, can be made from discrete logic components, with the memory being a ROM chip. It amounts to a binary counter with a clock stepping the counter. The counter outputs feed the address lines of the ROM. You program the ROM to produce the outputs from your state diagram. Some of the address lines to the ROM are controlled by the counter and some of them may be controlled by your floor pushbuttons so that conditonal decisions can be made. Some of the ROM outputs can be used to load the counter to generate a new address for the ROM.
 
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Contains solid state logic (OK...some diodes) ...and no microprocessor!

Ken ;)
 

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