Introduction
A lift looks simple: press a button — it comes. But in a house with three lifts there is work behind every button: which car goes, where it stops on the way, when it turns around, why one went past and another stands still. In this kit you build from transistors three lifts and a dispatcher — the screen shows three shafts, eight floors, the floor call buttons and the car panels.
Inside:
- the car — a machine with memory: where it is, where it goes, whether the doors are open, which buttons are pressed; one
CARchip, three copies; - the rule of real lifts — keep going one way while there is work there; floor calls are picked up on the way down;
- floor calls — a button, a latch, a square on the screen;
- the dispatcher — goes round the floors and gives every call to the cheapest car;
- the screen — a segment LCD with 152 segments: cars, doors, buttons, the dispatcher's decisions.
What you need
The kit is standalone. The gates NOT, NAND, NOR, AND, OR, XOR — from any kit of the series or from lesson 0. Latches, flip-flops, adders and decoders are built in lesson 1 (if they are not in your library yet).
How big it is
Three lifts with a dispatcher — 11,422 transistors: a car is 2,854, three cars are 8,562, the dispatcher is 2,478 (it holds three COST chips of 418, one per car), the rest are the floor calls.
It is a model, not a real lift
We build the control logic: who goes where and why. How our lift differs from a real one:
| What | A real lift | Our lift |
|---|---|---|
| where the car is | sensors in the shaft, an encoder | a position counter in the circuit |
| movement | the motor speeds up and slows down | a floor in 4 cycles, evenly |
| doors | a drive, an obstacle sensor, «<>» key | a 4-cycle timer |
| safety | safety gear, speed governor, locks | none — we have no rope and no motor |
| floor call | often two buttons: ↑ and ↓ | one button, collects on the way down |
| dispatcher | a program, counts load and waiting time | logic: distance and direction |
The main thing is as in a real one: each car decides where to go by itself from its buttons and assigned calls, and the dispatcher decides which car goes.
What you get
Four lessons: the screen and one car → a house with one lift → three lifts without a dispatcher → the dispatcher. At the end the screen shows three shafts, and you can see why exactly this car answered the call.