You have been requested by your Senior Engineer to design a lift control unit (LCU) and prepare a report detailing your proposed solution. The client requires a microcontroller based control unit to automate the operation of a passenger lift that services a three story building. The existing equipment including the winch, lift, cabling, doors and electrical switch gear has recently been refurbished, but the old electromechanical lift controller unit is to be replaced. The new LCU is also required to provide a display showing the location of the lift as a floor number.
The existing lift equipment includes the lift itself, the doors, the winch, a position sensor, a door ajar sensor, 4 call buttons on three floors and 3 in-lift floor select buttons. The detail for the electrical interface to equipment is shown in Figure 1, and explained below: