Lift Controller

Project code:- ?? Project Cost:- INR:- Rs. 10000/- USD:- 250$

Block Diagram Lift Controller Block Diagram

The project designed on the intel’s most powerful microcontroller 8051. I have designed this project only upto ground plus three floors with collespable gate features. Similar technique can be employed to design for more floors.


I don’t claim to be expert on the lift controller design , but having seen the behavior of the lift operating in multi story structures,I have designed this projects for the under graduate engineers.

Circuit explanation:

The project comprises of following blocks
Microcontroller main controller
Limit switch section to be connect on each floor in side the lift passage Operating switchs .
four switches onsite the lift car one switch on each floor.
Indication section one seven segment inside the lift compartment four indication leds should be fitted inside push buttons fitted inside the lift car.
Control Relay section: three relays are used to control the lift motor starter.two relays are for the up down movement of the lift motor one relay is for bell.

Power supply section to give the required power supply to the lift controller.

R2 and c4 gives the requird reset pulse to microcontroller. Capacitor c5,c6 along with crystal x1 gives the required clock to the microcontroller. Port 1 and port3 are used as input port where all the switches and limit switches are connected.default logic state of these two port is high and all the switches connected to the port pins hasone side connected to ground ,so whenever any switch makes contact that particular pin logic state becomes low, and switch made condition is detected. If no switch is in make condition, the logic state will remain high..
Port 0is a open sourse port so we have to connected an external pull up resistor in order to make this port also digital i/o port..this port drives the common cathode seven segment display through 74245 transreceiver ic which is used as buffer in our circuit,since microcontroller port pin current is not enough to drive seven segment leds..

Port2 drives four leds and three relays and this is also an output port..by default the logic state is high at start so all the relays and indication leds are in off state to switch on any led we have to make the port pin logic to low through our program since all the leds ate connected in common anode mode.
Operation of the relay circuit. If you look at the relay coil connected to transister Q1 and Q2,
Since the default logic state of the port 2 is high ,transister Q1 get high logic at it’s base through resistor R20, Q1 is in on state and collecter of Q1 is at low logic so Q2 is off and no current flows through coil.. when we make the logic low at the base of transister Q1 ,Q1 will become off and Q2 will become on since Q2 base will become high through a pull up resistor r21 at the base of Q2. Current will flow through the relay coil and it will chane it’s contacts. All the relays function in the same manner. Diodes d11, d12 ad d13 connected across the relay coil is to protect the circuit from the e.m.f. generated by the relay coil during make break operation. LD6,LD7 and LD8 are relay on/off indication leds. Resistances r16,r19 and r22 are current limiting resistances. Resistance r7 to r13 connected to seven segment display are also current limiting resistors

Power supply : 9v 1 ampere transformer is connected to pcon1 bridge rectifire diodes comprises of diodes d1 to d4 performs the rectification c1,c2 and c3 ate filter capacitors ld 1 is an power indication led.r1 is a current limiting resistor. ic1 is a 5v regulator ic its, input is 12v dc and output is 5v dc. 12v dc is required for our relays and 5v regulated supply is required to operate our entire circuit..alternatively battery back up canalso be connected to the power supply. In order to operate the controller during power failure, if you have emergency diesel generator set to operate your lift motors.

Operation of the lift is same as it is observed at all the places where collepsable door is used .
An emergency switch is also provided in the lift compartment in order to give an emergency alarm when lift get stuck up inbetween floors due to various reasons, so that person can be taken out safely.

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