DEVELOPMENT OF MICRO CONTROLLER 89C51 BASED DRIVER FOR ROBOTIC APPLICATIONS
UNDER THE GUIDENCE OF
This project deals with development of micro controller based stepper motor driver for robotic precession movements.
Here we use AT89c51 controller providing 4 I/O ports which is easy to connect.It has 8Kbytes of flash program memory and 256 Bytes of RAM.
Stepping motors can be viewed as electric motors which can be driven using TTL input NPN darlington pair.Typically all windings in the motor are part of the stator,and the rotor either a permanent magnet or a toothed block of some magnetically soft material.
Because steppers can be controlled by turning coils on and off,they are easy to control using digital circuitry and micro controller chips.The controller simply energizes the coils in a certain pattern and the motor will move accordingly.
MICRO CONTROLLER 89C51 DRIVER ULN2003 STEPPER MOTOR
Now-adays the advancement has created a revolution in the field of ROBOTICS.To move a robot according to our requirement we use a stepper motor.
We mainly choose stepper motor because it can be controlled effectively when compared to any other A.C or D.C motor and smallest angle can be achieved.
As micro controllers are silent workers in many apparatus ,so we use these micro controllers for controlling the movement of stepper motor.
These micro controllers are very low output devices which cannot drive a stepper motor,so we connect a high current gain circuits called drivers inbetween the microcontroller and the motor.
As a tiny base current is required to switch on the circuit,the output of microcontroller is given as input to the driver and the very high current gain of the driver is given as input to the motor.
EMBEDDED SYSTEMS The Embedded system is a combination of software and hardware designed to perform a specific function.It may use a micro processor or a micro controller to perform the task A Micro-controller is a processor with an on chip RAM, ROM, Timer, and I/O ports. Micro processors do not contain RAM, ROM, and I/O ports on the chip.They have to connected externally which makes them bulkier and costlier.
8051 is a 8-bit micro controller introduced by Intel Corp in 1981. It had 128 byte of RAM, 4K bytes of on-chip ROM, two timers,one serial port and four ports each of 8-bit wide on single chip.As it is 8-bit micro controller only 8 bits data can be processed at a time. 8051 has a total of 5+1 Interrupt sources, 5 software and 1 hardware. 8051 FAMILY
ĒĀ: External access, used mainly in 8031 family to connect to external memory, where it connected to GND. ĒĀ – 0 external memory, ĒĀ – 1 internal memory program store enable, used to access the program code stored in external memory. ALE: Address latch enable, O/P, active high. It is used in 8031 which multiplexes address and data on port 0,which is connected to external memory. PORTS: All the four ports are 8-bit ports. On RESET all the ports are configured as output. PORT0: It occupies pins from 32-39 and can be used for I/P or O/P. It is designated as AD0 – AD7 for both address and data when an external memory is connected. ALE=0 it provides data D0 – D7,when ALE=1, it provides address A0 – A7.
PORT1: Port1can also be used as I/O and O/P. It is also a 8-bit port occupying pins 1 – 8. PORT2: Port2 occupies pins 21 – 28 .It can be used as I/O and O/P. It is also used as A8 – A15, address lines when connected to an external memory. Along with port0 it provides the 16-bit address to the external memory. PORT3: It occupies pins 10 – 17 and can be used as I/O or O/P. Port3 has additional functions like interrupts, read, write, timers etc., The pins P3.0 and P3.1 are used for serial communication, P3.2 and P3.3 are used for external interrupts, P3.4 and P3.5 are used for timers and P3.6and P3.7 are used to write and read signals of external memories connected in 8031-based system. All the ports of 8051 family are bit addressable.
A stepper motor requires an electrical sequencer called a driver which is a specialized type of D.C power supply.
The driver consists of darlington pair which behaves like a single transistor with a very high current gain.
Basically this is two transistors connected together so that the current amplified by the first is amplified further by second transistor.
The overall current gain is equal to the individual gains multiplied together
hfe = hfe1 * hfe2
hfe1 and hfe2 are gains of individual transistors.
In the circuit diagram transistor TR1 requires low power but TR2 will require high power,so the maximum collector current Ic(max) is connected to TR2.
To turn on the circuit there must be 0.7v across both base emitter junctions which are connected in series inside the darlington pair,therefore it requires 1.4v to turn on.
A stepper motor is a electro mechanical device which converts electrical pulses into discrete mechanical movements.
The shaft of spindle of a stepper motor rotates in discrete step movements when electrical command pulses are applied to it in a proper sequence.
The sequence of the applied pulses is directly related to the direction of motor shafts rotation.
The speed of the motor shafts rotation is directly related to the frequency of the input pulses and the length of the rotation is directly related to the number of input pulses applied.
Man power can be reduced by the usage of robotics.
By using stepper motor accurate movement of robot can be achieved.
No need of higher power supplies as we use drivers to run a stepper motor.
A simple circuitry of darlington pair for high current gain is used in the drivers.
Robots are used to save human life in extremely harsh environment in the field of space explorations.
Automization of robots with artificial intelligence has spread its use in various fields.
In industrial sector robots are used in manufacturing,assembly,handling,inspection,union,cleaning etc.
In service sector robotics will be used for entertainment and personal assistance.
In the field of biomedical robotics are used in aspects of clinical activities for the exploration of physiological knowledge in the development of Bio-metric robots.
The main application is in the field of surgery,rehabilitation and bio robotics.