Dissertation submitted in partial fulfillment of the Btech. course.
MECHANICAL ROBOTIC ARM
Under the Guidance of
Submitted By
Abhishek Kaushik
SG-119836.
Submitted to:
Rimt Polytechnic
Mandi Gobindgarh
Introduction:-
In this project we will control robotic arm with switch Logic . we will make robotic arm which will move around axis., up and down finction and jaws. We will use servo motor to move arm up and down. There will be geared motors for jaws and around axis. Control of motor is done by the H bridge circuit. In the H bridge circuit we use two npn transistor and two pnp transistor. With the help of this two npn transistor and two pnp transistor we control the direction of the motor.
H bridge is interface with the microcontroller with the hel p of opto-coupler circuit., Opto-coupler circuit not only interface the microcontroller with the H bridge but also provide a electrical isolation between microcontroller and dc motor circuit.
Crane control,lift control. Robotic arm is part of the mechatronic industry todays fast growing industry. In this project we will three stepper motors for controlling purpose. But we will try to control three functions with two motors. We know it will not a easy task for meachnical industry because we will have to control the stepper motors using microcontrollers programming. In this project we will control the stepper motors with microcontroller. We will use 89c051 for this purpose because one of our friend have this ic’s programming kit and he will help us in programming.First of all we will make the PCB- printed circuit board or will design it from outer sources. Then we will soder components on PCB. In this project we will make 5volt power supply for microcontroller circuit.
First of all we will design the jaws of robotic arm. It will be of following shape
2”
3
3”
3”
Jaws will be metallic. They will be made of sheet metal.
ARM: arm will be made up of wood material.
2
1
3 inch
10 inch
Stepper motor
stepper motor have five wires . One for common supplies another four for winding purpose. By giving different signal to each we will control the stepper motor.
The wires from the Logic PCB connector to the stepper motor in a TM100 Disk Drive are as follows
This kind of motor has four coils which, when energised in the correct sequence, cause the permanent magnet attached to the shaft to rotate.
There are two basic step sequences. After step 4, the sequence is repeated from step 1 again.
Reversing the order of the steps in a sequence will reverse the direction of rotation.
a. Single-Coil Excitation - Each successive coil is energised in turn.
Step / Coil 4 / Coil 3 / Coil 2 / Coil 1a.1 / on / off / off / off /
a.2 / off / on / off / off /
a.3 / off / off / on / off /
a.4 / off / off / off / on /
This sequence produces the smoothest movement and consumes least power.
Single-Coil Excitation
Inside a Stepper Motor
The stepper motors we are concerned with are those taken out of old 5 ¼" floppy disk drives. Some of the comments below may therefore not apply in all cases…
The simplest way to think of a stepper motor is a bar magnet and four coils.
When current flows though coil "A" the magnet is attracted and moves one step to the right. Coil A is then turned off and coil "B" turned on. The magnet moves another step to the right. Coil "B" is then turned off and coil "C" turned on. The magnet moves another step to the right and so on…
A similar process occurs inside the stepper motor, but the 'magnet' is cylidrical and rotates inside the coils.
In order to make a stepper motor rotate you must turn on each coil in the correct sequence. The motor will continue to rotate as long as you continue the sequence. A typical code sequence would be:
count := 1repeat
port[888] := 1;
delay(50);
port[888] := 2;
delay(50);
port[888] := 4;
delay(50);
port[888] := 8;
delay(50);
count := count + 1;
until count > 50;
NOTE1: The "delay" is needed provide enough time for the magnetic field inside the coils to build up and the magnet to move. Without the 'delay', the coils will switch on and off so fast that the magnet will not get a chance to be attracted and it will not move.
NOTE2: To reverse the direction, simply reverse the output order.
The Coil Switch-on Sequence
The stepper motor in a 5 ¼" floppy drive (the one that moves the head back and forth over the disk - NOT the one that spins the disk) has FIVE wires coming out of it. If you are lucky they will be coloured Brown, Yellow, Red, Blue and White. (Many of the ones I've looked at have five brown wires!)
The 'four' coils described above are actually arranged as two 150 ohm coils with centre taps. The centre taps are lines "1" and "2" in Figure 1.1. This line is generally called the "common".
Figure 1.1
Measuring the resistance between each of the wires coming out of the motor produces the following readings:
Measured Resistance (ohms)
2 /
1a /
1b /
2a /
2b
1 /
- /
0 /
75 /
75 /
75 /
75
2 /
0 /
- /
75 /
75 /
75 /
75
1a /
75 /
75 /
- /
150 /
150 /
150
1b /
75 /
75 /
150 /
- /
150 /
150
2a /
75 /
75 /
150 /
150 /
- /
150
2b /
75 /
75 /
150 /
150 /
150 /
-
One of the five wires is the 'common'. You can easily identify the common with a multimeter. It will be the one that reads 75 ohms between it and all the other four lines in turn. The other four are impossible to identify using a multimeter. You will need to use an interface and connect it to a computer for the next step. (You could just use wires from a 12 volt battery if you wanted.)
Using the Demonstration Interface to Drive a Stepper Motor
(For details about the Demonstration Interface see: robokit.html)
· Connect a 12 volt DC supply to the demonstration interface (in place of the 9 volt battery).
· Solder the 'common' lead to the positive line on the Demonstration Interface.
· Solder each of the other four wires to the points where the resistor connects to a line from the ULN2803. (Keep the wires in order from the common wire and solder them to data lines 0, 1, 2, and 3.)
· Connect the interface to a computer and send 'out' commands of 1,2,4 and 8. The motor should 'step' in a clockwise, or anti-clockwise direction. - If it 'jerks' as it tries to change direction, or simply 'shudders' you will need to experiment with other control sequences.
Hopefully your motor moved in a consistent direction. Now you need to write code as outlined above and try for complete rotations
BLOCK DIAGRAM
Requirements:
· Software:-
Keil compiler for programming
Window xp
Item / Qty. / IDOPTOCOUPLER / 2 / IC 817
MCU / 1 / IC 89s52
CRYSTAL / 1 / 12 MHZ
CERAMIC / 2 / 27 PF
CONNECTING WIRES
IC BASE / 1 / 20 PIN
1 / 16 PIN
LEDS / 5 / RED 15 MM
REGULATOR / 1 / 7805
CAP / 1 / 1000 MICROFARAD
TR / 2 / TR548
IC speech recognition / 1
EEPROM / 1 / 64k
PCB’s / 4
Power supply 9v / 1
2 / TR 558
MICRO SWITCHES / 20 / PUSH TO ON
Bibiliography:-
For Stepper motor
http://www.ecawa.asn.au/home/jfuller/steppers.html