QuadRotors research by IIT-students (Robotekies)

Student Projects @ IIT-Delhi

2010-05-07T22:41:00.000+05:30

IIT-Delhi-Open House

2010-04-25T02:54:00.004+05:30

Open House is an annual event of IIT-Delhi, which held in IIT-Delhi on 24 April this year. IIT Delhi call upon various industries delegates and research scholar and also the students from all over Delhi visited IIT-d campus to have a look on various Innovative ideas which took a whole semester time to IIT-Delhi students for molding ideas into reality. All the labs and machinery present at IIT were kept functional on this day.

Here, I have gathered some data of the products kept on display this time.

Electronics

2010-04-23T15:26:00.000+05:30

Transcend 8 GB Class 6 SDHC Flash Memory Card TS8GSDHC6E

Transcend 8 GB Class 6 SDHC Flash Memory Card TS8GSDHC6

Belkin Neoprene Kindle Case (Fits 6" Display, Latest Generation Kindle) [Amazon Frustration-Free Packaging]

Flip UltraHD Camcorder, 120 Minutes (Black)

Brushless DC-Motors

2010-04-23T15:10:00.002+05:30

Brushed vs. Brushless RC Motors

Standard "canned" Motor

A standard brushed motor is often referred as a canned motor. Every canned motor consists of the following parts:

Armature- The rotating portion of the motor. It consists of the poles, terminals, and the commutator.

Poles- Copper wires wound around a piece of metal forming an electromagnet. The poles are attached to the armature. Most motors have 3 or more poles

Terminal- Point at which the copper wire of a poll attaches.

Commutator- A switch on the armature that reverses the current to the poles every 1/2 rotation so that the magnetic fields of each will always maintain rotation.

Brushes- Tabs in the motor cap that are wired to the battery and make contact with the plates on the commutator as the armature rotates.

Magnets- The outer shell (or can) of the motor is lined with two permanent magnets, of opposite polarity. This non-rotating portion of the motor is also referred as the motor stator.

The battery is wired directly to the brushes. The brushes make contact with the plates of the commutator as the motor turns. There are the same number of plates on the commutator as there are poles on the armature.

When the brushes come in contact with the appropriate plates of the commutator, a particular pole (electromagnet) is charged. When a pole is charged, it is attracted to one of the magnets in the can and repelled by the other.

The commutator acts as a switch by switching the polarity of each pole every time the pole passes a magnet. When the polarity is switched, the pole is attracted to the next magnet in the can while being repelled by the one it just passed. This process repeats as long as power is supplied to the motor.

Instruction Set-8051

2010-04-23T14:55:00.003+05:30

Alphabetical List of Instructions

Just click on the Instruction Set to study.

ACALL: Absolute Call
ADD, ADDC: Add Accumulator (With Carry)
AJMP: Absolute Jump
ANL: Bitwise AND
CJNE: Compare and Jump if Not Equal
CLR: Clear Register
CPL: Complement Register
DA: Decimal Adjust
DEC: Decrement Register
DIV: Divide Accumulator by B
DJNZ: Decrement Register and Jump if Not Zero
INC: Increment Register
JB: Jump if Bit Set
JBC: Jump if Bit Set and Clear Bit
JC: Jump if Carry Set
JMP: Jump to Address
JNB: Jump if Bit Not Set
JNC: Jump if Carry Not Set
JNZ: Jump if Accumulator Not Zero
JZ: Jump if Accumulator Zero
LCALL: Long Call
LJMP: Long Jump
MOV: Move Memory
MOVC: Move Code Memory
MOVX: Move Extended Memory
MUL: Multiply Accumulator by B
NOP: No Operation
ORL: Bitwise OR
POP: Pop Value From Stack
PUSH: Push Value Onto Stack
RET: Return From Subroutine
RETI: Return From Interrupt
RL: Rotate Accumulator Left
RLC: Rotate Accumulator Left Through Carry
RR: Rotate Accumulator Right
RRC: Rotate Accumulator Right Through Carry
SETB: Set Bit
SJMP: Short Jump
SUBB: Subtract From Accumulator With Borrow
SWAP: Swap Accumulator Nibbles
XCH: Exchange Bytes
XCHD: Exchange Digits
XRL: Bitwise Exclusive OR
Undefined: Undefined Instruction

Power Management in 8051

2010-04-23T14:49:00.001+05:30

POWER MANAGEMENT IN 8051

· YOU KNOW WHAT……microcontroller is inactive for the most part and just waits for some external signal TO ACT UPON ANYTHING.

· So it is regarded as the wastage of energy if not controlled.

· We can change its program in such a way which reduces its total consumption to approximately 40uA.

· There are two power-saving modes of operation::

1. Idle

2. Power Down.

PCON register

The purpose of the Register PCON bits is:

· SMOD Baud rate is twice as much higher by setting this bit.

· GF1 General-purpose bit (available for use).

· GF0 General-purpose bit (available for use).

· PD By setting this bit the microcontroller enters the Power Down mode.

· IDL By setting this bit the microcontroller enters the Idle mode.

Idle mode

· If the IDL bit of the PCON register is set, the microcontroller turns off the greatest power consumer- CPU unit while peripheral units such as serial port, timers and interrupt system continue operating normally consuming 6.5mA.

· In Idle mode, the state of all registers and I/O ports remains unchanged.

· In order to exit the Idle mode and make the microcontroller operate normally, it is necessary to enable and execute any interrupt or reset. It will cause the IDL bit to be automatically cleared and the program resumes operation from instruction having set the IDL bit.

Power Down mode

· By setting the PD bit of the PCON register from within the program, the microcontroller is set to Power down mode, thus turning off its internal oscillator and reduces power consumption enormously.

· The microcontroller can operate using only 2V power supply in power- down mode, while a total power consumption is less than 40uA.

· The only way to get the microcontroller back to normal mode is by reset.

· While the microcontroller is in Power Down mode, the state of all SFR registers and I/O ports remains unchanged.

· By setting it back into the normal mode, the contents of the SFR register is lost, but the content of internal RAM is saved.

· Reset signal must be long enough, approximately 10mS, to enable stable operation of the quartz oscillator.

verification

2010-04-23T14:03:00.002+05:30

"This post confirms my

ownership of the site and that this site adheres to Google AdSense program

policies and Terms and Conditions."

Stepper Motors

2010-04-16T11:32:00.001+05:30

What is a stepper motor?

A stepper motor is an electromechanical device which converts electrical pulses into discrete mechanical movements.

· The shaft or spindle of a stepper motor rotates in discrete step increments when electrical command pulses are applied to it in the proper sequence.

· The motors rotation has several direct relationships to these applied input pulses.

· 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 rotation is directly related to the number of input pulses applied

Before going any further you should know the benefits this motor provides over other motors. So let’s have advantages of motors first.

Advantages

1. The rotation angle of the motor is proportional to the input pulse.

2. The motor has full torque at standstill (if the windings are energized)

3. Precise positioning and repeatability of movement since good stepper motors have an accuracy of 3 – 5% of a step.

4. Excellent response to starting/stopping/reversing.

5. Very reliable since there are no contact brushes in the motor.

Therefore the life of the motor is simply dependant on the life of the bearing.

6. The motors response to digital input pulses provides open-loop control, making the motor simpler and less costly to control.

7. It is possible to achieve very low speed synchronous rotation with a load that is directly coupled to the shaft.

8. A wide range of rotational speeds can be realized as the speed is proportional to the frequency of the input pulses.

Disadvantages

1. Resonances can occur if not properly controlled.

2. Not easy to operate at extremely high speeds.

Open Loop Operation

One of the most significant advantages of a stepper motor is its ability to be accurately controlled in an open loop system. Open loop control means no feedback information about position is needed. This type of control eliminates the need for expensive sensing and feedback devices such as optical encoders. Your position is known simply by keeping track of the input step pulses. And this is achievable only when the external load doesn’t overcome its stall torque.

Torque v/s Speed Characteristics

You know what, torque v/s speed characteristics are the key to selecting the right motor and drive method for a specific application.

These characteristics are dependent upon

-The motor

-Excitation mode and

-Type of driver or drive method.

A typical “speed – torque curve” is shown in above.

To get a better understanding of this curve it is useful to define the different aspect of this curve.

Holding torque:- The maximum torque produced by the motor at standstill.

Pull-In Curve:- The pull-in curve defines a area refered to as the start stop region.

This is the maximum frequency at which the motor can start/stop instantaneously, with a load applied, without loss of synchronism.

Maximum Start Rate:- The maximum starting step frequency with no load applied.

Pull-Out Curve:- The pull-out curve defines an area refered to as the slew region. It defines the maximum frequency at which the motor can operate without losing synchronism.

Maximum Slew Rate:- The maximum operating frequency of the motor with no load applied.

The pull-in characteristics vary, depending on the load. Generally, and as per i experienced, the larger the load the smaller the pull-in area. The decreasing torque output as the speed increases is caused by the fact that at high speeds the inductance of the motor is the dominant circuit element.

Drive Method

· The shape of the speed – torque curve can change quite dramatically depending on the type of driver used.

· The bipolar chopper type drivers which Ericsson Components produces will maximum the speed – torque performance from a given motor.

· Most motor manufacturers provide these speed-torque curves for their motors.

· It is important to understand what driver type or drive method the motor manufacturer used in developing their curves as the torque vs. speed characteristics of an given motor can vary significantly depending on the drive method used.

When to Use a Stepper Motor

A stepper motor can be a good choice whenever controlled movement is required. They can be used to advantage in applications where you need to control rotation angle, speed, position and synchronism. Because of the inherent advantages listed previously, stepper motors have found their place in many different applications. Some of these include printers, plotters, high-end office equipment, hard disk drives, medical equipment, fax machines, automotive and many more.

Introduction To Microcontroller

2010-04-14T17:20:00.001+05:30

Introduction to Microcontrollers

· While the rest of the people were wondering what was going on, the plotters split in two groups - “software-oriented” and “hardware-oriented”. While the software group was developing gradually, the hardware-oriented people invented transistors.

· Integrated circuits and processors appeared soon. Ordinary people got hold of computers and computer times began to appear.

· And then hobbyists and professionals thought somewhat different” Why should not we make a universal component? A cheap, universal integrated circuit that could be programmed and used in any field of electronics, device or wherever needed? Then they got united and the first integrated circuit was designed and called the MICROCONTROLLER (uC).

What is a microcontroller?

They are what their name suggests. The controller of operations, logics, activities etc. Today they can be found in almost any complex electronic device for eg CAR stereo system, calculators, watches etc. They are programmable, cheap, small, convenient, require negligible power, and there are so many varieties to suit every need. This is what makes them so useful for robotics - they are like tiny affordable computers that you can put right onto your robot.

On the basis of these rules, numerous types of microcontrollers were designed and they quickly became man's invisible companion. Their incredible simplicity and flexibility conquered us a long time ago and if you try to invent something about them, you should know that you are probably late, someone before you has either done it or at least has tried to do it.

How do we work with microcontrollers?

1. Power supply is very much required.

2. Computer works on OS, it works on software which we load.

3. Everything works at lightning speed! The control logic unit keeps everything under control.

4. Quartz crystal operates. What we commonly say as crystal.

5. I/O ports. Source of interaction with environment.

GPS products

2010-04-06T14:18:00.010+05:30

You can avail GPS service provided by the network of 24-36 satellites launched by United States, FOR FREE...!!!

For that you just have to buy one GPS supporting gadget, that hardly cost around...

Rs. 4,000-10,000. After that you will be able to know your location and many more things for free.

If you want to buy any product you cand send your request to me or you can directly browse the website:: just click here .

GPS Systems:: How does it work???

2010-04-02T12:59:00.006+05:30

What is GPS? (click to view PDF)

GPS as navigation.(click to view PDF)

The LED

2010-04-02T11:39:00.004+05:30

OK, Let's make something happen, this LED has to turn on. I'll put it simply, even the greatest project of all times has to have a LED doing something and most likely it started from that.

Was it 0 or 1 for on? 0 I think. On which pin is it? Have a look at the schematic. How do I turn it on? Well, just declare this port pin to be an output and set it to 0. Have a look at the datasheet, you will find an example. Here is how it goes:

#include // header file
int main(void) // program starts here
{
    DDRB = 255; // set port B for output
    PORTB = 0; // set port B pins to 0
    return (0); // return something
}

Compile - Download! Has the LED turned on? Great! No? You press Back three times, by the way is the right code running into the micro?

Now, this code affected all Port B pins, not just the pin the LED is on, not nice. Can you rewrite it not to? Come on. Not to forget, did you check at your project's tree the external dependencies? Where are the registers declared?

Have a look at the datasheet, can you enable the internal pull-up? You supply more current now, can you notice any brightness difference? Great! We can add a delay now. ON Delay OFF Delay, ON Delay OFF Delay, ...

#include
/// Typedefs //////////
typedef unsigned char u8;
typedef unsigned int u16;
typedef unsigned long u32;

/// Defines ///////////
#define forever 117
#define LEDOFF PORTB = (1<<4)
#define LEDON PORTB &= ~(1<<4)

/// Prototypes ////////
void InitPorts (void);
void Delay (u32 count);
int main(void)
{
    InitPorts();
    while (forever)
    {
        LEDON; Delay(20000);
        LEDOFF; Delay(20000);
    }
}
void InitPorts(void)
{
    DDRB = 1<< font="">
}

void Delay(u32 count)
{
    while(count--);
}
Compile - Download! You are happy, aren't you? Experiment with different delays, make delay vary, can you relate Delay values with seconds? You will need to simulate your code with AVRStudio, remember to set the clock speed. How fast can your eyes sense blinking? Why 117? :-D.

Are these typedefs really needed or somewhere there are similar definitions? Can you write generic pin set/reset macros to avoid continuous bit tweaking and make your code more readable?

H BRIDGE AND BIDIRECTIONAL MOTOR CONTROL -1

2010-04-01T15:33:00.012+05:30

H-bridge:: USING SWITCHES

-Such type of circuit can be used for both heavy and small applications preferably for wired remote controlled bots.
-it is easy to make and very cheap.

We have two circuits:-
-one using SPST* press to on switches and
-the other using retractable DPDT* switches.

SPST (PUSH TO ON switches):-

Such switches turn on and connect one terminal to the other when pressed and returns to its position when not pressed.

-Here in this circuit when switch s1 and s4 are pressed then motor will run in one direction and
-when switches s2 and s3 are pressed it runs in the opposite direction.

DPDT switch

(RETRACTABLE DPDT SWITCH)

-A dpdt switch is equivalent to two spst switch.
-It can switch two paths for the flow of current simultaneously in two different directions.

following circuit can be used.

When you press the stick of the switch the motor will turn in one direction and in other direction when you press it down.
Now, since it is retractable, it will come to the center when you leave it free. You can use two such arrangements to drive two motors of a wired robot.

H-bridge USING RELAY

A simple and relatively cheap h-bridge circuit can be made using relays. Advantage of such circuit is that it can be used for heavy applications.

The circuit diagram given below:

When switch s1 is pressed the motor runs in one direction and switch s2 is pressed it turns in the other direction. The switches are simple spst switches used above(h-bridge using switches).

You can use any spst relay in such a circuit as I have marked12volts both for motor and relay however you can drive motor with higher voltages also which extreme values will be decided by the specification of relay you are using. One more thing, the two pins of relay opposite to no and nc are relay coil pins which must be supplied rated voltage only and not more than that.

NO: normally open

NC: normally closed

When no key is being pressed then in each relay ,the point between relay coil pins remains connected with NO , when switch is pressed the connection which was existing in the coil in off state breaks and now that pin gets connected to NC. Thus one lead of motor gets +12v and other gets ground. Similar thing happens with other relay when the other switch is pressed.

Motor will not run when either you press none of the keys or you press both the keys.

The relays I used for this circuit is called sugar cube relay and can withstand currents upto 10A!

Line Follwer Program::Assembly Language

2010-04-01T14:54:00.003+05:30

;Mohit "hey this is LFR's assembly language code, from this you can just take the idea of its program... soon ill be uploading the circuit dia too. ;So you would be able to directly copy it and run your Lfr and also the C version of it...
; 25,June,09
;Status::Working
;s/w version no.:1.00.01
;Microcontroller Used::AT89s52
;Crystal frequency:11.0592Mhz

;hardware declaration

sensleft equ p2.0
sensright equ p2.1
input1 equ p3.0
input2 equ p3.2
input4 equ p3.4
input3 equ p3.5

;ram declaration
stackval equ 70h

;Start of main program

Org 0000H

PowerON:
Mov SP,#stackval
Mov P0,#0ffH
Mov P1,#0ffH
Mov P2,#0ffH
Mov P3,#0ffH
Mov IE,#00H
Mov IP,#00H

mainloop:
jb sensleft,rightorforward
jb sensright,leftorforward
acall back
sjmp mainloop

rightorforward:
jb sensright,forward
acall right
ret

leftorforward:
jb sensleft,forward
acall left
ret

right:
clr input1
setb input4
setb input3
setb input2
ret

left:
clr input3
setb input4
setb input1
setb input2
ret

forward:
clr input3
clr input1
setb input2
setb input4
ret

back:
clr input2
clr input4
setb input1
setb input3
ret

end

ARCHITECTURE & HARDWARE DETAILS

2010-03-30T14:47:00.010+05:30

You know what microcontroller has nothing good in appearance….
4 Kb of ROM
128b of RAM
4 ports having in total of 32 input/output lines
But it has its implications in thousand spheres around us. That it why it is really handy.

PIN CONFIGURATIONS

PIN 1-8 PORT1: Each of these pins can be configured as an input or an output.
PIN 9 RS: A logic one on this pin disables the microcontroller and clears the contents of most registers.
By applying logic zero to this pin, the program starts execution from the beginning.
PIN 10-17 PORT3: Similar to port 1, each of these pins can serve as general input or output.
Besides, all of them have alternative functions:
PIN 10:RXD: Serial asynchronous communication input or Serial synchronous communication output.
PIN11-TXD: Serial asynchronous communication output or Serial synchronous communication clock output.
PIN12-INT0: Interrupt 0 input.
PIN13-INT1: Interrupt 1 input.
PIN14-T0: Counter 0 clock input.
PIN15-T1:Counter 1 clock input.
PIN16-WR: Write to external (additional) RAM.
PIN17-RD: Read from external RAM.
PIN18,19 -X2,X1:Internal oscillator input and output. A quartz crystal which specifies operating frequency is usually connected to these pins. Instead of it, miniature ceramics resonators can also be used for frequency stability. Later versions of microcontrollers operate at a frequency of 0 Hz up to over 50 Hz.
PIN20-GND: Ground.
PIN 21-28:PORT2: This port pins are configured as general inputs/outputs.
PIN29-PSEN: If external ROM is used for storing program then a logic zero (0) appears on it every time the microcontroller reads a byte from memory.
PIN30-T0: Before reading from external memory, the microcontroller puts the lower address byte (A0-A7) on P0 and activates the ALE output. After receiving signal from the ALE pin, the external register memorizes the state of P0 and uses it as a memory chip address. Immediately after that, the ALU pin is returned its previous logic state and P0 is now used as a Data Bus. As seen, port data multiplexing is performed by means of only one additional (and cheap) integrated circuit.
PIN 31-EA:By applying logic zero to this pin, P2 and P3 are used for data and address transmission with no regard to whether there is internal memory or not. By applying logic one to the EA pin, the microcontroller will use both memories, first internal then external.
PIN 32-39-PORT0: this port can be used as general inputs/outputs.
PIN 40-SUPPLY: +5V power supply.

NOTE-There are also some other functions of the microcontroller pins discussed above. I have not discussed it here it is out of scope of this level of tutorial. We will deal it in some higher level courses. For now concentrate upon these basics.

MAJOR CONSTITUENTS

Here are the major components of microcontroller which constitutes almost whole of it. I have discussed here some major properties of it.

Central Processor Unit (CPU)

As the name suggests, this is a unit which monitors and controls all processes within the microcontroller. It consists of several smaller subunits, of which the most important are:
Instruction decoder
Arithmetical Logical Unit (ALU)
Accumulator
There is a common convention which we follow in electronics is:-
High means “1”
Low means “0”

Random Access Memory (RAM)

Random Access Memory (RAM) stores data and intermediate results created and used during the operation of the microcontrollers.
The content of this memory is cleared once the power supply is off. For example, if the program performs an addition, it is necessary to have a register standing for what in everyday life is called the “sum”.
For that purpose, one of the registers in RAM is called the "sum" and used for storing results of addition.
The size of RAM goes up to a few KBs.

Read Only Memory (ROM)

Read Only Memory (ROM) is a type of memory used to permanently save the program being executed.
The size of the program that can be written depends on the size of this memory.
ROM can be built in the microcontroller or added as an external chip, which depends on the type of the microcontroller.
The internal ROM is usually smaller and more expensive, but leaves more pins available for connecting to peripheral environment.
The size of ROM ranges from 512B to 64KB.
Electrically Erasable Programmable ROM (EEPROM)
It is a special type of memory. Its contents may be changed during program execution (similar to RAM), but remains permanently saved even after the loss of power (similar to ROM).
It is often used to store values, created and used during operation (such as calibration values, codes, values to count up to etc.), which must be saved after turning the power supply off.
A disadvantage of this memory is that the process of programming is relatively slow. It is measured in milliseconds.

Special Function Registers (SFR)

Special function registers are part of RAM memory.
Their purpose is predefined by the manufacturer and cannot be changed therefore.
Since their bits are physically connected to particular circuits within the microcontroller, such as A/D converter, serial communication module etc., any change of their state directly affects the operation of the microcontroller or some of the circuits.
Each bit of this register controls the function of one single pin.

Program Counter

Program Counter points to the memory address containing the next instruction to execute.
After each instruction execution, the value of the counter is incremented by 1. For this reason, the program executes only one instruction at a time just as it is written.
However, the value of the program counter can be changed at any moment, which causes a jump to a new memory location. This is how subroutines and branch instructions are executed.

Input/output ports (I/O Ports)

In order to make the microcontroller useful, it is necessary to connect it to peripheral devices.
Each microcontroller has one or more registers (called a port) connected to the microcontroller pins.
It is possible to change a pin function according to the user's needs.

Oscillator

It is usually configured as to use quartz-crystal or ceramics resonator for frequency stabilization.
It can also operate without elements for frequency stabilization (like RC oscillator).
It is important to say that program instructions are not executed at the rate imposed by the oscillator itself, but several times slower.
It happens because each instruction is executed in several steps. For some microcontrollers, the same number of cycles is needed to execute any instruction, while it's different for other microcontrollers.
Suppose if a frequency of oscillator is 20MHz, the execution time of an instruction is not expected 50nS, but 200, 400 or even 800 nS, depending on the type of the microcontroller!

Timers/Counters

These are well known as miniature electronic stopwatches.
These are commonly 8- or 16-bit SFRs the contents of which is automatically incremented by each coming pulse.
Once the register is completely loaded, an interrupt is generated.
If the registers use pulses coming from external source, then such a timer is turned into a counter.
A register or a memory cell is an electronic circuit which can memorize the state of one byte.
All registers of ROM as well as those of RAM referred to as general-purpose registers are mutually equal and nameless.

Watchdog timer

The Watchdog Timer is a timer connected to a completely separate RC oscillator within the microcontroller.
If the watchdog timer is enabled, every time it counts up to the program end, the microcontroller reset occurs and program execution starts from the first instruction.
Current limitations of 8051
Single pins can receive a current of 10Ma if they are in sink state.
If all 8 bits of a port are active, a total current must be limited to 15mA (port P0: 26mA).

Serial communication

Parallel connections between the microcontroller and peripherals established over I/O ports are the ideal solution for shorter distances up to several meters.
For longer distances serial communication is the best solution.
Work of the programmer/user is reduced to a simple write (data to be sent) and read (received data).
A byte consists of 8 bits grouped together. If a bit is a digit then it is logical that bytes are numbers.
All mathematical operations can be performed upon them, just like upon common decimal numbers, which is carried out in the ALU.
It is important to remember that byte digits are not of equal significance. The largest value has the leftmost bit called the most significant bit (MSB). The rightmost bit has the least value and is therefore called the least significant bit (LSB).
Since 8 digits (zeros and ones) of one byte can be combined in 256 different ways, the largest decimal number which can be represented by one byte is 255 (one combination represents zero).

Program

In order to write a program for the microcontroller, several low-level programming languages can be used such as Assembly, C and Basic.
Unlike other integrated circuits which only need to be connected to other components and turn the power supply on, the microcontrollers need to be programmed first.
Writing program procedure consists of simple writing instructions in the order in which they should be executed.

SERVO-BASICS

2010-03-30T02:46:00.004+05:30

FEEDBACK CONTROL MECHANISM

Control theory is an interdisciplinary branch of engineering and mathematics, that deals with the behavior of dynamical systems. The desired output of a system is called the reference. When one or more output variables of a system need to follow a certain reference over time, a controller manipulates the inputs to a system to obtain the desired effect on the output of the system.

A transducer is a device that converts one type of energy to another. The conversion can be to/from electrical, electro-mechanical, electromagnetic, photonic, photovoltaic, or any other form of energy. While the term transducer commonly implies use as a sensor/detector, any device which converts energy can be considered a transducer.

Applications of servo mechanism:-

1. Servomechanisms were first used in military fire-control and marine navigation equipment. Today servomechanisms are used in automatic machinetools, satellite-tracking antennas, remote control airplanes, automatic navigation systems on boats and planes, and antiaircraft-gun control systems.

2. Many autofocus cameras also use a servomechanism to accurately move the lens, and thus adjust the focus. A modern hard disk drive has a magnetic servo system with sub-micrometre positioning accuracy.

3. A common type of servo provides position control. Servos are commonly electrical or partially electronic in nature, using an electric motor as the primary means of creating mechanical force. Other types of servos use hydraulics, pneumatics, or magnetic principles. Usually, servos operate on the principle of negative feedback, where the control input is compared to the actual position of the mechanical system as measured by some sort of transducer at the output. Any difference between the actual and wanted values (an "error signal") is amplified and used to drive the system in the direction necessary to reduce or eliminate the error. This procedure is one widely used application of control theory.

4. Another device commonly referred to as a servo is used in automobiles to amplify the steering or braking force applied by the driver. However, these devices are not true servos, but rather mechanical amplifiers.

SERVO Fundae

-Due to their affordability, reliability, and simplicity of control by microprocessors, RC servos are often used in small-scale robotics applications.

-The servo is controlled by three wires: ground (usually black/orange), power (red) and control (brown/other colour). This wiring sequence is not true for all servos, for example the S03NXF Std. Servo is wired as brown (negative), red (positive) and orange (signal). The servo will move based on the pulses sent over the control wire, which set the angle of the actuator arm. The servo expects a pulse every 20 ms in order to gain correct information about the angle. The width of the servo pulse dictates the range of the servo's angular motion.

-A servo pulse of 1.5 ms width will set the servo to its "neutral" position, or 90°. For example a servo pulse of 1.25 ms could set the servo to 0° and a pulse of 1.75 ms could set the servo to 180°. The physical limits and timings of the servo hardware varies between brands and models, but a general servo's angular motion will travel somewhere in the range of 180° - 210° and the neutral position is almost always at 1.5 ms.

-RC Servos are usually powered from either NiCd or NiMH packs common to most RC devices. More recently these systems are powered by Lithium Polymer (LiPo) packs or LiFePO4 packs. Voltage ratings vary from product to product, but most servos are operated at 4.8 V or 6 V DC from a 4 or 5 cell NiCd or NiMH battery, or a regulated LiPo pack.