Simple Robots and Microprocessor

Simple Robots and Microprocessor


This term paper includes the study of microprocessor and simple robots. Firstly the microprocessor defined and its evolution is given. Thereafter the simple robots defined. As simple robots I have taken the example of "Line Follower Robots". Its circuit diagram and its working described briefly. Finally the role of microprocessor in simple robots i.e. in the line follower robot and its future scope is discussed .


A robot is a virtual or mechanical artificial agent. In practice, it is usually an electro-mechanical machine which is guided by computer or electronic programming, and is thus able to do tasks on its own. Another common characteristic is that by its appearance or movements, a robot often conveys a sense that it has intent or agency of its own. While A microprocessor incorporates most or all of the functions of a central processing unit (CPU)on a single integrated circuit (IC).


A microprocessor incorporates most or all of the functions of a central processing unit on a single integrated circuit (IC)The first microprocessors emerged in the early 1970s and were used for electronic calculators, using binary-coded decimal (BCD) arithmetic on 4-bit words. Other embedded uses of 4- and 8-bit microprocessors, such as terminals, printers, various kinds of automation etc, followed rather quickly. Affordable 8-bit microprocessors with 16-bit addressing also led to the first general purpose microcomputers in the mid-1970s

Computer processors were for a long period constructed out of small and medium-scale ICs containing the equivalent of a few to a few hundred transistors. The integration of the whole CPU onto a single chip therefore greatly reduced the cost of processing capacity. From their humble beginnings, continued increases in microprocessor capacity have rendered other

Fig.1. Microprocessor with its different unit forms of computers almost completely obsolete (see history of computing hardware), with one or more microprocessor as processing element in everything from the smallest embedded systems and handheld devices to the largest mainframes and supercomputers.


First microprocessors were explicitly designed for embedded control (1971 Intel 4004, had 2300 transistors).

  • Later came the general purpose computing area.
  • Hobby computers: 1974
  • IBM PC: 1981
  • Today the two markets co-exist.
  • The embedded market is much larger (two times, in '97); it goes well beyond the control area and includes multimedia, communication, etc.

A. 1st generation

  • 1971: Intel 4004 (2300 transistors)
  • 1974: Intel 8080 (4500 transistors)
    • Instruction processing was strictly sequential. Instructions were fetched, decoded and executed strictly one at a time.

B. 2nd generation

  • 1979: Motorola MC68000 (68000 transistors)
    • Primitive pipelining with three stages: fetch, decode, execute; only one instruction is in execution at a certain time.

C. 3d generation

  • 1984: Motorola MC68020 (240000 transistors)
    • Five stage pipeline; increased parallelism

D. 4th generation

  • 1990: MotorolaMC88110, Intel 80960 - these are RISCs (over 1 Million transistors)
  • PowerPC604, Pentium
    • Superscalar architectures; parallel execution based on multiple pipelines and functional units.

E. 5th generation

  • 1996: P6, PowerPC 620 (over 5 Million transistors)
  • MIPS R10000, AMD K5/K6, Ultras arc (not exactly out of order) Super scalars with out of order execution and sophisticated


The International Organization for Standardization gives a definition of robot in ISO 8373: "an automatically controlled, reprogrammable, multipurpose, manipulator programmable in three or more axes, which may be either fixed in place or mobile for use in industrial automation applications."

The Robotics Institute of America (RIA) uses a broader definition: a robot is a "re-programmable multi-functional manipulator designed to move materials, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks".

According to Encyclopedia Britannica, a robot is "any automatically operated machine that replaces human effort, though it may not resemble human beings in appearance or perform functions in a humanlike manner" Merriam-Webster describes a robot as a "machine that looks like a human being and performs various complex acts (as walking or talking) of a human being", or a "device that automatically performs complicated often repetitive tasks", or a "mechanism guided by automatic controls".


Line follower robot is an autonomous mobile robot that can follow a path. The path can be a white pah on a black surface or a black path on a white surface. Line follower robots are usually entertainment hobby robots. However, they can be improved and used in industry in order to carry some loads on a definite path or in markets and cafes for similar purposes. The important point of building a line follower robot is a good control that is sufficient to follow the path as fast as possible

A. The circuit

All we need is an IR source, an IR photo-transistor and a couple of resistors! Here are the resources:

IR emitters and detector pairs: UK - Maplins,CH10L and CH11M, or SFH409 and SFH309. Obviously the line following robot will need to see the line, therefore we require an light detector of some sort. We also would like it if the line following robot could do this regardless of the ambient conditions (is the room dark or light? is it lit by sunlight or artificial light?). So the robot will also need its own illumination source. The weapon of choice here will be Infra Red light. To make this easy for ourselves the light only needs to be constant. if a white line is present then it will reflect a lot of IR from our source. If the line is black then we see the opposite effect.

IR emmiters and detector pairs: US - Solarbotics QRD1114 (this has both in one package)

On top of these, it would be nice if the signal that we get could be TTL (on or off, 0V, 5V). So to do this we will also require our favourite BEAM chip, the 74AC240, heres the circuit:

Circuit operation is simple.... no line to follow put the input to the inverter high, and therefore the inverter outputs a low, line detection turns on the transistor (or photodiode) and thus the inverter gets a low and outputs a high. If your robot is following a black line on a white page, then add another invereter after or before the first. So what should the values for R1 and R2 be? and how do I set up the 74AC240 chip exactly..... The value for R1 affects the source IR brightness, for maximum brightness we set R1 to give the maximum allowable forward current for the IR led. The chip setup is simple too... ground pins 1, 10 and 19, put 5V onto pin 20. Now choose a pin to input your signal to, if you look at the74AC240 datasheeton page 1, you will see a connection diagram, any pin with an I is an input, follow it across to find its output. Pins 1 and 19 are the enable pins, which we have grounded to permanently enable the inputs on both side of the chip, this leaves you free to use any of the input pins. For example (in case I haven't spelt it out enough already)... input your signal at pin 4 and takes the ouput from pin 16.

The output signal could be used to directly drive your motor... just connect one side of the motor to the ouput, and the other side to ground. If you do this for two motors (2 sets of line detectors will require two sets of emitters and detectors, but only one 74AC240 chip), then you have a basic line follower already. The left detector should be used to drive the right motor and vice versa .The behaviour of this robot as it stands will be too turn a motor on IF a line is present, if both detectors are over the line then it will drive straight, if the left detector goes of the line, it will turn off the right motor causing the robot to turn back onto the line, if the right detector goes off the line then it will turn off the left motor and again go back onto the line. If both detectors come off the line (end of line) then the robot will stop altogether



I have taken the example of line follower for simple robot. As shown in the fig. it consists of three units i.e. input, control, and output unit

The control unit comprises of microprocessor. The function of all the units is given below:

A. Input unit

Input units consist of the sensors that detect the white path on black surface or the black path on white surface. QRD1114 IR reflective line/object sensor and CNY70 reflective optical sensor are the most commonly used sensors for line follower robots.
The CNY70 is a reflective sensor that includes an infrared emitter and phototransistor in a leaded package which blocks visible light.
The emitted IR of CNY70 reflects on the surface back to the phototransistor part and affects the base of the phototransistor. The black or white colour of the IR reflection surface causes different analog signals on the output of CNY70. To convert the analog output signals of CNY70 into digital signals in order to transport them to the microprocessor, 74HC14 Schmitt Trigger can be used. When CNY70 sensor detects white, the analog signal is 5 V and 74HC14 converts it into logic 1. When CNY70 sensor detects black, the analog signal is 0 V and 74HC14 converts it into logic 0.

The QRD1113/14 reflective sensor consists of an infrared emitting diode and an NPN silicon photodarlington mounted side by side in a black plastic housing. The on-axis radiation of the emitter and the on-axis response of the detector are both perpendicular to the face of the QRD1113/14. The photo Darlington responds to radiation emitted from the diode only when a reflective object or surface is in the field of view of the detector.

B. Output unit:

For a line follower robot two dc geared motors are enough. The motor driver circuit can be prepared by using darlington transistor on a H bridge motor driver circuit or by using an integrated motor driver circuit like L293D or L298. The diagram shows the driving of the motors.

C. Microprocessor as control unit

The control unit is the microprocessor part of the robot. The microprocessor, also known as the central processing unit (CPU), is essentially what makes a computer work. The microprocessor forms the heart of the computer, along with the memory.

The balance of the computer -- keyboard, monitor and mouse -- is known as peripherals. While peripherals are important for users to be able to work with a computer, they are useless without a functioning microprocessor. Same is the case in case of robotics. There will be no use of input and output unit until microprocessor is not there ac control unit. As in case of computer it takes input control the execution of instruction similarly in Line Follower the microprocessor takes the input signals from the sensors, use them in its program and make decision of the next movement of the line follower robot to follow the path. The output signals are transferred to the motor driver parts of robot. The most commonly used microprocessors are the pic microprocessors produced by microchip.


  • Software control of the line type (dark or light) to make automatic detection possible.
  • "Obstacle detecting sensors" to avoid physical obstacles and continue on the line.
  • Distance sensing and position logging & transmission
  • Industrial automated equipment carriers
  • Automated cars.
  • Tour guides in museums and other similar applications.
  • Second wave robotic reconnaissance operations.


Till now we were trying to discover the robots which can help the human being in different ways like in medical science in industries, in defence etc. But now robot has become itself scientist. Recently in April 2009 the Robot Scientist has discovered its first discovery. Now ADAM is the first robotbut maybe not the lastto have independently discovered new scientific information, according to scientists who recently built themselves the mechanical colleague. So in future scope of robotics is quite bright.


Microprocessor is the brain of the robot. Imagine a man without brain. Just stable. No decision making capacity would be there. The man without brain will become a statue. Similar is the case with robot. The input unit will detect the input signal. But what to do now is decided by the microprocessor .If microprocessor would not be there the line follower will not move .so without microprocessor simple robots are incomplete.



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