Build Laser Range Meter Information Technology Essay

Usually, human measure the distance using conventional methods meter tape or ultrasonic range meter. It is limited to a distance and there are some weaknesses, particularly in the area that is difficult to achieve. To enhance the capability and suitability to measure, the project will be developed is intended to measure a distance between one point to another point with a laser beam. Laser is easily applied compared the conventional method.

This project will use the concept in which a laser will be emitted at the transmitter and then reflected from the object will be received at the receiver. The interval between transmission and reception will be calculated and translated into LCD for easy reading distance.

This project is mainly focused on a different approach of laser based on the capabilities of modern microcontrollers. The method implemented by this system is based on its capability of performing fast measurements of laser/optic characteristics. The proposed microcontroller configuration is capable to measure the frequency and the amplitude of each period of the incoming signal, along with the time of arrival of each period. These measured values are then being used to provide the desired characteristic of the transmitter and receiver unit. In this project, laser operating essentially operating at resonant frequency of 1163.7 Hertz (1.163 kHz).

1.2 Problem Statement

The problems described below are concerned with the measurement of the distance between 10 meters to 100 meters.

Accuracy problems when using a tape meter and ultrasonic.

Problem the number of people used during the measurement process.

Measurement problems when measure the distance in a hard to reach.

The objective

The objective for the project is build laser range meter. In addition the project also incorporates ideas and technology which could produce a better product innovative which marketed locally or internationally.

1.4 Scope of work

Expected results for the laser length meter project is a device that can measure distance using laser beam with a higher accuracy better than using conventional tools such as tape meter, or ultrasonic range meter. Laser range meter also can help in making measurements in places difficult to achieve.

In addition, these devices are expected to help the technical group to make the measurement more accurate and precise when they carry out work related to their field. Besides that, expected results for the proposed project are:-

Construct a laser light transmitter circuit.

Construct a receiver circuit suitable for transmitter circuit.

Identify and build the interface circuit for LCD display.

Obtain the computer programming and coding.

Thesis Outline

This report represents five chapters. The following is the outline of the design/analysis of Laser range meter project in chapter by chapter.

Chapter 1: This chapter is discussing about the overview of the project such as introduction, objective, problem statement and scope of the project.

Chapter 11: This chapter describes about the research and information about the project. Every facts and information which found through journals or other references will be compared and the better methods have been chosen for the project. The literature review and the circuit development of the project will be using software Multisim 2001 and Proteus 7 Professional.

Chapter 111: This chapter discuss about the project methodology used in this project such as data capture and comparison process. All these methodology should be followed for a better performance.

Chapter 1V: This chapter describes about the project the findings such as result and analysis of the electronics component.

Chapter V: Discussion and conclusion achieved in this project.

Chapter 2

Literature review

2.0 Literature Review

Lasers are focused, intense beams of light, usually of a single frequency. Laser very useful for measuring distances because it is travel at fairly constant rates through the atmosphere and travel much longer distances before divergence (the weakening and spreading out of a beam of light) reduces the efficacy of the meter. Laser light is also less likely to disperse like white light, which means that laser light can travel a much greater distance without losing intensity. Compared with ordinary white light, a laser pulse retains much of its original intensity when reflected off the target, which is very important when calculating distance to an object.

An electrical pulse generator periodically drives a semiconductor laser diode sending out infrared light pulses, which are collimated by the transmitter lens. Via the receiver lens, part of the echo signal reflected by the target hits a photodiode which generates an electrical receiver signal. The time interval between the transmitted and received pulses is counted by means of a quartz- stabilized clock frequency. The calculated range value is fed into the internal microcomputer which processes the measured data and prepares it for range (and speed) display as well as for data output.

Laser distance meters emit light pulses with a defined wavelength and frequency. The laser beam is reflected off the target and back to the distance meter at the speed of light. The returning wavelengths and light pulses change in relationship to the ones sent out by the meter. The difference between the two signals is proportional to the distance to the target.

2.1 An advantages of laser length meter

Unlike ultrasonic meters, the laser distance meter’s narrow laser beam prevents the reflection off objects that aren’t targeted, avoiding false readings. Laser distance meters are much more accurate and reliable, and measure much longer distances than ultrasonic meters. The advantages using laser length meter is:-

Fast measurements:

Turn on switch at point to measurement, the measurement is done. Anyone can use easier.

Easy access:

Just aim the laser at the point for measurement.

Reduce errors:

Laser distance meters not accidentally read the wrong scale.

One man operation:

Compare to conversional way to take measurement, laser distance meter only require one people to get result.

Highest accuracy:

The accuracy for this laser length meter is ± 1.5 mm (± 0.059 in).

Longer distances:

Laser distance meter can measure up to 100 meters (330 feet).

2.2 Another techniques for distance measurements

• Triangulation is a geometric method, useful for distances in the range of ∼ 1 mm to many kilometers.

Time-of-flight measurements (or pulse measurements) are based on measuring the time of flight of a laser pulse from the measurement device to some target and back again. Such methods are typically used for large distances such as hundreds of meters or many kilometers. Using advanced techniques, it is possible to measure the distance between Earth and the Moon with an accuracy of a few centimeters. Typical accuracies of simple devices for short distances are a few millimeters or centimeters.

The phase shift method uses an intensity-modulated laser beam. Compared with interferometric techniques, its accuracy is lower, but it allows unambiguous measurements over larger distances and is more suitable for targets with diffuse reflection.

• For small distances, one sometimes uses ultrasonic time-of-flight methods, and the device may contain a laser pointer just for getting the right direction, but not for the distance measurement itself.

Frequency modulation methods involve frequency-modulated laser beams, for example with a repetitive linear frequency ramp. The distance to be measured can be translated into a frequency offset, which may be measured via a beat note of the sent-out and received beam.

Interferometers allow for distance measurements with an accuracy which is far better than the wavelength of the light used.

Phase shift method technique is the suitable technique can be applied for this project. A laser beam modulated optical power is sent to a target. Some reflected light (from diffuse or specular reflections) is monitored, and the phase of the power modulation is compared with that of the sent light. Although the phase shift is directly proportional to the time of flight, the term time-of-flight method should be reserved to case where one really measures a delay time more directly.

2.3 Laser

A laser is a device that emits light (electromagnetic radiation) through a process of optical amplification based on the stimulated emission of photons. The term “laser” originated as an acronym for Light Amplification by Stimulated Emission of Radiation. The emitted laser light is notable for its high degree of spatial and temporal coherence, unattainable using other technologies.

Spatial coherence typically is expressed through the output being a narrow beam which is diffraction-limited, often a so-called “pencil beam.” Laser beams can be focused to very tiny spots, achieving a very high irradiance. Or they can be launched into a beam of very low divergence in order to concentrate their power at a large distance.

Temporal (or longitudinal) coherence implies a polarized wave at a single frequency whose phase is correlated over a relatively large distance (the coherence length) along the beam. A beam produced by a thermal or other incoherent light source has an instantaneous amplitude and phase which vary randomly with respect to time and position, and thus a very short coherence length.

Most so-called “single wavelength” lasers actually produce radiation in several modes having slightly different frequencies (wavelengths), often not in a single polarization. And although temporal coherence implies monochromaticity, there are even lasers that emit a broad spectrum of light, or emit different wavelengths of light simultaneously. There are some lasers which are not single spatial mode and consequently their light beams diverge more than required by the diffraction limit. However all such devices are classified as “lasers” based on their method of producing that light: stimulated emission? Lasers are employed in applications where light of the required spatial or temporal coherence could not be produced using simpler technologies.

Wavelengths of commercially available lasers, http://en.wikipedia.org/wiki/Laser

2.4 Transmitter

The key element of the laser transmitter is a small semiconductor laser, also known as diode laser or injection laser. The semiconductor laser converts electrical energy (a current pulse) into optical energy (the optical pulse) over a wide temperature range with high efficiency and high reliability. The laser itself consists of a small cube of semiconductor material (dimensions approx.1×0.3×0.3 mm) with two of the faces cleaved so they are flat and parallel thus forming the two mirrors of the laser cavity. The light generation process takes place in the very narrow active region. The divergent laser radiation emitted by the partly reflecting face of the semiconductor crystal is collected by a collimating lens which forms a very narrow laser beam ideally suited for optical range finding.

An amplitude modulated transmitter includes a laser and pulser electronics. A pulsed semiconductor laser is the most common type in laser range finders, because it is small, relatively cheap, and durable and it has good efficiency. The required power is defined by the measurement distance, optical losses and the reflection coefficient of the target. The higher is the power needed, the larger are the dimensions of the laser. The width, thickness and length of the active region of SH lasers vary in a range of 75 um to 400 um, 1 to 2 um and 200 to 300 um, respectively.

The semiconductors used operate over wavelength range of 850 to 910 nm. Lasers with a small output power (1 mW till 50 mW), small size and long wavelength (1300 – 1550 nm).

The length of the optical laser pulse does not correlate linearly with the length of the current pulse, when short current pulses. The optimum pulse length is defined by the bandwidth of the receiver. If the optical laser pulse is clearly shorter than the FWHMs calculated from the receiver bandwidth, the full gain of the receiver cannot be reached. If the pulse is longer and the rise and fall times are slower, the precision will deteriorate. In practice the minimum length of the current pulse will be limited by the speed of the switch and the serial inductances of the high current loop in the circuit.

2.5 Receiver

To ensure reliability, laser distance meters employ some method to minimize background light. Too much background light can interfere with the measurement when the sensor mistakes some part of the background light for the reflected laser pulse, resulting in a false distance reading.

The photodiode of the receiver operates as a low-pass filter and filters out the optical frequencies leaving the target information at a frequency, equal to the frequency difference (intermediate frequency) between the received signal and LO radiations. An electrical demodulator is needed to bring the signal frequency from the IF to the original baseband frequency. The distance of the target is calculated on the basis of the phase, amplitude or frequency of the IF (intermediate frequency) signal according to the modulation type chosen.

In the homodyne method the beam of the laser is divided into two beams, one of which is the target beam and the other operates as a local oscillator. In this case the signal is transferred directly to the baseband, to the original signal frequency. Other possibilities for local oscillators are using a two-frequency laser, in which the difference of the frequencies of the output light is small enough for amplifiers, for example about 1 GHz or modulating the current of the transmitter laser. The operating principle of a laser range finder was based on using the laser also as a receiver and measuring the selfmixing effect in the laser. The precision achieved was 1.8 mm in a distance of 3 m.

2.6 Reflectivity of Various Surfaces / Materials

The amount of light that is returned from a target’s surface is characterized by the reflection coefficient. For a diffusely reflecting target, the maximum value of is 100 %. For mirror-like or retro reflecting targets, the (theoretical) value of can exceed 100% by far. The reflection coefficient depending on the wavelength also.

Material

Reflectivity

White paper

Up to 100%

Dimension lumber

94%

Snow

80-90%

Foam

88%

White masonry

85%

Lime stone, clay

Up to 75%

News paper with print

69%

Tissue paper, two ply

60%

Decidous tree

60%

Coniforeus tree

30%

Carbonate sand (dry)

57%

Carbonate sand (wet)

41%

Beach sand

50%

Rough wood

25%

concrete

24%

Asphalt with pebbles

17%

Clear plastic

50%

Lava

8%

Black rubber tire wall

2%

Table 1 : Reflectivity of Various Surfaces / Materials

2.7 Microcontroller

Microcontrollers are developing from microprocessor. However, microcontroller differs from microprocessor in many ways. Primarily is the functionality. In order for a microprocessor to used, other components such as memory, or components for receiving and sending data must added into it. On the other hand, microcontroller is design to be all in one. No other external components required for its application because all the necessary peripherals already built into it. Thus, saves time and space needed to construct devices.

Laser range meter designed with selected hardware to ensure that the final product is efficient and robust. The main components of this project are PIC 16F877A microcontroller, laser transmitter and receiver unit.

The PIC16F877A is one of the most popular PIC microcontrollers and it’s easy to see why – it comes in a 40 pin DIP pin out and it has many internal peripherals.

Microcontroller is a highly integrated chip that includes, on a single chip, all or most of the parts needed for a controller. The microcontroller can be calling a “one-chip solution”. It requires very little external support hardware. It typically includes:

(i) CPU (Central Processing Unit).

(ii) RAM (Random Access Memory).

(iii) EPROM/PROM/ROM (Erasable Programmable Read Only Memory).

(iv) Input/Output – serial and parallel mode.

(v) Timer.

(vi) Interrupt controller.

Microcontroller is a key of any embedded control applications. Suitable or best fit criteria in microcontroller must be chosen in order to achieve the objectives.

The PIC 16F877A microcontroller used in this project is a low power, high performance Reduce Instruction Set Computer (RISC) with only 35 single word instructions to learn and provide10 bit, up to 8 channels Analog-to-Digital Converter (A/D) module. The device is developed using Microchip’s high-density nonvolatile memory technology. By combining an enhanced 16-bit CPU with high-speed FLASH/EEPROM technology on a monolithic chip, the Microchip PIC 16F874A is a powerful computer that provides a highly flexible and cost effective solution to many embedded control applications.

Figure 3: Pin diagram for PIC 16F877A

Parameter Name

Value

Operating frequency

DC – 20MHz

Reset (and Delays)

POR, BOR (PWRT,OST)

Flash Program Memory (14Bit)

8K

Data Memory (bytes)

368

Data EEPROM (bytes)

256

Interrupts

15

I/O Ports

Port A,B,C,D,E

Timers

3

Capture/Compare/PWM module

2

Analog comparators

2

Instruction Set

35 instruction

Table 2 : Table characteristic of PIC 16F877A

2.8 LCD display

LCD is based controlled 4 lines x 20 characters LCD display with BLACK characters on GREEN background and backlight. It is a parallel interface so you will need 7 GPIO pins for 4-bit mode or 11 GPIO pins for 8-bit mode to interface to this LCD screen.

2.8.1 Features:

• Wide viewing angle and high contrast

• Industry standard HD44780 equivalent LCD controller built-in

• +5V DC LED backlight

• No separate power supply for backlight

• Supported 4 or 8 bit parallel interface

• Display 4-line X 20-character

• Operate with 5V DC.

2.8.2 Specifications:

• Module Size (W x H x T): 98mm X 60mm X 14mm

• Black Metal Bezel (W x H): 98mm X 40mm

• Viewing Area (W x H): 76mm X 25.2mm

2.8.3 Pin assignment

Pin No

Symbol

Function

Remark

1

GND

Power supply

0V

2

Vdd

+5V

3

V5

For LCD

Variable

4

RS

Register Select ( H=Data,L=Instruction

Read/write L=MPU to LCM, H = LCM to MPU

5

R/W

6

E

Enable

7

DB0

Data bus bit 0

8

DB1

Data bus bit 1

9

DB2

Data bus bit 2

10

DB3

Data bus bit 3

11

DB4

Data bus bit 4

12

DB5

Data bus bit 5

13

DB6

Data bus bit 6

14

DB7

Data bus bit 7

15

A

Anode of LED Unit

16

K

Cathode of LED Unit

2.9 Laser Diode

Laser range meter used laser diode from OSRAM Company. It is operate refer to pulse of 100ns pulse width at 1 KHz rate with 5A operating current. The laser diode is an active semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current. The former devices are sometimes referred to as injection laser diodes to distinguish them from optically pumped laser diodes.

A laser diode is formed by doping a very thin layer on the surface of a crystal wafer. The crystal is doped to produce an n-type region and a p-type region, one above the other, resulting in a p-n junction, or diode.

Laser diodes form a subset of the larger classification of semiconductor p-n junction diodes. Forward electrical bias across the laser diode causes the two species of charge carrier – holes and electrons – to be “injected” from opposite sides of the p-n junction into the depletion region. Holes are injected from the p-doped, and electrons from the n-doped, semiconductor. (A depletion region, devoid of any charge carriers, forms as a result of the difference in electrical potential between n- and p-type semiconductors wherever they are in physical contact.) Due to the use of charge injection in powering most diode lasers, this class of lasers is sometimes termed “injection lasers “or” injection laser diode” (ILD). As diode lasers are semiconductor devices, they may also be classified as semiconductor lasers. Either designation distinguishes diode lasers from solid-state lasers.

2.9.1 Applications

• Hand-held Laser Range Finders (LRF) for golfers, hunters, civil engineers

• Automotive applications (Adaptive Cruise Control (ACC), pre-crash detection, collision avoidance, adaptive rear lighting)

• Traffic surveillance (Laser speed gun, traffic recording, vehicle classification, distance measurement, fog detection.

2.9.2 Safety Advices

Depending on the mode of operation, these devices emit highly concentrated non visible infrared light which can be hazardous to the human eye. Products which incorporate these devices have to follow the safety precautions given in IEC 60825-1 “Safety of laser products”.

Parameter

min

max

Unit

Peak output power

–

5

W

Peak forward current

–

6

A

Pulse width

–

100

ns

Duty cycle

–

0.1

%

Reverse voltage

–

3

V

Operating temperature

-40

+85

0C

Storage temperature

-40

+100

0C

Soldering temperature

–

+260

0C

Emission wavelength

895

915

nm

Spectral width

–

–

nm

Peak output power

3

5

W

Threshold power

0.15

0.5

A

Operating voltage

2.7

4.0

V

Standard operating refer to pulse of 100ns pulse width at 1 KHz rate with 5A operating current at Ta = 250C

2.10 PicBasic programming Language

The low-cost PicBasic Compiler (PBC) makes it easy to write programs for the fast Microchip PICmicro MCU. PBC converts these programs into hex or binary files that can be programmed directly into a PICmicro microcontroller. The easy-to-use BASIC language makes PICmicro MCU programming available to everyone with its English-like instruction set.

PicBasic Compiler Features:

Quicker and easier than “C” or assembler

Expanded BASIC Stamp I compatible instruction set

True compiler provides faster program execution and longer programs than BASIC interpreters

I2CIN and I2COUT instructions to access external serial EEPROMs

Peek and Poke instructions to access any PICmicro MCU register from BASIC

Serial speeds to 9600 baud

In-line assembler and Call support

Supports most 14-bit core PICmicro microcontrollers

Use in DOS or Windows

Compatible with most PICmicro MCU programmers (see EPIC Plus PICmicro MCU Programmer)

2.11 Boot loader

Among the many features built into Microchip’s Enhanced FLASH Microcontroller devices is the capability of the program memory to self-program. This very useful feature has been deliberately included to give the user the ability to perform boot-loading operations. Devices like the PIC16F874A are designed with a designated “boot block”, a small section of protect able program memory allocated specifically for boot load firmware. Once a program is ready and a hex file (*.hex) is generated. The Bootloader will load the program into the microcontroller using the Universal Synchronous Asynchronous Receive Transmit (USART) module in the PIC to receive data with hardware handshaking.

In this project, CYTRON PIC Microcontroller Start-up Kit UIC00BUSB ICSP PIC PROGRAMMER is used as a Bootloader to ease the process of loading program further save development time and cost.

2.12 MikroC Cross Compilers

MikroC is a powerful, feature rich development tool for PIC microcontrollers developed by MikroElektronika. It is designed to provide the programmer with the easiest possible solution for developing applications for embedded systems, without compromising performance or control. PIC and C fit together well. PIC is the most popular 8-bit chip in the world, used in a wide variety of applications, and C, prized for its efficiency, is the natural choice for developing embedded systems. MikroC provides a successful match featuring highly advanced IDE, ANSI compliant compiler, broad set of hardware libraries, comprehensive documentation, and plenty of ready-to-run examples. MikroC allows user to quickly develop and deploy complex applications. The C source code can be written using the built-in Code Editor (Code and Parameter Assistants, Syntax Highlighting, Auto Correct, Code Templates, etc.).

The MikroC libraries are also included to dramatically speed up the development data acquisition, memory, displays, conversions, communication and many more. Practically all P12, P16, and P18 chips family are supported. With MikroC, it is now possible to monitor the program structure, variables, and functions in the Code Explorer. It also generates commented, human-readable assembly, and standard HEX compatible with all programmers. Inspecting program flow and debugging executable logic is no longer a problem with the integrated Debugger. Besides, user can get detailed reports and graphs such as RAM and ROM map, code statistics, assembly listing, calling tree, and etc.).

PICkit 2 programmer

2.13 LM 741

LM741 can use for amplifier and comparator. For laser range meter this IC is used as a comparator and not an amplifier. The difference between the two is small but significant. Even if used as a comparator the 741 still detects weak signals so that they can be recognized more easily. It is important to understand these circuits as they very regularly appear in examinations.

A ‘comparator’ is a circuit that compares two input voltages. One voltage is called the reference voltage (Vref) and the other is called the input voltage (Vin). When Vin rises above or falls below Vref the output changes polarity (+ becomes -). 

Positive is sometimes called HIGH.

Negative is sometimes called LOW.

Connection diagram IC 741

2.14 Voltage Regulator 

Voltage regulator usually having three legs converts varying input voltage and produces a constant regulated output voltage. It is available in a variety of outputs. 

 

The most common part numbers start with the numbers 78 or 79 and finish with two digits indicating the output voltage. The number 78 represents positive voltage and 79 negative one. The 78XX series of voltage regulators are designed for positive input. And the 79XX series is designed for negative input.

Project laser range meter use LM7805 and LM7809 voltage regulator. It is simply connect the positive lead unregulated DC power supply, 9V or 12V to the Input pin, connect the negative lead to the Common pin and then 5V and 9V will get at output pin with stable voltage.

LM 7809 voltage regulator (top view)

CHAPTER 3

RESEARCH METHODOLOGY

Methodology

Procedure to achieve the objective of this project:

Understand the concept and the actual needs of the project to be implemented.

Research about the effects of infrared towards any types of liquid and its relationship, the light propagation techniques (infrared signal) in different media and also research about chemistry associated with the use of electronic devices.

Research to find the suitable circuit.

Simulation of the circuit.

Construct the actual circuit.

Test the functionality of the actual circuit.

Calibration to find the difference and similar result by using the actual pH meter and also by using the litmus paper.

Construct the model.

3.1 Block diagram

Figure below show block diagram for circuit laser length meter.

Figure 1: Block diagram for laser length meter project

Circuit

Description

Oscillator

As generator for generate pulse for trigger the transmitter circuit.

Transmitter

Transmit laser signal for device application.

Receiver

Receiver unit to detect the reflected signal.

Comparator

This circuit will compare voltage between transmitting and receiving laser beam

Microcontroller

Interface for display unit and transmitter/receiver unit.

Display

LCD show the distance for laser range meter

3.2 Flowchart of project

  Flowchart below is a visual representation of the sequence of this project methodology.

Start

Literature review

Find the suitable circuit

Design & simulate circuit

Circuit functionality

no

Circuit assemble yes

Circuit test

PCB design

Circuit functionality

no

1

1 yes

Calculate distance using comparison between transmit and reflected

Build software configuration for

PIC & LCD display No

Calibration

Yes

END

Success

Display value on LCD

Run the circuit

Combine software & hardware

END No Yes

3.3 Circuit

3.3.1 Transmitter circuit

Transmitter circuit using ISIS 7 profesional

Transmitter circuit using Multisim 2001

This circuit used for transmit laser signal for measuring range. IC 555 will give pulse wave for transmit laser signal. This IC will function as an oscillator for laser transmitter. This is the square wave osci