Engineering Design of a Light Meter for Photography

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DESIGNING A
PRODUCT THAT
MEETS
CUSTOMER’S
REQUIREMENTS
Light Meter
Student Name
Date

Contents
Introduction............................................................................................................................................4
LO1 Plan a design solution and prepare an engineering design specification in response to a
stakeholder’s design brief and requirements......................................................................................5
1. Design specifications from client..............................................................................................5
2. Weightage of client specification in design development.......................................................5
3. Light meter target design specifications..................................................................................5
4. Design process of Real Time Clock..........................................................................................6
4.1 Light meter block diagram...............................................................................................6
4.2 Design process scheduling.................................................................................................6
5. Comparison of light sensors......................................................................................................7
LO2 Formulate possible technical solutions to address the student-prepared design
specification specifications....................................................................................................................9
Methodology.......................................................................................................................................9
1. Technical solutions of project...................................................................................................9
1.1 Technical design 1..............................................................................................................9
1.2 Technical design 2............................................................................................................10
1.3 Technical design 3............................................................................................................10
2. Evaluation of technical designs...............................................................................................11
3. Selection of final design solution.............................................................................................11
4. Use of tools for modeling and prototyping............................................................................11
5. Improvement for design..........................................................................................................11
LO3 Prepare an industry-standard engineering technical design report...................................12
1. Technical design.......................................................................................................................12
2. Final design limitation.............................................................................................................12
3. Role of specification in finished product................................................................................13
4. Compliance, safety and risk management issues..................................................................13
5. Effectiveness of technical design.............................................................................................13

LO4 Present to an audience a design solution based on the design report and evaluate the
solution/presentation...........................................................................................................................16
1. Presentation of technical design to target audience..............................................................16
2. Strategy to present technical report.......................................................................................17
3. Effectiveness of presentation strategy....................................................................................17
4. Feedback of client on designed product.................................................................................17
5. Improvement suggestion for presented design......................................................................18
Conclusion............................................................................................................................................19
References..............................................................................................................................................20
Appendix 1: Schematic of selected design.........................................................................................21
Appendix 2: 3D view of Light Meter..................................................................................................21
Appendix 3: Code for Light Meter.....................................................................................................22

List of Figures
Figure 1 Weightage graph of client's specification and desired parameter for design selection.............5
Figure 2 Block diagram of light meter.....................................................................................................6
Figure 3 Gantt chart of design process schedule.....................................................................................7
Figure 4 Critical path analysis of project schedule..................................................................................7
Figure 5 Schematic of design 1................................................................................................................9
Figure 6 Schematic of design 2..............................................................................................................10
Figure 7 Evaluation of technical designs...............................................................................................11
Figure 8 Design elements of selected design.........................................................................................12
Figure 9 Contribution design specification in finished product............................................................13
Figure 10 The display screen when unit first turned on........................................................................14
Figure 11 ISO reading of light sensor....................................................................................................14
Figure 12 Display screen when ND filter set to ND4............................................................................15
Figure 13 Display screen showing all light readings from light sensor.................................................15
Figure 14 Complete light meter unit......................................................................................................16
Figure 15 Analysis of presentation strategy..........................................................................................17
List of Tables
Table 1 Comparison of available light sensors........................................................................................8
Table 2 Sample feedback questionnaire................................................................................................18

Introduction
In photography light intensity is determined to capture better photograph. A light meter is
used in this regard which measure the intensity of light. With help of light meter
photographer can determine the proper exposure required for photograph. There are various
applications of light meter, such as it is in cinematography to determine level of light to shoot
a scene. It also used in field of architectural lighting design to verify the proper working of
installed lighting system. In this perspective we are assign with the project of designing a
light meter. For this purpose we document our project in this report according to available
standards. This report provide brief overview of project different phases and light meter unit
delivery.

LO1 Plan a design solution and prepare an engineering design
specification in response to a stakeholder’s design brief and
requirements.
1. Design specifications from client
We are assign with project of designing a light mater for client. Client requires a reasonably
accurate and easy to use light meter. Design of light meter can be based on development
board or op-amp based light mater. If microcontroller development board is choose for
designing light mater then Arduino development board is preferable for designing.
2. Weightage of client specification in design development
From design brief, we try to identify the important specifications of a light meter.
Additionally, we studied a light meter working as reference to understand the working of
light meter. The reference study help us in identification of important components of a light
meter. The major component of light meter is light intensity sensor, development board, and
LCD display. Now, we assign these components importance weightage according to project
and to parameters which will use for evaluation of design solution. We assign weightage on
the scale of 1 to 50, where 1 being lowest and 50 being highest importance. The figure 1
illustrate assigned importance weightage to different components and evaluation parameters.
Light Intensity Sensor Development Board LCD Display
47
42
38
40
45
35
46
40 39
42
45
35
47
40
37
Weightage of Specification Durability Ease of Use
Reconfiguration Assembling
Figure 1 Weightage graph of client's specification and desired parameter for design selection

3. Light meter target design specifications
We meet with client to discuss design specifications from design brief. We also propose some
alternatives for design specifications. After meeting with client, we able to have some
requirement for project. The requirements are as follows:
 Light intensity sensor – BH1750 or LM393
 Development board – PIC or Arduino
 LCD display
4. Design process of Real Time Clock
Design process of a RTC unit is consist of following stages: Light sensor measure the intensity of light Development board controls the overall operation of light meter LCD displays the reading of light sensor (Hwang et al, 2016)
4.1 Light meter block diagram
Considering design stages of light meter, figure 2 illustrate the block diagram of light meter.
Figure 2 Block diagram of light meter
4.2 Design process scheduling
Our first task in design process is to meet with client to get understanding of desired product.
Requirement are gathered about product, discuss implications of requirements. When
requirements fully understood then process of developing different design concepts will be
started. These design concepts will be evaluated on basis of certain parameters to select a
final design. When final design selected, its prototype modeling take place. After developing
prototype testing will perform keeping in view its applications. Suggested improvement
implement on the basis of feedback and this process will continues to test design till it satisfy
desired requirement. When requirement are satisfied, a final meeting with client conducted.
In this meeting we present final product and elaborate its design working.

Figure 3 Gantt chart of design process schedule
Figure 4 Critical path analysis of project schedule
5. Comparison of light sensors
In this section we compare different available light sensors for light meter. The table 1 shows
the comparison of light sensors.

Table 1 Comparison of available light sensors
Light Sensor Applied
Voltage
Power
Dissipation
Operating
Temperature
Soldering
Temperature
PDV – P8103 150V 100mW/°C -30°C ~ 75°C +260°C
TEMT6000 6V 100mW/°C -40°C ~ 100°C +260°C
BH1750 4.5V 260mW/°C -40°C ~ 85°C -
ColorPal –
TSL12
6V 100mW/°C -25°C ~ 85°C 260°C

LO2 Formulate possible technical solutions to address the student-
prepared design specification specifications.
Methodology
Before discussing possible design solution, we are devising a common methodology for
design solutions. Our main focus is light sensor module because it is the most important
component of light sensor unit. To measure intensity of light, we need suitable light sensor
module. Then measured light intensity pass to microcontroller which display the light
intensity on LCD. As for microcontroller, we use PIC or Arduino for that purpose according
to each design solution.
1. Technical solutions of project
After extensively analyzing requirements, next thing is to develop technical designs for light
meter unit. In this regard, we consider three design solution for evaluation to select a final
design for light meter. While develop technical solution for project, client requirement for
light meter design followed completely. Connection wires and breadboard are generic in all
technical designs.
1.1 Technical design 1
We use PDV – P8103 light sensor in this design along with Arduino UNO board. As
illustrated in figure 5, light sensor and 10KΩ connect with Arduino board and also provide
5V supply. This circuit forms a potential divider and protect circuit from short circuit. We use
Arduino analog to digital converter to read the voltage level of input from light sensor. When
we expose light sensor to light, we get decrease in resistance and increase in voltage. Then
we block light and get increase in resistance and decrease in voltage. During testing of design
we find that USB supply of 5V is not ideal for unit and also design does not completely
satisfy requirements.

Figure 5 Schematic of design 1
1.2 Technical design 2
In technical design 2, we use TEMT6000 light sensor in this design along with Arduino UNO
board. As illustrated in figure 6, light sensor connect with Arduino board and also provide 5V
supply. This circuit does not forms a potential divider because there is not resistor placed in
circuit. Hence, there is a chance of short circuit. The TEMT6000 light sensor work same as
PDV – P8103, so we use Arduino analog to digital converter to read the voltage level of input
from light sensor. When we expose light sensor to light, we get decrease in resistance and
increase in voltage. Then we block light and get increase in resistance and decrease in
voltage. The main drawback of design it does not has any resistor to protect it from short
circuiting. Additionally, design does not fulfil the all criteria’s of client (Tumlinson 2015).
Figure 6 Schematic of design 2

1.3 Technical design 3
In this technical design, we use Arduino Nano R3; BH1750 light sensor; SSD1306 OLED;
two generic rotary potentiometer; 10KΩ resistor; and 12mm pushbutton. First we assemble
all components on generic breadboard and connect them using jumper wires. We connect
Arduino board with light sensor and OLED. We place 10KΩ resistor in series between
Arduino and light sensor to protect circuit from damage. Then connect generic rotary
potentiometer which use for adjusting aperture and ISO. Additionally, a pushbutton place
which start operation of light sensor when pressed. The light sensor take light readings and
pass it Arduino board which display theses reading on OLED. The technical design 3,
perform better than other two designs and also fulfil the criteria of user friendly device.
2. Evaluation of technical designs
In this section, evaluation of technical designs carried out using certain parameters. This
evaluation activity helps in selecting final design for project. On the basis of evaluation we
will choose a final technical design. All parameters will be rated on scale of 1 – 10, 1 being
lowest and 10 being highest. Each evaluation carry out by keeping in mind technical designs
and client’s requirements.
Design 1 Design 2 Design 3
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Durability Reconfiguration Assembling Ease of Use
Figure 7 Evaluation of technical designs