1. MACE 61062: ENGINEERING DESIGN II
Design of Automated Roller Blind
-Group Report-
Assigned by: Dr. Jim Methven
Group Number: GROUP 5
Submitted by: ID:
Ayman Siddique 7669311
Mert Nihat Iskender 9842357
Rumeel Ahmad Bhutta 9850164
Sobaan Sheikh 9785848
3. 4.5. Motor Mount................................................................................................ 19
5. Electrical/electronic system............................................................................... 20
5.1. Arduino Uno U3 development board........................................................... 20
5.2. Arduino motor shield ................................................................................... 20
5.3. Infra-red remote controller and receiver ...................................................... 20
5.4. Limit switches.............................................................................................. 21
5.5. Push buttons ............................................................................................... 21
5.6. Description of Arduino Code ....................................................................... 21
5.7. Circuit Diagram and Description.................................................................. 25
5.8. Circuit Connection on Frame....................................................................... 27
6. FINAL ASSEMBLY............................................................................................ 29
6.1. Motor – Roller Blind Connection (Sub-Assembly) ....................................... 30
6.2. Electrical/Electronic Component Consideration .......................................... 31
7. BILL OF MATERIALS (COSTING).................................................................... 32
8. POst mortem / DESIGN IMPROVEMENTS ...................................................... 33
9. GROUP MEETINGS / AGENDAS..................................................................... 34
10. CAD DRAWINGS ........................................................................................... 35
11. REFERENCES............................................................................................... 42
12. Appendix ........................................................................................................ 42
4. LIST OF FIGURES
Figure 1 : House of Quality......................................................................................... 4
Figure 2 : Concept 1................................................................................................... 5
Figure 3 : Concept 2................................................................................................... 5
Figure 4: Concept 3.................................................................................................... 6
Figure 5 : Concept 4................................................................................................... 6
Figure 6 : Selected motor........................................................................................... 9
Figure 7: Free body diagram of roller blind............................................................... 10
Figure 8 Torque vs Speed Characteristics ( N/cm vs pps) ....................................... 11
Figure 9 : CAD of Bearing mounts ........................................................................... 12
Figure 10 : Coupling concept 1 ................................................................................ 13
Figure 11 : Coupling concept 2 ................................................................................ 14
Figure 12 : Coupling concept 3 ................................................................................ 14
Figure 13 : Motor Casing.......................................................................................... 15
Figure 14: Bearing mounting Left side...................................................................... 16
Figure 15 : Coupling (Motor side)............................................................................. 17
Figure 16 : Revised coupling A ................................................................................ 17
Figure 17 : Revised coupling B ................................................................................ 18
Figure 18: Coupling (free side)................................................................................. 18
Figure 19 : Motor casing evaluation ......................................................................... 19
Figure 20: Motor casing base................................................................................... 19
Figure 21 : Circuit connections layout ...................................................................... 26
Figure 22 : Types of resistors and LED used ........................................................... 27
Figure 23: Sub Assembly (Right- shown above), Sub Assembly (Left- shown below)
................................................................................................................................. 30
Figure 24: Electrical/Electronic component layout (front- shown above) and (back-
shown below) ........................................................................................................... 31
List of Tables
Table 1 : List of Needs specified for project ............................................................... 2
Table 2 : Metric table.................................................................................................. 3
Table 3 : Concept ranking based on evolution points................................................. 7
Table 4: Roller blind dimensions .............................................................................. 10
Table 5: Torque and stresses Results...................................................................... 10
Table 6 : Motor Optimization ................................................................................... 11
5. Page | 1
1. INTRODUCTION
Below section deals with introducing
1.1. Design Specifications
The blind should be fitted with UP and DOWN buttons to enable the user to
operate it in close proximity.
The blind should stop and start at any intermediate position
The blind should be able to operate by remote control using infrared, R/F or
an App.
The blind should reset to either the raised or lowered position automatically
when power is restored after a power failure
The mechanism should know where the blind is (by indexing) at any time.
The drive mechanism and control elements must be unobtrusive
The control and actuating system should run from a DC supply.
Any gearing or mechanical actuation should, ideally, be made in plastic by 3D
printing.
A full, detailed costing should be included in the final group report
6. Page | 2
1.2. Needs
Using the customer specifications, and by researching commercial roller blinds, the
following market needs were determined, and subsequently shown in Table 1.
Table 1 : List of Needs specified for project
No. NEED Importance
1 The device must be remote control operated 5
2
The device must have adjustable upper and lower limits (light
control) 5
3 The device must operate quietly 4
4 The device must fit within the space constraints 5
5 The device must be lightweight and easy to carry 4
6 The device must be easy to assemble/disassemble 4
7 The device must have the specified fabric 3
8 The device must be cost-efficient 4
9 The device must have high aesthetic value 4
10 The device's position must be known to the control system 5
11 The device must have start/stop buttons 5
12 The device must be able to sustain specified weight 5
13 The device must not have visible installation wiring 5
14 The device must have (relatively) fast operation 4
15 The device must be able to be used for extensive periods of time 4
16 The device must have replaceable parts 4
17 The device must be easily maintainable with readily availabe tools 4
18 The device must adhere to BS-EN13120 standards (Safety) 5
19 The device must reset to upper and lower limits after power failure 5
20 The device must not be operated by loose chords 5
21 The device must be electro-mechanically controlled 5
7. Page | 3
1.3. Metrics
The market needs in the previous section were translated to engineering metrics,
and is shown in Table 2.
Table 2 : Metric table
No. METRICS Needs No. Importance Units
1 Mass of device 5, 12, 17 5, 5, 4 kg
2 Displacement of blind 2, ,11, 14, 21 5, 5, 4, 5 m
3 Dimensions of device 4,5 5, 4 m
4 Linear speed of blinds 3,10 4, 5 m/s
5 Bending stiffness 7,9,14 3, 4, 4 N/m
6
Second moment of area of
device 14 4 mm^4
7 Yield strength of material used 12, 14 5, 4 MPa
8 No. of cycles to failure 14, 17, 21 4, 4, 5 cycles
9 Unit manufacturing cost 7, 8, 21 3, 4, 5 £
10 Distributed load capacity 12, 14 5, 4 N/m
11 Motor power 9, 14, 16, 21 4, 4, 4, 5 W
12 Surface finish (Ra) 8,9 4, 4 μm
13 Reliability/ Availability of device 17, 18, 20, 21 4, 5, 5, 5 %
14 Motor torque 14, 16 4, 4 Nm
15 Time to assemble 7, 18, 19, 21 3, 5, 5, 5 mins
16 Infrared Frequency 1 5 Hz
17 Weight of blind 3, 14 4, 4 N
18 System temperature 3, 18 4, 5 °C
8. Page | 4
1.4. House of quality
The House of Quality for the roller blind design is illustrated in Figure 1.
Figure 1 : House of Quality
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2. CONCEPTS
2.1. Concept Generation
A mechanical drive system was to be chosen for the roller blind, and the following
concepts were made:
Criteria: Cost Simplicity (Purchasable components, cost, simplicity, torque/efficiency)
2.1.1. Concept 1: Belt and Pulley
One pulley would be attached to the motor shaft, the other to the blind shaft. Pulley
belt would be Connection required to accommodate for differences in diameters.
2.1.2. Concept 2: Gear System
Figure 2 : Concept 1
Figure 3 : Concept 2
10. Page | 6
This concept consisted of utilising industrial metal gears, one shaft connecting to the
motor, and the other to the blind shaft. Connection required to accommodate for
differences in diameters.
2.1.3. Concept 3: Direct Coupling
This concept consisted of attaching the roller blind to a motor via an industrial
coupling. As micro-controllers are part of the design specification, the direction of
motor rotation could be altered, hence raise and lower the blind. Additionally, this
would allow for a relatively ‘clean’ and uncomplicated system, with few parts, i.e. cost
effective. Connection required to accommodate for differences in diameters.
2.1.4. Concept 4: Slotted Coupling
Figure 5 : Concept 4
Figure 4: Concept 3
11. Page | 7
Component A will be attached to the motor. Component B teeth will be interlocked
with the component A. The tapered end of component B will be inserted into the
shaft. Component C is a bearing holder device. This component is in 2 parts and
screws and nuts will be used to combine the parts and to hold the bearing in place.
This holder will then be screwed to the wooden frame. The bearing inner diameter
should be slightly smaller than the diameter as the shaft so that it can be securely
attached to the shaft. Limit switch at the top and proximity sensor at the bottom will
limit the movement of the roller blind at extreme ends.
2.2. Concept Selection
Following the generation of concepts, the best concept (or combination of concepts)
is to be chosen. For this purpose, it was useful to use a concept selection matrix,
whereby each concept would be scored to determine which one(s) would be taken
into the next stage: Embodiment Design.
Table 3 : Concept ranking based on evolution points
Selection criteria Concept 1 Concept 2 Concept 3 Concept 4
(Reference)
Cost - - + 0
Safety - + + 0
Power consumption - - + 0
Power transmission - + + 0
Ease of use + + + 0
Noise + - + 0
Manual operation + + + 0
Number of
components
- - + 0
Alignment + + - 0
Assemble/disassemble + - + 0
Lose parts + - + 0
Less moveable parts + - + 0
Readily available tools + - + 0
Aesthetic - - + 0
Maintainability + + + 0
Sum ‘+’ 9 6 14
Sum ‘-‘ 5 9 1
Total score 4 3 13
Rank 2 3 1
2.3. Embodiment
Figure below shows the embodiment design
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3. MECHANICAL SYSTEM
This section aims to fully describe the mechanical system of the roller blind design.
Each component will be analysed (starting at the conceptual phase where
applicable), and their selection criteria (if purchased) or final design (if 3D-printed in-
house) will be outlined, with justification.
3.1. Motor
In order to rotate the blind for both roll-up and roll-down operations, a motor drive
was required.
13. Page | 9
There were two types of motors that could be included in this design- a stepper
motor, and a servo motor.
With regard to operation. Stepper motors utilise discrete steps, and offer better
position control than a servo motor. Referring back to the stated roller blind
specifications, good stand-still capabilities and instance position control is desirable.
Stepper motors can work in an open loop, (i.e. no feedback is required), whereas the
servo motor would need a controlled loop, with feedback being necessary for its
intended application. The process of initially tuning a servo motor (tune its control
loop parameters) in order to provide desired responses is both complex and time-
consuming. Stepper motors on the other hand require no tuning, but only a stepper
motor drive. An Arduino Motor Shield has been chosen for this purpose, and will be
addressed in the Electrical/Electronic System Section (.)
Stepper motors have a comparatively higher holding torque than a stepper motor
(due to the continuous flow of current through the stepper windings) and high torque
at low speeds. As this design assessment does not require relatively high speeds,
(Insert value), but requires torque to lift the blind, these are both desirable attributes.
When considering the longevity of the entire
design assessment, and from a maintenance
standpoint, a brushless stepper motor was
preferred to a brushed servo motor. Stepper
motors are also relatively cheaper than a
servo motor, thereby making it preferable
over its counterpart when considering long
and short-term implications. Hence, for this
design assessment, a stepper motor will be
utilised. (Fig.)
3.1.1. Motor Calculations
Components Mass(kg)
Shaft 0.279
Canvas 0.742
Bar 0.12
Total mass 1.141
Figure 6 : Selected motor
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Shaft dimensions (m)
Length 1.2
Outer diameter 0.031
Inner diameter 0.023
Thickness 4.00E-03
Table 4: Roller blind dimensions
Polar moment of inertia 𝐽 =
π
2
(𝑐2
4
− 𝑐1
4
)
J = 6.31931E-08 m4
Moment Of Inertia, I = 3.16 E-08 m4
Torque = F * r = 11.41*0.0155 = 0.177Nm
Stress τ =
Tr
J
Stress τ = 0.043MPa
σ=
Mc
I
σ = 1.68MPa
Figure 7: Free body diagram of
roller blind
Torque (Nm) 0.177
Moment (Nm) 3.423
Stress (MPa) 0.043
Bending Stress
(MPa)
1.679
Table 5: Torque and stresses Results
Bearing Frictional moment
M=0.5 *μ*P*D P=load(N), μ= friction of bearing, d= bore diameter
M=0.5 * 0.0015* 11.41*(30/1000) =0.0003Nm (Less so ignored)
3.1.2. Motor Optimisation
The following table tabulates the power needed to raise the blind over the same
distance at varying time intervals. This indicates how much power is need to raise
the motor blind by a distance of 1 m = 1000mm at different speeds.
5.705
N
11.41N 5.705
N
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Time Speed ω=v/r
Power =
T(ω)
Length to
travel=
1000mm
Seconds m/s rev/min Watts
5 0.200 123.190 2.28
10 0.100 61.593 1.14
15 0.067 41.070 0.76
Table 6 : Motor Optimization
The design that was chosen and fabricated can travel 0.9m (900mm) in about 14.5
seconds. The stepper motor speed was set at 30(rpm) revolutions per minute. As
seen from figure 2 as we increase the speed the torque decreases.
Figure 8 Torque vs Speed Characteristics ( N/cm vs pps)
3.2. Bearings
The outer diameter of the blind shaft was measured
to be 32mm. Considering the deformable nature of
the blind shaft material (cardboard), bearings of a
smaller diameter could be “forced” (by use of a
rubber mallet) in and around the shaft. This would
ensure a tight-fit, and minimum slippage between
shaft and bearing. Hence, bearings of 30mm outer
diameter were chosen.
3.3. Bearing case
Considering that 3D-printing and cost-efficiency were key requirements, a two-part
bearing casing was designed to be made of Poly Lactic Acid (PLA), instead of
purchasing a pillow block bearing.
16. Page | 12
The first concept incorporated a male and female piece, each with a hole of diameter
(.) The hole was designed to allow the blind shaft to yet maintain minimal bearing-
casing contact to reduce effects of friction. The two parts would be combined via sets
of pin-and-slot, to ensure tight fit.
Upon reviewing this concept, it was seen that the clamping force of the bearing case
restricted the rotary motion of the inner bearing guide ring. However, to determine
the possible shrinkage ratio that might occur during 3D-printing manufacturing, the
embodiment design was printed as a “test piece.”
Therefore, a new concept was introduced.
The second concept was a simplification of the previous design. The shrinkage ratio
of the 3D-printing was taken into account (1.57%) and geometric dimensions of the
bearing casing were adjusted accordingly when carrying out CAD/FEA.
Figure 9 : CAD of Bearing mounts
17. Page | 13
3.4. Flexible coupling
An industrial coupling was chosen for the drive transmission. Its flexibility allowed
compensation for any alignment issues. One end of the coupling was to be attached
to the stepper motor shaft, whereas the other end would be attached to the roller
blind shaft.
3.5. Shaft-coupling connector (right)
A connecting part was required, in order to compensate for the difference in inner
diameters of the blind shaft and the flexible coupling. Upon reviewing strength
properties of Poly Lactic Acid (PLA), it was feasible to manufacture the shaft-
coupling connector using 3D-printing.
The following concepts were generated:
3.5.1. Concept 1
Description: Two-part design. The shafts that extend from all around the cylindrical
surface of the connector (arms) have torsional springs attached to them, and fit
securely into the second piece. The second piece has flat surfaces (blades) all
around its diameter, thereby ensuring constant contact with the inner diameter of the
blind shaft.
Advantages: Universal, can fit into any shaft diameter (due to the elastic spring
component)
Disadvantages: The shafts that extend around the surface could break easily, due
to their relatively small size and strength properties of PLA. The connector has
complex geometry, which might be difficult to manufacture using 3D- printing.
Figure 10 : Coupling concept 1
18. Page | 14
3.5.2. Concept 2: Tight-secure
Description: In order to achieve secure contact on both the outer and inner
diameters of the shaft, this concept consists of a cylinder with a cavity large enough
for the roller blind shaft to slot in.
Advantages: Simple, easy to use, secure
Disadvantages: Too much contact, could cause deformation
3.5.3. Concept 3: Blades
Description: This concept borrows from both the previous concepts, incorporating
contact blades and a cavity, to achieve optimal locking, minimal slippage, and low
stresses acting on the blind shaft.
Figure 11 : Coupling concept 2
Figure 12 : Coupling concept 3
19. Page | 15
Advantages: Ensures axial-symmetric contact with blind shaft and can sustain
operation for prolonged working periods
Disadvantages: None
Concept 3 was chosen. The roller blind shaft was manufactured using cardboard,
and thereby could deform, unlike a metal shaft. Therefore, uniaxial, axial-symmetric
blades were incorporated into the design to ensure constant contact with the inner
diameter of the blind shaft (thereby minimising twist).
The connector design was reviewed, and to increase the integrity of its structure, an
aluminium shaft was attached along the component’s central axis.
3.6. STEPPER MOTOR CASING
The casing was designed to be 3D printed. Maximum temperatures arising in
stepper motors were seen to be less than the melting tempe rature of Poly Lactic
Acid.Stepper motors tend to experience overheating issues; therefore heat vents had
been incorporated into the design. The casing was a two-part design, with one part
to be mounted onto the wooden frame, and account for alignment of the motor shaft
with the rest of the mechanical system. The second part was to securely fix the
motor in place. This was critical, as an unstable mounting of the motor would lead to
damage of the system.
Figure 13 : Motor Casing
20. Page | 16
4. DESIGN VALIDATION
This section aims to test the designed parts, and to confirm whether they can be
brought with confidence to the assembly section.
After passing from decision stage and calculation phase, final design validations are
made via simulations to perform checks based on maximum deflections, stresses
which will be introduced as a result of elevated loads/torques on components.
Components to be tested are as,
1) Bearing Case
2) Shaft-Coupling Connector
3) Coupling (free side)
4) Motor casing base.
5) Motor casing.
They are subjected to following loading conditions, which are approximately double
than calculated one to test them under extreme. Sign convention on result depends
on respective axis.
Load of 5N to 7N.
Torque of 5Nmm
4.1. Bearing Case
Figure 14: Bearing mounting Left side (same results for right side) maximum
deflection and stresses
Figure 14, bearing mounting for roller blinder are tested, each side in blinder
assembly is composed of two of these bearing one being mirror of another. Material
tested polylactic acid (PLA plastic) showed,
Maximum deflection of 2.1e-6mm and minimum of -0.0011mm.
Maximum stress which material under goes is 0.069 MPa.
21. Page | 17
Deflection is well under the range of 1% allowable range. Similarly PLA has an
ultimate tensile strength (UTS) of 50 MPa where maximum stress which material
showed is 0.069 MPa. These results justify the design and its safe use for this
project.
4.2. Shaft-Coupling Connector
Figure 15 : Coupling (Motor side) stresses and total deformation
Figure 19, couplings are tested to deduce whether introducing fillet section reduces
stresses or not. In this section coupling for design one is tested and from fig. 2
maximum stress that this design can hold is 0.13 MPa with total maximum
deformation of 0.000681mm, total deformation is used as evaluation criteria due to
incoming torque form motor which will introduce moment in connected shaft. As
stresses propagates from shaft to fillet area, as seen in fig. 3, so in final design this
area is changed to flat surface i.e. excluded.
4.2.1. Reviewed Design
Figure 16 : Revised coupling A
22. Page | 18
Figure 17 : Revised coupling B
4.3. Connector 2 (Free Side)
Figure 18: Coupling (free side) stresses and direction deformation
Coupling on free side ensures proper fit that is why it is subjected to static load of 5N
as it would hold one side of the roller. From simulation it is observed that,
Maximum deflection is -0.0001513mm with stress of 0.0723MPa.
23. Page | 19
4.4. Motor Casing
Figure 19 : Motor casing evaluation
Motor case needs to hold motor only and same validation condition like motor
mounting base are applied to it. From it following results are obtained, Max deflection
of -6.8427e-5 mm, with minimum of -0.0008895mm. (-ve sign depends on direction
analogy).
Stresses of 0.083165 MPa maximum
Total deformation of 0.000963 mm.
4.5. Motor Mount
Figure 20: Motor casing base directional deformation and induced stresses
This base was designed with intention to hold motor weight addition to blinder
weight. It is subjected to a total of 7 N force. Under these conditions,
Maximum deformation it goes is 3.11e-5 mm.
Stresses of 0.00836 MPa to 0.0006 MPa.
24. Page | 20
As it is intend to hold the weight by means of screws so in terms of stresses those
holes points are the one undergoing such condition and from results it is well below
the UTS of PLA. So this base passes the validation point.
5. ELECTRICAL/ELECTRONIC SYSTEM
This section aims to fully describe the electrical/ electronic system, and discuss the
various components used in the micro-controller (Arduino) circuit.
5.1. Arduino Uno U3 development board
5.2. Arduino motor shield
5.3. Infra-red remote controller and receiver
The mechanism should know
where the blind is (by indexing) at
any time.
The blind should reset to either the
raised or lowered position
automatically when power is
restored after a power failure
The blind should be able to operate by
remote control using infrared, R/F or an
App.
The blind should stop and start at any
intermediate position
The mechanism should know where the blind is (by
indexing) at any time.The blind should reset to
either the raised or lowered position automatically
when power is restored after a power failure
An advantage of the Arduino Motor Shield is; it has
all the digital pin inputs as we have on a regular
Arduino UNO board. Therefore, connecting signal
cables of the other components are not going to be
effected
25. Page | 21
5.4. Limit switches
5.5. Push buttons
5.6. Description of Arduino Code
In this section, the Arduino code is separated into parts to explain the logic behind it.
Before defining any pin or relation between the components, libraries for IR receiver
and stepper motor in imported to compile much simple code for the following stages.
#include <IRremote.h>
#include <Stepper.h>
After the library import, the signal pins of the buttons and switches were introduced
to board. For the stepper, since we are using the Arduino Motor Shield R3 is used,
the connections were made through phase inputs of the driver but pins were defined
according to default layout of Arduino pins (PWM to pin 3 and 11, brake to pin 8 and
9, direction to pin 12 and 13).
The mechanism should know where the
blind is (by indexing) at any time.
The blind should reset to either the
raised or lowered position automatically
when power is restored after a power
failure
Limit switches prevent damage to the
motor when roller blind is raised and
wraps onto itself. (extreme case)
The blind should be fitted with UP and DOWN
buttons to enable the user to operate it in
close proximity. The blind should stop and
start at any intermediate position
Push buttons are required to make user able
to decide the position of the blinder from close
distance as well or if there is a problem with
the IR. Two push buttons were used in the
system as up and down button.
26. Page | 22
// Define the motor control pins names
const int pwmA = 3;
const int pwmB = 11;
const int brakeA = 9;
const int brakeB = 8;
const int dirA = 12;
const int dirB = 13;
// Define IR Receiver, Buttons and Switches
const int receiver = 7; // Signal Pin of IR receiver
const int up = 2; // Signal Pin of Up Button
const int down = 4; // Signal Pin of Down Button
const int limit1 = 5; // Signal Pin of Upper Limit Switch
const int limit2 = 6; // Signal Pin of Lower Limit Switch
In this part if code, the stepper motor is initialized for the first time. Note that the
stepper that we used has 200 steps per revolution therefore, if user wants to use
another stepper, stepsPerRevolution value needs to be changed.
// Initialize the Stepper Library on the Motor Shield
const int stepsPerRevolution = 200; // Stepper has 200 steps per
revolution
Stepper myStepper(stepsPerRevolution, 12, 13);
After initializing the stepper, IR receiver is also initialized to start collecting data from
the remote controller.
IRrecv irrecv(receiver); // Create instance of 'irrecv'
decode_results results; // Create instance of 'decode_results'
uint16_t lastCode = 0; // This keeps track of the last code RX'd
A flag is defined as a checkpoint which we used for the startup loop in the case of
electricity shortage.
int flag = 0; // Define checkpoint for startup loop
In void setup section of the code, just like in any other code, the OUTPUT pins were
defined in order to digitally control them. Void setup only includes the start-up
procedure which includes the setting of the stepper speed and start of the IR
receiver. For this system, considering the weight of the blinder, load on the stepper
and the linearity of the motion the speed is set to 30 RPM.
void setup() {
// Set the PWM Brake and Direction Pins
pinMode(pwmA, OUTPUT);
pinMode(pwmB, OUTPUT);
pinMode(brakeA, OUTPUT);
27. Page | 23
pinMode(brakeB, OUTPUT);
digitalWrite(pwmA, HIGH);
digitalWrite(pwmB, HIGH);
digitalWrite(brakeA, LOW);
digitalWrite(brakeB, LOW);
Serial.begin(9600); // Initialize the Serial Port
myStepper.setSpeed(30); // Set Stepper Speed
irrecv.enableIRIn(); // Start the IR Receiver
}
Void loop is the part of the code which keeps running throughout the operation. At
beginning of the loop, the signal value from buttons and limit switches are read since
we need their value for every single cycle to be sure that blinder is always stay within
the limits of the frame.
void loop() {
int lmu = digitalRead(limit1); // Upper Limit Switch
int lmd = digitalRead(limit2); // Lower Limit Switch
int u = digitalRead(up); // Up Button
int d = digitalRead(down); // Down Button
The start-up loop is used to return the blinder to its zero position (upper side of the
frame), in case electricity cuts out and comes back after a certain time. Note that the
flag value, arranged at the beginning of the code, is only going to match (with the if
condition) at the resets and at the end of start-up loop, it is going to be changed to
another value, therefore, start-up loop works for one time only.
// Start-up Loop
if (flag ==0)
for (int i = 0; i <= 2000; i++)
if (digitalRead(limit1) == LOW) {
myStepper.step(1);
}
else if (digitalRead(limit1) == HIGH) {
flag = 1;
break;
}
In every single void loop cycle, the IR receiver checks for new signal from the remote
controller. Normally IR receivers use NEC protocol for generating and collecting data
in 32 bit size. In our code, those data were converted into 16 bit size to run the code
faster and decrease the possible lag between the IR receiver and Arduino. The
repeat codes were also recorded (they have 0 bit size) in order to prevent them
during operation. At the end of each cycle, the system checks for a repeat code. In
the cases, which receiver reads a repeat code, it will use the one from previous loop.
28. Page | 24
// IR Control Code
{
if (irrecv.decode(&results)) // Did we received an IR signal?
{
uint16_t resultCode = (results.value & 0xFFFF); // Include repeat
codes
if (resultCode == 0xFFFF) {
resultCode = lastCode;
}
else {
lastCode = resultCode;
}
{
IR receiver section is divided into 2 main parts as hold down a button or pre-defined
position. For IR receiver code, system works under two requirements. The IR data
from the receiver should match the Arduino code and the value of the limit switches
is need to be LOW. For keep pressing conditions in every single press the stepper
makes 10 steps in selected direction until it reaches the limit switch. Unlike buttons,
for IR, we defined the number of steps as 10 since we do not have any physical
connection between the remote and Arduino so, system will have lags between
cycles if we define the number of steps as 1. With number of steps as 10, the lag is
minimized.
For predefined positions, system is capable of going full up and full down with one
press (up and down buttons if the remote). Normally blinder needs around 1300-
1400 steps to complete a full motion but in order to show that the limit switches are
going to work in any condition, number of steps is arranged to 2000 steps inside a
for loop. In every single step of the for loop stepper makes 1 step and checks for the
position of the limit switches. When limit switch generates HIGH value, for loop is
going to terminate.
At the end of each cycle, IR receiver checks for the next code to prepare system to
next cycle.
//--Keep pressing conditions--//
if (resultCode == 0x10EF && digitalRead(limit1) == LOW) // LEFT is
pressed
myStepper.step(10);
if (resultCode == 0x807F && digitalRead(limit2) == LOW) // RIGHT is
pressed
myStepper.step(-10);
//--Pre-defined position cases--//
if (resultCode == 0xA05F) // UP is pressed
29. Page | 25
for (int i = 0; i <= 2000; i++)
if (digitalRead(limit1) == LOW) {
myStepper.step(1);
}
else if (digitalRead(limit1) == HIGH) {
break;
}
if (resultCode == 0x00FF) // DOWN is pressed
for (int i = 0; i <= 2000; i++)
if (digitalRead(limit2) == LOW) {
myStepper.step(-1);
}
else if (digitalRead(limit2) == HIGH) {
break;
}
irrecv.resume(); // Receive the
next value
}
}
For button operation, just like in IR receiver, system works under two requirements.
For up button case; up button needs to be pressed while down button is not pressed.
This approach has been selected to prevent stepper from unnecessary load if the
user presses both buttons at the same time. In every single cycle, Arduino checks
which button is pressed and the position of the related limit switch if the conditions
are valid stepper makes 1 step.
For down button, the logic is same but stepper makes -1 step to provide the motion
in the reverse direction.
// Button Control Code
if (u == HIGH && d == LOW && lmu == LOW) { // UP Button Code
myStepper.step(1);
delay(.01);
}
if (d == HIGH && u == LOW && lmd == LOW) { // DOWN Button Code
myStepper.step(-1);
delay(.01);
}
}
}
5.7. Circuit Diagram and Description
The circuit designed to meet the initial specifications is given below.
30. Page | 26
Figure 21 : Circuit connections layout
Bread board circuit consist of,
Two 330 ohm resisters.
Four LED’s.
Two limit switches.
Two push buttons.
Jumper cables, signal cables for Arduino.
IR receiver power cables.
Circuit is shown in Figure power for bread board is taken from Arduino as 5V live line
shown in red and ground shown in black. Jumper cables are of green colour, signal
for push buttons are of white and signal for limit switch is orange. Since purpose of
limit switch and push buttons is to control motion of motor they are connected is
parallel connection as,
Both push button in series in individual set (one push button with one LED) with
led.
Resistor is connected to ground then connected to LED completing one circuit
loop.
When push button is pressed circuit gets complete and high signal is obtained at
white cable.
White cable will be used by Arduino.
31. Page | 27
Figure 22 : Types of resistors and LED used
Both push buttons follows the same principle for getting high voltage at the end. LED
are used to consume extra current in circuit such that every time same signal is
obtained irrespective of current/voltage fluctuations. In start during making
connection it was observed that current difference across buttons and Arduino was
not same resulting in no or jerk motion by motor. Addition of LED consumes that
extra current giving same difference across all connections.
Limit switches are attached with same analogy working under same principle as
push buttons, but there signal is defined by orange cables. IR receiver is getting its
power from board. All connections are in parallel to get same voltage across all
components.
5.8. Circuit Connection on Frame
Circuit connection on frames are done to make them as neat as possible without
harming the assembly with the help of self-adhesive cable mounts and other
components as shown below,
33. Page | 29
6. FINAL ASSEMBLY
The final assembly is shown below. Wires have not been included in the drawings.
Front view of assembly Back view of assembly
34. Page | 30
6.1. Motor – Roller Blind Connection (Sub-Assembly)
Bearing
Case
Shaft-
Coupling
Connector
Motor
Mount
Motor
Housing
Roller
Blind
Stepper
Motor
Industrial
Coupling
Figure 23: Sub Assembly (Right- shown above), Sub Assembly (Left- shown below)
Bearing
Case
Shaft
Connector
(Left)
35. Page | 31
6.2. Electrical/Electronic Component Consideration
IR
Receiver
Push
Buttons
Limit
Switch
Breadboard
connected to
Arduino and
system circuit
Arduino and
Arduino Motor
Shield
Figure 24: Electrical/Electronic component layout (front- shown above) and
(back-shown below)
36. Page | 32
PART NO. PART DESCRIPTION NO. OF UNITS PRICE/UNIT (£) TOTAL PRICE (£) WEBSITE
1 HX1838 Infrared Remote Control Module and Receiver 1 5.4 5.4 http://www.hobbytronics.co.uk/sensors/light-sensors/hx1838-infra-red-remote
2 3 V dc, 4.5 V dc, 5 V dc, 6 V dc, 7.5 V dc, 9 V dc, 12 V dc, 1 Output 1 17.48 17.48 http://uk.rs-online.com/web/p/plug-in-power-supply/6796707/
3 Arduino Board USB Cable 1 3.89 3.89 http://uk.rs-online.com/web/p/usb-cable-assemblies/8134738/
4 Stepper Motor 1 30.9 30.9 http://uk.rs-online.com/web/p/stepper-motors/5350423/
5 Arduino UNO R3 Development Board 1 24.99 24.99 http://www.maplin.co.uk/p/arduino-uno-r3-development-board-n30ku
6 Breadboard Prototyping Board 80 x 60 x 10mm 1 6.84 6.84 http://uk.rs-online.com/web/p/products/1029147/?tpr=1
7 Arduino Motor Shield 1 19.99 19.99 http://www.maplin.co.uk/p/arduino-motor-shield-n36ku
8 MIKROE-513, 10 Piece Breadboard Jumper Wire Kit 1 2.12 2.12 http://uk.rs-online.com/web/p/breadboard-jumper-wire-kits/7916463/
9 MIKROE-512, 10 Piece Breadboard Jumper Wire Kit 1 2.12 2.12 http://uk.rs-online.com/web/p/breadboard-jumper-wire-kits/7916454/
10 RS Pro Metal Deep Groove Ball Bearing 30mm I.D, 55mm O.D 2 3.71 7.42 http://uk.rs-online.com/web/p/ball-bearings/6190480/
11
Ruland Aluminium Flexible Beam Coupling, PSR12-4-4-A, Bore A 1/4in
Bore B 1/4in Set Screw
1 16.83 16.83 http://uk.rs-online.com/web/p/flexible-beam-couplings/3643060/
12 Heatsink, BGA, 27.4K/W, 14 x 14 x 10mm 1 0.92 0.92 http://uk.rs-online.com/web/p/heatsinks/6744756/
13 HTSN-M3-20-6-2, 20mm High Nylon Threaded Hex Spacer 1 0.207 0.207 http://uk.rs-online.com/web/p/threaded-hex-spacers/1026536/
14 Push Button Switch, IP65, 16.2mm, NO, Panel Mount, Momentary 2 6.34 12.68 http://uk.rs-online.com/web/p/push-button-switches/6903264/
15 V3 Style Alarm Tamper Switch 2 2.99 5.98 http://www.maplin.co.uk/p/v3-style-alarm-tamper-switch-nf21x
16 DC Axial Fan, 50 x 10 x 50mm, 22m³/h, 1.30W, 5 V dc 1 7.76 7.76 http://uk.rs-online.com/web/p/axial-fans/7980773/
165.527
GROUP5
Company Units Price
Hobbytronics 1 5.4
RS component 50+ 13.99
RS component 100+ 3.73
RS component 10+ 29.3
Amazon 1 18.01
RS component 50+ 5.47
Maplin 19.99
RS component 25+ 1.95
RS component 25+ 1.95
RS component 25+ 3.4
RS component 10+ 15.79
RS component 1 0.92
RS component 1 0.207
RS component 250 4.02
Maplin 1 5.98
RS component 50 5.13
Total Price 135.237
7. BILL OF MATERIALS (COSTING)
37. Page | 33
8. POST MORTEM / DESIGN IMPROVEMENTS
The final design has been further evaluated, and the following design
improvements could be made:
Once the power is switched off, the roller blind continues to move downwards
due to minimal friction in the bearings. This could be remedied by introducing
either a worm gear system, or by introducing a magnetic relay (powered by a
battery)
The coupling shaft connector on the right (Concept 3: Blades) could be made in
the same design as the shaft connector on the left. This would ensure that no
amount of fabric would have to be cut.
The ideal motor for this design would be a stepper motor with a lower torque.
Differences in the torque of the motor and that required to raise the blind could be
addressed by introducing a gearbox mechanism. Additionally, this would reduce
the heating that would occur in the Arduino Motor Shield. This would also reduce
the need for a cooling fan, thereby reducing the overall cost of the final design.
In order to make a cleaner (market-ready) product, a proximity sensor could be
placed at the bottom of the roller blind path, instead of a limit switch. The
cantilever arm of the limit switch would wear out with prolonged use, whereas the
work life of an embedded proximity sensor would be significantly higher.
When the power is disconnected, the roller blind starts to move under its own
weight. A jack screw system could be implemented as a connector between the
motor and the coupling to stop this unwanted motion.
The range of the infra-red receiver is somewhat limited. A wireless adaptor
(Bluetooth) can be used to minimise this problem as the user can also control the
position of the blind from his smart phone/ computer.
The roller blind could come equipped with three variable speeds, each with
varying power consumption (higher speeds corresponding to higher power).
A manual override should be designed. (See concept in Appendix) This would
provide a safety option, and ensure normal operation of the roller blind, even in
the event of a power shortage.
