automated blinds

8/7/2019 AUTOMATED BLINDS

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AUTOMATED BLINDS

Prepared for

Professor Rashdee

EET-344: Microprocessor with PeripheralsDeVry University, Fremont

Prepared by

Mai Zoua VangJustin Niel

Joshua Quintero

February 13, 2007


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CONTENTS

Page

ABSTRACT...................................................................................................................1

INTRODUCTION/FEASIBILITY..1

MATERIALS AND EQUIPMENTS...5

Basic information of ADC ..5Basic information of reversed-bias LED....6

Basic information of 3-to-8 line decoder....6

Basic information of stepping motor ..7Basic information of ULN2003 ..7

PROGRAMMING AND INTERFACING APPROACH...8

Flowchart 8Hardware ...12

SOFTWARE CODE..14

RESULTS .19

CONCLUSION .19

WORKS CITED ...20

APPENDIX ...21

ii


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LIST OF ILLUSTRATIONS

Figures Page

1. Figure 1: Light Sensors 2

2. Figure 2: Left Sensor 2

3. Figure 3: Center Sensors 3

4. Figure 4: Right Sensor 3

5. Figure 5: Blinds 4

6. Figure 6: ADC Pin out 5

7. Figure 7: 3-to-8 Decoder Pin out (MM74HC138M) 6

8. Figure 8: Stepper Motor sequence 7

9. Figure 9: ULN2003 pin out 7

10. Figure 10: ADC connection to decoder 12

11. Figure 11: ULN2003 connection to Stepper Motor 13

12. Figure 12: Circuit 13

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1

ABSTRACT

Background

Have you ever had trouble with your blinds letting out too much heat at night when you forget to

close them? Or would you like your blinds to be open, letting in sunlight and heat as soon as youget up in the morning? Well we are here to help! We at Solar Blind Systems Inc. have devised a

solution for all of your troubles. It is automatic blinds! These specially designed blinds will

allow the shutters to follow the sunlight in order to let in an optimal amount of heat for your

home and close up when not in use.

Results

We found that we can create blinds that will follow light using light sensors and a simple

program in C++ that will compare the inputs, after the comparison is made, and the output will

be sent to our motor to change the position of the blinds. When there is no sunlight outside to let

in, the blinds will simply close up to retain the heat that is in your home already. This systemwill not only be convenient to the average homeowner, but it will also save you money on

electricity bill.

Conclusion

If you would like to save possibly hundreds of dollars on your electricity bill over the next fewyears, automatic blinds are the answer for you! With our unique power saving techniques of

blind management, we will save you both time and energy.

INTRODUCTION/ FEASABILITY

These electronic blinds are the future of the world as we know it. No longer will we be required

to maintain our own household blinds to gain optimal lightning and contain the heat stored in our

homes. The natural heating provided by the sun will be sufficient to allow the owner to use lessnatural gas and/or electricity to heat their home. The homeowners will also benefit from the

optimal lightning procedures of the system to enable the users to be able to worry less about

using indoor lights. This also can be used on focusing solar cells toward the sun.

The process is simple; we take in light from four strategic locations and compare their values to

locate the position of the sun.


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There are four light sensors located at different angles.

Figure 1: Light Sensors

Divider

Light sensors

If the sun shines to the left, the left sensor will receive the most amount of light.Figure 2: Left Sensor


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If the sun shines in the center, the two center sensors will receive the most amount of light.Figure 3: Center Sensors

If the sun shines more to the right, the most right will get most of the sunlight.Figure 4: Right Sensor


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Whichever location brings in the most light can be considered the location of where the sun is

most closely located at. The motor will turn the blind using the corresponding steps to the

position with the most light. The whole process of taking and comparing the values from the foursensors repeat over again; closing if there is no longer enough light to bring in.

Figure 5: Blinds

Stepper motor

sensorblinds


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5

MATERIALS AND EQUIPMENTS

The materials used in the automated blind are listed in Table 1.

Table 1: List of Materials

Quantity Part Num. Description Cost

4 Green LEDs $0.40

1 Stepping motor $17.95

4 ADC0804Analog-to-digitalconverter $7.96

1 MM74HC138 3-to-8 line decoder $0.17

5 103 Ceramic capacitor $0.17

1 Blind $15.63

Wires

6 General diodes

1 Triple power supply

1 ULN2003 Current driver $0.69

Resistors $0.01

2 Banana-to-banana cord

Total expense $42.98*

*Price does not include power supply, general diodes and wires.

Basic information of ADC

The ADC (Analog-to-Digital Converter) converts a single analog signal into a digital signalbased upon the percentage of a reference voltage that the output is. Thus we can take the inputvoltage, divide it by the reference voltage and multiply it by 256 (eight outputs) to receive the

digital output in increments of 1/256.

Figure 6: ADC Pinout

Source: Alldatasheet.com


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Four ADC sensors were used to take in the varying sunlight values based upon their locations.

One ADC sensor is located at 22.50; one at 67.5

0; one at 112.5

0; and one at 157.5

0. Only one

ADC is actively sending the data to our microprocessor at a time. A decoder is used to activatethe desired ADC chip. This output is taken into a microprocessor which then compares the value

with the other ADC outputs.

Basic information of reversed-bias LED

When a normal Light Emitting Diode is set in reversed bias it will act as a phototransistor.

Whenever light is focused upon the LED, the current will flow freely through the diode atdifferent voltages based upon the amount of light the LED is absorbing. The more light focused

upon the LED, the more voltage the LED will let pass freely through it. This gives us a point of

reference and comparison. Reversed-bias LEDs are used as phototransistor in the automatedblind. When a LED is reversed-bias, the depletion zone widens. When the atoms inside the LED

absorb the light, the energy band inside the atom raises. But instead of releasing the energy

through light, like it usually does, it releases electrons.

Basic information of 3-to-8 line decoder

A 3-to-8 line decoder takes in three inputs to select one of eight outputs. The three inputs are

binary values (0 and 1) which would result in a value from 0 through 7 which then selects the

corresponding output (output 0 output 7) to be set at a low state. The outputs of the decoder

are active-low. The outputs of the decoder can then be used to enable the chips connected tothem.

The decoder was used in this project to select one of four ADC to send their digital outputs to themicroprocessor. To do this, the decoder is sent a binary value that signifies the desired ADC

chip. Then the decoder will send a low state to the ADCs chip select pin. The ADC chip select

pin is active-low.

Figure 7: 3-to-8 Decoder Pinout (MM74HC138M)



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Table 2: Truth table. This table shows the value of the inputs of the decoder that select the corresponding ADC

chip.

S0 S1 S2 Y0(ADC1) Y1(ADC2) Y2(ADC3) Y3(ADC4)

0 0 0 0 1 1 1

0 0 1 1 0 1 1

0 1 0 1 1 0 1

0 1 1 1 1 1 0

Basic information of stepping motor

The stepping motor is a four-phase stepper motor. This means that the stepper motor has four

stator windings with a center-tapped common. This common allows the motor to change thecurrent direction within each of the two coils which changes the polarity of the stator.

The stepper motor used is a 4.7 V motor with 1.5 angle step. To determine the required numberof steps to turn the rotor to a desired position, the following formula was used:

Steps = Desired Angle / Angle step (Specified by the motor).

This stepper motor has a four step sequence as displayed below.

Figure 8: Stepper Motor Sequence

Clockwise Step # Winding A Winding B Winding C Winding D Dec # Counter-clockwise

1 1 0 0 1 9

2 1 1 0 0 C

3 0 1 1 0 6

4 0 0 1 1 3

Basic information of ULN2003

The ULN2003 is the stepper motors driver. It takes in the datas from Port B. The ULN2003

inverses the inputs. After that, each bit is sent to its own Darlington pair, where the voltage is

stepped up to the voltage desired to run the stepper motor.

Figure 9: ULN2003 Pin out



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PROGRAMMING AND INTERFACING APPROACH

Flowchart

Initialized char stepper = 0x33HInitialized ADC

Initialized blind to position 1

Read values from LEDs

Set greater = sensor_1Set Position = 1

Greater < sensor_2

Set greater = sensor_2

Set new_position = 2


Set new_position = 3

True

Greater < sensor_3

Greater < sensor_4

False

True

False


Set new_position = 3Difference = position new_positionTrue

False


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Switch( difference)

Print position 1

Steps = 120

Print position 2

Steps = 241

Print position 3

Steps = 482

Print position 4

Steps = 723

0 1, -1 2, -2 3, -3

Print position 4

Steps = 723

Default

Position = new_position

While(steps !=0 &&

difference =0)

True False

Do while loop


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Send stepper value to Port B

Rotate value to the left once

Steps = steps - 1

Difference = positon - 1

False

While keyboard is notpressed

True

False

Switch( difference)

Steps = 120 Steps = 361 Steps = 600 Steps = 860

0 1, -1 2, -2 3, -3

Steps = 0

Default

While steps != 0

Send stepper value to Port B

TrueWhile loopFalse

Do while loop


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Rotate stepper value to the light

once

Steps = steps - 1

While loop

End propram

False


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Hardware

Figure 10: ADC connection to decoder. Figure 11 shows how the 3-to-8 decoder is connected to eachADC chip select and Port C.

1S1

2S2

S33___

G2A4

16

15

14

13

Vcc

Out0

Out1

Out2

9

Out6

MM74HCT138

5

___

G2B12

Out3

6G1

11Out4

7Out7

10Out5

GND

8

1

__

CS

2

__

RD___

WR3

CLK IN4

19

18

17

16

CLK R

DB0

DB1

DB2

Vcc1

20

5

____

INTR15

DB3ADC0804

6Vin(+)

7Vin(-)

GND8

Vref/29

14

13

12

11

DB4

DB5

DB6

DB7 (MSB)GND

10

1

__

CS

2

__

RD___

WR3

CLK IN4

19

18

17

16

CLK R

DB0

DB1

DB2

Vcc1

20

5

____

INTR15

DB3

6Vin(+)

7Vin(-)

GND8

Vref/29

14

13

12

11

DB4

DB5

DB6

DB7 (MSB)GND

10

1

__

CS

2

__

RD___

WR3

CLK IN4

19

18

17

16

CLK R

DB0

DB1

DB2

Vcc1

20

5

____

INTR15

DB3ADC0804

6Vin(+)

7Vin(-)

GND8

Vref/29

14

13

12

11

DB4

DB5

DB6

DB7 (MSB)GND

10

1

__CS

2__RD

___

WR3

CLK IN4

19

18

17

16

CLK R

DB0

DB1

DB2

Vcc1

20

5

____

INTR15

DB3ADC0804

6Vin(+)

7Vin(-)

GND8

Vref/29

14

13

12

11

DB4

DB5

DB6

DB7 (MSB)GND

10

PORT C

330 ohm

330 ohm

330 ohm

330 ohm

50 3 421 6

PORT A

Data

210

5V

10 nF

5V

10nF

5V

10 nF

5V

10 nF

0.47 uF

0.47 uF

0.47 uF

0.47 uF


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Figure 11: ULN2003 connection to the stepper motor. It shows how Port B is connected to the inputs

of the ULN2003. The ULN2003 is connected to the stepper motor.

Figure 12: Circuit


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SOFTWARE CODE

#include // header for Sleep#include #include

#include #include "mdedriverdll.h"

This portion links the necessary header files to our project.

void main(){int iwork;unsignedchar sensor_1 = 0, sensor_2 = 0, sensor_3 = 0, sensor_4 = 0,

greater = 0;

int position = 1, new_position, difference, steps = 120;unsignedchar stepper = 0x33;

This portion enters the main then initializes all the variables used in ourprogram.

iwork = MDEOpenLPTPort(0x378); // initialize driverMDEConfigPort(0x378, 0x90);

cout


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// clear screensystem ("cls");

This portion initializes the ADC and clears the screen afterwards.

// initialized blind to position 1- 22.5 degreeMDEOutPB(0x378, 0xff);

MDEOutPB(0x378,stepper);Sleep(10);MDEOutPB(0x378,0x00);Sleep(10);

while(steps !=0){MDEOutPB(0x378,stepper);Sleep(10);MDEOutPB(0x378,0x00);

Sleep(10);

_asm{mov al, stepperROR al,1mov stepper,al

}

steps = steps - 1;}

This portion initializes the blinds to position 1(or 22.5 degree). One of thestepper motor values 33(in hex) is sent to port B. Then we rotated the valueand it became 99(in hex).

do{

//cout


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Sleep(50);

// cout new_position;

This portion checks what position the stepper motor should be in.

difference = position - new_position;

switch( difference){case 0:

cout


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RESULTS

The results we got were as proposed. The lights sensors would send the value through the ADCto the microprocessor. The Microprocessor would then interpret these values and determine

which sensor is absorbing the most light. The microprocessor would then send determine the

amount of steps required to reach the desired point. Then the microprocessor would output thevalues to the ULN2003 which would then output to the stepper motor. This process would then

enable the blinds to move to the desired position and repeat the process above.

The initial proposal as initially proposed, except we decided to replace the photodiodes with areversed bias LED, which in fact was more sensitive compared to the other photodiodes that we

obtained.

CONCLUSION

From this project we learned many important and pertinent facts concerning electronic devices

and microprocessor. This experience helped strengthen our knowledge of the curriculum coveredin this course. We, the group, will now be able to walk away with a strong knowledge in the

design of electronic circuits using microprocessors and interfacing various devices. Amongthose devices includes the use of a strong stepper motor.


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Work Cited

ADC0804 : 8-Bit, Microprocessor- Compatible, A/D Converters. Intersil Corporation. 1999.http://pdf1.alldatasheet.com/datasheet-pdf/view/66283/INTERSIL/ADC0804.html.

ULN2003 : SEVEN DARLINGTON. STMICROELECTRONICS. 2002.

http://pdf1.alldatasheet.com/datasheet-

pdf/view/25575/STMICROELECTRONICS/ULN2003.html.

MM74HCT138N : 3-to-8 Line Decoder. Fairchild Semiconductor Coporation. 1999.

http://pdf1.alldatasheet.com/datasheet-pdf/view/53791/FAIRCHILD/MM74HCT138N.html


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APPENDIX

automated blinds

Documents