In partial fulfillment of the requirements of the Undergraduate Research Attachment Programme Department of Electrical and Computer Engineering Faculty of Engineering, National University of Singapore.

1. SOLAR PANEL CHARGE
CONTROLLER FOR INDOOR ROBOT
Ngo Khac Hoang
University of Engineering and Technology
Vietnam National University, Hanoi
Supervisor – Dr. Aaron James Danner
Internship Final Presentation

2. Contents
Overview of project
Power charging circuit
Future work
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2
3
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3. • Objective – Build a power charging circuit for a lightweight INDOOR ROBOT
• Required input voltage of robot: 1.8 – 3.6 V
• 24 amorphous silicon solar cells being used
Overview
Robot from Wall – E movie Mobile Detection and Response System
(MDARS)
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4. 0 1 2 3 4 5 6 7
0
100
200
300
400
500
600
Power(µW)
Voltage (V)
256 lux
315 lux
417 lux
561 lux
631 lux
720 lux
Intensity value  256 – 720 lux
Maximum Power Point  190.464 – 600.237 μW
Overview
 With stable light intensity
• Non-linear relationship between current and voltage
• 1 Maximum Power Point (MPP)
 Solar cell parameters change when the intensity of light changes
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5. Charge controller
Overview
Non-linear
I-V
characteristic
Track the
MPP
Current and
Voltage
Unstable
Maintain
parameters
(voltage)
Charge
Controller
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Make useful
combinations for
charging circuit
Use a micro-
controller circuit
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6. Internship Final Presentation
Power Charging Circuit
 Arranging solar cells in a useful combination to get the target output voltage
 Required conditions – maintain target voltage and maximum power
 Solution – Symmetrical combination of solar cells
n = solar panels
MPP of each: (V, I)
𝑴𝒂𝒙𝒊𝒎𝒖𝒎 𝑷𝒐𝒘𝒆𝒓 = 𝒂𝑽 ∗ 𝒃𝑰 = 𝐚𝐛𝐕𝐈 = 𝐧𝐕𝐈
𝒂𝑽 = 𝑽𝒐𝒍𝒕𝒂𝒈𝒆 𝒐𝒇 𝒘𝒉𝒐𝒍𝒆 𝒔𝒚𝒔𝒕𝒆𝒎
𝒃𝑰 = 𝑪𝒖𝒓𝒓𝒆𝒏𝒕 𝒐𝒇 𝒘𝒉𝒐𝒍𝒆 𝒔𝒚𝒔𝒕𝒆𝒎
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7. Simplify: Divide 24 panels into (6 blocks * 4 panels)
n = 24
Power Charging Circuit
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8. a  columns
b  rows
No. Combination
Switches
Closed
1. a = 1, b = 4 1,2,7,5,6,9
2. a = 2, b = 2 1,2,3,4,6
3. a = 4, b = 1 3, 8,4
Power Charging Circuit
𝑴𝒂𝒙𝒊𝒎𝒖𝒎 𝑷𝒐𝒘𝒆𝒓 = 𝒂𝑽 ∗ 𝒃𝑰 = 𝐚𝐛𝐕𝐈 = 𝐧𝐕𝐈
3 USEFUL
SYMMETRICAL COMBINATIONS
Internship Final Presentation
1 Block = 4 solar cells
𝒏 = 𝟒 = 1 ∗ 4 = 2 ∗ 2 = 4 ∗ 1
Switch = MOSFET
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9. No. Combination
Switches
Closed
1. a = 1, b = 6
1,2,5,6,9,10,11,
12,13,14
2. a = 2, b = 3
1,2,3,4,6,7,8,1
0
3. a = 3, b = 2 1,3,4,7,8,10
4. a = 6, b = 1 3,4,7,8,15
6 Blocks = 24 solar cells 𝒏 = 𝟔 = 6 ∗ 1 = 2 ∗ 3 = 3 ∗ 2 = 6 ∗ 1
4 USEFUL
SYMMETRICAL COMBINATIONS
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10. No.
Combination of 24
panels
Combination of 6
blocks
Combination in each
block
1. (1,24) (1,6) (1,4)
2. (2,12) (2,3) (1,4)
3. (3,8) (3,2) (1,4)
4. (4,6) (1,6) (4,1)
5. (6,4) (6,1) (1,4)
6. (8,3) (2,3) (4,1)
7. (12,2) (6,1) (2,2)
8. (24,1) (6,1) (4,1)
(m*x , p*y) (m , p) (x , y)
Combination of 24 solar panels (6 Blocks)
𝒏 = 𝟐𝟒 = 1 ∗ 24 = 2 ∗ 12 = 3 ∗ 8 = 4 ∗ 6 = 6 ∗ 4 = 8 ∗ 3 = 12 ∗ 2 = 24 ∗ 1
8 USEFUL SYMMETRICAL COMBINATIONS
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11. Internship Final Presentation
Combination of 24 solar panels (6 Blocks) with microcontroller
Microcontroller
Bit combinations
000 100
001 101
010 110
011 111
SYSTEM
24 solar panels
+
microcontroller
Vmeas
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 A microcontroller uses 3 bits to select one of the 8 combinations.
 The bits are then used to open and close the appropriate MOSFET switches.

12.  Construction of real charging circuit
 Program a low power microcontroller
 Conduct test experiments to find the best symmetrical
combination
Future Work
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13. 12
Acknowledgements
 Department of Electrical and Computer Engineering,
National University of Singapore for giving me this
internship opportunity.
 Dr. Aaron James Danner for guiding me in this project.
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14. Internship Final Presentation
Thank You
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