Signage display, which is used to convey message or information, has evolved from conventional to digital display. Conventional signage which may be hand written or printed papers are being wiped out by digital displays used by industries because of its attractive features of efficient involvement of consumers. However, extensive use of digital signage displays contributes a notable amount of power consumption (about 1000W for a 14inch × 48inch display) of a region. In this literature, we have devised a novel approach for reducing power consumption of digital signage as well as satisfying human visibility by exploiting duty cycle. Our proposed technique is capable of relinquishing a significant amount (about 14.54% in comparison with existing display system) of power consumption occurred by digital display by keeping an eye on expected human vision.

1. An Approach Towards Greening the Digital Display
System
Alvi Md.Ishmam
Department of Computer Science and Engineering
Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
1305092.am@ugrad.cse.buet.ac.bd
December 20, 2017
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2. Overview
1 Background and Motivation
2 Our Proposed Methodology
Research Context
3 User Evaluation
4 Future Work
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3. Background of Our Study
Figure: Digital signage display
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4. Background of Our Study
Versatile application such as displaying information on electrical
equipment, advertisement on billboard.
About 70% of American people who notice a digital video display,
among 47% of them can specifically recall them
14inch * 48inch LED billboard(10000 diode) consumes 162,902 KWh
per year
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5. Motivation Behind Our Study
The power hungriness of a LED display system such as dot matrix
display is higher than any other components of an electronic device
[dotmatrix]
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6. Motivation Behind Our Study
The power hungriness of a LED display system such as dot matrix
display is higher than any other components of an electronic device
[dotmatrix]
Pulse width modulation (PWM) operation, i.e., varying the duty cycle
is selected as the best dimming strategy
[Rodrigues,Morais, Garcia,Dalla-Costa]
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7. Motivation Behind Our Study
The power hungriness of a LED display system such as dot matrix
display is higher than any other components of an electronic device
[dotmatrix]
Pulse width modulation (PWM) operation, i.e., varying the duty cycle
is selected as the best dimming strategy
[Rodrigues,Morais, Garcia,Dalla-Costa]
Varying the duty cycle on dot matrix display and finding the optimal
operating point is yet to be addressed.
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8. Related Research Work
[Koh,Wang]
A low voltage DC (LVDC) grid powered LED lighting system was proposed
here. About 44.2% energy saving is possible in this proposed system which
is a perfect dominance over AC fluorescent system.
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9. Related Research Work
Focuses on only power consumption reduction ignoring brightness,
visibility etc.
No trade-off between brightness and power consumption reduction
An optimal operating point is yet to be proposed
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10. Our Research Context
Reducing the power consumption of LED dot matrix based signage display
by exploiting the three fundamental parameters.
Duty Cycle
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11. Our Research Context
Reducing the power consumption of LED dot matrix based signage display
by exploiting the three fundamental parameters.
Duty Cycle
Frame Rate
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12. Our Research Context
Reducing the power consumption of LED dot matrix based signage display
by exploiting the three fundamental parameters.
Duty Cycle
Frame Rate
System Frequency
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13. Can We Experiment with a Large Signage Display?
Figure: Digital signage display
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14. Can We Experiment with a Large Signage Display?
Figure: Digital signage display
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15. Solution
Figure: 8*8 dot Matrix Display
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16. Overview of Experimental Procedure
Figure: Block Diagram
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17. The Instrumentation
2*4 dot matrix display
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18. The Instrumentation
2*4 dot matrix display
8 display arranged in 2 row
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19. The Instrumentation
2*4 dot matrix display
8 display arranged in 2 row
Shift registers & Darlington transistor arrays
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20. The Instrumentation
2*4 dot matrix display
8 display arranged in 2 row
Shift registers & Darlington transistor arrays
Power consumption reduction
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21. The Instrumentation
Figure: Setup of Experiment
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22. Unveiling the Parameters
Duty Cycle: At which proportion system is operational
Pavg = Ppeak × dutycycle (1)
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23. Unveiling the Parameters
Duty Cycle: At which proportion system is operational
Pavg = Ppeak × dutycycle (1)
By pausing the row selection for small amount of time (95% duty
cycle) brightness does not reduce significantly.
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24. Unveiling the Parameters
Frame Rate: Determines how fast LED’s are illuminated
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25. Unveiling the Parameters
Frame Rate: Determines how fast LED’s are illuminated
Cannot animate all LED’s at once
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26. Unveiling the Parameters
Frame Rate: Determines how fast LED’s are illuminated
Cannot animate all LED’s at once
Animate one by one within 0.1 second to deceive human eye.
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27. Unveiling the Parameters
Frame Rate: Determines how fast LED’s are illuminated
Cannot animate all LED’s at once
Animate one by one within 0.1 second to deceive human eye.
Reduced frame time or high frame rate reduces power consumption
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28. Unveiling the Parameters
System Frequency Frequency of micro-controller( Atmega32)
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29. Unveiling the Parameters
System Frequency Frequency of micro-controller( Atmega32)
Two system frequency (16MHz, 8MHz)
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30. Unveiling the Parameters
System Frequency Frequency of micro-controller( Atmega32)
Two system frequency (16MHz, 8MHz)
Reduced frequency leads to reduced power consumption
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31. Experimentations and Findings
Luminous Efficacy
Luminous efficacy(per unit area) = Illuminance / Power consumption
A portion of Calculation Table:
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32. Experimentations and Findings
Figure: Duty cycle versus luminous efficacy per unit area at 16 MHz system
frequency
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33. Experimentations and Findings
Figure: Duty cycle versus luminous efficacy per unit area at 8 MHz system
frequency
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34. Summary of findings
The minimum frame rate to avoid flickering are 50% and 100% for
16MHz and 8MHz system frequency.
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35. Summary of findings
The minimum frame rate to avoid flickering are 50% and 100% for
16MHz and 8MHz system frequency.
The maximum efficacy is at 85% and 60% duty cycle at 16MHZ and
8MHz frequency.
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36. Summary of findings
The minimum frame rate to avoid flickering are 50% and 100% for
16MHz and 8MHz system frequency.
The maximum efficacy is at 85% and 60% duty cycle at 16MHZ and
8MHz frequency.
Power reduction at those points are 14.54% and 40% and brightness
decreased about 12.5% and 37.5%
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37. User Evaluation and Optimality
User selection criteria:
Wear no spectacles
Both male and Female
Optimality
The optimal operating point is 85% duty cycle, 50Hz frame rate and
16MHz system frequency.
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38. Future Work
Color blind people
People with eyesight problem
All other dot matrix display
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39. References
Dot Matrix Display datasheet. https://goo.gl/RpGnLj.
Rodrigues, W.A., Morais, L.M.F., Donoso-Garcia, P.F., Cortizo, P.C. and Seleme,
S.I., 2011, September. Comparative analysis of power LEDs dimming methods. In
XI Brazilian Power Electronics Conference (pp. 378-383). IEEE.
Garcia, J., Dalla-Costa, M.A., Cardesin, J., Alonso, J.M. and Rico-Secades, M.,
2009. Dimming of high-brightness LEDs by means of luminous flux thermal
estimation. IEEE transactions on Power Electronics, 24(4), pp.1107-1114.
L. H. Koh, Y. K. Tan, Z. Z. Wang and K. J. Tseng, An energy-efcient low voltage
DC grid powered smart LED lighting system, IECON 2011 - 37th Annual
Conference of the IEEE Industrial Electronics Society, Melbourne, VIC, 2011, pp.
2883-2888.
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40. Thank You
Questions Are Welcome!!
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