Design and Development of Cost-Effective Solar Rechargeable Led Lantern

Volume 6, Issue 3, March – 2021 International Journal of Innovative Science and Research Technology
ISSN No:-2456-2165
Design and Development of Cost-Effective Solar

Rechargeable Led Lantern
Azubuike Aniedu1, Azubogu A.C.O2, Ufoaroh S.U3, Obioma Peace Chibueze4
1,2,3,4
Department of Electronic and Computer Engineering
Nnamdi Azikiwe University
Awka, Nigeria
Abstract:- In many countries of sub-Saharan Africa performance of the fixture after being used for a short period.
including Nigeria, more than 70% of the people live in In many instances, users of the solar lanterns end up
off-grid communities where they depend on kerosene discarding them after few months of usage because they lack
hurricane lanterns and candles to light their homes and access to affordable spare parts.
batteries for their torches and radios. Battery charging
using portable generating set is an increasingly common Based on the results of technical analysis of selected
service in these communities. The fume from the solar rechargeable lanterns and general discussions with
generating sets and from burning kerosene and candle is users, some important features were considered and they
toxic and lead to respiratory illnesses over time. For include:
most people in this setting, their living conditions could  Lantern should provide white light equivalent to the
be improved simply by providing cost effective output of a 15 Watt CFL for up to 6 hours every day
renewable energy power sources that would power LED  The lighting fixture should be able to cover a 360 degree
lamps, radio sets and other electronic appliances. It is spread of light
the goal of this project to develop affordable solar  The lighting fixture will be portable with a good base
lantern kit for use in rural households in Nigeria. The  The lighting fixture shield should will be translucent with
solar lantern kit consists of an 8-W solar panel, 2 light minimum dispersion effects
sources consisting of high efficiency LED lamp capable  The fixture will also have a charging indicator to indicate
of producing 6-hours of light of ≥ 800 lumen each, and a charging, and under-discharge light to indicate that the
charge control circuit capable of fully charging 2 battery is low.
rechargeable 3.7V lithium-ion batteries in 6 hours of  An auxiliary socket for powering small electronic devices
direct sunlight using the external 8-W solar panel. with minimal power rating.
Keywords:- Rechargeable Lamptern; Solar; LED; Styling; II. DESIGN PARAMETERS
Insert.
It is the aim of this research to develop a solar
I. INTRODUCTION rechargeable lantern kit capable of producing 6-hours of
light of ≥800 lumen, and a charge control circuit capable of
In many countries of sub-Saharan Africa, more than fully charging 2 rechargeable 3.7V lithium-ion batteries in 6
70% of the people are off grid. The situation is even worst hours of direct sunlight using 8-W solar panel.
for rural areas where about 95% of the populace are without
electrical power supply. Largely, the people depend on Table 1: Design parameters for the proposed Solar
kerosene and candles for lighting, and batteries for small rechargeable lamp
appliances [1]. For instance, in a country like Nigeria, more
than 120 million people are without access to electricity,
consequently leading to the use of costly and even harmful
energy sources [2].
Successive World Bank surveys have always shown the

prospects for decentralized power supplies for lighting, both
at community and household level in these countries [1]. The major goal of this project is to develop an
These studies showed that solar rechargeable lanterns are an improved and cost-effective solar rechargeable LED-based
affordable, environmentally-friendly, and portable lighting lantern as an alternative solution for kerosene lamps. This
option for large sections of the rural communities in these demands developing specific characteristics to exceed that
countries. However, despite the growing interest in solar of those available in the market. The proposed solar lighting
lantern, available products in Nigerian market are imported fixture consists of a PV module, which provides solar
and highlighted a number of technical shortcomings. The energy; a rechargable Lithium Ion battery for storing
shortfalls often highlighted include inferior construction of energy; a charge controller to control charging rate of the
the lighting fixture, poor illuminance, and the relatively poor battery so as to prevent over-charging; auxiliary supply
IJISRT21MAR469 www.ijisrt.com 1168

ISSN No:-2456-2165
socket to power small appliances; LED’s and the LED
driver.
III. DESIGN FLOW
The design flow process of all the segments of this

research is as shown in the block diagrams below:
Figure 3: Current vs Voltage curve of Li-ion battery [3]
The block diagram of the Pulse Width Modulated

(PWM) charge controller is shown in Figure 2. The DC
source (an 8 watts PV panel) provides power to charge the
Figure 2: Block Diagram of the entire process Li-ion cell, as well as power the PWM generator circuit. The
power switch is a power transistor switched by the high
frequency PWM pulses from the PWM Generator. The
Voltage Monitor monitors the terminal voltage of the Li-Ion
cell, when the terminal voltage gets to 4.2V (Full Charge
voltage of the Li-Ion cell), it sends a short-off signal to the
PWM generator, stopping the charging process. The flow of
electricity is regulated by the charge controller as power
flows from the PV modules to the battery and the load. The
charge controller prevents the battery from being over
Figure 3: Design process of Circuit board charged after being fully charged. During the charging
process, as soon as the controller senses that the battery is
fully charged, it will stop the flow of charge from the
modules.
The charge controller is based on TL494, it houses in a

single chip, most of the features required to construct of a
pulse-width modulation (PWM) control circuit. It contains
Figure 4: Design process of Casein two error amplifiers, an adjustable oscillator embedded on
the chip, a dead-time control (DTC) comparator, a pulse-
steering control flip-flop, a 5-V, 5%-precision regulator, and
output-control circuits [4].
Figure 5: Design process of Diffuser During operation, the oscillator helps to provide a
positive saw tooth waveform to both the dead-time and
PWM comparators to enable comparison of the various
control signals. To program the frequency of the oscillator,
the timing components RT and CT are altered. The external
Figure 6: Complete Design process
timing capacitor (CT) is charged by the oscillator with a
constant current. This value is determined by the external
IV. SYSTEM DESCRIPTION
timing resistor, RT. This produces a linear-ramp voltage
waveform. When the voltage across CT reaches 3 V, the
The Li ion charger designed for this system is a
oscillator circuit discharges it, and the charging cycle is
voltage-limiting device and is similar to the charging system
reinitiated.
of a lead acid. They are some differences between the two
systems; Li-ion has a higher voltage per cell, alongside a
To enable modulation control of the output pulse, the
tighter voltage tolerances. Li-ion cells are designed in such a
comparator is employed. To achieve this, the control signal
way that they follow the correct settings placed by the
at the error amplifiers is compared to the ramp voltage
manufacturers, because Li-ion cannot accept overcharge.
across the timing capacitor CT. A diode is connected in
Charging a Li-ion battery consists of three stages: pre-
series with the timing capacitor and it is usually omitted
charging stage (slow charging), constant current charge (fast
from the control signal input. When the error amplifier
charge) and constant voltage charging stage [3]. Figure 7
output signal is approximately 0.7 V greater than the voltage
shows a plot of the current vs voltage curve of the Li-ion
across CT, it will inhibit the output logic. This connection
battery.
helps to ensure that the it gets to maximum duty cycle

ISSN No:-2456-2165
operation without requiring the control voltage to sink to a The circuit printed circuit board is as shown in figure 9.
true ground potential [4]. As the voltage of the error
amplifier output varies from 0.5 V to 3.5 V, the output pulse
width varies from 97% of the period to 0 respectively. The
circuit diagram of the system is as shown in figure 8:
Figure 9: Circuit PCB
V. CONCLUSION
Figure 8: Circuit diagram of the TL494 circuitry In this paper, a solar powered lantern kit consisting of
an 8-W solar panel with 2 rechargeable 3.7V lithium-ion
The power supply range of the TL494 is between 7 V batteries and LED luminaires has been designed. The system
and 40 V which is usually regulated properly [4]. A bulk is capable of producing a luminance value greater than or
capacitance alongside a ceramic bypass capacitor is required equal to 800 lumens. The charge controller unit circuit
to be added to the circuit if the power supply is located some designed is capable of fully charging 2 rechargeable 3.7V
inches away from the device. In this design, a 47 μF tantalum lithium-ion batteries in 6 hours of direct sunlight using the
capacitor was used. A low EMI inductor with a ferrite type external 8-W solar panel.
closed core was used. Since the ceramic input filter capacitor
has a low value, it was located very close to the VCC pin of ACKNOWLEDGMENT
the IC. This helps to reduce the inductance effects to as much
lower value as possible. This provides a cleaner voltage This project is being done under the Tertiary Education
supply to the internal IC rail. Trust Fund (TETFund) Institution Based Research Fund
(IBRF). The support of TETFund is immensely appreciated.
To determine the size of the inductor (L), the following The authors would like to thank all the staff of Electronics
calculation was done: Lab, ECE department, Nnamdi Azikiwe University..
d = duty cycle = VO/VI = 5 V/32 V = 0.156
f = 20 kHz (design objective) REFERENCES
ton = time on (S1 closed) = (1/f) × d = 7.8 μs
toff = time off (S1 open) = (1/f) – ton = 42.2 μs [1]. Moussa P. Blimpo and Malcolm Cosgrove-Davies,
L ≉ (VI – VO) × ton/ΔIL “Electricity Access in Sub-Saharan Africa: Uptake,
≉ [(32 V – 5 V) × 7.8 μs]/1.5 A Reliability, and Complementary Factors for Economic
≉ 140.4 μH Impact, International Bank for Reconstruction and
Development / The World Bank, 2019, DOI:
After calculating the value of the filter inductor, the 10.1596/978-1-4648-1361-0.
value of the output filter capacitor is selected to match the [2]. Kayode Olaniyan, Benjamin C. McLellan ID , Seiichi
requirement of the output ripple. Ogata and Tetsuo Tezuka, “Estimating Residential
Electricity Consumption in Nigeria to Support Energy
The design also monitors the battery temperature of the Transitions”, MDPI sustainability, May 2018.
device using an NTC (Negative Temperature Co-efficient) [3]. AnnaTomaszewska, Zhengyu Chu, Xuning Feng,
thermistor. To monitor the temperature, a 10kΩ, B = 3380 Simon O'Kane, Xinhua Liu, Jingyi Chen, Chenzhen Ji,
NTC thermistor is connected from the NTC pin to ground. et al, “Lithium-ion battery fast charging: A review”,
This pin monitors the voltage dropped across the 10kΩ eTransportation, Volume 1, 2019, 100011, ISSN2590-
thermistor and sources about 50μA. During operation, when 1168.
the voltage on the NTC pin is above 1.36V (0°C) or below [4]. Tl494 Datasheet, available online
0.29V (40°C), the temperature of the battery is considered to www.alldatasheet.com/tl494. Accessed 23 July, 2019
be out of range. When this happens, the circuit will indicate [5]. EE power, available online
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except the voltage on the NTC pin falls within the range of thermistor/#. Accessed on 28th , July, 2019.
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Volume 6, Issue 3, March – 2021 International Journal of Innovative Science and Research Technology

Design and Development of Cost-Effective Solar

Successive World Bank surveys have always shown the

IJISRT21MAR469 www.ijisrt.com 1168

III. DESIGN FLOW

The design flow process of all the segments of this

Figure 3: Current vs Voltage curve of Li-ion battery [3]

The block diagram of the Pulse Width Modulated

The charge controller is based on TL494, it houses in a

IJISRT21MAR469 www.ijisrt.com 1169

Figure 9: Circuit PCB

IJISRT21MAR469 www.ijisrt.com 1170

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