1 Introduction

Recent years have seen a crucial demand for sustainable and efficient tracking systems due to the widespread use of GPS trackers in numerous industries. These devices provide immediate and up-to-date location information, allowing for applications such as managing a group of vehicles, monitoring valuable assets, ensuring personal safety, and tracking vehicle movement. Nevertheless, the dependability and effectiveness of these systems are greatly dependent on their energy sources. Conventional GPS trackers that rely on batteries encounter issues such as the need for regular recharging and a restricted battery lifespan, which hampers the ability to consistently monitor and track operations. This research project seeks to overcome the aforementioned issues by creating a self-sustaining GPS tracker that harnesses solar energy. This will guarantee continuous and dependable operation, improve functionality and durability, and also promote environmental sustainability [1,2,3,4].

Since the 1980s, the US Department of Defence has extensively used GPS technology in civilian applications, initially developed for military purposes. The advancement in satellite navigation technology and the reduction in the size of electronic components have propelled the growth of small and energy-efficient GPS trackers. Previous studies have mostly concentrated on enhancing the precision, cost-effectiveness, and energy efficiency of these gadgets, resulting in their widespread use in transportation, logistics, and personal security sectors [5, 6]. In has investigated the incorporation of other energy sources, such as solar and kinetic energy, into GPS trackers in order to overcome the constraints of battery-powered devices. For instance, GPS trackers powered by solar energy extend their usage duration and reduce the need for manual recharging. Additionally, kinetic energy harvesting mechanisms capture energy from movement or vibrations to generate electricity independently [6,7,8].

However, a significant challenge remains: ensuring a reliable and long-lasting power source. Traditional GPS trackers rely significantly on batteries, requiring frequent recharging or replacement. This can hinder their efficacy and continuous operation, particularly in remote or difficult environments. As a result, there is a critical need for a self-sufficient resolution that can power GPS trackers consistently and on its own, reducing the need for maintenance and increasing the overall effectiveness of operations. The goal of this work is to develop a novel charge controller that optimises the integration of solar PV systems with GPS trackers, thereby ensuring a reliable and uninterrupted power supply [9,10,11].

This work makes two significant contributions. Firstly, it meticulously chooses components to guarantee the charge controller's optimal performance and durability. Secondly, it experimentally verifies its efficacy in consistently supplying power to the GPS tracker. This text investigates the integration of GPS technology with solar PV charging to enable continuous monitoring. The results indicate that the suggested charge controller maintains a stable power distribution to the GPS tracker and safeguards the battery against voltage fluctuations, hence ensuring dependable functionality and prolonged battery lifespan.

The manuscript structures the remaining portion as follows: Sect. 2 provides an explanation of the proposed charge controller and discusses the specific factors taken into account when choosing its components. Section 3 provides a comprehensive account of the boost converter's development and its subsequent experimental evaluation. The conclusion provides a succinct summary of the important scientific contributions.

2 Proposed charge controller and description

Figure 1 shows the circuit topology of the proposed charge controller. Table 1 shows the component ratings used to develop a prototype. Table 2 displays the specifications of the solar PV system. The provided photovoltaic panel can produce 10W of electricity, has a 22 V open circuit voltage, 0.6A short circuit current, 18 V maximum power, 0.560A maximum current, and a 5% tolerance. The selection of this panel to charge a 12 V, 7.5Ah battery. The battery only has a 12 V rating, but the panel can charge it to 18 V, which is more than enough because it allows for efficient charging and makes up for voltage drop losses. Furthermore, despite being lower than the battery's charging current, the panel's maximum power output meets the recommended slower charge for the battery's lifespan. The panel’s 10W output maintains power transfer efficiency without overcharging the battery, aligning with its charging requirements. The panel's 5% tolerance provides a margin of safety and performance flexibility, enabling it to adjust to varying levels of sunlight and environmental factors. The chosen PV panel is ideal for charging the 12 V, 7.5Ah battery since it provides an ideal combination of voltage, current, and power output.

Fig. 1
figure 1

Charge controller for GPS tracker

Full size image
Table 1 Design specification
Full size table
Table 2 Solar PV specification
Full size table

The LM317, as a linear regulator, can modify its consistent output voltage by using external resistors or a potentiometer. This versatility makes it well-suited for a diverse array of applications. In battery charging circuits, the LM317 regulates the charging voltage accurately, ensuring safe and efficient charging of various battery types, such as lead-acid batteries commonly found in automotive and solar applications. The adjustable output voltage feature enables users to customise the charging voltage according to the unique needs of the battery being charged, thereby ensuring optimal charging performance and prolonging battery life. In addition, the LM317 incorporates integrated overcurrent and heat protection capabilities, which improve the safety and dependability of the battery charging procedure. The comparatively inexpensive cost and widespread availability of the battery charger circuit enhance its appeal, making it a preferred option for amateurs, electronics enthusiasts, and professionals. The LM317 voltage regulator uses the 5 K-rated potentiometer, also referred to as Pot, as a variable resistor to precisely modify the regulator's output voltage. By manipulating the potentiometer, users can precisely calibrate the output voltage to match the specific voltage requirements of the battery under charge. This enables meticulous regulation of the charging procedure, guaranteeing that the battery obtains the accurate voltage necessary for optimal charging efficiency and durability.

Conversely, the resistor with a value of 240 ohms establishes the maximum current allowed for the LM317 voltage regulator. This resistor determines the maximum current that can flow through the regulator and reach the battery during the charging process. Users can regulate the charging current to a safe and suitable level by selecting a specified resistance value. This helps to avoid overcharging and any harm to the battery. The purpose of this resistor is to control the amount of current flowing throughout the charging process, ensuring both battery safety and efficiency. The 0.1 μF capacitor that is connected across the solar photovoltaic (SPV) panel is used as a coupling capacitor in the battery charger circuit. This component is really important for making sure that the charging process runs smoothly and without any issues. It provides DC isolation, effectively blocking the DC voltage from the SPV panel while maintaining the flow of AC signals, which is one of its main benefits. It’s important to make sure that no DC bias interferes with the other components in the circuit. In addition, the capacitor helps eliminate any high-frequency noise or ripple that may be present in the output of the SPV panel. This ensures that the input signal to the LM317 voltage regulator is cleaner and more stable. This noise filtering improves the performance and reliability of the regulator. In addition, the coupling capacitor provides a certain level of protection to the LM317 by effectively filtering out any voltage spikes or transients that could potentially occur in the SPV panel's output. This helps to safeguard the regulator and extend its lifespan. Adding a stable AC signal to the LM317 improves the stability and efficiency of the battery charging circuit, thanks to the coupling capacitor’s contribution. The LM317 filters out any AC components or noise in the SPV panel's output before it reaches the regulator by connecting the positive terminal to the third pin and the negative terminal to ground. This helps to optimise the circuit’s performance and reliability.

The 10 μF capacitor that connects the output pin (pin 2) and the adjust pin (pin 1) of the LM317 voltage regulator plays a crucial role in stabilising the output voltage and minimising ripple in the charging circuit. The LM317 regulates the output voltage by continuously monitoring the voltage difference between its output pin and its adjustment pin. This capacitor, also called a bypass capacitor, plays a crucial role in stabilising the voltage regulation process. It achieves this by creating a low-impedance pathway for high-frequency AC signals between these two pins. When this is done, it helps to minimise voltage fluctuations or ripples in the output voltage. This results in a more stable and reliable voltage supply for the battery under charge. Improved stability enhances the charging circuit's performance and extends the lifespan of the connected components, resulting in reliable and efficient charging over time. The 10μF capacitor has a couple of functions in the circuit. By connecting it between the output pin (pin 2) and the adjust pin (pin 1) of the LM317 voltage regulator, it actually helps to stabilise the output voltage and minimise any ripple in the charging circuit. The capacitor helps to maintain a stable voltage supply to the connected battery by creating a direct path for high-frequency AC signals. This leads to better charging efficiency and reliability, as it reduces voltage fluctuations. In addition, when the 10μF capacitor is connected in parallel with the 12 V, 7.5 Ah lead-acid battery, it helps to improve the stability of the battery's voltage supply. This feature helps to smooth out any changes or surges in the battery voltage, resulting in a consistent and dependable power supply to the connected load or system. Adding extra capacitance in parallel with the battery helps to eliminate unwanted noise and fluctuations, resulting in smoother power delivery and enhancing the overall efficiency and lifespan of both the battery and the system it supplies.

Designed to effectively convert higher input voltages into lower output voltages, the LM2596 is a commonly used step-down voltage regulator integrated circuit (IC). It is frequently used in various electronic circuits because of its excellent efficiency and ability to handle higher currents. The IC usually comes in a TO-220 package and has multiple pins, each with its own specific function within the circuit. Pin 1 is used as the input voltage pin, where the higher voltage supply is connected. In this circuit, the battery voltage is received through a 650μF capacitor that is connected in parallel to pin 1. This capacitor helps to stabilise the input voltage and filter out any noise. Pin 2 serves as the ground or common reference point, while pin 3 supplies the regulated output voltage. Pin 4 serves as the feedback pin, allowing you to adjust the output voltage by using a resistor divider network. Grounding pin 5 activates the regulator and ensures voltage regulation. This use of the LM2596 allows the circuit to effectively control voltage levels, ensuring a steady and reliable power supply for connected devices. To safeguard the LM2596 voltage regulator from overvoltage, you can connect pin 2 to ground using a zener diode, like the IN5824. When the applied voltage is higher than the zener voltage, the zener diode will start to conduct current. In this setup, the zener diode will start to conduct if the voltage at pin 2 goes over its breakdown voltage. This will effectively limit the voltage at pin 2 to the zener voltage. By preventing the voltage at pin 2 from exceeding a safe limit, this protects the LM2596 from potential harm caused by overvoltage situations.

In the buck converter circuit that uses the LM2596 voltage regulator, the inductor (L1) is crucial. The inductor is an essential component for energy storage and transfer, located between the LM2596’s ground and pin 2 (the input voltage pin). The buck converter activates the LM2596, which, in turn, stores energy from the input voltage source. As the LM2596 turns off, the inductor releases the stored energy, allowing the energy to flow through the load while keeping the output voltage constant. The inductor essentially converts larger input voltages to lower output voltages by controlling the current flow. The inductor stores energy during the on-cycle and releases it during the off-cycle, ensuring a steady and consistent power supply to the load. This effectively smooths out oscillations in the output voltage. This procedure improves the buck converter circuit's overall efficiency and reliability by controlling the load current and output voltage.

The buck converter circuit that uses the LM2596 voltage regulator relies on the 220 μF capacitor, which is placed between the inductor s second terminal and ground. To ensure a steady and noise-free power supply to the attached load, it filters out any ripple or undesired noise from the LM2596’s output voltage. The output voltage of a buck converter might fluctuate because of the inductor's energy storage and release mechanisms. These fluctuations may cause poor performance in some of the sensitive electrical components in the load circuit, manifesting as noise or ripple. The 220F capacitor functions as a low-pass filter, letting through only the intended DC voltage by reducing or eliminating high-frequency noise or ripple components. The capacitor's ability to filter out noise and ripple promotes reliable operation by reducing the risk of electrical interference or malfunctions, ensuring a clean and stable power supply to the load. Electronics, communication systems, and other power-sensitive equipment rely on accurate and consistent voltage control; hence, this is of the utmost importance in these areas.

3 Experimental validation and discussion

The experimental setup for the proposed self-powered GPS tracker involves connecting solar PV panels to the input of a battery charge controller. The charge controller plays a crucial role in converting the variable input voltage from the solar panels into a steady voltage, ensuring the battery receives a constant voltage for charging. Without this regulation, fluctuating voltages could potentially damage the battery. Additionally, the GPS tracker is connected in parallel to the battery, drawing the required voltage for operation, typically around 5 V. This setup ensures the GPS tracker receives a stable power supply, enabling its functionality alongside the charging process of the battery.

The experiment setup shown in Fig. 2 shows how the suggested charge controller for self-powered GPS trackers was tested and found to work. First, the solar PV system’s input voltage is checked, and a reading of 10 V is obtained, as shown in Fig. 3. Even though the solar PV system's highest voltage rating is 18 V, the actual voltage output is usually lower because of the weather. This shows how important it is to test in real life. The voltage across the battery was later measured and found to be 12.4 V, as shown in Fig. 4. This means that the battery is fully charged and can meet the needs of the GPS tracker. This shows that the charge controller is effective at handling the charging process well, making the battery work better, and making it last longer. After more research, it was found that the voltage across the GPS tracker is 5 V, as shown in Fig. 5. This matches perfectly with the voltage that the GPS tracker needs to work, proving that the charge controller can control the voltage output to meet the needs of the device. A voltage regulator is put between the battery and the GPS tracker to make sure that the voltage is regulated correctly. This protects the device from damage that could happen from voltage changes. Notably, a GD-1052-U oscilloscope is used for these measures, which guarantees the accuracy and dependability of the evaluation of the self-powered GPS tracker's performance. The detailed study of voltage readings proves that the system works well, showing that it can keep tracking continuously and reliably. The results of the experiments show that the proposed charge controller works well at giving the GPS tracker stable power, which means that monitoring and tracking can continue without any problems. The results of this study show that adding green energy sources, like solar power, to GPS tracking systems is important for making them more efficient and long-lasting for many uses. The significance of proposed methodology as mentioned below:

Fig. 2
figure 2

Hardware implementation

Full size image
Fig. 3
figure 3

Solar PV output voltage

Full size image
Fig. 4
figure 4

Voltage across battery

Full size image
Fig. 5
figure 5

Voltage across GPS tracker

Full size image

The selection of the proposed tracking method, integrating a self-powered GPS tracker with a novel charge controller utilizing solar PV technology, offers numerous advantages that justify its use. This method significantly enhances sustainability by harnessing solar energy, reducing reliance on conventional battery power, and promoting the use of renewable resources, thus aligning with global sustainability goals and minimizing environmental impact from battery waste. The charge controller ensures a continuous and reliable power supply, eliminating downtime due to battery depletion and extending battery life by maintaining optimal charging conditions and protecting against voltage variations. This enhances the reliability of the GPS tracker and reduces maintenance costs. The method's versatility makes it suitable for applications in remote or harsh environments where conventional power sources are limited or impractical, such as wildlife monitoring, remote asset tracking, and maritime navigation. By minimizing the need for manual intervention related to battery recharging or replacement, the proposed solution also reduces operational costs and maintenance efforts, making it cost-effective for long-term deployment. Technologically, the innovative charge controller design incorporates advanced components and features like overcurrent and heat protection, voltage regulation, and noise filtering, which enhance the performance and safety of the GPS tracker. Additionally, the scalability and adaptability of the tracking method allow for customization based on specific application needs, making it a versatile solution for a wide range of tracking scenarios.

4 Discussions

Wireless sensor nodes designed for GPS applications often encounter challenges related to excessive power consumption. Utilising different sources of energy such as light, motion, heat, etc., is a widely used method to address this issue. The new charge controller selects components in an optimised manner to guarantee a consistent power supply for the GPS tracker. This is achieved through a solar PV system that maintains the battery at a stable voltage of 12.4 V and continuously provides 5 V to the tracker. This focused optimisation guarantees a decrease in power usage as compared to more general energy collecting techniques. A hybrid GPS sensor tracker utilises piezoelectric transducers that have been optimised using the Taguchi method to efficiently harvest energy. The design results in a peak power output of 217 milliwatts from piezoelectric devices. The solar PV system attains a maximum output voltage of 10 V, surpassing and exhibiting greater stability than piezoelectric outputs. This guarantees a continuous power supply to the GPS tracker, resolving the issue of fluctuating energy production from piezoelectric sources. Autonomous dual-axis solar tracking systems optimise the efficiency of PV panels by maintaining a perpendicular alignment with the sun's rays. These systems have undergone empirical testing and have been found to have global application while using a small amount of electricity (0.62% to 0.68% of energy gain). The integration of a solar PV system for GPS trackers in the proposed work aims to ensure a consistent and dependable power supply for GPS devices, hence improving the feasibility of remote monitoring and asset tracking. This is achieved by optimising energy capture through the use of a dual-axis system. Moreover, a self-sustaining, automated dual-axis solar tracking system is developed to optimise the collection of photovoltaic (PV) energy with maximum efficiency, eliminating the need for GPS or external sources of power. The new charge controller for GPS trackers, while not explicitly designed for dual-axis capability, guarantees a consistent power supply that is essential for the proper operation of GPS devices. The solar PV component effectively sustains battery levels, prioritising longevity and reliability rather than solely focusing on maximising energy output.Apps such as Cheeka make use of GPS technology in smartphones to enhance personal security by offering features like friend tracking, panic warnings, and speed monitoring. The GPS tracker, equipped with an innovative charge controller, is not exclusively intended for smartphones but has been specifically built for a wider range of uses in remote monitoring and fleet management. This ensures reliable and uninterrupted functioning by utilising solar PV support. Fleet Tracker utilises solar energy collection with LoRa modulation to provide self-powered GPS tracking in cars, hence enhancing dependability in subpar network infrastructures. The suggested system, like Fleet Tracker, prioritises the provision of dependable power using solar PV. Its main objective is to optimise power management for GPS trackers. This guarantees improved long-term efficiency and minimises the necessity for regular upkeep. The charge controller maintains a steady 5 V power supply to the GPS tracker, with the support of a stable battery voltage of 12.4 V, hence improving reliability while dealing with fluctuating energy sources. The careful selection of components for the charge controller guarantees optimal efficiency and minimised power usage. Integrating solar PV enables continuous GPS tracking, which is essential for applications in remote monitoring and asset tracking. The system is specifically designed for use cases such as fleet management, where it is crucial to have a continuous and reliable power source. This method reduces the frequency of battery replacements and maintenance, providing similar advantages to self-powered IoT systems [12,13,14,15].

5 Conclusion

This paper presents a novel charge controller specifically developed for self-powered GPS trackers, aiming to fulfil the requirement for durable and efficient tracking systems. The research shows that the charge controller effectively delivers consistent power to the GPS tracker by choosing components that are essential for performance and durability. The combination of GPS technology with solar PV charging guarantees uninterrupted tracking, as confirmed by experimental testing that demonstrates consistent power supply and safeguards against voltage variations, resulting in continuous operation and prolonged system lifespan. The suggested charge controller is significant due to its capacity to offer a dependable and uninterrupted power source, beyond the restrictions of traditional battery-powered devices that necessitate frequent recharging or replacement. The charge controller utilises solar photovoltaic (PV) technology to regulate the voltage at a constant level of 12.4 V for the battery and 5 V for the GPS tracker, guaranteeing continuous and uninterrupted functionality. This invention not only improves the durability and effectiveness of GPS trackers but also supports environmental sustainability by utilising renewable energy. It is especially beneficial for use in remote monitoring, asset tracking, and fleet management, where the ability to sustain uninterrupted power is essential. The careful selection of components for maximum performance and longevity highlights the significance of this invention in creating self-sustaining GPS tracking technologies.