Optimization of cadmium sulfide light-dependent resistor (CdS-LDR) sensor is one of the suitable circuit elements to be used as the sun-pointing sensor. The sun-pointing sensor is used in solar energy tracking systems to capture maximum power by photovoltaic (PV) cells or systems at the time of uniform or partial irradiance of the sun and effect of shade during clouds. PV cells or modules' generating power is affected due to partial shading. The PV cells are able to produce maximum power, as long as the sun's irradiance is projected perpendicular to the panel's surface. Optimization of lightdependent resistor CdS-LDR sensor is designed based on the intensity of the sun. A relation is obtained between intensity and photo-resistance of CdS-LDR sensor with coefficient of regression (R 2) value of 0.99. Maximum intensity of the sun is captured using CdS-LDR sensor which is designed with characteristic curve of intensity and photo-resistance using power algorithm. Minimum dull intensity of the sunlight is used to place the panel in initial position. In addition to that cloud effects with sudden transients are also analyzed using temperature humidity index term. The power gained by optimized dual axis solar tracking (DAST) system is 50.63% with reference to fixed panel. The generated power of DAST system is also analyzed under shading effect of cloud. Data are collected for every 2-3 s of time interval from 6:32:00 to 17:38:33 using real-time virtual instrumentation Parallax Data Acquisition tool.

In solar tracking system, general stepper motor is used to control the stepwise movement and low speed of solar panel in vertical motion. Degree of rotation is directly proportional to stepwise movement (stepping method) of stepper motor. But it is cumbersome process to hold a solar panel at a particular vertical position depending on the sun’s position using low cost stepper motors. So, geared DC motor is implemented into stepper motor for low-speed applications using Stepping Method (GDCSM). Degree per step movement of geared DC motor is identified using Step angle switching delay time signal (A) of microcontroller. Speed of geared DC motor is controlled by passing fixed time interval between the pulses where the pulses have fixed width. Controlling speed is implemented by using Step delay time signal (D) of microcontroller. Combining effect of switching delay time signals A and D represents the Stepping Method. Stepping method resembles the step movement and controlling speed of the stepper motor. Speed of 10RPM & 30RPM geared DC motors is operated at 10V DC power supply. Microcontroller ATmega 328P with switching delay time signals is used to control the geared DC motors. Performance of 10RPM & 30RPM GDCSM is analyzed with stepper motors in terms of Relative slip degree error per revolution (RE$$_\mathrm{{S}}$$ S ) and acceptable slippage degree tolerance under open loop condition. Change in consuming voltage tolerance ($$\varDelta$$ Δ ) during rotation of GDCSM is another parameter which is used to maintain the constant actual total step count per revolutions of GDCSM. At 40 ms of step angle delay time (A), 10RPMGDCSM has 120 steps per revolution. At 25 ms of A, 30RPMGDCSM has 55 steps per revolution. Speed of 10RPM & 30RPM GDCSM is controllable up to 2RPM when its RE$$_\mathrm{{S}}$$ S or acceptable slippage degree tolerance value is less than or equal to 1%. If $$\varDelta$$ Δ value of GDCSM is less than or equal to − 0.4%, then it behaves like stepper motor. GDCSM is suitable to hold and control vertical position of solar tracking system with low speed and step movement. Performance of geared DC motor experimentally showed better result than commercial available stepper motors like 28BYJ-48 or STP-43d1027-01.

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A correction to this paper has been published: https://doi.org/10.1007/s42452-021-04542-3