In this work, the design of an inexpensive and reliable pyranometer used for measuring broadband solar irradiance is proposed. A BPX43 – 4 phototransistor is used as a light detector, which has the spectral response in the range approximately 450 to 1100 nm. This system is controlled by an Arduino pro mini ATmega328P (5 V, 16 MHz) microcontroller and all components are located inside a FB05 black box. Due to a high level of solar radiation in the different environmental conditions, the pyranometer encountered the voltage saturation. Therefore, a 0.25 mm thick of Teflon is selected for attenuating the sunlight. After investigating against a reference sensor, the transmittance of this attenuator is found to be about 12.5%. Finally, the experimental results from the system are compared with a standard pyranometer performed at Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center (PMOD/WRC, 46.80 °N, 9.83 °E and 1, 610 meters above sea level), Switzerland. The results demonstrate a satisfactory agreement between the global irradiance obtained from our proposed pyranometer and the standard pyranometer.