The device used for measuring daily insolation has been developed. The device was built with a PIC18F458 and the 128MB Multimedia Memory Card, MMC. The solar radiation is measured by a calculator solar cell. The PIC chip interfaces the MMC using SPI mode. The interval between samples is set to one minute. The firmware detects the memory card, assignes the file name and begins recording automatically. The LCD displays the file name, current sample and real-time ADC data. With the MMC flash technology and a cheap media card reader, the devices will be able to record huge amount of data and quick data uploading to the PC.
To estimate the sun energy for a given location, we record the irradiance (W/m^2) with time. Figure 2 shows a sample plot of irradince with time (5mins interval). The daily insolation can be computed easily by integraing the curve. For accurate total radiation measurement, we use the expensive pyranometer. However for simplicity and cheap instrument we can replace it with a small colar cell as the input sensor. The article shows the use of PIC microcontrolller and the Multimedia Memory Card for data storage.