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A device to measure the rays all around us, but it doesn't come under the 'tin-foil helmet' category. File it under delta-sigma ADC - it is a very detailed Solar Server project to measure the solar radiation striking Earth ("insolation"), recording the daily data to a file, which is then emailed. The device used for measuring daily insolation is designed by Wichit Sirichote in Thailand. He introduces the project, thus:
"The total solar radiation is measured by a Kipp & Zonen CM11 pyranometer (pictured). The EMF output of 5.14 uV/W/m2 is fed to the 24-bit resolution Delta-Sigma A/D converter, LTC2400. The microcontroller circuit built with a PIC18F2550 controls the A/D converter and provides one second time base for data sampling period. The insolation is computed by accumulated summation of the converted data in a whole day.
The data is saved in buffer memory and is sent to the Ubuntu Server through the serial port, ttyS0. Shell scripts have been written for receiving the data from microcontroller board and for saving the record as the text file. The scheduler is set using cron process for sending the data file as attachment of email to the receiver everyday."
When the EMF signal from the pyranometer is fed to a 24-bit Delta-sigma converter, the converter board consits of three IC chips (labelled U1, U2 and U3), and the block diagram is below.
In an excellently detailed write-up Wichit also gives a parts list, a sample of the data stream sent to his Unbuntu server, the code of the Shell scripts (Unix system commands), both for data capture and dealing with the file saver, and a state sequence diagram for the C-based firmware of the board.
In terms of software on the server side, he uses LAMP (Linux, Apache, MySQL and PHP), with his station using Sendmail as the mail transfer agent, running on a Linux kernel 2.6.22-14.
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