Solar Recorder V2.0

Wichit Sirichote,

New version with RTC for time stamping and DC amplifier for pyranometer.

The new version of the Solar recorder includes the real-time clock (RTC) DS1307 for time stamping and the DC amplifier for pyranometer sensor.

Figure 1: The new Solar Recorder in the black box and the pyranometer. The display shows file name, sample number, ADC reading for Ch0 and Ch1, clock HOUR:MIN.

Hardware Schematic

The EMF from pyranometer is 14uV/Wm-2. For 1000W/m-2, the output EMF will be .0014V. The PIC ADC is +5VFS, thus the gain of the DC amplifier is adjusted to 357. The noninverting DC amplifier is built with TI TLV2451. It was used to amplify an EMF signal from pyranometer to approx. +5V for 1000W/m-2. RD5 and RD6 are two bits PORTD. It used for software generated I2C bus. The RTC chip, DS1307 is connected to the I2C bus with SDA and SCLK signals. The coin Lithium battery powers the RTC chip when main power is turned off. Time setting is done by shorting the ADC channel 1 (thermistor) when power up the board.

Figure 2: Hardware schematic, click the image to open pdf schematic.


Figure 3: The pyranometer is connected to the DC amplifer using binding post.


Figure 4: Binding-post terminal and time setting button.


Figure 5: The MMC must be inserted as shown in the picture.


Figure 6: Push the MMC card until the the card has been locked.


Figure 7: The pyranometer with shield cable.


Figure 8: Push button for time setting of RTC clock. Setting is done by pressing the button when power up the solar recorder. The clock display will show current time. While the key has been pressed, the time being set will automatic adjusting. When the button was released, the time will be set.


Figure 9: The thermistor sensor.


Schematic solarrecorder2.pdf
Executable code in HEX file MMC.HEX

New firmware with selectable preset interval

The new firmware includes selectable preset interval between data sample from 10 sec, 1 min, to 5 min. User can enter the 8-bit data at EEPROM location 0. The picture below is the EEPROM window of the PICKIT2 Loader. (The default is 1 min interval with FF at location 00)

Table below shows the 8-bit value for each interval.

Interval Data
10 sec 00
1 min FF
5 min 01

The readings shown in the data file and on the LCD are 0.000V to 5.000V.

Download HEX file for PIC18F458. The default value at EEPROM location 00 is FF. User can modify it for the preset interval shown above.

19 January 2008