Digital Designs and Scientific Hardware - Open-Source Lab: How to Build Your Own Hardware and Reduce Research Costs - page 224

FIGURE 6.66 (a) The completed pHduino and (b) details.
In addition, the pHduino can be improved with the addition of an open-source (hardware
and software) pHduino Datalogger 63 shown in Figure 6.67 . The datalogger is a shield using an
I2C real-time clock (RTC) and an I2C EEPROM memory. The circuit is relatively simple as can
be seen in the PCB layout for the datalogger in Figure 6.68 and the electronic schematic shown
in Figure 6.69 . Users can mount the datalogger using a breadboard or a universal prototyp-
ing board. The datalogger is functional, but somewhat limited as the AT24C512 I2C EEPROM
(512 kB) is not a large amount of memory, although it is inexpensive and easy to use. The
DS1307 I2C real-time clock is a standard RTC for microcontrollers. Finally, a CR2032 battery is
used to retain the parameters. For full build instructions and details, see Carlos' detailed and
updated web pages.