What is a Real Time Clock?
When logging data, it’s often really really useful to have timestamps! That way you can take data one minute apart (by checking the clock) or noting at what time of day the data was logged.
The Arduino does have a built-in timekeeper called millis() and theres also timers built into the chip that can keep track of longer time periods like minutes or days. So why would you want to have a separate RTC chip? Well, the biggest reason is that millis() only keeps track of time since the Arduino was last powered – that means that when the power is turned on, the millisecond timer is set back to 0. The Arduino doesnt know its ‘Tuesday’ or ‘March 8th’ all it can tell is ‘Its been 14,000 milliseconds since I was last turned on’.
OK so what if you wanted to set the time on the Arduino? You’d have to program in the date and time and you could have it count from that point on. But if it lost power, you’d have to reset the time. Much like very cheap alarm clocks: every time they lose power they blink 12:00
While this sort of basic timekeeping is OK for some projects, a data-logger will need to have consistent timekeeping that doesnt reset when the Arduino battery dies or is reprogrammed. Thus, we include a separate RTC!
- SD card interface works with FAT16 or FAT32 formatted cards. 3.3v level shifter circuitry prevents damage to your SD card.
- Real time clock (RTC) keeps the time going even when the Arduino is unplugged.
- Included libraries and example code for both SD and RTC mean you can get going quickly Prototyping area for soldering connectors, circuitry or sensors.
- Prototyping area for soldering connectors, circuitry, or sensors.
- Two configurable/programmable indicator LEDs
- Onboard 3.3v regulator is both a reliable reference voltage and also reliably runs SD cards that require a lot of power to run
- Uses the “R3 layout” I2C and ICSP/SPI ports so it is compatible with a wide variety of Arduinos and Arduino-compatibles
x1 unit Data Logger Shield with DS1387
x1 unit CR1220 cell