{"product_id":"i2c-rtc-real-time-clock-module-ds3231-ds1302-ds1307-pcf8563-arduino-esp32","title":"I2C RTC Real-Time Clock Module | DS3231 \/ DS1302 \/ DS1307 \/ PCF8563 \/ PCF8523T | Arduino ESP32 Raspberry Pi","description":"\u003ch2\u003eI2C RTC Real-Time Clock Module — DS3231 \/ DS1302 \/ DS1307 \/ PCF8563 \/ PCF8523T | Arduino \/ ESP32 \/ Raspberry Pi\u003c\/h2\u003e\n\n\u003cp\u003eA \u003cstrong\u003ereal-time clock (RTC) module\u003c\/strong\u003e provides accurate timekeeping for microcontroller projects that need to track time, date, and day-of-week independently of the main processor — even when the system is powered off (using a backup coin cell battery). Without an RTC, microcontrollers lose track of time every time they are reset or powered off. This listing covers the most popular RTC chips used in Arduino and embedded projects: \u003cstrong\u003eDS3231\u003c\/strong\u003e (highest accuracy, temperature-compensated), \u003cstrong\u003eDS1302\u003c\/strong\u003e (3-wire SPI, low power), \u003cstrong\u003eDS1307\u003c\/strong\u003e (I2C, most common), \u003cstrong\u003ePCF8563\u003c\/strong\u003e (I2C, ultra-low power), \u003cstrong\u003ePCF8523T\u003c\/strong\u003e (I2C, integrated capacitor backup), and \u003cstrong\u003eDS3231 Mini\u003c\/strong\u003e (compact DS3231). Select the chip that matches your accuracy, power, and interface requirements.\u003c\/p\u003e\n\n\u003ch3\u003eModule Comparison\u003c\/h3\u003e\n\u003ctable\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003cth\u003eModule\u003c\/th\u003e\n\u003cth\u003eChip\u003c\/th\u003e\n\u003cth\u003eInterface\u003c\/th\u003e\n\u003cth\u003eAccuracy\u003c\/th\u003e\n\u003cth\u003eBackup\u003c\/th\u003e\n\u003cth\u003eBest For\u003c\/th\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eDS3231\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eDS3231\u003c\/td\u003e\n\u003ctd\u003eI2C\u003c\/td\u003e\n\u003ctd\u003e±2ppm (TCXO)\u003c\/td\u003e\n\u003ctd\u003eCoin cell\u003c\/td\u003e\n\u003ctd\u003eHighest accuracy, temperature-compensated\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eDS3231 Mini\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eDS3231\u003c\/td\u003e\n\u003ctd\u003eI2C\u003c\/td\u003e\n\u003ctd\u003e±2ppm (TCXO)\u003c\/td\u003e\n\u003ctd\u003eCoin cell\u003c\/td\u003e\n\u003ctd\u003eDS3231 accuracy in compact form factor\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eDS1307\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eDS1307\u003c\/td\u003e\n\u003ctd\u003eI2C\u003c\/td\u003e\n\u003ctd\u003e±~2 min\/month\u003c\/td\u003e\n\u003ctd\u003eCoin cell\u003c\/td\u003e\n\u003ctd\u003eMost common, widely supported\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eDS1302\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eDS1302\u003c\/td\u003e\n\u003ctd\u003e3-wire SPI\u003c\/td\u003e\n\u003ctd\u003e±~2 min\/month\u003c\/td\u003e\n\u003ctd\u003eCoin cell + trickle charge\u003c\/td\u003e\n\u003ctd\u003eLow power, trickle-charge backup\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePCF8563\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003ePCF8563\u003c\/td\u003e\n\u003ctd\u003eI2C\u003c\/td\u003e\n\u003ctd\u003e±~1 min\/month\u003c\/td\u003e\n\u003ctd\u003eCoin cell\u003c\/td\u003e\n\u003ctd\u003eUltra-low power, IoT and wearables\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePCF8523T\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003ePCF8523\u003c\/td\u003e\n\u003ctd\u003eI2C\u003c\/td\u003e\n\u003ctd\u003e±~1 min\/month\u003c\/td\u003e\n\u003ctd\u003eIntegrated capacitor\u003c\/td\u003e\n\u003ctd\u003eNo coin cell needed, compact backup\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePI RTC DS1307\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eDS1307\u003c\/td\u003e\n\u003ctd\u003eI2C\u003c\/td\u003e\n\u003ctd\u003e±~2 min\/month\u003c\/td\u003e\n\u003ctd\u003eCoin cell\u003c\/td\u003e\n\u003ctd\u003eRaspberry Pi HAT form factor\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eDS2121SN\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eDS2121\u003c\/td\u003e\n\u003ctd\u003eI2C\u003c\/td\u003e\n\u003ctd\u003eStandard\u003c\/td\u003e\n\u003ctd\u003eCoin cell\u003c\/td\u003e\n\u003ctd\u003eGeneral purpose RTC\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eSpecifications (All Modules)\u003c\/h3\u003e\n\u003ctable\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eSupply Voltage\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e3.3V – 5.5V DC\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eOperating Temperature\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e-40°C to +85°C\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePackage\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eSMD (surface mount chip on through-hole module)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eApplication\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eArduino, ESP32, STM32, Raspberry Pi timekeeping\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eOrigin\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eMainland China\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eWhy Your Project Needs an RTC\u003c\/h3\u003e\n\u003cp\u003eMicrocontrollers like Arduino and ESP32 have no internal clock that persists through power cycles. Without an RTC:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eTime resets to zero\u003c\/strong\u003e on every power cycle or reset\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eData logging is inaccurate\u003c\/strong\u003e — timestamps are meaningless without real time\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eScheduled tasks fail\u003c\/strong\u003e — alarms, timers, and scheduled events cannot be set to real-world times\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNTP sync is unavailable offline\u003c\/strong\u003e — WiFi-connected devices can sync via NTP, but offline devices need an RTC\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eAn RTC module with a coin cell backup maintains accurate time for years without main power, providing reliable timestamps for data loggers, alarm clocks, irrigation controllers, and any time-aware embedded system.\u003c\/p\u003e\n\n\u003ch3\u003eKey Features\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e✅ \u003cstrong\u003eMultiple chip options\u003c\/strong\u003e — DS3231 (highest accuracy), DS1307 (most common), DS1302 (SPI), PCF8563 (ultra-low power)\u003c\/li\u003e\n  \u003cli\u003e✅ \u003cstrong\u003e3.3V–5.5V supply\u003c\/strong\u003e — compatible with Arduino (5V), ESP32 (3.3V), and Raspberry Pi (3.3V)\u003c\/li\u003e\n  \u003cli\u003e✅ \u003cstrong\u003eCoin cell backup\u003c\/strong\u003e — maintains time through power cycles and system resets\u003c\/li\u003e\n  \u003cli\u003e✅ \u003cstrong\u003eI2C interface\u003c\/strong\u003e — only 2 wires (SDA + SCL) for most modules\u003c\/li\u003e\n  \u003cli\u003e✅ \u003cstrong\u003e-40°C to +85°C\u003c\/strong\u003e — suitable for industrial and outdoor applications\u003c\/li\u003e\n  \u003cli\u003e✅ \u003cstrong\u003eArduino library support\u003c\/strong\u003e — all chips have well-maintained Arduino libraries\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eCommon Applications\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003eData logger with accurate timestamps\u003c\/li\u003e\n  \u003cli\u003eArduino alarm clock and timer\u003c\/li\u003e\n  \u003cli\u003eAutomatic irrigation and lighting scheduler\u003c\/li\u003e\n  \u003cli\u003eIndustrial process time recording\u003c\/li\u003e\n  \u003cli\u003eEnergy meter with time-of-use tracking\u003c\/li\u003e\n  \u003cli\u003eAttendance and access control system\u003c\/li\u003e\n  \u003cli\u003eWeather station data logging\u003c\/li\u003e\n  \u003cli\u003eRaspberry Pi real-time clock (offline timekeeping)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eArduino Quick Start (DS3231)\u003c\/h3\u003e\n\u003col\u003e\n  \u003cli\u003eConnect VCC to Arduino 5V (or 3.3V), GND to GND, SDA to A4, SCL to A5.\u003c\/li\u003e\n  \u003cli\u003eInstall the \u003cstrong\u003eRTClib\u003c\/strong\u003e library by Adafruit via Arduino Library Manager.\u003c\/li\u003e\n  \u003cli\u003eUse \u003ccode\u003eRTC.adjust(DateTime(F(__DATE__), F(__TIME__)))\u003c\/code\u003e to set the time to compile time.\u003c\/li\u003e\n  \u003cli\u003eUse \u003ccode\u003eDateTime now = RTC.now();\u003c\/code\u003e to read the current time.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Which RTC module is most accurate?\u003c\/strong\u003e\u003cbr\u003eA: The DS3231 is the most accurate, with a temperature-compensated crystal oscillator (TCXO) rated at ±2ppm (±63 seconds per year). The DS1307 and DS1302 are less accurate (±2 minutes per month typical) but adequate for most applications.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: How long does the coin cell backup last?\u003c\/strong\u003e\u003cbr\u003eA: A CR2032 coin cell provides backup power for 5–10 years in most RTC modules, depending on the chip’s backup current draw. The PCF8563 has the lowest backup current and longest coin cell life.\u003c\/p\u003e\n\n\u003ch3\u003ePackage Contents\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e1× RTC Real-Time Clock Module (chip variant as selected)\u003c\/li\u003e\n  \u003cli\u003eCoin cell battery may or may not be included depending on variant — check variant details\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Keszoox","offers":[{"title":"DS1307","offer_id":46991413084395,"sku":"14:201659813#DS1307","price":5.0,"currency_code":"USD","in_stock":true},{"title":"DS3231","offer_id":46991413117163,"sku":"14:4044226#DS3231","price":7.0,"currency_code":"USD","in_stock":true},{"title":"DS1302","offer_id":46991413149931,"sku":"14:10#DS1302","price":4.6,"currency_code":"USD","in_stock":true},{"title":"PI RTC DS1307","offer_id":46991413182699,"sku":"14:29#PI RTC DS1307","price":13.64,"currency_code":"USD","in_stock":true},{"title":"DS3231 MINI","offer_id":46991413215467,"sku":"14:94#DS3231 MINI","price":8.04,"currency_code":"USD","in_stock":true},{"title":"PCF8563","offer_id":46991413248235,"sku":"14:173#PCF8563","price":6.64,"currency_code":"USD","in_stock":true},{"title":"PCF8523T","offer_id":46991413281003,"sku":"14:175#PCF8523T","price":16.64,"currency_code":"USD","in_stock":true},{"title":"DS2121SN","offer_id":46991413313771,"sku":"14:193#DS2121SN","price":9.2,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0677\/1005\/8731\/files\/pcf8563-ds3231-ds1302-i2c-rtc-module-arduino.webp?v=1761966041","url":"https:\/\/keszoox.com\/products\/i2c-rtc-real-time-clock-module-ds3231-ds1302-ds1307-pcf8563-arduino-esp32","provider":"Keszoox","version":"1.0","type":"link"}