DS3231 mini RTC module, chip side, showing the DS3231S chip and the 5 way Pi header socket underneath

DS3231 Mini High-Precision RTC Module - I2C, Arduino & Raspberry Pi

$6.89 NZD
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DS3231 mini RTC module, chip side, showing the DS3231S chip and the 5 way Pi header socket underneath
  • DS3231 mini RTC module, chip side, showing the DS3231S chip and the 5 way Pi header socket underneath
  • Top view of the DS3231 mini RTC module chip side: DS3231S chip, two resistors, a capacitor and the five header joints
  • Back of the DS3231 mini RTC module: DS3231 For PI print, + D C NC and ground pin labels above the 5 way socket, empty backup cell pads, no cell fitted
  • DS3231 mini RTC module dimensions: board about 14 x 14 mm, 11.5 mm tall including the header, 11 mm from the header to the far edge
DS3231 Mini High-Precision RTC Module - I2C, Arduino & Raspberry Pi
SKU: MOD-DS3231

DS3231 Mini High-Precision RTC Module - I2C, Arduino & Raspberry Pi

$6.89 NZD
5.0 1 review
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A tiny DS3231 real-time clock module that plugs straight onto the first five pins of a Raspberry Pi header, and wires to Arduino, ESP32 or any I2C board. The DS3231 is temperature compensated, so while powered it holds time to about 5 seconds a month, far steadier than a microcontroller's own timer or a DS1307. No backup cell is fitted: set the time at start-up, for example from NTP.

Specifications

RTC chipDS3231S, commercial grade (16-pin SO, 300 mil)
Timing accuracy±2 ppm (0 to +40°C); ±3.5 ppm (0 to +70°C)
Temperature sensorDigital, ±3°C
CalendarSeconds to year, leap-year correction to 2100
Alarms2 calendar alarms (status read over I2C)
InterfaceI²C, Fast-mode up to 400 kHz (address 0x68)
Supply voltage3.3V to 5.5V; use 3.3V on a Pi or ESP32
Operating temperature0°C to +70°C
Backup batteryNot fitted; time is lost when power is removed
Pinout+ (VCC), D (SDA), C (SCL), NC, - (GND)
Not broken outINT/SQW, 32 kHz and RST pins
Board sizeApprox. 14 x 14 mm, 11.5 mm tall including the header

Datasheets

Full technical datasheet PDF Quick Start guide PDF

What's in the box

1×
Mini DS3231 real-time clock module

With the 5-way header socket fitted. No backup cell.

Great for

Keeping an ESP32 clock steady between NTP syncs
Clock and alarm projects that run from mains power
Timestamping data-logger readings after a start-up time set
Switching relays, lights or pumps on a schedule
Compact builds where a full-size RTC board will not fit
Replacing a drifting DS1307 in always-powered builds

Wiring & getting started

  1. Connect it

    On a Pi, push it onto the first GPIO header pins so + D C NC - line up with pins 1, 3, 5, 7 and 9. On any other board, wire + to the supply (3.3V on a 3.3V board such as an ESP32, 3.3V or 5V on a 5V Arduino), D to SDA, C to SCL and - to GND.

  2. Enable / add a library

    On a Pi, enable I2C and the DS3231 overlay. On Arduino or ESP32, use RTClib (RTC_DS3231).

  3. Set the time at start-up

    With no backup cell, the time is lost whenever power is removed. Set it each time the board powers up, for example from NTP on an ESP32 or network time on a Pi.

  4. Let it run

    While powered, it holds the time to about 5 seconds a month at room temperature.

Note: If your project must keep time through a power cut, choose the DS1307 Tiny RTC instead. It has a coin-cell holder.
  • 5 stars: 1 (100%)
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T
Tim B.

Gives your invention a realtime clock. This has a pad for a battery, but not installed. Drift is seconds per year (program the esp32 to grab time from NTC over wi-fi for perfection).
Has a temp read out too, which is +/- 3deg C.

Frequently Asked Questions

Answers to the questions buyers ask most.

Does it have a backup battery?
No. There are pads on the back for a small backup cell, but none is fitted. When main power is removed the clock stops and forgets the time, so set it again at start-up. On an ESP32 or a networked Pi, syncing from NTP at boot is the easy way.
Why use it without a battery?
While powered, the DS3231 holds time to about 5 seconds a month at room temperature, far steadier than a microcontroller's internal clock. You only need an occasional network sync. If your project must keep time through a power cut, choose our DS1307 Tiny RTC, which has a coin-cell holder.
How accurate is it versus a DS1307?
The DS3231 is temperature compensated. This module uses the DS3231S, specified to ±2 ppm from 0 to +40°C and ±3.5 ppm across its full 0 to +70°C range. That is much steadier than a typical DS1307 module.
Can I use it outdoors or below freezing?
The chip is the commercial-grade DS3231S, rated for 0 to +70°C. Below 0°C it is outside its rating, so keep it indoors or in an enclosure that stays above freezing.
Does it only work with Raspberry Pi?
No. It is a standard I2C device at address 0x68. Wire +, D, C and - to VCC, SDA, SCL and GND for Arduino, ESP32 or another compatible controller.
What do the pins mean?
+ is VCC, D is SDA, C is SCL, NC is not connected, and - is GND. Check the markings on the module before connecting power.
Does it have onboard EEPROM?
No. This compact version is RTC-only and has no AT24C32 EEPROM.

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