Real-time clock modules are the quiet timekeepers behind countless electronics projects, ensuring accurate date and time tracking even when main power is lost. They’re commonly used in microcontroller builds, data loggers, automation systems, and embedded devices where timing matters. A reliable RTC module is defined by low drift, dependable battery backup, and seamless integration with popular development boards.
| Pyramid Auto-Aligning Time Clock Bundle for Small Business |
| Best Small-Business Bundle | Type: Time clock bundle | Interface/Communication: N/A (time clock) | Clock Type/Chip: Pyramid Auto Time Clock (not a DS3231) | VIEW LATEST PRICE | Read Our Analysis |
| DS3231 RTC Module for Arduino/Raspberry Pi (i2c) |
| High-Volume I2C Real-Time | Type: DS3231 RTC module | Interface/Communication: I2C | Clock Type/Chip: DS3231M | VIEW LATEST PRICE | Read Our Analysis |
| DS3231 RTC Module Pack (3.3V/5V) |
| Industrial-Grade DS3231 | Type: DS3231 RTC module | Interface/Communication: I2C | Clock Type/Chip: DS3231M | VIEW LATEST PRICE | Read Our Analysis |
| AITRIP 3PCS DS3231 RTC Module for Arduino/RPi |
| Cost-Effective Triple Pack | Type: DS3231 RTC module | Interface/Communication: I2C | Clock Type/Chip: DS3231SN (DS3231 family) | VIEW LATEST PRICE | Read Our Analysis |
| 4Pcs DS3231 RTC Clock Module for Raspberry Pi |
| Pi/RPi Ready Precision | Type: DS3231 RTC module | Interface/Communication: I2C | Clock Type/Chip: DS3231 | VIEW LATEST PRICE | Read Our Analysis |
| DS3231 AT24C32 I2C RTC Module Kit with Wires |
| Jumper-Wable Starter Kit | Type: DS3231 RTC module kit | Interface/Communication: I2C | Clock Type/Chip: DS3231 | VIEW LATEST PRICE | Read Our Analysis |
| DS3231 AT24C32 I2C RTC Module Set (2) |
| Two-Pack Reliability | Type: DS3231 RTC module set | Interface/Communication: I2C | Clock Type/Chip: DS3231 | VIEW LATEST PRICE | Read Our Analysis |
| Pyramid Time Systems 5000 Auto Time Clock Kit |
| All-In-One Timekeeping | Type: Time clock bundle | Interface/Communication: N/A (time clock) | Clock Type/Chip: Pyramid Time Systems | VIEW LATEST PRICE | Read Our Analysis |
| Pyramid 3800 Auto Time Clock Bundle with Cards |
| Daily Punch Essential | Type: Time clock bundle | Interface/Communication: N/A (time clock) | Clock Type/Chip: Pyramid Time Clock 3800 | VIEW LATEST PRICE | Read Our Analysis |
| Pyramid 4000 Pro Auto Time Clock Bundle (4000PROK) |
| Pro-Grade Auto Kit | Type: Time clock bundle | Interface/Communication: N/A (time clock) | Clock Type/Chip: Pyramid 4000 Pro | VIEW LATEST PRICE | Read Our Analysis |
More Details on Our Top Picks
Pyramid Auto-Aligning Time Clock Bundle for Small Business
If you run a small business and need a reliable, all-in-one timekeeping solution, the Pyramid Time Systems 2500 Auto-Aligning Bundle is a strong choice—especially if you want quick setup and easy-to-read records. You install the bundle by placing the 10-slot rack on a desk or wall, loading the 100 time cards, and inserting ink ribbons. The auto-aligning punches ensure readable entries, and the backlit display helps in low light. Set formats to 12- or 24-hour, enable automatic DST, and run up to three punches daily. This bundle reduces payroll corrections and fits offices, retail, and warehouses.
- Type:Time clock bundle
- Interface/Communication:N/A (time clock)
- Clock Type/Chip:Pyramid Auto Time Clock (not a DS3231)
- Power/Backup:Not specified (clock bundle)
- Accuracy/Precision:Auto-aligning punches, no clock ppm spec
- Power/Formats Supported:12/24-hour formats
- Additional Feature:100 time cards included
- Additional Feature:Backlit display
- Additional Feature:Wall-mount option
DS3231 RTC Module for Arduino/Raspberry Pi (i2c)
The DS3231 RTC Module stands out for its high-precision timekeeping, making it the best choice when you need accurate timestamps for Arduino or Raspberry Pi projects. You’ll use the I2C interface to connect the module to your board. The package includes 10 pieces, each a DS3231M-based clock with integrated AT24C32 memory for enhanced data storage. It supports a versatile voltage range from 3.3V to 5.5V, so you can power it from common boards. Ensure compatibility with DS3231M modules and hook up SDA/SCL lines correctly. Verify timing with a simple read/write test and log results.
- Type:DS3231 RTC module
- Interface/Communication:I2C
- Clock Type/Chip:DS3231M
- Power/Backup:Battery input for timekeeping
- Accuracy/Precision:High-precision DS3231M
- Power/Formats Supported:3.3V–5.5V, I2C
- Additional Feature:10 pieces in package
- Additional Feature:AT24C32 memory
- Additional Feature:3.3V–5.5V operation
DS3231 RTC Module Pack (3.3V/5V)
Choose the DS3231 RTC Module Pack when you need reliable timekeeping that works directly with common microcontrollers. This pack supports 2.3V–5.5V input, so it connects to Arduino and Raspberry Pi without extra level shifting, and operates at 3.3V or 5V to reduce hardware design steps. It uses an ultra-stable temperature-compensated crystal oscillator for accuracy, with a -40°C to 85°C range and about ±5 ppm. It includes a ±3°C sensor for drift compensation and a full calendar with leap-year support to 2100. It offers I2C at 400 kHz, backup power, and anti-interference features for robustness.
- Type:DS3231 RTC module
- Interface/Communication:I2C
- Clock Type/Chip:DS3231M
- Power/Backup:Backup calendar, battery input implied
- Accuracy/Precision:Ultra-stable TCXO, ±5 ppm
- Power/Formats Supported:2.3V–5.5V, 3.3V/5V
- Additional Feature:Temperature-compensation crystal
- Additional Feature:Leap year automatic compensate
- Additional Feature:Dual calendar architecture
AITRIP 3PCS DS3231 RTC Module for Arduino/RPi
AITRIP’s DS3231 modules stand out for high precision and reliability, making them ideal if your project needs accurate timekeeping across power blips. You’ll use the three modules together or separately in Arduino or Raspberry Pi projects. The DS3231SN is the clock chip with I2C, an integrated crystal, temperature sensor, TCXO, and voltage detection. Connect VCC, GND, SDA, and SCL following your board’s 3.3V or 5V level. Note AT24C32 memory is present. Batteries aren’t included; add a local battery. Power up, verify I2C address, then read time and set alarms as needed for routines.
- Type:DS3231 RTC module
- Interface/Communication:I2C
- Clock Type/Chip:DS3231SN (DS3231 family)
- Power/Backup:Battery input implied
- Accuracy/Precision:High-precision DS3231 variant
- Power/Formats Supported:3.3V/5V
- Additional Feature:Includes 3 modules
- Additional Feature:Battery-not-included note
- Additional Feature:Alarm/timer functionality
4Pcs DS3231 RTC Clock Module for Raspberry Pi
Need a reliable time base for your Raspberry Pi projects? The Pcs DS3231 RTC Clock Module for Raspberry Pi provides a complete clock calendar: seconds, minutes, hours, day, date, month, year. It supports leap year compensation until 2100 and runs with low power consumption, offering 1 Hz and 32.768 kHz outputs. It operates on 3.3 V or 5 V systems and tolerates −40°C to +85°C. The module includes ±5 ppm accuracy and a ±3°C digital temperature sensor. It’s easy to use with Raspberry Pi, ensuring you have precise time without manual resets. Install, configure, and verify clock function steps accordingly.
- Type:DS3231 RTC module
- Interface/Communication:I2C
- Clock Type/Chip:DS3231
- Power/Backup:Battery input implied
- Accuracy/Precision:±5 ppm, ±3°C sensor
- Power/Formats Supported:3.3V/5V
- Additional Feature:4-piece set
- Additional Feature:3.3V/5V operation
- Additional Feature:Temperature sensor included
DS3231 AT24C32 I2C RTC Module Kit with Wires
The DS3231 AT24C32 I2C RTC Module Kit with Wires is the right choice when you need a compact, highly accurate timekeeper for embedded projects. You wire it into your board using the included 20 male-to-female jumper wires, connect I2C pins, and power it to start. The module uses the DS3231 with AT24C32 memory, offering two configurable alarms and a calendar. It features a TCXO and crystal for long-term accuracy, a battery input for timekeeping during power loss, and a square wave option. Follow steps: set address, verify I2C communication, test alarms, check VCC monitoring.
- Type:DS3231 RTC module kit
- Interface/Communication:I2C
- Clock Type/Chip:DS3231
- Power/Backup:Battery input for timekeeping
- Accuracy/Precision:High-precision RTC with TCXO
- Power/Formats Supported:3.3V–5V, I2C
- Additional Feature:Includes 20 jumper wires
- Additional Feature:I2C bidirectional bus
- Additional Feature:Battery input for timekeeping
DS3231 AT24C32 I2C RTC Module Set (2)
If you need precise timekeeping with minimal setup, this DS3231 AT24C32 I2C RTC Module Set (2) is your best choice because it combines a highly accurate RTC with onboard memory and a built-in battery backup. You connect via I2C, using the two configurable alarms and calendar features to schedule events. The module includes DS3231‑style 16‑pin memory and AT24C32 memory for data storage, plus a backup battery input to maintain time during power loss. Use the included jumper wires to link VCC, GND, SDA, and SCL, and verify VCC monitoring. Replace DS1307 if needed, and test alarms.
- Type:DS3231 RTC module set
- Interface/Communication:I2C
- Clock Type/Chip:DS3231
- Power/Backup:Battery input for timekeeping
- Accuracy/Precision:High-precision RTC with TCXO
- Power/Formats Supported:3.3V/5V, I2C
- Additional Feature:Replacement for DS1307
- Additional Feature:Includes jumper wire cable
- Additional Feature:Two modules per set
Pyramid Time Systems 5000 Auto Time Clock Kit
For a reliable, no-fuss time-tracking solution, this model stands out with its 100-employee totalizing capability and auto time card handling. You plug it in, start tracking minutes, and the device auto-aligns cards for clean punches. Use the backlit LCD to read time, date, and day. It auto-adjusts for short months, leap years, and daylight saving time. It calculates total hours per pay period for up to 100 employees, with clear punches from a long-lasting ribbon and no overwriting. It tracks in, out, break, and lunch, supports 12- or 24-hour formats, and mounts on a desk or wall.
- Type:Time clock bundle
- Interface/Communication:N/A (time clock)
- Clock Type/Chip:Pyramid Time Systems
- Power/Backup:Not specified
- Accuracy/Precision:Not a DS3231 clock (time clock)
- Power/Formats Supported:1200x? (not applicable)
- Additional Feature:25 time cards
- Additional Feature:Auto-adjusts for DST
- Additional Feature:Desk or wall mount
Pyramid 3800 Auto Time Clock Bundle with Cards
Choose the Pyramid 3800 Auto Time Clock Bundle with Cards if you need a ready-to-use, small-business timekeeping solution that prints accurate, daily and overtime hours on a durable card. You receive the 3800 Auto Totaling Time Clock, plus 50 time cards, 1 ink ribbon, and 2 security keys. The system tracks worked time and prints date, cumulative time, daily overtime, month, in and out punches, and total time between punches. Use the auto aligning feature to prevent over-printing, and view time, date, and day on the backlit LCD. Ivory finish matches office decor and improves record accuracy.
- Type:Time clock bundle
- Interface/Communication:N/A (time clock)
- Clock Type/Chip:Pyramid Time Clock 3800
- Power/Backup:Not specified
- Accuracy/Precision:Not a DS3231 clock (time clock)
- Power/Formats Supported:3.3V/5V
- Additional Feature:Ivory color
- Additional Feature:50 time cards
- Additional Feature:Overtime printing
Pyramid 4000 Pro Auto Time Clock Bundle (4000PROK)
The Pyramid 4000 Pro Auto Time Clock Bundle (4000PROK) stands out for its complete, ready-to-use setup that fits small businesses. You connect power, place the unit, and start tracking minutes. The bundle includes 125 time cards, two ink ribbons, a ten-slot rack, and two security keys, with no software or monthly fees. It auto-aligns cards for clean punches, and the backlit LCD shows time, date, and day. It supports 12- or 24-hour formats and rounds or calculates actual times. It adjusts for short months, leap years, and daylight saving time, with a tamper-proof lock for protection.
- Type:Time clock bundle
- Interface/Communication:N/A (time clock)
- Clock Type/Chip:Pyramid 4000 Pro
- Power/Backup:Not specified
- Accuracy/Precision:Not a DS3231 clock (time clock)
- Power/Formats Supported:3.3V/5V
- Additional Feature:125 time cards
- Additional Feature:Ten-slot rack
- Additional Feature:Tamper-proof lock
Factors to Consider When Choosing Real Time Clock Modules
When choosing real-time clock modules, start by evaluating clock accuracy and decide if you need ppm-level precision or behavior under drift. Next, assess power backup options and voltage compatibility, outlining whether you need battery/CR2032 support and if the supply rails match your system’s voltage (3.3V vs 5V). Finally, check for I2C interface ease and consider temperature compensation features, providing concrete steps to test each option in your setup.
Clock Accuracy Matters
Clock accuracy matters because small errors can compound over time and affect systems that rely on precise timestamps. You evaluate modules by accuracy specs, drift range, and temperature effects. DS3231-based clocks offer ±5 ppm, about ±0.432 seconds per day, across 3.3V–5V operation. Check how temperature compensation helps; TCXO and an integrated crystal reduce drift from -40°C to 85°C. Ensure calendar support for leap years through 2100 to avoid manual adjustments. Look at interface quality; I2C at up to 400 kHz enables precise timestamp synchronization and reliable data transfer. Verify power resilience; battery backup or VCC monitoring maintains time during outages. Consider long-term stability, supported features, and how you’ll monitor accuracy in your system, then select a module that matches your timing needs.
Power Backup Importance
Backup power is a fixed requirement for any reliable RTC. You must ensure a backup path keeps time when main power fails. Choose a dedicated battery or a supercapacitor to preserve the clock during outages, confirming it has separate energy for timekeeping. Look for low standby current in backup mode, ideally in the nanoamp to microamp range, to extend battery life and reliability. Some modules provide dual calendars and continuous power by storing time and date in backup memory during outages; evaluate how this feature fits your system’s needs. Ensure a reset or PWR-fail monitoring feature exists so time resumes correctly after power returns. Verify installation steps: connect backup to the designated input, test power loss, and confirm time remains accurate.
Voltage Compatibility
Voltage compatibility matters for reliable RTC operation. You should check whether the DS3231 module supports 3.3V to 5.5V operation, which allows direct connection to both 3.3V and 5V controllers without level shifting. If the module explicitly supports dual voltage (3.3V/5V), verify your platform’s voltage and choose the matching mode. Ensure you stay within the recommended supply range to maintain clock accuracy, typically within ±5 ppm. Remember that modules with built-in TCXO and crystal preserve performance across 3.3V–5V, but excessive voltage can raise power use and affect results. Consider backup and main power domains, noting that loss of main power may involve a separate voltage domain. Evaluate these choices against your controller’s voltage and available power circuitry.
I2C Interface Ease
I2C interface options are straightforward and practical to evaluate. You connect the SDA and SCL lines with power and ground, then verify basic operation. Most modules run at 3.3V to 5V, so you can interface directly with common microcontrollers like Arduino or Raspberry Pi without extra level shifting. Check the I2C address: fixed or selectable, and confirm you can place multiple devices on the same bus with unique addresses. Look for DS3231-based modules for high-precision timekeeping, with optional battery backup for continuity. Confirm features such as alarm clocks and calendar support meet your needs. Ensure the module includes an integrated oscillator or external crystal as appropriate. Validate that the bus can tolerate your system’s reach and noise environment before commissioning.
Temperature Compensation
Temperature confirmation is essential for keeping time accurate as temperatures change. You choose a clock with a temperature confirmation strategy to control drift. A typical DS3231 uses a built-in TCXO to maintain accuracy across a wide range, so select modules that advertise this feature. If you need ambient readings, pick one that provides a temperature sensor output (±3°C) to enable software-side drift compensation. Temperature-induced frequency drift can be several ppm per degree Celsius without confirmation, so TCXO-based clocks are preferred for precision. Some modules expose both timekeeping and temperature data, letting you calibrate in software. Verify how you’ll apply ambient data to adjust timing, and ensure the interface supports your programming workflow and accuracy requirements.
Calendar Features
Calendar features matter for long-term accuracy and reliability. You look for full calendar support: seconds, minutes, hours, days, weeks, dates, months, and years, with leap year compensation until 2100. Ensure your module handles automatic leap year adjustment to maintain date accuracy over years. Check if it uses a dual calendar architecture and backup battery input to preserve the calendar during power loss. Evaluate temperature stability with a temperature-compensated crystal oscillator to reduce drift across temperatures. Consider I2C-based modules that offer programmable alarms and a square-wave output alongside calendar data, useful for timekeeping tasks. Verify documentation shows steps to enable calendar features, configure leap-year handling, and test date rollovers in your project.
Installation Versatility
Choosing an RTC module for installation versatility starts with confirming it fits your hardware and power needs. You should verify I2C compatibility and voltage range, noting that DS3231-based modules run on 3.3V to 5V and connect directly to Arduino or Raspberry Pi without level shifting. Check for AT24C32 memory, which supports timestamped logging across power cycles, and decide if you need on-board storage. Confirm calendar features, including leap year handling and backup battery inputs, so time remains accurate during power loss. Look for dual calendar support and temperature compensation for drift resistance from -40°C to 85°C, ensuring reliability in your environment. Assess kit contents, such as jumper wires or multiple modules, for parallel deployments or rapid prototyping. Plan layout, wiring, and testing steps accordingly.
Final Thoughts
To choose the right RTC, start by defining your needs: precision, backups, and I2C compatibility. Compare options like DS3231 variants with TCXO and memory, and 3.3V/5V packs for your MCU. Check dual power backups and address options for multi-device setups. For Raspberry Pi projects, prioritize modules with easy wiring and robust stability. Consider temperature sensing for drift, calendar support, and firmware updates. Pick a bundle that fits your hardware and budget, then test with a simple time setup.
Meet Ry, “TechGuru,” a 36-year-old technology enthusiast with a deep passion for tech innovations. With extensive experience, he specializes in gaming hardware and software, and has expertise in gadgets, custom PCs, and audio.
Besides writing about tech and reviewing new products, he enjoys traveling, hiking, and photography. Committed to keeping up with the latest industry trends, he aims to guide readers in making informed tech decisions.