Real-Time Clock Modules, RTC ICs and Digital Timers

Real-time clock ICs, modules and digital timing products

This collection brings together several different ways to keep time or control a timed event. It includes component-level real-time clock (RTC) chips and breakout boards for embedded electronics, as well as finished countdown clocks, interval timers and programmable switching devices. These are not interchangeable product classes: an RTC maintains calendar time for a host circuit, a display timer presents a count or schedule to a user, and an AC timer switch controls an external load. Choose the individual product and selected variant by its actual model, electrical interface, supplied hardware and intended installation environment.

Embedded RTC chips and boards

RTC devices are used when a microcontroller, data logger or other host needs a persistent time and date reference. Listings in this collection include DS3231-series, DS1307, DS1302 and PCF8563-related chips or modules. Depending on the product, the offering may be a bare surface-mount or through-hole IC, a populated breakout board, a board with battery holder, or a bundle with another component. A chip alone does not include a carrier PCB, header, battery or clock display unless the selected variant explicitly says so.

• DS3231 / DS3231SN: Look for the precise marking and package in the listing. DS3231-family boards commonly use a two-wire serial interface and may add a battery holder or separate memory. The oscillator and temperature-compensation claims of a particular chip must not be assumed for every board or for a different DS3231-suffixed part.
• DS3231M: Treat this as a distinct RTC option rather than an automatic substitute for DS3231SN. Its oscillator implementation, package and accuracy specifications differ. Confirm the exact selected model, footprint, host voltage and timing requirements against the appropriate device documentation.
• DS1307, DS1302 and PCF8563: These are separate RTC families with different interfaces, supply requirements, pinouts and backup-power arrangements. Match firmware, board wiring and battery design to the actual part; a similar-looking module is not proof of drop-in compatibility.
• AT24C32 on certain RTC boards: This is an additional EEPROM, not the RTC itself. A 32-kilobit memory stores approximately 4 kilobytes, not 32 kilobytes. Its presence and usable address depend on the particular board and selected option.

How to choose the right embedded option

1. Identify whether the selected variant is a standalone IC, a populated RTC board or a kit. Check package, pin pitch, board dimensions and the actual quantity in the purchase option.
2. Check the host interface and software requirements for the exact device. Two-wire/I²C-style and three-wire RTC parts are not software- or pin-compatible merely because they keep time.
3. Verify the allowed supply and logic levels of both the IC and the assembled board. A module's regulator, pull-ups, EEPROM and other fitted parts can change the usable voltage range; never extrapolate one listing's voltage claim to the entire collection.
4. Review the backup supply before inserting a cell. Some boards include charging circuitry, and a non-rechargeable coin cell must not be used in a circuit that charges it unless that circuit has been independently verified and made safe. Battery type, included battery and backup duration are listing-specific.
5. For an accuracy-sensitive application, verify the device suffix, oscillator type, temperature range and specified drift in the exact manufacturer's documentation. Do not apply DS3231SN timing figures to DS3231M or to an unverified assembled module.

Finished countdown clocks and event timers

The collection also contains complete kitchen-style countdown timers, visual timers, sports or fitness interval clocks, chess timers and other user-facing time displays. These are finished devices rather than embedded RTC ICs. Compare whether a particular listing counts up, counts down, shows calendar time, provides audible or visual alerts, supports presets or remote operation, and how it is powered. Display size, enclosure, accessories and operating modes vary by selected variant; a finished display should not be described as a bare clock chip or an RTC breakout board.

Programmable switch timers and mains equipment

Some listings are socket timers, DIN-rail timers or other scheduled electrical switches, including products described for three-phase applications. They are control equipment, not low-voltage RTC development modules. Before purchase, verify the selected device's supply voltage and frequency, contact arrangement and load rating, mounting format, local plug or wiring standard, and required protective enclosure. Ratings for one model do not transfer to another. Mains and three-phase installation should be assessed and carried out by a qualified professional under applicable local rules; this collection does not provide a universal wiring procedure.

Selection and delivery checklist

The collection is assembled from products whose titles mention real-time clocks or timers, so some listings are adjacent timing products rather than an RTC. Read the product description and choose the exact variant before ordering. Confirm model marking, chip versus module versus finished device, package or enclosure, interface, power source, battery handling, quantity and included accessories. A listing with several model or pack-size options supplies the selected option, not every model named in the title. Where a title and detailed specifications disagree, seek confirmation of the supplied model before designing a PCB or installing equipment.

Common questions

Does every product maintain the time and date when power is removed? No. RTC backup behavior depends on the exact chip, board and compatible backup supply. A simple countdown timer or mechanical/electrical switch may work differently.

Can I replace a DS3231SN with a DS3231M? Not on the name alone. Check package, pinout, oscillator and accuracy specification, electrical requirements and your design's firmware assumptions.

Is an AT24C32 a 32 KB memory? No. The 32 Kb designation corresponds to 32 kilobits, approximately 4 KB of storage.

Is a coin cell included and safe for every RTC board? Neither is guaranteed. Check the exact listing and the board's battery or charging circuit before fitting a cell.