Tag Archives: RTC

DS1307 RTC Module


The module based on DS1307, The DS1307 serial real-time clock (RTC) is a low-power, full binary-coded decimal (BCD) clock/calendar plus 56 bytes of NV SRAM. Address and data are transferred serially through an I²C, bidirectional bus. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. The DS1307 has a built-in power-sense circuit that detects power failures and automatically switches to the backup supply. Timekeeping operation continues while the part operates from the backup supply.


  • Supply 5V DC
  • Completely Manages All Timekeeping Functions
  • Real-Time Clock Counts Seconds, Minutes, Hours, Date of the Month, Month, Day of the Week, and Year with Leap-Year Compensation Valid Up to 2100
  • 56-Byte, Battery-Backed, General-Purpose RAM with Unlimited Writes
  • Programmable Square-Wave Output Signal
  • Simple Serial Port Interfaces to Most Microcontrollers

DS1307 RTC Module – [Link]

0.8A step-up DC/DC converters in a tiny package


Torex Semiconductor’s XC9141/XC9142 series of 0.8A step-up DC/DC converters come with an input–output disconnection function (load disconnection function) to prevent malfunctioning during standby, and for device functionality that enables power supply to RTC.

When the output voltage is 3.3V, the IC can start from an input voltage of 0.9V with a resistance load of 100Ω, enabling use in devices driven by one alkaline or nickel-hydrogen battery. The input voltage range is 0.65V to 6.0V, and the output voltage range can be set from 1.8V to 5.5V (accuracy ±2.0%) in steps of 0.1V. A switching frequency of 1.2MHz or 3.0MHz can be selected to match the application.

0.8A step-up DC/DC converters in a tiny package – [Link]

Multi-Function SSD Shield for the Raspberry Pi 2


We came across this kickstarter campaign that features a multifunction SSD shield for Raspberry Pi 2. The shield includes SSD, WiFi, RTC w/Battery and high power USB:

Pi 2 Design is excited to introduce the first offering in a new line of Embedded and Media-based I/O shields for the popular Raspberry Pi 2. The CSB502SSD Multi-Function Solid State Drive shield allows users to create a low cost, high performance, embedded network storage device. The powerful combination of the CSB502SSD and the Raspberry Pi 2 lets you leverage the ever expanding RPi 2 ecosystem for a wide variety of Embedded, Data Storage, Medical and Industrial applications.

Multi-Function SSD Shield for the Raspberry Pi 2  – [Link]

Using a $2 DS3231 RTC & AT24C32 EEprom from eBay


Edward Mallon @ edwardmallon.wordpress.com gives us a detailed explanation about cheap RTC modules found on ebay and other places.

I built the first few beta units with the DS3231 Chronodot from Macetech (about $18 each), but I kept on stumbling across cheap RTC modules on eBay, Amazon, etc. and I eventually bought a couple to try them out. While I waited for them to ship on the proverbial slow boat, I did some digging, because these modules were (almost) selling for less than the chip itself if I bought them directly from trusted sources like Digikey, Mouser, etc.

Using a $2 DS3231 RTC & AT24C32 EEprom from eBay – [Link]

LCD clock with 4″ display


mcs.uwsuper.edu has build a big LCD clock based on MSP430 mcu and DS3231 RTC clock chip. They write:

The clock is built on a 4″ (101 mm) LCD displays OD-103 manufactured by Orient Display. The LCD provides high contrast of digits and easy reading from a large distance. The unit runs on batteries and can also be powered from mains. Here is how it looks under direct sun.

The time keeping is provided by DS3231 RTC chip with an integrated high accuracy (± 5ppm) MEMS crystal. This makes PCB design very simple, as one does not need to take care on special traces design around the crystal.

LCD clock with 4″ display – [Link]

PIC24 bedside table alarm clock


Markus Gritsch posted pictures and code of his PIC24 bedside table alarm clock:

Another year, another clock, but for the first time for my alarm clocks. I am not using an MSP430 but a PIC24 instead. Standby current is with 5.5 µA only slightly higher than that of my MSP430 based ones. Time keeping is done using the RTCC pheripheral, which I also used for the first time.
It can be seen in action in this YouTube video
Friendly green digits 🙂
And of course it has a LiFePO4 battery on its back, being charged every few years using my new USB charger.
A photo transistor is also included to dim the display in the dark. Much nices to the eyes when checking what time it is in the middle of the night.

PIC24 bedside table alarm clock – [Link]

Meter Clock using a DS1307 RTC and Trinket Microcontroller


by MIKE BARELA @ adafruit.com:

Trinket lends itself very well to building clock projects, its small and easy to hide behind a larger display. And clocks don’t need a lot of logic, this example only has maybe 20 lines of code. Adding a digital display via I2C is possible using seven segment or character-based displays (with the library code posted for other projects).

This project interfaces Trinket to the the Adafruit DS1307 real-time clock (RTC) breakout board to form a clock. But in a twist, the display is done using two analog meters. One for hours, one for minutes.

The Trinket can output to a meter without digital to analog converters. Trinket has pulse width modulation (PWM) on three of its pins. The meter uses a moving coil inductance movement, acting to average the indication of current flowing through it. If you have narrow pulses, the average voltage it sees is lower, thus the current is lower for the fixed resistance attached to it. For wide pulses, the meter sees nearly the supply voltage and will stay around the full scale. This circuit varies the pulse width sent to the meters proportional to the hour of the day and the minutes after the hour.

Meter Clock using a DS1307 RTC and Trinket Microcontroller – [Link]

Tiny real-time clock consumes only 240 nA

Micro Crystal RV8803C7

by Susan Nordyk @ edn.com:

Furnished in a ceramic surface-mount package that is just 3.2×1.5×0.8 mm, the RV-8803-C7 real-time clock module from Swiss manufacturer Micro Crystal consumes 240 nA and operates from a supply voltage as low as 1.5 V to increase the life of backup supplies. The device gives designers the option to replace expensive batteries and supercapacitors with low-cost multilayer ceramic capacitors for battery backup.

The temperature-compensated real-time clock is accurate to within ±3.0 ppm (±0.26 seconds/day) over a temperature range of -40°C to +85°C. In addition to low current consumption and high accuracy, the RV-8803-C7 has one of the smallest ceramic packages in the industry with an integrated 32.768-Hz quartz crystal. It operates from a supply voltage ranging from 1.5 V to 5.5 V and employs an I2C interface.

Tiny real-time clock consumes only 240 nA – [Link]

Neat E-ink HAT for RPi


by elektor.com:

Startup Percheron Electronics Ltd is looking to fund their rather neat E-Paper display HAT for the Raspberry Pi. Unlike some similar display solutions for the Pi this E-ink HAT attaches without any long ribbon cables. An advantage of this type of display (similar to those used on the Kindle) is that the image persists on the screen when power is removed so they use less power than a TFT display but the E-Paper technology does not support fast moving images.

The PCB is compliant with the Raspberry Pi Foundation’s HAT specification, including device tree configuration of the required GPIO pins by the HAT EEPROM. The board is able to drive a 2.7″ 264 x 176 pixel E-Paper display panel and is also suitable for the 1.44″ and 2″ display panels from the same manufacturer.

The board also features a DS3231 real time clock (RTC) IC with a CR1220 lithium coin cell for battery backup when the Pi is powered down. The DS3231 is accurate to 5 parts per million, or within 3 minutes per year. The RTC can generate an interrupt/alarm signal and also a 32 KHz clock signal which can be connected through to GPIO pins by solder pad links, if required.

Neat E-ink HAT for RPi – [Link]