Kerry Wong writes:
DS3232 is an extremely accurate RTC with a guaranteed accuracy of 2.5 ppm (0 °C to 40 °C), which translates into an error of just 80 seconds over the course of a year under the worst case scenario. I had done a few projects using this chip before (you can read about them here).
While by default DS3232 is already very accurate, we can push its accuracy even higher by adjusting its aging offset register (8bit). This adjustment works by adding or subtracting the corresponding capacitance to or from the oscillator capacitor array. The adjustable range is represented as 2′s complement (-128 to 127) and each LSB change corresponds to roughly 0.1 ppm of change in frequency. So the overall adjustment range can be achieved programmatically is roughly ±13 ppm.
DS3232 clock frequency calibration - [Link]
by Shawon Shahryiar @ embedded-lab.com:
Okay firstly the reason I wrote about the clock system instead of I/O ports or something else in this second post of the XMega series is simply because of the fact that without understanding clock configurations you won’t get what you want from your chip. Since XMega’s clock system is software-level configurable and complex at first, it makes itself the first priority module before anything else.
XMega Clock System - [Link]
Once all the components and headers were soldered in, I attached my Arduino and configured it as an ISP. I then burned the bootloader for an Arduino Uno.
I then connected my FTDI programmer and uploaded the blink sketch.Success!
Wow, that LED is super bright! It’s actually blinding and kind of hard to look at. With that, I swapped out the resistor for a 1K one in order to bring the brightness down.
Knowing that the Atmega worked, it was time to solder in the rest of the components, except for the display. Again, I don’t want to come this far and then waste a $15 LCD.
LCD clock version 2 - [Link]
Markus Gritsch build another bedside table alarm clock, the schematic and source code is available here:
recently some vintage bubble displays popped up at various places , so I felt the urge to build another bedside table alarm clock, this time a really tiny one, roughly the size of an AAA battery.
Bubble display alarm clock - [Link]
VFD Moduar Clock IV-4 6-digit by akafugu.jp:
This new shield design for the VFD Modular Clock is a variant of the original IV-4 shield, but with 6 digits. IV-4 tubes are Russian 16-segment VFD tubes, and can display numerals and the letters A-Z.
We’ve also designed a completely new enclosure for the IV-4 6-digit shield. It uses 2mm semi-transparent blue acrylic, and is designed to give a low-profile rounded appearance.
Creating a 6-digit IV-4 shield without redesigning the base board presented a unique challenge: The HV5812 driver used to drive the VFD tubes has 20 channels. IV-4 tubes are 16 segment displays, 20 – 16 = 4, so in other words the HV5812 driver can only support 4 IV-4 tubes.
New Product – VFD Moduar Clock IV-4 6-digit - [Link]
Marcus Linderoth built a clock using a TI MSP430g2553 microcontroller and a HPDL-1414 display, that is available at Github:
After having ported Contiki to the Launchpad, I was eager on doing something with it. I built this simple clock with a vintage HPDL-1414 “smart four-character 16-segment alphanumeric” display and a msp430g2553.
Clock with retro display - [Link]
frankenroc @ instructables.com writes:
You don’t have to be in Times Square to enjoy large bright displays of lights. You can create that in the comfort of your own home with some foam board, LEDs, and our little friend Arduino.
My sister-in-law decided to get married on New Year Eve, and the venue she chose stays open until 1am that night, so I started thinking it would be great to have a nice big countdown clock. I ran the idea past her and her fiance and they both loved it, so I went to work.
When I made it I intended it for just one use, but it’s a very impressive display that can be seen across a huge room. This is pretty simplified and what I’m showing you is on a breadboard. Optimizing and taking it beyond prototyping (e.g. replacing the breadboard with some pcb boards) are outside of the scope for this but shouldn’t be too difficult.
Giant Two-Digit Countdown Clock - [Link]
Electro-Labs informed us about his latest project:
One of the most enjoyable part of being an electronics person is creating your own gadgets and using them in daily life. In this article, we are building one of those with the help of SoloPCB design tools, a digital desk clock with temperature display feature.
The brain of the circuit is a Microchip PIC18F252 microcontroller. It acquires precise time information from DS1307 real time clock via I2C interface and displays it on four digit 38 mm seven-segment display with the help of MAX7219CNG display driver. The temperature data is read by the on-chip ADC module of the microcontroller from LM335 temperature sensor which outputs 10mV per kelvin degree linearly. The temperature data is also displayed periodically.
DIY Digital Desk Clock with Temperature Display – Part 1 - [Link]
Andrea Biffi build a nice vertical nixie clock using ATmega8 mcu. He writes:
After the success of my first nixie clock made out from a rosewood block, I decided to lose no time and to carry on with the next one. As some of you guys already know, or imagine, lately I’m indeed a little bit addicted to nixie-mania. I’ve bought many nixie tubes on eBay, and I experienced in electronics so to build my own high voltage power supply and then the ultimate nixie clock circuit. Digits for this clock are nice rounded and fully transparent IN-4 tubes, the same I used in the first model, but as I previously announced, I aligned them vertically, so to read from top to bottom hours, minutes, and seconds. Indeed you will see the undeniable influence of Max Pierson’s vertical clock. I guide you now through the full process to make your own unique nixie clock.
Vintage style nixie wall clock - [Link]
svkatz80 @ fritzing.org build a nice LED clock. He writes:
This clock is based on ATmega328p microcontroller, with combination of DS1307 – Real Time Clock, MAX7219 – 64 LEDs drivers, 74HC595 – shift registers, DS18B20 – temperature sensor, GL5528 – photoresistor, LEDs and other electronic components.
- Clock with RGB seconds — Four 74HC595 control 10 RGB leds. But TLC5940 is a better choice.
- Ellipse clock — Three MAX7219 control all LEDs. No shift registers needed.
Each MAX7219 can control 64 LEDs. For ellipse clock I used tree of them. The first one controls 2 hour’s digits (2x7x4=56 green leds + 6 blue leds + 2 dots between hours and minutes ). The second one controls 2 minute’s digits (2x7x4=56 green leds + 6 blue leds). The third MAX7219 controls second’s 60 red leds .
For making a 7 segment digits, I used 5×7 cm prototype PCB circuit board. Before solder the LEDs, I wired the board for 4 digits and 7 segments each of four boards with copper wire. See circuit.
As a main board I used a coroplast (polygal) sheet. Just print the sketch and make on polygal holes with a needle for LEDs.
ATmega328p based LED wall clock - [Link]