The crystals you’ll find attached to microcontrollers or RTCs are usually accurate to 100 parts per million at most, but that still means if you’re using one of these crystals as a clock’s time base, you could lose or gain a second per day. For more accuracy without an atomic clock, a good solution is an oven controlled crystal oscillator – basically, a temperature controlled crystal. It’s not hard to build one, and as [Roman] demonstrates, can be built with a transistor and a few resistors.
The heating element for this OCXO are just a few resistors placed right on the can of a crystal. A thermistor senses the heat, and with more negative feedback than the Hackaday comments section, takes care of regulating the crystal’s temperature. A trimpot is used for calibrating the temperature, but once everything is working that can be replaced with a fixed resistor.
This deadbugged circuitry is then potted in five minute epoxy. That’s a bit unconventional as far as thermal management goes, but the results speak for themselves: [Roman] can get a clock with this circuit accurate to a few seconds per year.
If you’re dealing with RF, you’ll probably have the need to generate a variety of clock signals. Fortunately, [Jason] has applied his knowledge to build a SI5351 library for the Arduino and a breakout board for the chip.
The SI5351 is a programmable clock generator. It can output up to eight unique frequencies at 8 kHz to 133 MHz. This makes it a handy tool for building up RF projects. [Jason]‘s breakout board provides 3 isolated clock outputs on SMA connectors. A header connects to an Arduino, which provides power and control over I2C.
If you’re looking for an application, [Jason]‘s prototype single-sideband radio shows the chip in action. This radio uses two of the SI5351 clocks: one for the VFO and one for the BFO. This reduces the part count, and could make this design quite cheap.
The Arduino library is available on Github, and you can order a SI5351 breakout board from OSHPark.
There are LED clocks, and then there are LED clocks that can blind you from 30 paces. [Stiggalicious's] LED ring clock is of the latter variety. 200 WS2812B/Neopixel RGB LEDs drive the ring clock to pupil searing levels. The clock runs on ATMega1284P, with timekeeping handled by an NXP PCF8563 real-time clock chip. Code is written in Arduino’s wiring language using Adafruit’s Neopixel library.
Building the clock with a single Printed Circuit Board (PCB) would be both expensive and wasteful. [Stiggalicious] cleverly designed his clock to be built with 8 copies of the same PCB. Each board makes up a 45° pie slice of the ring. All 8 PCBs have footprints for the CPU, clock chip, and other various discrete parts, but only the “master” section has these parts populated. 7 “slave” sections simply pass clock, data, power and ground through each LED. He used Seeedstudio’s board service to get 10 copies of his PCB made, just in case there were any mistakes.
[Stiggalicious] rolled the dice by buying exactly the 200 LEDs he needed. Either he got really lucky, or the WS2812 quality testing has improved, because only one LED had a dead blue LED.
If you’d like to find out more, [Stiggalicious] gives plenty of details in his Reddit thread. He doesn’t have a webpage setup for the clock but he’s uploaded his source code (pastebin link) and Altium schematic/PCB files (mega.nz link). We may be a bit biased, but hackaday.io would be a perfect spot for this or any other project!
As fun as micro-controllers and RTCs are, sometimes it’s truly fascinating to see a completely mechanical clock. Using only gravity this Pendulum Marble Clock (German version) by [Turnvater Janosch] runs for 12 hours at a time and has an accuracy error of less than one second per day!
It works by raising a 2.5kg weight which sinks approximately 1 meter during that 12 hours. A series of steel ball bearings count the minutes, 5 minute increments, and hours. Every minute one ball is released on the track — when the track fills up, trap doors open releasing the balls to the next level. The first level is minutes, the second, 5 minutes, and the third, hours.
The entire thing is made out of wood, plastic gears, brass and steel wire, and an old flat iron (although we’re really not too sure what that’s used for…)
Continue reading “Mechanical Clock Relies On Marbles To Tick”
This clock is the first thing that [Kevin] ever made, way back before the Arduinofication of making, and long before the open hardware community exploded, and before the advent of cheap, custom PCBs. It’s an elegant design, with six seven-segment displays, a time base derived from line frequency, controlled entirely by 74-series logic chips. There was only one problem with it: it kinda sucked. Every so often, noise would become a factor and the time would be displayed as 97:30. The project was thrown in the back of the closet, a few revisions were completed, and 13 years later, [Kevin] wanted to fix his first clock.
The redesign used the same 1Hz timebase to control the circuitry, but now the timebase is controlled by a DS3231 RTC with an ATtiny85. The bridge rectifier was thrown out in favor of a much simpler 7805 regulator, and a new board was designed and sent off to OSHPark. Oh, how times have changed.
With the new circuitry, [Kevin] decided to construct a new case. The beautiful Hammond-esque enclosure was replaced with the latest and greatest of DIY case material – laser cut acrylic. Before, [Kevin] would put a jumper on the 1Hz timebase derived from the line frequency to set the clock – a task that makes plugging a clock in exactly at midnight a much simpler solution. Now, the clock has buttons to set the hours and minutes. Much improved, but still an amazing look at how far DIY electronics have come in a little over a decade.
Clocks have taken many forms of the years, starting with shadow clocks and sundials in Egypt around 3500 BC. Obviously, these could only tell the time while the sun was out. Water Clocks followed which could track time in the dark. Water Clocks are basically a bowl with a hole in the bottom. This bowl was set in a container filled with water. The water entered the bowl at a consistent rate and graduations on the inside of the bowl showed how much time had passed.
Mechanical clocks followed, as did quartz and the atomic clock. We have now entered a new era in time-telling, the Bamboo LED Clock. [Pascal] brings us this funky fresh chronometer all the way from Germany.
The front face is made from a bamboo pizza plate and gives the clock some modern minimalist pizzazz. A 1-meter long LED strip is attached to the circumference of the plate and contains 60 individually assignable RGB LED’s. An Arduino and Real Time Clock are responsible for the time keeping and coordination of the LED’s.
As you can see in the photo, 2 of the LED’s colors are used. The single red LED indicates the hour. The strip of blue LED’s show the minutes. If you’d like to build one of these [Pascal] has shared the Arduino code on his Instructables page.
After several months of work, [Greg] has completed one of the most polished LED clocks we’ve ever seen. It’s based on the WS2812 RGB LEDs, with an interesting PCB that allowed [Greg] to make a huge board without spending a lot of money.
The board is made of five interlocking segments, held together with the connections for power and data. Four of these boards contain only LEDs, but the fifth controller board is loaded up with an MSP430 microcontroller, a few capsense pads for a 1-D touch controller, and programming headers.
Finishing up the soldering, [Greg] had a beautiful LED ring light capable of being programmed as a clock, but no enclosure. A normal plastic case simply wouldn’t do, so [Greg] decided to try something he’d never done before: casting the PCB inside a block of resin.
A circular mold was made out of a piece of MDF and a router, and after some problems with clear resin that just wouldn’t cure, his ring light was embedded in a hard, transparent enclosure. Conveniently stuck in the mold, of course. The MDF had absorbed a little bit of the resin, forcing [Greg] to mill the resin ring free from the wood, with a lot of finish sanding to make the clock pretty.
It’s a clock that demonstrates [Greg]‘s copious manufacturing skills, and also his ability to troubleshoot the problems that arose. While he probably won’t be casting things inside an MDF mold anymore, with the right tools [Greg] could easily scale this up for some small-scale manufacturing.