Light programming for a clock

May 8, 2012 By Leave a Comment

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So at first glance we were thinking there wasn’t much special about this clock. It’s based on an Arduino and displays the time using a character LCD screen. But then we realized that there’s no battery-backed RTC and no buttons. How the heck do you set the time on this thing? [Mossblaser] is using a light programmer to set the time using a computer screen.

We’ve tried nearly the same data transfer technique before, using a white and black flashing computer screen to push Manchester encoding to a light dependent resistor. We were met with limited success, but you can see that [Mossblaser’s] rig is much more reliable and we think there’s a few reasons behind this. First, he’s only sending five bits per seconds, a very slow speed when it comes to digital transmissions. This helps to make up for slow LCD screen refresh. Also, the LDR is surrounded by material on the back of the case that will help to block out ambient light. And finally, he’s using a smaller part of the screen instead of flashing the whole thing. This may result in more accurate timing. You’ve got to admit, this is pretty slick!

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Filed Under: clock hacks, Microcontrollers Tagged With: , , , ,

A novel binary clock from Hackaday's own

April 29, 2012 By Leave a Comment

Hackaday’s very own [Mike Szczys] just shared an awesome binary clock he’s been working on. Unlike a normal binary clock that is only readable by self-admitted geeks and nerds, [Mike]’s clock is nearly comprehensible by the general population.

There are 12 lines of three LEDs around the face of [Mike]’s clock. These LEDs represent the time in minutes in binary – the inner LED is 1, the middle LED is 2, and the outer LED is 4. Adding up each of the LEDs around the clock face gives the number of minutes passed since the top of the hour.

To display the hour, [Mike] used a red/blue bi-color LED in the center of each line of LEDs. For example, at 1:03 the one ‘o clock hand will have a blue LED in the first position and a purple LED in the second position. A minute later at 1:04, this changes to blue, red, blue.

If that is a little confusing, there’s a wonderful video demonstrating the pattern of LEDs throughout the hour.

For such an interesting clock, the build is fairly simple – just an ATtiny44 with an STP16CP05 LED driver. Time is kept with a battery-backed MCP7940 real-time clock, and power is provided by a simple USB port.

[Mike] had enough boards manufactured for several dozen clocks, but only had enough parts (and patience) to solder up four clocks. You can check out the time-lapse of him going to town with a soldering iron on one of these boards after the break. As with all good builds, the code and schematics are provided on GitHub if you’d like to make your own.

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Filed Under: clock hacks, led hacks Tagged With: , , , ,

A glorious mechanical seven segment display

April 15, 2012 By Leave a Comment

If you’ve ever wondered why you’ve never seen a mechanical seven-segment display, now you know. They’re fairly complicated and most likely absurdly expensive, especially when a few light bulbs or LEDs would do the same job equally well. This didn’t stop [kiu] from completing his mechanical seven-segment clock he calls SevenBlocks, and for that we are thankful.

Each of the 28 segments in [kiu]’s clock is made of three layers of acrylic and a short section of a rack gear. Unlike every seven-segment display you’ve ever seen, tiny hobby servos provide the indication for each segment. For the electronics, An ATMega8 is used for the brains of the outfit with a 74HC595 shift register to expand the number of I/O lines. A DS1307 RTC module provides accurate timekeeping, and the dozens of servo outputs visible in the ‘guts shot’ makes you realize why you’ve never seen a mechanical seven segment display before – they’re really friggin’ complex.

If you want to build your own mechanical seven-segment clock, [kiu] put all the files up on Github. Everything is there, from the .DXF files ready to feed to a laser cutter to the schematic and board files for each of the three PCBs. A video showing this clock in action is sort of necessary, so you can check that out after the break.

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Filed Under: clock hacks Tagged With: , ,

Quieting a pendulum clock every night

April 1, 2012 By Leave a Comment

[Vinnie] has a wonderful old clock from his grandmother; it’s an exquisite antique with a real mechanical movement and a charming set of bells that ring every hour. Unfortunately, those chimes are a bit of a disturbance to neighbors at 2 o’clock in the morning. Previously, [Vinnie] had been stopping the clock every evening, and hoped he would remember to start the pendulum in motion 12 hours later. This was a chore, so he decided to automate the process.

The build is simple and clever; a small stepper motor is mounted in the clock just underneath the pendulum. Every 12 hours, the stepper motor moves a lever and slowly stops the pendulum over the course of a dozen or so seconds, silencing the clock movement. Twelve hours later, the motor turns again setting the pendulum in motion.

The parts count for this build is very low – basically just an ATmega88, a Darlington array to drive the stepper, and a 32.768kHz crystal. We can think of a few friends and relatives with loud clocks in their house, so we might have to build a few of these to give away.

Take a look at the demo video after the break to see how [Vinnie] stops his grandmother’s clock every night.

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Filed Under: clock hacks Tagged With: , ,

Rolling digit clock is a wonderful piece of engineering

March 1, 2012 By Leave a Comment

A long time ago and on a scrounging trip he barely remembers, [Victor] bought a quartet of digits from an old Dutch Railways clock. These antique displays used a strip of plastic coated cloth that rolls around itself with the help of a motor to display the digits 0 through 9. It’s been many years, but [Victor] finally got around to building a clock out of these single digit displays and we’re loving the results.

Because these displays were manufactured in a time when mechanical devices were king, [Victor] had to slightly modify each digit so they could display numbers with the help of a continuous rotation servo. The four servos are controlled by an Arduino – each digit changing one at a time to reduce current consumption – and a magnet and reed switch was added to each digit so the numbers could be repeatedly displayed.

Before [Victor] replaced the plastic servo gears with metal cogs, the clock was quite noisy. He’s since put each digit underneath a bell jar (actually a vase turned upside down), and we’ve got to say that [Victor] has a nice clock on his hands. Check out the videos of the clock changing digits to display the time after the break.

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Filed Under: clock hacks Tagged With: , ,