A Watch For Curiosity’s Drivers

September 9, 2012 by Brian Benchoff 37 Comments

Eight long years ago, when the Martian rovers Spirit and Opportunity were steaming towards our dusty neighbor, JPL systems engineers [Julie Townsend] and [Scott Doudrick] were stuck trying to solve a very strange problem. After the twin rovers landed, the rover drivers would have to live on Mars time. Because a Martian day lasts 24 hours, 39 minutes, rover team members would have to report to work 39 minutes later than the previous day. After much cajoling, a watchmaker by the name of [Garo Anserlian] was convinced to create a mechanical watch that lost 39 minutes per day, giving the team responsible for driving Spirit and Opportunity across the Martian desert these last eight years a temporal connection to the task at hand.

Of course, a lot happens in eight years. Now we have incredibly inexpensive, fully programmable TI Chronos watch, used by [Arko] to make a wristwatch set to Martian solar time. Instead of a master watchmaker selling the slowest wristwatch ever for hundreds of dollars, staying on Curiosity time is a simple matter of reprogramming a $50 wrist-mounted computer.

The build began by taking the default firmware for the Texas Instruments EZ430 Chronos wristwatch. In its stock configuration, the Chronos takes a 32.768khz clock signal, counts out clock pulses, and increments the number of seconds every time a counter reaches 32,768.

Because a Martian Sol is 24 hours, 39 minutes and 35 seconds of Earth time, [Arko] needed to program the seconds display to change every 1.027 Earth seconds. This meant changing the seconds every 33,668.833 clock cycles, instead of the Earth-oriented 32,768 clock cycles.

There’s one small glitch with that plan: the timer in the Chronos wristwatch can’t deal with floating point numbers, meaning [Arko] had to settle for incrementing the number of seconds ever 33,668 or 33,669 clock cycles. After a bit of math, [Arko] found using a value of 33,669 would mean his Martian time watch would only lose about 2 seconds a day, a minute after 78 Martian Sols, or 8.57 Martian minutes after one Martian year.

The build only took [Arko] five hours in front of his computer, and he doesn’t consider this to be a finished product. He plans on adding a few bells and whistles such as being able to display both Earth and Mars time. Still, an awesome build if your job description includes driving a rover across the Martian plains.

Word Clock Of A Different Nature

August 30, 2012 by Mike Szczys 8 Comments

This work clock functions in an unexpected way. With each passing second it displays a random four letter word on the right side of the display. Traditional word clocks tell the time in natural language, but this one is simply used as a learning opportunity.

[Iron Jungle] got his hands on the display for just five buck from Deal Extreme. Looks like the price has gone up two dollars but that’s still a bargain. He wanted to use all eight digits of the display, and was looking for an opportunity to control more than one i2c device at a time. He ended up rolling an EEPROM and DS1307 RTC into the design. He figured the could display 24-hour time on four of the digits, and pull a library of four-letter words off of the EEPROM to fill the rest. He grabbed a word list off of the Internet then used a Python script to remove words containing 7-segment unfriendly characters (K, M, V, W, X, Z). The final touch was to use a salvaged relay to give the clock a ticking sound. Hear it for yourself in the clip after the break.

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Wide Word-clock Takes A Modular Approach

August 28, 2012 by Mike Szczys 8 Comments

[Ishan Karve] took on the challenge of building his own word clock. This is a timepiece that displays the current time in the same syntax you would use if someone asked you what time it was. You’ll find a lot of these projects around, with one of our favorites using etched copper clad as a bezel. But [Ishan] departed for the ordinary by building a clock that is rectangular rather than square. To do so he uses a 16×8 LED matrix that is made up of small modules.

He designed a board that holds a 4×4 LED matrix and includes pin headers on each edge. This way he can arrange these 16-pixel blocks into arrays to make a larger grid. For the clock he used eight boards. These are driven by two MAX7219 chips, with an ATmega168 as the main controller and a DS1307 to keep time. Each LED is isolated by a thick layer of acrylic which as one hole for each pixel. This prevents light from bleeding over into letters that should not be illuminated. Check out the result in the clip after the break.

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A Desktop Binary Clock

August 27, 2012 by Mike Szczys No comments

This is the desktop binary clock which [Tim the Floating Wombat] recently finished building. He calls it the Obfuscating Chronoscope since it’s a bit more difficult to read than your traditional analog or digital timepieces. But the simple design looks neat and it’s a great way to learn about board layout and microcontroller code.

He started by solving a few questions about the display technique. He wanted to use as few LEDs as possible. He settled on just four, and to prevent unnecessary confusion, decided to make sure each type of display (seconds, minutes, hours) would have at least one LED on at a time. Hours are easy enough to display, but with just four bits how can minutes be shown? He uses a 5-minute resolution, always rounding up to the next division of five. This way the first bit will be illuminated on the hour.

A PIC 24F16KA102 microcontroller keeps time using its built-in RTC and a clock crystal. It puts itself into deep sleep mode after displaying the time. The black knob at the bottom is a push-button which resets the chip, waking it up just long enough show the time once again.

Volt Meter Clock Also Displays The Temperature

August 24, 2012 by Brian Benchoff 10 Comments

[IronJungle] got around to putting together every tinkerers favorite project: a clock with a strange way of displaying the time. For his clock, [Jungle] took a trio of voltmeters and turned them into a clock that displays the current hour, minute, and second on custom paper dials.

[IronJungle] connected a PIC 14M2 microcontroller to a DS1307 real time clock to keep track of the current time. As for display, [Jungle] took a trio of volt meters and wired them in to the PWM outputs on his PIC. With this, he was able to precisely control the position of the needle in the meter, and thus display the time.

In addition to displaying the time, [IronJungle] added a small temperature sensor to his build. By pressing a button below the seconds display, the clock is able to display the current temperature in Fahrenheit, Celsius, and Kelvin.

After the break you can check out a time-lapse video of [IronJungle]’s voltmeter clock going through the hours.

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Network Time Clock For A Home Media Center

August 22, 2012 by Brian Benchoff 22 Comments

[Derek] wanted a clock for his media center. A simple wish, but he had a few requirements: he didn’t need an alarm, wanted it to automatically set its time after a power outage, needed a big display, and also wanted it to look good. After shopping around [Derek] couldn’t find a clock that would fit his requirements so he decided to build one.

[Derek]’s project is called the SNTP clock. As you might expect, it gets its name from the protocol used to automatically synchronize the clock in your computer with other network time servers. The clock itself is built around an ATMega168 gathering time data from the Internet with the help of a Lantronics XPort. One inch seven segment LEDs serve as the display for the clock, and everything, from the time offset from UTC, the brightness of the display, and whether the clock displays 12 or 24-hour time is controlled by an infrared Apple remote.

A bare PCB or bundle of wires would look out of place in [Derek]’s media shelf, so he used a metal picture frame and smoked acrylic to dress up his clock. Now he’s got a beautiful and elegant clock that fits right in to his media servers and receiver.

CMOS Logic Clock Tracks 24-hour Time

August 20, 2012 by Mike Szczys 18 Comments

Here’s an IC logic project that displays 24-hour time. Planning was the name of the game for this project. [Mattosx] took the time to layout his design as a PCB in order to avoid the wiring nightmare when build with point-to-point connections.

Much of the complexity is caused by the display itself. Each of the six digits has its own binary-coded decimal chip and array of discrete resistors. Timekeeping is handled by six decade counters, two divider chips, one AND gate chip, and one OR gate chip. He chose a SOIC crystal oscillator chip as the clock signal. We’re more partial to the idea of using mains voltage as the clock signal.

[Mattosx] posted the board artwork if you’d like to etch your own 5″x8″ PCB. Just make sure you read through all of his notes as not all of the chips are oriented in the same direction.

[via Reddit]