Wiring Up A Lot Of LED Segment Displays

September 21, 2012 by Mike Szczys 16 Comments

One look at this display and you know there’s a whole lot of pins that need to be wired up. Now look at what those display modules are mounted on. That’s right, [Kemley] is using point-to-point soldering to rig up this big display. It sports four sixteen segment modules on top for alpha-numeric information, and eight large seven segment modules for displaying numbers only.

We’re not certain as to how the electronics are arranged. When talking about the 16-segment modules he mentions that all four are in parallel with NPN transistors to switch the common anode of each. That’s easy enough to understand. But when you get a look at the transistor board you’ll see 24 of them in use. He’s included a 150 ohm resistor on the collector of each transistor. It must be set up to only allow one segment of each group to switch on at a time? We’d guess that each segment is divided into two (upper and lower pins are multiplexed separately), which would explain the double set of transistors. As for date and time, an Arduino board monitors a DS1307 RTC and manages the scanning of the display.

Incredible Fabrication Process Makes This Word Clock Stand Out

September 17, 2012 by Mike Szczys 13 Comments

From the look of it his is just another Word Clock, right? From the outside maybe. But if you take a look at the build photos this a good example of extreme fabrication.The design uses a five-layer lamination of glass bezel, vinyl lettering, diffuser, mounting plate, and back panel. The mounting and lettering layers were labor intensive, but are also the reason for the gorgeous finished look.

The bezel consists of black adhesive foil applied to the back of the glass faceplate. The letters were cut out using a vinyl cutter, and the lamination process happened in a pool of water. This technique helps to ensure that no fine particles end up between the glass and the foil.

The wooden mounting bracket was ordered from a local kitchen cabinet fabricator. It’s MDF that is 17.7″ and has been edge wrapped in glossy white PVC. Once it arrived, [Muris] started drilling the 248 holes and their counter sinks. This is on the front side of the layer and when sprayed with silver paint the countsinks act as reflectors. On the back side he milled groves to accept PCB strips to host the LEDs as well as the breakout boards that hold the MAX7219 drivers.

Don’t miss the video clip after the break that shows off the final product.

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An Ice Tube Clock For The TI Launchpad

September 17, 2012 by Brian Benchoff 8 Comments

Because Nixies, Decatrons, and VFD tubes really are that cool, [cubeberg] over on the 43oh forums designed an IV-18 clock for the TI Launchpad.

Like adafruit’s Ice Tube clock, [cubeberg]’s project uses a surplus Russian IV-18 VFD tube conveniently sourced on eBay. On the board, there are three buttons for changing the time and setting the alarm along with a MAX6921 VFD tube driver and a small switching regulator to boost the 5 Volts on the Launchpad to the 50 V the tube requires.

There was a little bit of space left on [cubeberg]’s PCB design, and he filled that space with a header for a buzzer and a temperature sensor. Right now, the code doesn’t support an alarm function and he’s still waiting on a few components to finish off the thermometer portion of the board, but it’s still the makings of a very nice clock.

If you’d like to grab your own Launchpad ice tube clock, [bluehash] is organizing a group buy for 430h forum members. If they can get 15 pieces built, the clock will cost less than $5/unit. Very cool, and very cheap when you consider TI is practically giving Launchpads away.

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.