LiquidWatch Is Dripping With Style

December 26, 2017 by Tom Nardi 13 Comments

Some of the entries for the 2017 Coin Cell Challenge have already redefined what most would have considered possible just a month ago. From starting cars to welding metal, coin cells are being pushed way outside of their comfort zone with some very clever engineering. But not every entry has to drag a coin cell kicking and screaming into a task it was never intended for; some are hoping to make their mark on the Challenge with elegance rather than brute strength.

A perfect example is the LiquidWatch by [CF]. There’s no fancy high voltage circuitry here, no wireless telemetry. For this entry, a coin cell is simply doing what it’s arguably best known for: powering a wrist watch. But it’s doing it with style.

The LiquidWatch is powered by an Arduino-compatible Atmega328 and uses two concentric rings of LEDs to display the time. Minutes and seconds are represented by the outer ring of 60 LEDs, and the 36 LEDs of the inner ring show hours. The hours ring might sound counter-intuitive with 36 positions, but the idea is to think of the ring as the hour hand of an analog watch rather than a direct representation of the hour. Having 36 LEDs for the hour allows for finer graduation than simply having one LED for each hour of the day. Plus it looks cool, so there’s that.

Square and round versions of the LiquidWatch’s are in development, with some nice production images of [CF] laser cutting the square version out of some apple wood. The wooden case and leather band give the LiquidWatch a very organic vibe which contrasts nicely with the high-tech look of the exposed PCB display. Even if you are one of the legion that are no longer inclined to wear a timepiece on their wrist, you’ve got to admit this one is pretty slick.

Whether you’re looking to break new ground or simply refine a classic, there’s still plenty of time to enter your project in the 2017 Coin Cell Challenge.

Joule Thief Steals In Favor Of Christmas

December 22, 2017 by Kristina Panos 14 Comments

A lot of things tend to get stretched during the holiday season, like shopping budgets and waistbands and patience. This year, [Chris] is stretching the limits of both the mini breadboard and the humble 1.5 V LR44 coin cell with his joule thief-driven LED mini Christmas tree.

With the push of a micro momentary, the joule thief circuit squeezes enough power from an LR44 to boot an MSP430 microcontroller, which needs 1.8 V – 3.6 V. After boot, the micro takes control of the joule thief circuit and milks it whenever the voltage falls below 3.2 V. This tree may be small in stature, but it’s feature-rich. A push of the same momentary button cycles through four different light shows, ending with a medley of all four. Be dazzled after the break.

The code for this tiny tree, which features an awesome ASCII breadboard layout and schematic, is up on GitHub. [Chris] has it listed among a few other manageable bare-metal ‘430 projects that would be great for beginners at pure C. If that sounds like you, why not give yourself the gift of learning a new language?

We’ve seen some spirited ways of lighting LEDs, but doing it with candle power takes the fruitcake.

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Welding Batteries With Batteries

December 19, 2017 by Brian McEvoy 8 Comments

Welding equipment is always expensive and bulky, right? Heavens no! [Jaromir Sukuba] is making a welder for battery tabs which can fit in a pocket and gets its power from a coin cell. It may be expensive to power compared to a mains welder, but for the sake of portability this is quite the hack. Not only that, but it uses 555 timers in the charging circuit.

His entry for the 2017 Coin Cell Challenge saps every bit of power from a coin cell and stores it up in a 100F supercapacitor bank. All that stored energy takes a long time to get into the supercapacitors but it comes out in a flash. In fact, it can take 12 hours to fully charge. For the convenience of size, we have to trade the convenience of speed. This should be a strong contestant for the Supernova and Heavy Lifting categories.

We see a quick demonstration of a successfully welded tab which shows that using coin cells to weld metal to coin cells is equally ironic and apropos. Other welders on Hackaday feature a quicker way to control your battery tab welding, safety-rich spot welding, or just go off the rails completely and use an arc welder to make a coil gun.