Simple Timer Evolves Into Custom Kid’s Watch

February 27, 2019 by 10 Comments

Sporting a new wristwatch to school for the first time is a great moment in a kid’s life. When it’s a custom digital-analog watch made by your dad, it’s another thing altogether.

As [Chris O’Riley] relates, the watch he built for his son [Vlad] started out as a simple timer for daily toothbrushing, a chore to which any busy lad pays short shrift unless given the proper incentive. That morphed into an idea for a general purpose analog timepiece with LEDs taking the place of hands. [Chris] decided that five-minute resolution was enough for a nine-year-old, which greatly reduced the number of LEDs needed. An ATtiny841 tells a 28-channel I2C driver which LEDs to light up, and an RTC chip keeps [Vlad] on schedule. The beautiful PCB lives inside a CNC machined aluminum case; we actually commented to [Chris] that the acrylic prototype looked great by itself, but [Vlad] wanted metal. The watch has no external buttons; rather, the slightly flexible polycarbonate crystal bears against a PCB-mounted pushbutton to control functions.

With a snappy wristband, [Vlad] will be rolling fancy on the schoolyard. It’s a great looking piece that needed a wide range of skills to execute, as all watches do. Check out some other watch builds, like this lovely pure analog, another digital-analog hybrid, or this pocket watch that packs an Enigma machine inside.

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Casio Watch Gets A MEMS Oscillator Upgrade

February 20, 2019 by 22 Comments

We’ve got to admit to being a bit of a Casio G-Shock watch geek. The big, chunky watches were every day carry items that survived everything we dished out, right up until the smartphone made wearing one seem redundant. But others continue to use and abuse G-Shocks, and some brave souls even hack them.

Replacing the standard quartz crystal with a temperature-compensated MEMS oscillator is one hack that [Alex] tried, and it appears to have worked out well. His project write-up doesn’t specify which MEMS oscillator was used, but we suspect it’s the SiT1552 TCXO. With its extremely small size, stability over a wide range of temperatures, and ultra-low power requirements, the chip is a natural choice to upgrade the stock 32.768-kHz quartz crystal of the watch. Trouble is, the tiny 1.5 mm x 0.8 mm chip-scale package (CSP) device presented some handling problems. After overcooking a few chips in the reflow oven, [Alex] was able to get one mounted to a tiny breakout board, which went into the space formerly occupied by the watch’s quartz crystal. He stole power for the TCXO from a decoupling capacitor, sealed the watch back up, and it’s back in service with better stability and longer battery life to boot. The video below shows the TCXO undergoing tests alongside the original quartz crystal and a comparatively huge DS3231 RTC module, just for fun.

[Alex]’s MEMS transplant seems a long way to go and a lot of fussy work for marginal gains, but who are we to judge? And it does make the watch susceptible to punking with a little helium, which might make things interesting.

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Linux Fu: Easier File Watching

January 31, 2019 by 22 Comments

In an earlier installment of Linux Fu, I mentioned how you can use inotifywait to efficiently watch for file system changes. The comments had a lot of alternative ways to do the same job, which is great. But there was one very easy-to-use tool that didn’t show up, so I wanted to talk about it. That tool is entr. It isn’t as versatile, but it is easy to use and covers a lot of common use cases where you want some action to occur when a file changes.

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This Satellite Finder Can Watch Amateur TV

January 30, 2019 by 28 Comments

Setting up satellite dishes can be a finicky business. To aid in the alignment of these precision antennas, satellite finders are often used which can display audio and video feeds from the satellite while also providing signal strength readouts for accurate adjustment. However, these devices can also be used in interesting ways for more terrestrial purposes (Youtube link).

Using the DMYCO V8 Finder, [Corrosive] demonstrates how to set up the device to pick up terrestrial amateur streams. Satellite reception typically involves the use of a low-noise block downconverter, which downconverts the high frequency satellite signal into a lower intermediate frequency. Operating at the 1.2GHz amateur band, this isn’t necessary, so the device is configured to use an LNB frequency of 10000, and the channel frequency entered as a multiple of ten higher. In this case, [Corrosive] is tuning in an amateur channel on 1254 MHz, which is entered as 11254 MHz to account for the absent LNB.

[Corrosive] points out that, when using an F-connector to BNC adapter with this setup, it’s important to choose one that does not short the center pin to the shield, as this will damage the unit. This is due to it being designed to power LNBs through the F-connector for satellite operation.

By simply reconfiguring a satellite finder with a basic scanner antenna, it’s possible to create a useful amateur television receiver. If you’re wondering how to transmit, [Corrosive] has that covered, too. Video after the break.

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Silent Stepper Drive Makes A Nicer Watch Winder

January 24, 2019 by 12 Comments

Mechanical watches are great in that they never need batteries, but they are simultaneously less than great in that they will lose time if not worn or otherwise regularly agitated. The ridiculous solution to this is the watch winder, which automatically rotates your mechanical watches for you, while you’re not wearing them. This is probably the item you’ll miss the least once the apocalypse hits. [Kristopher] wanted a nice quiet watch winder for his bedside table, but existing solutions were either too loud or too expensive. As is often the case, hacking ensued.

[Kristopher] had decided that starting from scratch was too much hassle. The cheaper watch winders on the market had acceptable quality enclosures, but were simply too loud. [Kristopher] sourced a $40 unit from Amazon, and proceeded to gut the drivetrain. This was replaced with a Sparkfun stepper motor and a Trinamic SilentStepStick – an advanced stepper motor driver that uses several techniques to reduce noise during operation.

An Arduino Nano was substituted as the brains of the operation, communicating with the stepper driver and allowing the winder to be configured for different wind rates. [Kristopher] reports that the device operates near-silently, and the total cost came in well below that of a high-end luxury winder.

Mechanical watches don’t always get a lot of attention these days, but we’ve seen one built from the ground up before. As always, with tips – send ’em if you got ’em.

The Clementine Spacecraft

Preventing Embedded Fails With Watchdogs

January 12, 2019 by 24 Comments

Watchdog timers are an often overlooked feature of microcontrollers. They function as failsafes to reset the device in case of a software failure. If your code somehow ends up in an infinite loop, the watchdog will trigger. This is a necessity for safety critical devices. If the firmware in a pacemaker or a aircraft’s avionics system gets stuck, it isn’t going to end well.

In this oldie-but-goodie, [Jack Ganssle] provides us with a great write up on watchdog timers. This tells the story of a failed Clementine spacecraft mission that could have been saved by a watchdog, and elaborates on the design and implementation of watchdog techniques.

If you’re designing a device that needs to be able to handle unexpected failures, this article is definitely worth a read. [Jack] explains a lot of traps of using these devices, including why internal watchdogs can’t always be trusted and what features make for a great watchdog.

Thanks to [Jan] for the tip!

A Smartwatch You Can Easily Build Yourself

January 1, 2019 by 16 Comments

The concept of a smartwatch was thrown around for a long time before the technology truly came to fruition. Through the pursuit of miniaturisation, modern smartwatches are sleek, compact, and remarkably capable for their size. Companies such as Apple and Samsung throw serious money into research and development, but that doesn’t mean you can’t create something of your own. [Electronoobs] has done just that, with this Arduino-based smartwatch build.

The brain of the watch is that hacker staple, the venerable ATmega328, most well known for its use in the Arduino Uno and Nano platforms. An FTDI module is used for USB communication, making programming the board a snap. Bluetooth communication is handled by another pre-built module, and a smartphone app called Notiduino handles passing notifications over to the watch.

This is a build that doesn’t do anything crazy or difficult to understand, but simply combines useful parts in a very neat and tidy way. The watch is impressively thin and compact for a DIY build, and has a host of useful functions without going overboard.

We’ve seen other DIY builds in this space, too – such as this ESP8266-based smartwatch. Video after the break.

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