Antique Pocket Watch Project Updates Antique Pocket Watch

Here at Hackaday we have a bit of a preoccupation with timepieces. Maybe it’s the deeply personal connection to an object you wear on your body, or the need for ultimate reliability. Perhaps it’s just a fascination with the notion of time itself. Whatever the case, we don’t seem to be alone as there is a constant stream of time-related projects coming through our virtual doors. For this article we’ve unearthed the LED Pocketwatch 1.0 by [Dr. Paul Pounds] from way back in 2009 (ironically via a post about a wristwatch from last year!). Fortunately for us the Internet Archive has saved this heirloom nouveau from the internet dustbin so we can appreciate the craftsmanship involved in [Dr. Pounds]’ work.

Check out the wonderful, spiral routing!

My how far we’ve come; a decade after this project was posted a hacker might choose to 3d print a case for a new wearable, but in 2009 that would have been an entire project by itself! [Dr. Pounds] chose to use the casing from an antique Elgin pocket watch. Even through the mists of a grainy demo video we can imagine how soft the well-worn casing must be from heavy use. This particular unit was chosen because it was a hefty 50mm in diameter, leaving plenty of room inside for a 44mm double sided PCBA with 133 0603 LEDs (60 seconds, 60 minutes, 12 hours), a PIC 16F946, an ERM, and a 110mAh LiPo. But what really sets the LED Pocketwatch 1.0 apart is the user interface.

The ERM is attached directly to the rear of the case in order to best conduct vibration to the outside world. For maximum authenticity it blips on the second, to give a sense that the digital watch is mechanically ticking like the original. The original pocket watch was designed with a closing lid which is released when the stem is pressed. [Dr. Pounds] integrated a button and encoder with the end of the stem (on the PCBA) so the device can be aware of this interaction; on lid open it wakes the device to display the time on the LEDs. The real pièce de résistance is that he also integrated a minuscule rotary encoder, so when the stem is pressed you can rotate it to set the time. It’s all quite elegantly integrated and imminently usable.

At this point we’d love to link to sources, detailed drawings, or CAD files, but unfortunately we haven’t found any. If this has you inspired check out some of the other pocket watches we’ve posted about in the past. If you’re interested in a live demo of the LED Pocketwatch 1.0, check out the original video after the break.

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Many Ways To Drive A Small Motor

Tiny motors used for haptic feedback and vibration come in a variety of shapes and sizes. The most familiar is the “eccentric rotating mass” (ERM) variety which just spins an imbalanced weight on a small motor and comes packaged in two form factors. The classic is the pager “pager motor” which just looks like a tiny, adorable motor and the squat cylindrical “pancake style”. ERMs are simple to use but provide imprecise response when compared to their new-age cousin the “linear resonant actuator”. Unlike the motor in an ERM, LRAs are typically an enclosed mass on a spring placed near a coil which pushes the mass back and forth. The name LRA might not be familiar but Apple’s branded implementation, the Taptic Engine, might be a little more recognisable.

[Precision Microdrives] is a vendor of these sorts of devices who happens to have a pleasantly approachable set of application notes covering any conceivable related topic. A great place to start is this primer on ways to drive motors with constant voltage in a battery powered environment. It starts with the most simple option (a voltage divider, duh) and works through a few other options through using an LDO or controller.

If you’re thinking about adding haptics to a project and are wondering what kind of actuator to use (see: the top of this post) AB-028 is a great resource. It has a thorough discussion on the different options available and considerations for mounting location, PCB attachment, drive modes, and more. Digging around their site yields some other interesting documents too like this one on mounting to fabric and other flexible surfaces. Or this one on choosing PWM frequencies.