Inverse Kinematics Robot Arm Magna-Doodles The Time For You

Following a surge of creativity fueled by the current lockdown, [Diglo] writes in with his tabletop clock driven by a robotic arm drawing on a Magna Doodle tablet. And if you have one of those still lying around with some old toys and don’t mind cannibalizing it for the project, you too can follow along the source files to build your own.

The clock works by exploiting the principle that Magna Doodle tablets work by being drawn on with a magnetic stylus. That way, to draw on one of them you don’t need to add a point of articulation to bring the pen up and down, [Diglo] simply attached a controllable electromagnet to the end of a two-dimensional SCARA arm. In total, the whole build uses three stepper motors, two to control the movement of the arm, and one on the back of the tablet to sweep a magnetic bar which “erases” it.

This clock is similar to another we’ve featured a few years ago, which also used a Magna Doodle, but greatly improves on the idea. If a Magna Doodle seems too childish to build a magnetic clock however, there’s always ferrofluidic displays to try to dip your fingers into, but we really think you should watch this one in action after the break first.

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CalClock Keeps You Tied To The Mast

Now that most of what we do revolves around our phones and/or the internet, it’s nearly impossible to take a short break from work to check the ol’ calendar without being lured by the sirens on the shore of social media. Well, [samvanhook] was tired of being drawn in when all he really needs is a vague idea of what’s coming up for him in the next 12 hours. Enter the CalClock.

Thanks to color-coded segments, [sam] can tell at a glance if he has something coming up soon in Google Calendar, or if he can dive back into work. When nothing is scheduled, the segments are simply unlit.

We love the mid-century minimal look and craftsmanship of CalClock. This beauty runs on a Raspi Zero W, which fetches the 411 through the gooCal API and lights up the appropriate NeoPixels arrayed behind standard clock movement-driven hands.  [sam] could have diffused the NeoPixels with a single sheet of acrylic, but he went the extra mile to route and sand little acrylic ice cubes for all 24 segments.

Want more control of your day? [sam] took the time to upload both the clock face model and the code so you can. If you need help just getting started each day, check out this calendar-polling Raspi alarm clock.

Saturday Clock: An 0.000011574Hz ATtiny85 Clock

In these times when we try to squeeze out extra clock cycles by adding more cores to our CPUs and by enlisting the aid of GPUs, [Ido Gendel] thought it would be fun to go in the exact opposite direction, supply a clock to the ATtiny85 that cycles only once per day, or at 0.000011574Hz. What application could this have? Well, if he could do it in seven instructions or less, how about turning on an LED at sunset Friday evening, to indicate the start of the Jewish Shabbat (Saturday), and turn it off again at sunset Saturday evening.

Notice the subtlety. A clock that cycles once per day means you can execute at most one instruction per day. Luckily on AVR microcontrollers, the instructions he needed can execute in just one cycle. That of course meant diving down into assembly code. [Ido] wasn’t an assembly wizard, so to find the instructions, he compiled C code and examined the resulting assembly until he found what he needed. One instruction turns on the LED and the instruction immediately following turns it off again, which normally would make it happen too fast for the human eye to register. But the instruction to turn it on runs on Friday evening and the very next instruction, the one that turns it off, doesn’t run until Saturday evening. Do you feel like you’re in a science fiction story watching time slowed down? Freaky. A few NOPs and the jump for the loop take up the remaining five cycles for the week.

For the source of the clock he chose to use an LDR to detect when the light level dropped at the end of the day. The problem he immediately ran into was that clouds, bird shadows, and so on, also cause drops in the light level. The solution he found was to widen the light and dark range by adding a TLV3702 push-pull output comparator and some resistors. [Ido] gives a detailed explanation of the circuit in the video after the break.

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Exquisitely Crafted Nixie Tube Weatherclock

The Weatherclock is more than just a clock sporting Nixie tubes and neon lamps. There is even more to it than the wonderful workmanship and the big, beautiful pictures in the build log. [Bradley]’s Weatherclock is not only internet-connected, it automatically looks up local weather and sets the backlights of the numbers to reflect current weather conditions. For example, green for roughly room temperature, blue for cold, red for warm, flashing blue for rain, flashing white for lightning, scrolling white for fog and ice, and so on.

neonixieclock_02The enclosure is custom-made and the sockets for the tubes are seated in a laser-cut plastic frame. While seating the sockets, [Bradley] noticed that an Adafruit Neopixel RGB LED breakout board fit perfectly between the tube leads. By seating one Neopixel behind each Nixie indicator, each number could have a programmable backlight that just happened to look fabulous.

Witpreboxh an Electric Imp board used for WiFi the capabilities of the Weatherclock were rounded out on the inside. On the outside, a custom enclosure ties it all together. [Bradley] says his family had gotten so used to having the Weatherclock show them the outside conditions that they really missed it when it was down for maintenance or work – which shouldn’t happen much anymore as the project is pretty much complete.

It’s interesting to see new features in Nixie clocks. Nixie tubes have such enduring appeal that using them alone has its own charm, and at least one dedicated craftsman actually makes new ones from scratch.