A solar-powered device with a small LCD screen

Low Power Challenge: LCD Solar Creatures Live On Sunlight, Sleep At Night

March 13, 2023 by Robin Kearey 8 Comments

With all those e-paper based projects doing the rounds these days, including in our Low Power Challenge, you’d almost forget that monochrome LCDs were the original ultra-low-power display. Without them, we wouldn’t have had watches, calculators and handheld games operating off button cell batteries or tiny solar panels back in the ’80s and ’90s. [Gabor] decided to build a set of gadgets with a 1990s LCD aesthetic, called LCD Solar Creatures. These cute little beasts live on nothing but solar power and provide some amusing animations on a classic seven-segment LCD screen.

The Creatures’ activity depends entirely on the amount of power that’s available to them. If their supercapacitors dip below 3.3 V, their micros enter a deep sleep state and do nothing except briefly flash an LED every now and then as a sign of life. When light hits the solar panel, the supercaps are charged up and the Creatures come to life and display a few basic stats. Once the caps hit 4.1 V, they really start their day and run a few programs, including a Game of Life-style simulation and an animation of Euclidean rhythms. Continue reading “Low Power Challenge: LCD Solar Creatures Live On Sunlight, Sleep At Night” →

A display based on magnetic viewing film

Moving Magnet Draws Stylish Shapes On Flexible Film

March 8, 2023 by Robin Kearey 2 Comments

[Moritz v. Sivers] has a knack for making his own displays, which are typically based on some obscure physical effect. Magnetic viewing films, those thin plastic sheets that change color in response to a magnetic field, are his latest area of interest, as you can see in his Magnetic Kinetic Art Display.

The overall idea of the display is similar to a kinetic sand art table, in which a ball traces out shapes in a pile of sand. In [Moritz]’s project, the magnetic viewing film is the sand, and a 2 mm diameter magnet is the ball. The magnet is moved along the film by two sets of coils embedded inside a flex PCB mounted just below the film. One set of coils, on the top layer of the PCB, moves the magnet in the x direction, while a second set on the bottom layer moves it in the y direction.

A flex PCB with coils on both sides — The flex PCB is small, but carries lots of windings

[Moritz] used a flex PCB not because it had to be bendy, but to keep the two sets of coils as close together in the z direction as possible. This helps to avoid a big difference in strength between the two directions. To drive the coils, he used a pair of TB6612FNG stepper motor drivers, controlled by a Wemos D1 Mini.

The housing was 3D printed mostly from PLA, but with a few bits done in PETG. This was for structural rigidity as well as thermal performance — the coils can carry up to two amps and get pretty warm as a result.

The video, embedded below, shows some of the shapes that can be drawn: squares, spirals and even digits to turn the display into a clock. [Moritz] got the PCB coil idea from a project by [bobricius], and cleverly extended it into a useful product. It’s not the first time [Moritz] used magnetic viewing film to make a clock, either.

Continue reading “Moving Magnet Draws Stylish Shapes On Flexible Film” →

A yellow computer with a black keyboard and a small monochrome LCD screen

Low Power Challenge: The PotatoP Runs Lisp For Months Without Recharging

March 6, 2023 by Robin Kearey 54 Comments

A common complaint among laptop users is that while battery technology has vastly improved over the past decades, a simulltaneous shrink in form factors has meant that a typical laptop today doesn’t last much longer on a battery charge than one from the early 2000s. But it doesn’t have to be that way, as [Andreas Eriksen] demonstrates with his entry for the Low Power Challenge. The PotatoP is a portable computer that should be able to run for about two years on a single battery charge, and can be topped up through an integrated solar panel.

Granted, it doesn’t have the processing power of even the cheapest laptop you can buy today, but it’s perfectly fine for [Andreas]’s use case. He’s a Lisp hacker, and a Sparkfun RedBoard Artemis can run uLisp just fine on its 48 MHz Cortex-M4F processor. The operating environment is very basic though, even requiring [Andreas] to write his own text editor, called Typo, to give him editing luxuries like backspace functionality and a movable cursor.

The Artemis board is very power-efficient by itself – typical power consumption is less than 1 mA. [Andreas] added a simple monochrome black-and-white LCD screen capable of displaying 53 columns of text, plus an SD card reader for data storage, and designed a sleek 3D-printed case to hold everything together. When running a typical piece of code, the entire system uses around 2.5 mA, which translates to about 125 days of continuous run-time on the beefy 12000 mAh lithium battery. Add a bit of solar power, plus a more realistic eight-hour working day, and the two year runtime estimated by [Andreas] appears entirely reasonable.

This has to be one of the most power-efficient portables we’ve ever seen, and one running Lisp at that. Despite its age, Lisp keeps popping up in interesting custom computers like the Lisperati1000 cyberdeck and The Lisp Badge.

Continue reading “Low Power Challenge: The PotatoP Runs Lisp For Months Without Recharging” →

A man riding a motorized wooden sled up a snowy hill

Never Walk Uphill Again With This Motorized Sled

March 2, 2023 by Robin Kearey 11 Comments

If you grew up in a snowy climate, chances are you’ve ridden a sled or toboggan when you were young. The downhill part of sledding is great fun, but dragging the thing back up gets boring quickly. [Luis Marx] had been dreaming of sledding uphill since he was a child, and decided to make his dream come true by building himself a motorized sled (video, in German, embedded below).

The sled is powered by two DC electric motors driving a continuous track, like a rudimentary snowmobile. The motors were originally designed for electric bikes, and can develop 30 newton-meters of torque each. [Luis] designed and 3D-printed a custom set of drive wheels to link the track to the bike motors. Two motor controllers enable basic speed control, while a beefy battery carries enough juice for multiple trips up and down a slope.

The motorized track is mounted on a clever frame that can swing up or down and is held in place by two spring-loaded pins. This way, you can simply lift the system off the snow when you’re ready to slide downhil, and swing it down again when you want the sled to do the pulling.

With winter nearing its end, the snow near [Luis]’s home in southern Germany was too soft to get much traction, but subsequent tests in a ski resort up in the Alps showed the system working perfectly. It even had enough traction to pull a second sled behind it. Perhaps some proper suspension could make it go faster on the downhill run, too.

Continue reading “Never Walk Uphill Again With This Motorized Sled” →

An electromechanical clock based on sliding frames

Watch Time Slide By With This Electromechanical Clock

February 27, 2023 by Robin Kearey 13 Comments

Back in the 18th century, clockmakers were held in high esteem, as turning pieces of metal and wire into working timepieces must have seemed like magic at the time. The advent of mass production made their profession largely obsolete, but today there are several hardware hackers whom you could consider modern heirs of the craft. [Hans Andersson] is one of them, and has made a name for himself with an impressive portfolio of electromechanical clocks. His latest work, called the Time Slider, is every bit as captivating as his previous work.

The mechanical display is almost entirely made of 3D printed components. Four flat pieces of red PLA form a basic 88:88 indicator, onto which the correct time is displayed by sliding frames that black out certain pixels. Those frames are moved up and down by a rack-and-pinion system driven by stepper motors. Evertyhing is controlled by an Arduino Mega, acoompanied by a DS3231 RTC and eight ULN2003-based stepper motor drivers.

[Hans] wrote a detailed assembly guide to go along with the STL files and Arduino code, so it should be easy make your own Time Slider if you have a decent supply of PLA filament. The display takes about ten seconds to update, but the process has certain hypnotic quality to it, helped by the mechanical whirring of the stepper motors in the background. Especially the hourly change of three or four digits at once is mesmerizing, as you can see in the video embedded below.

Time Slider is the latest in [Hans]’s long line of mechanical clocks, which includes the Time Twister series that evolved from a clever Lego-based design to a neat 3D-printed model. The rack-and-pinion system can also be used to make a compact linear clock.

Continue reading “Watch Time Slide By With This Electromechanical Clock” →

A clock with an e-paper display in a 3D-printed case

Low Power Challenge: E-Paper Shelf Label Becomes Ultra-Frugal Clock

February 24, 2023 by Robin Kearey 12 Comments

Over the past two decades, e-paper has evolved from an exotic and expensive display technology to something cheap enough to be used for supermarket price tags. While such electronic shelf labels are now easy to find, actually re-using them is often tricky due to a lack of documentation. Luckily, [Aaron Christophel] has managed to reverse engineer many types of shelf labels, and he’s demonstrated the results by turning one into an ultra-low-power clock called Triink. It’s based on a 128×296 pixel e-ink display paired with an nRF52832 BlueTooth Low-Energy SoC and uses just 65 micro-amperes on average: low enough to keep it running for more than a year on a single battery charge.

A PCB for an e-ink clock — Power on the left, e-ink on the right: the custom PCB is clever and compact, too

The clock is housed in an enclosure that’s simple but effective: a 3D-printed triangular prism with a slot for the screen and space for the 18650 lithium battery. One side can be opened to access the internal components, although that’s really only needed to charge the battery. You can see how cleverly everything snaps together in the video embedded below. Continue reading “Low Power Challenge: E-Paper Shelf Label Becomes Ultra-Frugal Clock” →

Low Power Challenge: Weather Station Runs For Months Thanks To E-Ink Display

February 20, 2023 by Robin Kearey 2 Comments

Having a device in your living room that shows weather information is convenient, and building one of those is a great project if you enjoy tinkering with microcontrollers and environmental sensors. It’s also a great way to learn about low-power design, as [x-labz] demonstrated with their e-ink weather station which works for no less than 60 days on a single battery charge. It has a clear display that shows the local temperature and humidity, as well as the weather forecast for the day.

The display is a 4.2″ e-paper module with a resolution of 400 x 300 pixels. It uses just 26 mW of power for a few seconds while it updates its image, and basically zero watts when showing a static picture. It’s driven by a tiny ESP32C3 processor board, which downloads the weather forecast from weatherapi.com every two hours. The indoor climate is measured by an SHT-21 temperature and humidity sensor mounted behind the display, while the outdoor data is gathered by a WiFi-connected sensor installed on [x-labz]’s balcony.

The key to achieving low power usage here is to keep the ESP32 in sleep mode as much as possible. The CPU briefly wakes up once every five minutes to read out the indoor sensor and once every fifteen minutes to gather data from outside, using the relatively power-hungry WiFi module.

To further reduce power consumption, the CPU core is driven at the lowest possible clock speed at all times: 10 MHz when reading the indoor sensor, and 80 MHz when using the WiFi connection. All of this helps ensure that just one 600 mAh lithium battery can keep everything running for those 60 days.

E-ink displays are perfect for text and simple graphics that don’t change too often, which is why they’re very popular in weather stations. With a bit of tweaking though, LCDs can also be optimized for low power.