Jewelry making offers many opportunities for the electronics tinkerer, and on these pages we’ve seen some eye-catching creations using LEDs to great effect. They all have the same limitation though, it’s difficult to power something that tiny without a cumbersome battery. In seeking to solve that problem there have been a variety of inventive solutions tried, but they haven’t matched the approach of [Lloyd Konneker] who has turned the whole premise of most electronic jewelry on its head.
Instead of LEDs, the party trick of his earring is an electric motor that makes it spin, and instead of giving out light it takes it in as solar power. The motor is a pager alert device, the solar cells are repurposed photodiodes, and the power is stored in a capacitor until there is enough to drive the motor, at which point a MOSFET is triggered to do the work. It’s all made possible by a Texas Instruments TPS3839 supply voltage supervisor chip, and it works well enough to turn from time to time in bright sunlight. The prototype uses a conventional PCB, but a better version is in the works with a flexible board.
His write-up should be of interest to anyone with a need to learn about micropower circuits, as it goes into significant detail on their tuning and operation. Last year’s Hackaday Prize had an entire section devoted to energy harvesting which is well worth searching the site for, a typical example was this solar powered microcontroller board.
The Tiny Solar Energy Module (TSEM) by [Jasper Sikken] is not only physically tiny at one-inch square, but it is all about gathering tiny amounts of solar energy — amounts too small to be useful in a conventional sense — and getting meaningful work done, like charging a battery for later use. Elements that make this board easy to integrate into other projects include castellated vias, 1.8 V and 3.3 V regulated outputs that are active when the connected battery has a useful charge, and a low battery warning that informs the user of impending shutdown when the battery runs low. The two surface-mount solar cells included on the tiny board are capable of harvesting even indoor light, but the board also has connection points for using larger external solar cells if needed.
The board shows excellent workmanship and thoughtful features; it was one of the twenty Power Harvesting Challenge finalists chosen to head to the final round of The Hackaday Prize. The Hackaday Prize is still underway, with the Human-Computer Interface Challenge running until August 27th. That will be followed by the Musical Instrument Challenge before the finals spin up. If you haven’t started yet, there’s still time to make your mark. All you need is a documented idea, so start your entry today.
[Mile]’s PTPM Energy Scavenger takes the scavenging idea seriously and is designed to gather not only solar power but also energy from temperature differentials, vibrations, and magnetic induction. The idea is to make wireless sensor nodes that can be self-powered and require minimal maintenance. There’s more to the idea than simply doing away with batteries; if the devices are rugged and don’t need maintenance, they can be installed in locations that would otherwise be impractical or awkward. [Mile] says that goal is to reduce the most costly part of any supply chain: human labor.
The prototype is working well with solar energy and supercapacitors for energy storage, but [Mile] sees potential in harvesting other sources, such as piezoelectric energy by mounting the units to active machinery. With a selectable output voltage, optional battery for longer-term storage, and a reference design complete with enclosure, the PPTM Energy Scavenger aims to provide a robust power solution for wireless sensor platforms.
Every scrap of power is precious when it comes to power harvesting, and working with such designs usually means getting cozy with a microcontroller’s low-power tricks and sleep modes. But in the case of the Ultra Low Power Energy Harvester design by [bobricius], the attached microcontroller doesn’t need to worry about managing power at all — as long as it can finish its job fast enough.
The idea is to use solar energy to fill a capacitor, then turn on the microcontroller and let it run normally until the power runs out. As a result, a microcontroller may only have a runtime in the range of dozens of microseconds, but that’s just fine if it’s enough time to, for example, read a sensor and transmit a packet. In early tests, [bobricius] was able to reliably transmit a 16-bit value wirelessly every 30 minutes using a small array of photodiodes as the power supply. That’s the other interesting thing; [bobricius] uses an array of BPW34 photodiodes to gather solar power. The datasheet describes them as silicon photodiodes, but they can be effectively used as tiny plastic-enclosed solar cells. They are readily available and can be arranged in a variety of configurations, while also being fairly durable.
Charging a capacitor then running a load for a short amount of time is one of the simplest ways to manage solar energy, and it requires no unusual components or fancy charge controllers. As long as the load doesn’t mind a short runtime, it can be an effective way to turn even indoor light into a figuratively free power source.
The SPINES (Self-Powered IoT Node for Environmental Sensing) Mote is a wireless IoT environmental sensor, but don’t let the neatly packed single PCB fool you into thinking it’s not hackable. [Macro Yau] specifically designed SPINES to be highly modular in order to make designing an energy harvesting sensor node an easier task. The way [Macro] sees it, there are two big hurdles to development: one is the energy harvesting itself, and the other is the software required to manage the use of every precious joule of that harvested energy.
[Macro] designed the single board SPINES Mote in a way that the energy harvesting portion can be used independently, and easily integrated into other designs. In addition, an Arduino library is being developed to make it easy for the power management to be done behind the scenes, allowing a developer to concentrate on the application itself. A solar-powered wireless sensor node is one thing, but helping people get their ideas up and running faster in the process is wonderful to see.
This half-inch square ultra-low power energy harvesting LiPo cell charger by [Kris Winer] uses a low voltage solar panel to top up a small lithium-polymer cell, which together can be used as the sole power source for projects. It’s handy enough that [Kris] uses them for his own projects and offers them for sale to fellow hackers. It’s also his entry into the Power Harvesting Challenge of the Hackaday Prize.
The board is essentially a breakout board for the Texas Instrument BQ25504, configured to charge and maintain a single lithium-polymer cell. The BQ25504 is an integrated part that takes care of most of the heavy lifting and has nifty features like battery health monitoring and undervoltage protection. [Kris] has been using the board along with a small 2.2 Volt solar panel and a 150 mAh LiPo cell to power another project of his: the SensorTile environmental data logger.
It’s a practical and useful way to test things; he says that an average of 6 hours of direct sunlight daily is just enough to keep the 1.8 mA SensorTile running indefinitely. These are small amounts of power, to be sure, but it’s free and self-sustaining which is just what a remote sensing unit needs.
We are smack-dab in the middle of our Energy Harvesting Challenge, and [wasimashu] might have this one in the palm of his hand. Imagine a compact flashlight that doesn’t need batteries or bulbs. You’d buy a 10-pack and stash them everywhere, right? If there’s nothing that will leak or break or expire in your lifetime, why not have a bunch of them around?
Infinity uses nothing but body heat to power a single white LED. It only needs a five-degree temperature difference between the air and your hand to work, so it should be good in pretty much any environment. While it certainly won’t be the brightest light in your collection, it’s a whole lot better than darkness. Someday, it might be the only light around that works.
As you might expect, there’s a Peltier unit involved. Two of them, actually. Both are embedded flush on opposite sides of the hollow aluminum flashlight body, which acts as a heat sink and allows air to pass through. After trying to boost the output voltage with a homemade feedback oscillator and hand-wound transformers, [wasimashu] settled on a unipolar boost converter to reach the 5V needed to power the LED.
[wasimashu] has made it his personal mission to help humanity through science. We’d say that Infinity puts him well on the way, and can’t wait to see what he does next.