[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.
What does your benchtop power supply have that [Pete Marchetto]’s does not? Answer: an extension cord draped across the floor. How often have you said to yourself, “I just need to energize this doodad for a couple seconds,” then you start daisy chaining every battery in the junk drawer to reach the necessary voltage? It is not uncommon to see battery packs with a single voltage output, but [Pete] could not find an adjustable one, so he built his own and put it on Tindie.
Presumably, the internals are not going to surprise anyone: an 18650 battery, charging circuit, a voltage converter, display, adjustment knob, and a dedicated USB charging port. The complexity is not what intrigues us, it is the fact that we do not see more of them and still wind up taping nine-volt batteries together. [Editor’s note: we use one made from an old laptop battery.]
This should not replace your benchtop power supply, it does not have the bells and whistles, like current regulation, but a mobile source of arbitrary voltage does most of the job most of the time. And it’s what this build hasn’t got (a cord) that makes it most useful.
Arguably the biggest hurdle to implanted electronics is in the battery. A modern mobile phone can run for a day or two without a charge, but that only needs to fit into a pocket and were its battery to enter a dangerous state it can be quickly removed from the pocket. Implantable electronics are not so easy to toss on the floor. If the danger of explosion or poison isn’t enough, batteries for implantables and ingestibles are just too big.
Researchers at MIT are working on a new technology which could move the power source outside of the body and use a wireless power transfer system to energize things inside the body. RFID implants are already tried and tested, but they also seem to be the precursor to this technology. The new implants receive multiple signals from an array of antennas, but it is not until a couple of the antennas peak simultaneously that the device can harvest enough power to activate. With a handful of antennas all supplying power, this happens regularly enough to power a device 0.1m below the skin while the antenna array is 1m from the patient. Multiple implants can use those radio waves at the same time.
The limitations of these devices will become apparent, but they could be used for releasing drugs at prescribed times, sensing body chemistry, or giving signals to the body. At this point, just being able to get the devices to turn on so far under flesh is pretty amazing.
Recently, we asked what you thought of the future of implanted technology and the comment section of that article is a treasure trove of opinions. Maybe this changes your mind or solidifies your opinion.
Thanks to microcontrollers, RTC modules, and a plethora of cheap and interesting display options, digital clock projects have become pretty easy. Choose to base a clock build around a chip sporting a date code from the late 70s, though, and your build is bound to be more than run-of-the-mill.
This is the boat that [Fran Blanche] finds herself in with one of her ongoing projects. The chip in question is a Mostek MK50250 digital alarm clock chip, and her first hurdle was find a way to run the clock on 50 Hertz with North American 60-Hertz power. The reason for this is a lesson in the compromises engineers sometimes have to make during the design process, and how that sometimes leads to false assumptions. It seems that the Mostek designers assumed that a 24-hour display would only ever be needed in locales where the line frequency is 50 Hz. [Fran], however, wants military time at 60 Hz, so she came up with a circuit to fool the chip. It uses a 4017 decade counter to divide the 60-Hz signal by 10, and uses the 6-Hz output to turn on a transistor that pulls the 60-Hz output low for one pulse. The result is one dropped pulse out of every six, which gives the Mostek the 50-Hz signal it needs. Sure, the pulse chain is asymmetric, but the chip won’t care, and [Fran] gets the clock she wants. Pretty clever.
You might be reading this six minutes early. Assuming that the Hackaday editors have done their job, this article should have appeared in your feed right on the half-hour. We have a set schedule to keep you supplied with the tastiest of hardware hacks and news. For some of you though perhaps there has been a treat, you’ve seen it and all the other stories six minutes early.
Think for a minute of a modern car on a hot day. When you turn on the air conditioning you will hear a slight dip in the engine revs as it accommodates the extra load. So it is with an alternating current power grid; a simple example is a power station supplying a city. In periods such as cold nights when the demands of the city go up, the result would be that the power station needs to work harder to satisfy it, and until that happens there would be a slight dip in its line frequency. Power grids compensate for this by increasing and decreasing the available generating capacity in real time, maintaining a mean frequency such that the “grid time” of a clock controlled by it matches an atomic clock as closely as possible over time.
It is at this point we leave the realm of electrical engineering and enter that of international politics, normally something far removed from Hackaday’s remit. It is fair to say that the history between Serbia and Kosovo is extremely delicate, and to understand some of the context of this story you should read about the war at the end of the 1990s. After the conflict the Serbian-majority region of what is now Kosovo refused to pay the Kosovan utility for its electricity, eventually leading to the Kosovans refusing to pay for that region’s share of the power received by Kosovo from Serbia. The resulting imbalance between demand and supply was enough to drag the supply frequency down across the whole continent, and though a short-term agreement has been reached the problem still remains on the grid.
Clocks and Mains Frequency
So if you are a continental European and you find yourself six minutes behind your British or American friends, don’t worry. We know that among our readers are people with significant experience in the power generation world, perhaps some of you would like to use your six minutes to give us a bit of insight in the comments. Meanwhile here at Hackaday we maintain an interest in the mechanics of power distribution even if some might say that it is Not A Hack. We’ve taken a look at utility poles, and examined how power grids are synchronised.
As for those slow clocks, the use of mains frequency to keep accurate time is quite brilliant and has been used reliably for decades. Tightly regulating grid frequency means that any clock plugged into an outlet can have the same dead-on accuracy for the cost of a few diodes. These clocks count the zero crossing of the alternating current. There may be moment to moment drifts but the power utility injects or removes cycles over the long term so the sum of crossings is dead on over the course of the day. It’s an interesting phenomenon to experiment with and that’s why we see it in microcontroller projects from time to time.
Perhaps the most important consideration to make when designing a battery-operated device of any kind is the power consumption. Keeping it running for longer between battery changes is often a key design point. To that end, if you need to know how small programming changes will impact the power consumption of your device then [Daniel] has a great tool that you might find helpful: an ESP8266-based live power meter.
The power meter itself is battery-powered via a 600 mAh battery and monitors an e-paper module, which also displays information about power consumption. It runs using a NodeMCU and measures voltage and current across a 100-ohm resistor to calculate the power use, although the resolution does start to get noisy when the device is in standby/sleep mode. One presumes this could be solved by changing the value of the resistor in order to get more accurate measurements at the expense of losing accuracy during moments of high power consumption.
While this power monitor was built specifically to monitor power consumption on this particular e-paper display project, it should be easily portable into other battery-based systems that need fine tuning in order to maximize battery life. As a bonus, the display is already included in the project. There are ways of getting even more information about your battery usage, although if power consumption is important than you may want to stick with a more straightforward tool like this one.
As a civilization, we are proficient with the “boil water, make steam” method of turning various heat sources into power we feed our infrastructure. Away from that, we can use solar panels. But what if direct sunlight is not available either? A team at MIT demonstrated how to extract power from daily temperature swings.
Running on temperature difference between day and night is arguably a very indirect form of solar energy. It could work in shaded areas where solar panels would not. But lacking a time machine, or an equally improbable portal to the other side of the planet, how did they bring thermal gradient between day and night together?
This team called their invention a “thermal resonator”: an assembly of materials tuned to work over a specific range of time and temperature. When successful, the device output temperature is out-of-phase with its input: cold in one section while the other is hot, and vice versa. Energy can then be harvested from the temperature differential via “conventional thermoelectrics”.
Power output of the initial prototype is modest. Given a 10 degree Celsius daily swing in temperature, it could produce 1.3 milliwatt at maximum potential of 350 millivolt. While the Hackaday coin-cell challenge participants and other pioneers of low-power electronics could probably do something interesting, the rest of us will have to wait for thermal resonator designs to evolve and improve on its way out of the lab.