What’s the best way to turn a high-powered brushless DC motor optimized for hobby use into a decent low-RPM generator? Do you take a purely mechanical approach and slap a gearbox on the shaft? Or do you tackle the problem electrically?
The latter approach is what [GreatScott!] settled on with his BLDC rewinding and rewiring project. Having previously explored which motors have the best potential as generators, he knew the essential problem: in rough terms, hobby BLDCs are optimized for turning volts into RPMs, and not the other way around. He started with a teardown of a small motor, to understand the mechanical challenges involved, then moved onto a larger motor. The bigger motor was stubborn, but with some elbow grease, a lot of scratches, and some destroyed bearings, the motor was relieved of both its rotor and stator. The windings were stripped off and replaced with heavier magnet wire with more turns per pole than the original. The effect of this was to drive the Kv down and allow better performance at low RPMs. Things looked even better when the windings were rewired from delta to wye configuration.
There was a time, not so long ago, when hype for desktop 3D printing as so high that it seemed you could print anything. Just imagine it, and your handy dandy magical 3D printer could manifest it into reality. But now that more people have had first hand experience with the technology, the bubble has burst. Reality has sobered us up a bit, and today we’ve got a much better idea of what can and cannot be printed on a traditional desktop 3D printer.
But that doesn’t mean we aren’t surprised from time to time. As a perfect example, take a look at this almost entirely 3D printed wind turbine designed and built by [Nikola Petrov]. Outside of the electronics, the pole it’s mounted to, and some assorted bits and bobs, he produced all the parts on his own large-format TEVO Black Widow printer. He mentions there are a few things he would do differently if he was to build another one, but it’s hard to find much to complain about with such a gorgeous build.
To be sure, this one isn’t for the 3D printing novice. First of all, you’ll need a printer with a bed that’s at least 370 mm wide just to print the blades. [Nikola] also recommends printing the parts in ABS and coating them with acetone to smooth and harden the outside surfaces. We’d be surprised if you could print such large objects in ABS without a heated enclosure as well, so plan on adding that to your shopping list.
On the flip side though, the electronics are about as simple as they come. The blades are spinning a standard NEMA 17 stepper motor (through a 1:5 gearbox) to produce AC power. This is then fed into two W02M rectifiers and a beefy capacitor, which gives him DC with a minimum of fuss. In theory it should be capable of producing 1A at 12V, which is enough to light LEDs and charge phones. In this design there’s no battery charging circuit or anything like that, as [Nikola] says it’s up to the reader to figure out how to integrate the turbine into their system.
What’s great about the Power Generation Modules project headed by [Cole B] is the focus on usability and modularity. The project is a system for powering and charging small devices using any number and combination of generator modules: wind turbine, hand-crank, and water turbine so far. Power management and storage is handled by a separate unit that acts as a battery bank to store the output from up to six generators at once. There’s also a separate LED lamp module, designed to be capable of being powered directly from any of the generator modules if needed.
The hand crank is straightforward in concept, but key to usability was selecting a DC gearmotor with a gear ratio that made cranking by hand both comfortable and sustainable; too weak of a crank and it’s awkward, too hard and it’s tiring. The wind turbine has three compact vanes that turn a central shaft, but testing showed the brushless motor it uses as a generator isn’t a good match for the design; the wind turbine won’t turn well in regular wind conditions. The water turbine prototype showed great success; it consists of an epoxy-glazed, 5 inch diameter 3D printed propeller housed in a section of PVC pipe. The propeller drives a brushless motor which [Cole B] says easily outputs between eight to ten volts when testing in a small stream.
The team has plans for other generators such as solar, but this is a great start to an array of modules that can be used to power and charge small devices while off the grid. We’re happy to see them as a finalist for The Hackaday Prize; they were selected as one of the twenty projects to receive $1000 cash each in the Power Harvesting Challenge. The Human-Computer Interface Challenge is currently underway which seeks innovative ideas about how humans and computers can interface with one another, and twenty of those finalists will also receive $1000 each and be in the running for the Grand Prize of $50,000.
The Seebeck effect (part of the broader thermoelectric effect) is how a difference in temperature can be directly converted into a voltage, and it is the operating principle behind things like thermocouples and Peltier junctions. Harnessing this effect in an effort to wrangle a useful electrical current out of the environment has led to some interesting ideas, like the Lily Power Pods by [Josh Starnes].
What’s interesting about this particular design is that the artistic angle crosses over with functionality. Electrically speaking, the pods have one side of the thermoelectric generator heated by the sun while the other is cooled by being submerged in water, and the temperature differential creates a measurable voltage. [Josh] designed the pods to resemble flowers, with foil petals that help direct sunlight towards the blackened “hot side” of the thermoelectric generator while water takes care of the cool side.
Are foil petals the best way to gather and direct sunlight? They are not, but the idea is to have the pods look like something other than the floating hunks of machinery that they are. Since the pods must float in water and be exposed to sunlight, they will as a result have high visibility. [Josh] seems to feel that it’s important that they not be an eyesore. After all, a less efficient generator that doesn’t overstay its welcome still generates more power than one that has figuratively been handed its hat and told to move along.
[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.
We just wrapped up the Power Harvesting challenge in the Hackaday Prize, and with that comes some solutions to getting power in some very remote places. [Vijay]’s project is one of the best, because his project is getting power in Antarctica. This is a difficult environment: you don’t have the sun for a significant part of the year, it’s cold, and you need to actually get your equipment down to the continent. [Vijay]’s solution was to use one of Antarctica’s greatest resources — wind — in an ingenious flat pack wind turbine.
There are a few problems to harvesting wind power in a barren environment. The first idea was to take a standard, off-the-shelf motor and attach some blades, but [Vijay] found there was too much detent torque, and the motor would be too big anyway.
The solution to this problem was to wind his own motor that didn’t have the problems of off-the-shelf brushless motors. The design that [Vijay] settled on is a dual axial flux generator, or a motor with a fixed stator with magnets and two rotors loaded up with copper windings. Think of it as a flattened, inverted version of the motor on your drone.
One interesting aspect of this design is that it takes up significantly less space than a traditional motor, while still being able to output about 100 Watts with the wind blowing. Add in some gearing to get the speed of the rotor right, and you have a simple wind generator that can be set up in minutes and carried anywhere. It’s a great project, and we’re glad to see this make it into the finals of The Hackaday Prize.
We can certainly relate to an incomplete project sowing the seed for a better one, and that’s just what happened in [JohnnyQ90]’s latest video. He initially set out to create an air compressor powered by a nitro engine, and partially succeeded – air was compressed, but not nearly enough to be useful.
Instead, he changed tack and decided to use the 1 cc engine to make a small electric generator. [JohnnyQ90] is, of course, no stranger to the nitro engine, having previously brought us the micro chainsaw conversion, and nitro powered rotary tool. This time round, the build is a conceptually simple task: connect an engine to a DC motor and you’re done. But physically implementing it in an elegant way is a different story, and this is always where [JohnnyQ90] shines; we never get tired of watching him produce precision parts on the lathe. A fuel tank is made from a modified Zippo can and, courtesy of a CNC milled fan and 3D printed shroud, the motor air cools itself.
Towards the end of the video, [JohnnyQ90] plays with the throttle a little, causing the bulb connected to the generator to brighten accordingly. It might be fun to control the throttle with a servo and try to regulate the voltage on the output under different load conditions.