3D-Printed Halbach Motor Part Two: Tuning, Testing

Building your own Halbach-effect brushless DC motor is one thing. Making sure it won’t blow up in your face another matter, and watching how [Christoph Laimer] puts his motor to the test is instructive.

You’ll remember [Christoph]’s giant 3D-printed BLDC motor from a recent post where he gave the motor a quick test spin. That the motor held together under load despite not being balanced is a testament to the quality of his design and the quality of the prints. But not wishing to tempt fate, and having made a few design changes, [Christoph] wisely chose to perform a static balancing of the rotor. He also made some basic but careful measurements of the motor’s parameters, including the velocity constant (Kv) using an electric drill, voltmeter, and tachometer, and the torque using a 3D-printed lever arm and a kitchen scale. All his numbers led him to an overall efficiency of 80%, which is impressive.

[Christoph] is shipping his tested BLDC off to the folks at FliteTest, where he hopes they put it to good use. They probably will — although they might ask for three more for a helicarrier.

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New Efficiency Standards for Wall Warts in the US

The common household wall wart is now under stricter regulation from the US Government. We can all testify to the waste heat produced by many cheap wall warts. Simply pick one at random in your house, and hold it; it will almost certainly be warm. This regulation hopes to save $300 million in wasted electricity, and reap the benefits, ecologically, of burning that much less fuel.

The old standard.

We don’t know what this means practically for the consumer. Will your AliExpress wall warts be turned away at the shore now? Will this increase the cost of the devices? Will it make them less safe? More safe? It’s always hard to see where new regulation will go. Also, could it help us get revenge on that knock-off laptop adapter we bought that go hot it melted a section of carpet?

However, it does look like most warts will go from a mandated 50-ish percent efficiency to 85% and up. This is a pretty big change, and some hold-out manufacturers are going to have to switch gears to newer circuit designs if they want to keep up. We’re also interested to hear the thoughts of those of you outside of the US. Is the US finally catching up, or is this something new?

Two-Axis Solar Tracker

Solar panels are an amazing piece of engineering, but without exactly the right conditions they can be pretty fickle. One of the most important conditions is that the panel be pointed at the sun, and precise aiming of the panel can be done with a solar tracker. Solar trackers can improve the energy harvesting ability of a solar panel by a substantial margin, and now [Jay] has a two-axis tracker that is also portable.

The core of the project is a Raspberry Pi, chosen after [Jay] found that an Arduino didn’t have enough memory for all of the functionality that he wanted. The Pi and the motor control electronics were stuffed into a Pelican case for weatherproofing. The actual solar tracking is done entirely in software, only requiring a latitude and longitude in order to know where the sun is. This is much easier (and cheaper) than relying on GPS or an optical system for information about the location of the sun.

Be sure to check out the video below of the solar tracker in action. Even without the panel (or the sun, for that matter) the tracker is able to precisely locate the panel for maximum energy efficiency. And, if you’d like to get even MORE power from your solar panel, you should check out a maximum power point tracking system as well.

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Graphing the efficiencies of LED light strips

After adding a few LED light strips above his desk, [Bogdan] was impressed with the results. They’re bright, look awesome, and exude a hacker aesthetic. Wanting to expand his LED strip installation, [Bogdan] decided to see if these inexpensive LED strips were actually less expensive in the long run than regular incandescent bulbs. The results were surprising, and we’ve got to give [Bogdan] a hand for his testing methodology.

[Bogdan]’s test rig consists of a 15 cm piece of the LED strip left over from his previous installation. A Taos TSL2550 ambient light sensor is installed in a light-proof box along with the LED strip, and an AVR microcontroller writes the light level from the sensor and an ADC count (to get the current draw) of the rig every 6 hours.

After 700 hours, [Bogdan]’s testing rig shows some surprising results. The light level has decreased about 12%, meaning the efficiency of his LED strip is decreasing. As for projecting when his LEDs will reach the end of their useful life, [Bogdan] predicts after 2200 hours (about 3 months), the LED strip will have dropped to 70% of their original brightness.

Comparing his LED strip against traditional incandescent bulbs – including the price paid for the LED strip, the cost of powering both the bulb and the strip, the cost of the power supply, and the time involved in changing out a LED strip, [Bogdan] calculates it will take 2800 hours before cheap LEDs are a cost-effective replacement for bulbs. With a useful life 600 hours less than that, [Bogdan] figures replacing your workshop lighting with LED strips – inexpensive though they are – isn’t an efficient way to spend money.

Of course with any study in the efficiency of new technology there are bound to be some conflating factors. We’re thinking [Bogdan] did a pretty good job at gauging the efficiency of LED strips here, but we would like to see some data from some more expensive and hopefully more efficient LED strips.

Reviewing the numbers from one month of solar harvesting

[Mathieu] just finished analyzing the numbers from a month of solar energy harvesting. You may remember that he was curious to see what kind of energy can be collected from small solar cells used indoors. He built several copies of a test platform which collected data between December 16th and January 16th.

First of all, it’s not shocking to find out that rooms with no sunlight produced negligible energy during that time. When you think about it, if they had been gathering a statistically significant amount wouldn’t that mean the lighting used in those rooms was incredibly inefficient? In other words, there’s no way you need to be making that much light.

But he did find that proper positioning in rooms that catch sunlight during the day can result in usable energy for small loads. He established that a 0.5 Watt panel harvested just a bit more than half of what a 1 Watt panel did. But perhaps the most useful discovery was that it’s quite a bit more efficient to have a charging circuit store energy in a battery rather than directly powering a fixed load.

It will take us a few more viewings to really decide what we can take away from the experiment for our own projects. But we appreciate [Mathieu’s] quest for knowledge and his decision to put this information out there so that others can learn from it.

Getting the lead out of the Arduino runtime


Ah, the Arduino.

Love it or hate it, there’s no denying that part of its accessibility comes at the expense of speed and efficiency. We honestly like the platform as well as all of the others out there, because we believe that everything has its proper place and purpose. The crew over at Make, Hack, Void think that the Arduino dev boards are well and good, but that the core of the Arduino runtime could use some improvement.

They have taken it upon themselves to dig deep into the code and make some of the improvements that many advanced Arduino users have been clamoring for. Their MHVLib is an efficiency oriented runtime library which works on all AVR microcontrollers, whether they be standalone uCs or Arduino-branded hardware.

They have changed the way that the Arduino handles pin and port information, as well as how object and buffers are allocated in memory. Their code still relies on an Arduino-style bootloader, though they recommend Optiboot since it’s about a quarter of the size of the Arduino version.

There’s a complete list of what has been implemented available on their site, and you can grab the code via their GIT repository if you want to give it a try yourself.

Cheap hack may double solar panel power

MIT researchers have devised something they call the Solar Concentrator which is to be placed on top of existing solar cells. Its purpose is to separate the visible and infrared spectra of light by absorbing the visible spectrum and routing the energy to specialized cells. They claim this could lead to doubling the panel’s efficiency and greatly reducing costs.

We have seen many promising advances to solar panel efficiency in the past few years, but what is special about this one is the amazingly simple and cheap technique. Essentially, all the team has done is coat a piece of glass with simple organic dyes. After the organic molecules absorb the visible light, they remit the energy to the sides of the glass where it can be routed to their specific cells. The process is more efficient because the dye absorbs the light rather than something expensive like silicon. That means less silicon, and thus a better price range. Also, the fact that this material is just a piece of glass also opens up the possibility of solar windows.