Are You Down With MPPT? (Yeah, You Know Me.)

Solar cells have gotten cheaper and cheaper, and are becoming an economically viable source of renewable energy in many parts of the world. Capturing the optimal amount of energy from a solar panel is a tricky business, however. First there are a raft of physical prerequisites to operating efficiently: the panel needs to be kept clean so the sun can reach the cells, the panel needs to point at the sun, and it’s best if they’re kept from getting too hot.

Along with these physical demands, solar panels are electrically finicky as well. In particular, the amount of power they produce is strongly dependent on the electrical load that they’re presented, and this optimal load varies depending on how much illumination the panel receives. Maximum power-point trackers (MPPT) ideally keep the panel electrically in the zone even as little fluffy clouds roam the skies or the sun sinks in the west. Using MPPT can pull 20-30% more power out of a given cell, and the techniques are eminently hacker-friendly. If you’ve never played around with solar panels before, you should. Read on to see how!

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Sculptural Nixie Clock has Shockingly Exposed Design

Single tube Nixie clocks? Been there, seen that. A single tube Nixie clock with sculptural wiring that exposes dangerous voltages? Now that’s something you don’t see every day.

[Andrew Moser]’s clock is clearly a case of aesthetic by anesthetic — he built it after surgery while under the influence of painkillers. That may explain the questionable judgment, but we won’t argue with the look. The boost converter for the Nixie lives near the base of the bent wire frame, with the ATmega 328 and DS1307 RTC supported in the midsection by the leads of attached passive components and jumper wires. A ring at the top of the frame supports the octal socket for the Nixie and a crown of driver transistors for each element.

In the video after the break, [Andrew] speaks of rebuilding this on a PCB. While we’ve seen single tube Nixie PCB clocks before, and we agree that the design needs to be safer, we wouldn’t ditch the dead bug style at all. Maybe just throw the whole thing in a glass bell jar or acrylic tube.

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Russian Hacker Multiplies Value of Boost Converter

We have a love/hate relationship with LiIon batteries. They pack all this power in such a small and light package. But for running 3.3 V devices, they’re cumbersome. They need to be stepped down a little bit when they’re fully charged at 4.2 V, but then they need to be stepped up at the end of their charge around 3.0 V.

A simple boost or buck converter can’t do both jobs, although you’d be tempted because they can be purchased for peanuts online. So [Kirich] hacked cheap boost converters into the more capable SEPIC topology, which sell for nearly 10x as much. (Google translated version here.) The bottom line? With a little desoldering, a cut trace here and an extra inductor there, and [Kirich] had a very capable circuit that would maintain a constant 3.3 V output when the input swung between 1 V and 5 V.

95aa17If SEPIC power converters are foreign to you, have a read through Maxim’s white paper on the subject. Basically, it’s a boost converter with a capacitor in the middle that lets the output voltage drop below the input voltage. An extra inductor keeps the output side of this capacitor at ground potential (on average).

If you want more detail, [Kirich] doesn’t disappoint. He tested his modifications in multiple configurations on two different models of boost converter. As you’d expect with power circuitry, layout and trace length matters, and [Kirich] took good notes. This is a great read for the frugal hacker, or anyone who’s interested in boost/buck converters.

Speaking of boost/buck circuits, we’ve got some more links for you. This video from Sparkfun’s [Pete Dokter] is worth fifteen minutes, and if you want to get your hands really dirty in the construction of such circuits, this ATtiny-based boost converter circuit is fun to play with.

Thanks [kirillre4] for the great tip!

How a Hacker Jump Starts a Car

Here’s the Scenario: you need to get somewhere in a hurry. The problem is that your car has a dead battery and won’t turn over. The Obvious solution would be to call a friend for a jump. But is the friendless hacker out of luck in such a situation? Not if you can whip up a quick parts bin jump starter.

Clearly, [Kedar Nimbalkar]’s solution would be practical only under somewhat bizarre circumstances, so we’ll concentrate on what we can learn from it. A spare PC power supply provides the electrons – [Kedar]’s 250W supply pushes 15A at 12 volts, which is a pretty respectable amount of current. The voltage is a little anemic, though, so he pops it up to 14.2 volts with a 150W boost converter cooled with a PC fan. A dual panel meter reads out the voltage and current, but a VOM could substitute in a pinch. About the only thing you might not have on hand is a pair of  honking 10A diodes to keep current from creeping back into the boost converter. [Kedar] claims he got enough of a charge back in the battery in five minutes to start his car.

As jump-starting goes, this hack is a bit of a stretch. It’s not the first time we’ve seen a MacGyver’d jump starter, though, and you never know when the principles and hardware behind these hacks will come in handy.

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Programmable DC Backup Power Supply

The uninterruptible power supply was once a standard fixture in the small office/home office as a hedge against losing work when the electrons stop flowing from your AC outlet. Somewhat in decline as computing hardware shifts away from dedicated PCs toward tablets, phones and laptops, the UPS still has a lot of SOHO utility, and off-the-shelf AC units are easy to find. But if your needs run more to keeping the electrons flowing in one direction, then you might want to look at [Kedar Nimbalkar]’s programmable DC backup power system.

Built inside a recycled ATX power supply case, [Kedar]’s project is heavy on off-the-shelf components, like a laptop power supply for juice, a buck converter to charge the 12 volt sealed lead acid battery, and a boost converter to raise the output to 19.6 volts. An Arduino and an optoisolator are in charge of controlling the charging cycle and switching the UPS from charging the battery to using it when mains voltage drops.

 If you need a DC UPS but would rather skip the battery, you could try running a Raspberry Pi with electrons stashed in a supercapacitor. Or if you’ve got an aging AC UPS, why not try beefing it up with marine batteries?

[Thanks for the tip, Morris]

Crowdfunding Follies: Debunking The Batteriser

It’s not on Kickstarter yet, but this product is already making its media debut, with features in all the tech blogs, an astonishing amount of print outlets, and spouted from the gaping maws of easily impressed rubes the world over. What is it? It’s the Batteriser, a tiny metal contraption that clips over AA, C, and D cells that reclaims the power trapped inside every dead battery. Yes, every dead battery you’ve ever thrown away still has up to 80% of its power remaining. Sounds like complete hogwash, right? That’s because it is.

[Dave Jones] put together a great video on the how comes and why nots of the Batteriser, and while doing so gives a great tutorial for debunking a product, heavily inspired by [Carl Sagan]’s Baloney Detection Kit. The real  debunking starts by verifying any assumptions, and the biggest fault of the Batteriser campaign is claiming 80% of a battery’s power is unused. Lucky for us, [Dave] has tons of tools and graphs to demonstrate this is not the case.

To verify the assumption that battery-powered devices will brown out after using only 20% of a battery’s available power, [Dave] does the most logical thing and looks at the data sheets for a battery. After using 20% of available power, these datasheets claim these batteries should be around 1.3V. Do devices brown out at 1.3V? Hook it up to a programmable power supply and find out.

It turns out every battery-powered device [Dave] could find worked perfectly until around 1.1V. Yes, that’s only 0.3V difference from 1.4V claimed by the patent for the Batteriser, but because of the battery discharge curve, that means 80% of the power in a normal device is already being used up. The premise of the Batteriser is invalid, and [Dave] demonstrates it’s a complete scam.

If a through debunking of the Batteriser’s claims wasn’t enough, [Dave] goes on to explain how it may actually be dangerous. The positive terminal of a battery is also the metal can, while the negative terminal is just a tiny nib of metal seperated from the rest of the battery by a gasket. Since the Batteriser is made of metal and serves as the ground for the boost converter circuit, it’s very, very close to shorting through the branding and logo emblazoned on a mylar wrapping each battery is shrouded with. One tiny nick in this insulator, and you have a direct short across the battery. That’s going to turn to heat, and there’s a lot of energy in a D cell; a failure mode for the Batteriser is a fire. That’s just terrible product design.

Video below.

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A Primer on Buck (and Boost) Converters

We all know that the reason the electrical system uses alternating current is because it’s easy to step the voltage up and down using a transformer, a feature which just isn’t possible with a DC system… or is it? Perhaps you’ve heard of mysterious DC-DC transformers before but never really wanted to look at the wizardry that makes them possible. Now, SparkFun Director of Engineering [Pete Dokter] has a tutorial which explains how these mysterious devices work.

Known as buck converters if they step the input voltage down and boost converters if they step the voltage up, [Pete] explains how these circuits exploit the properties of an inductor to resist changes in current flow. He goes into exquisite detail to explain how components like transistors or MOSFETs are used to switch the current flow to the inductor very rapidly, and just exactly what happens to the magnetic field which makes these devices possible.

The video gives a good amount of background knowledge if you’ve always wanted to understand these devices a little bit better. There are also a few projects floating around that exploit these devices, such as one that uses an AVR microcontroller to perform the switching for a small circuit, or another that uses the interesting properties of these circuits to follow the I-V curve of a solar panel to help charge a bank of batteries. The possibilities are endless!

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