Standalone air quality monitor based around Raspberry Pi

rpi-air-quality-monitor

You can have a lot of fun tinkering with the Raspberry Pi. But in addition to the low-cost hobby potential it is actually a great choice for serious data harvesting. This air quality monitor is a great example of that. The standalone package can be taped, screwed, bolted, or bungeed at the target location with a minimum of effort and will immediately start generating sample data.

The enclosure is a weather proof electrical box. The RPi board is easy to spot mounted to the base of the case. On the lid there is an 8 Ah battery meant to top off an iPhone. It works perfectly as it provides a USB port and enough current to operate the Pi. On top of that battery is a 3G modem used to access the data remotely — although it can log to the SD card for collection at a later time if you’d rather not mess with a cell network.

Look closely at the GPIO header and you’ll notice that an ADC add-on board has been plugged in. This is used to take the readings from the gas sensor which is monitoring for air pollutants in Paris.

Open source capactive charger resurrects an electric skateboard

mikey-sklar-on-electric-skateboard

Here’s [Mikey Sklar] posing on his new electric skateboard. Well, it’s new to him at any rate. He bought it used on eBay for $250. That may not sound like much of a deal, but these will run more like $800 retail. The savings comes because the thing would no longer charge. But it took him just an hour and a half with his capacitive charger to resurrect the flat lithium cells.

The first thing he did in trouble shooting the situation was to measure the voltage of the battery pack. It registered 5V, which is a far cry from the 36V it should supply. The built-in charger does nothing, as it’s circuitry isn’t designed to work in a situation like this one. But [Mikey] has a tool perfect for this purpose. Da Pimp is a capacitive charger which we’ve seen before. It succeeds where the other failed because it is able to adapt itself to the internal resistance of the battery, no matter what voltage level it starts at.

[Mikey] shows off the use of his charger in the clip after the break. His first test run was more than two miles without issue.

[Read more...]

iPad external battery case forced to work with a non-iPad tablet

[Carnivore] uses a Pipo Max M1 tablet. It’s an Android device that is very responsive thanks t the 1.6 GHz dual-core processor and it runs Jellybean (latest version of Android OS). The one thing he wasn’t so happy with is battery life. Under heavy load it lasts about three hours. When reading an eBook that use can be stretched to 10 hours. His solution was to add an external battery. It turns out the 9.7″ screen makes the body of the device almost exactly the same size as an iPad, so he made an iPad external battery case work with the Android tablet.

[Carnivore] started the hack by disassembling an iP6000 case which houses a 6000 mAh battery. He removed the dock connector and fitted in a 2.5mm power jack. Luckily the buttons on the Android tablet are in nearly the exact same place as those on an iPad, with the power button hole needing just a bit of enlargement. The case charges itself and the tablet’s internal battery using a microUSB port which means he no longer needs to carry around a special power cord. The new hardware increased the battery life by about 75%.

Laser power system keeps UAVs flying indefinitely

Drone technology is driving the aerospace industry as companies trip over each other trying to develop the next big thing. Here’s a good example of what we’re talking about. Lasers can no be used to keep a UAV in the air indefinitely. The trick is to add an array of photovoltaic cells specifically tuned to an IR laser’s wavelength. A ground system then directs a high-intensity laser beam onto the aircraft’s cell array to transfer energy while in flight.

After the break you can catch a video from a trade show where a Lockheed Martin employee describes the successful testing of such a system. But there’s a lot more information available in the white paper (PDF) which Laser Motive has released. They’re the folks behind the technology who have teamed up with LM to implement the system. The laser unit on the ground can track a UAV visually, but there is also a method of using GPS coordinates to do so in the case of overcast skies.

[Read more...]

Testing 30 brands of batteries

Batteries come packaged in bright blister packs emblazoned with vague guarantees such as “45% more pictures” and “five times longer lasting.” During his internship at BitBox this summer, [Thomas] decided to put those statements to the test. He tested thirty brands of batteries on a homebrew rig to find the batteries with the most power and the most bang for your buck.

The hardware [Thomas] used an STM32 microcontroller to perform two different tests: a high drain and a low drain condition. For the high drain, 1000 mA were sucked out of the batteries until the voltage reached 0.8 V. For the low drain, 200 mA were used. Data including milliwatt-hours, milliamp-hours, joules, voltage, current, power, and effective load resistance were all logged for both conditions for all 30 batteries.

Generalizing the results for both low and high drain conditions, lithium batteries were better than alkaline, which were both better than zinc AA cells. Perhaps unsurprisingly, batteries marketed as ‘long life’ and ‘extended power’ were the worst batteries for the money, but a brand-name battery – the Kodak Xtralife cells – were actually the best value for the money.

Ugly upgrade keeps the tunes playing longer

[Sam] picked up a Sansa Clip audio player to listen to some tunes while working on projects. He liked the fact that he could run the Rockbox alternative firmware on the device, but thought the 15 hour battery life needed some improving. He swapped out the stock cell with a larger Lithium cell for a long life of 50-60 hours. It’s an upgrade fom 300 mAh to 1100 mAh, but as you can see, the size of the replacement made for some interesting case modification.

The battery swap required more than just taking one battery out and putting in the other. [Sam] is using a cellphone battery as the replacement and he didn’t want to have issues with the internal circuitry. He took the cell out of its plastic enclosure, removing the circuit board in the process. That PCB is the charging circuit, which he replaced with the one from the stock battery. After insulating the cell with a layer of Kapton tape he soldered it to the MP3 player and did his best to adhere all the parts to each other.

Sure, its ugly, but that makes it right at home on the work bench.

Passion Fruit acquire laser defenses

Apparently being overrun by ripe Passion Fruit is a problem if you live in Hawaii. [Ryan K's] solution to the situation was to use his extra fruit to power a laser. In an experiment that would make [Walter White] proud, [Ryan] gathered everyday supplies to form a battery based on the fruit.

He used some galvanized bolts as the source of zinc. It forms one pole of each cell, with a thin copper tube as the other pole. Each cell is rather weak, but when combined with others it makes a respectable battery. We’ve seen acidic fruit used to power LEDs, but [Ryan] wanted to do a little more. He built a circuit that would store electricity until he had enough potential to power an LED diode. After the break you can see a four second clip of the fruit wielding its new laser defense system.

[Read more...]

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