$4 volt meter from a dollar store pedometer

[Paulo]’s got a few solar panels on his shed, and while he does have a fairly nice setup with a battery charge controller, he found himself looking around for a panel voltmeter. Of course you can buy a panel voltmeter for under $20, but [Paulo] wanted something that fit his 4-4-4 plan; his voltmeter should cost under $4, draw less than 4mA, and last for 4 years. The jury is still out on the 4 year qualifier, but he did manage to meet his other goals by repurposing a dollar store pedometer as a voltmeter.

The pedometer in question is a very simple device. After inspecting the PCB, [Paulo] found it operates by looking at a trigger pin and incrementing the number on the display each time the circuit closed. [Paul] designed a very small PIC12F-powered circuit that reads the voltage of his batteries and triggers the pedometer’s LCD for every 10th of a volt. To display 12.6 Volts, [Paulo]’s code triggers the LCD 126 times, for example.

After wiring up the reset button so the display will go back down to zero for each new reading, [Paulo] encased his new volt meter in a plastic box. It’s not exactly a fast way of measuring voltage, but seeing as how that won’t change very fast, it’s the perfect solution for [Paulo]’s solar charger setup.

Saving the ISS by hacking a toothbrush

 

We absolutely love these stories of hacker ingenuity saving peoples lives. In this case, it was aboard the ISS, and the item being hacked was a toothbrush.

The story is as follows. Some equipment failed, as space junk tends to do, and the astronauts found themselves needing to do some repairs. Upon inspection, they couldn’t remove some modules due to an accumulation of “space dust” around some bolts.  This was especially troubling as the unit in question was something that was supposed to route power from some of the solar arrays to the ISS. Even more troubling is that another unit failed while they were assessing the situation.

Realizing they had to act fast so as not to lose too much power to function, they cobbled together some tools to allow them to clean out the access ports and remove the units for repair. A task that sounds like an easy solution here on earth proved to be life threatening in space. Eventually though, their makeshift tools came to the rescue and they were able to repair and restore power.

A perpetually powered wireless outpost

For [Justin], the topic of remotely powering electronics in the field comes up often. So often in fact he decided to put up a tutorial for powering electronics from solar power and batteries, as well as sending and retrieving data with the help of a cellular connection.

The electronics [Justin] chose for his remote wireless project include an AT&T 3G connection to the Internet provided by a Beaglebone, BeagleTouch display, and BeagleJuice battery pack. Of course an Arduino had to make it into this project, so a few light sensors were wired into a few Arduino Unos and connected to the Beaglebone.

After finding a few deep cycle boat batteries, [Justin] wired up a pair of solar panels that put out about 200 mA in full sun. This equates to about 2700 mAh a day, about 300 mAh more than his Beaglebone/Arduino/3G connection/WiFi setup needs per day.

As for what [Justin] can do with his wireless outpost, it makes setting up remote sensors for agriculture a breeze, and could easily be used to automagically send pictures from a game camera straight to a web page. Pretty neat, and very useful if you need to wire up sensors in the field to the Internet.

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Raspberry Pi keeps tabs on your solar power setup

raspberrypi-solarlogger

[Brian Dorey] has been adding green power solutions to his home for some time now, and as things have progressed, he has experimented with several different iterations of data loggers. The latest system watching over his solar power setup is a Raspberry Pi armed with a custom-built I2C analog/digital converter.

The Rasp Pi is responsible for monitoring several different temperature sensors related to his solar water heating and storage system, but that’s just the beginning. It also keeps watch over his roof-mounted solar electric panels, his battery bank, and its charge controller. For good measure, he also monitors his home’s temperature and his water tank’s recirculation pump because, why the heck not?

All of the collected data is relayed to his web server where it is handsomely displayed for his perusal and analysis. [Brian] has made his code available here, so you can monitor your home in the same fashion with little fuss.

A quick kludge to view the transit of Venus

[Justin] is a bit of an astronomy geek, but that doesn’t mean he’s always prepared for celestial phenomena. When he realized the May 20th annular eclipse was only a few days away, [Justin] dropped everything, built a pinhole solar viewer, and drove three hours for the best view of the eclipse. He learned something watching the eclipse; these sort of things sneak up on you, and you really need to plan ahead if you want to truly enjoy the music of the celestial spheres. After the eclipse, [Justin] set to work building a filter to watch a Venusian eclipse with his telescope.

If [Justin] pointed his 8 inch Schmidt–Cassegrain directly at the sun, he would most likely damage the optics in his ‘scope, burn several retinas, and other very, very bad things. The best way to view the Sun with a telescope is with an expensive Hydrogen alpha or a general solar filter, but these are expensive and the clock was rapidly ticking down to the transit of Venus. After reading that blocking most of the light from coming into the ‘scope, [Justin] built an aperature reducer out of a few bits of foam board, foil, and dark fleece.

How did viewing the transit with a telescope turn out? Well, if you don’t compare [Justin]’s pictures to the multi-million dollar toys NASA and astronomers have, pretty good. It’s a very good job considering the entire foam-core aperture reducer was built in the course of an evening.

While it may be a little early to be planning for the next Venusian transit in the year 2117, there will be a transit of Mercury on May 9, 2016. All [Justin] has to do is remember when it will happen.

2 horse power 3 wheeled beast

This beast above is the result of what is probably the coolest class project ever.  The instructors[Michael Ham] and [Kenny Ham] gave their students a pile of junk and said “build something”. The goal was a “vehicle that could recharge itself”. In the pile were motorcycle tires, an old classroom seat, the front suspension from a VW bug, some old power drills, a solar panel, and a battery, amongst other bits and pieces.  What you see above was the result.  While it may not win any drag races any time soon, it was a fantastic class project that had the students thinking their way around many problems.

The videos on the project page show that this thing isn’t quite as sluggish as we would have expected for its size.

[via Make]

Using diodes and transistors as solar cells

When you get down to it, solar cells aren’t much different from the diodes and transistors in your parts drawers or inside your beloved electronics. They’re both made of silicon or some other semiconductor, and surprisingly can produce electricity in the presence of light. Here’s two semiconductors-as-solar panel projects that rolled into the tip line over the past few days.

[Steven Dufresne] cut open a 2N3055 power transistor to expose the semiconductor material to light. In full sunlight, he was able to produce 500 millivolts and 5.5 milliamps. In other words, he’d need around 5000 of these transistors wired up to turn on a compact fluorescent light bulb. A small calculator has a much lower power requirement, so after opening up five transistors he was able to make a solar-powered calculator with a handful of transistors.

[Sarang] was studying solar cells and realized a standard silicon diode is very similar; both are p-n junctions and the only real difference is the surface area. He connected a 1N4148 to a multimeter and to his surprise it worked. [Sarang] is able to get about 150 millivolts out of his diode with the help of a magnifying glass. While he doubts his diode is more efficient than a normal solar cell, he thinks it could be useful in low-cost, low power applications. We’re thinking this might be useful as a high-intensity light detector for a solar cooker or similar.

After the break, you can check out the videos [Steven] and [Sarang] put up demonstrating their solar cells.

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