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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Solar charging a Buddha Machine

While having ambient music playing in the background can lead to a more relaxed state of mind, we can’t imagine the annoyance of having to replace the batteries constantly. Thankfully, [Phil] added solar charging to his Buddha Machine so he won’t have to worry about batteries anymore.

If you’re not familiar, the Buddha Machine is a small plastic box that loops nine tracks of ambient music inspired the Buddhist temples of south-east Asia. There’s not much to these little boxes; they’re just a plastic box with a speaker, on/off knob and an EEPROM loaded up with samples of music.

A year or so ago, the people behind the Buddha Machine posted a prototype of a solar-powered meditative noise box that was unfortunately never made. Thankfully, [Phil Stearns] stepped in posted a guide on how to convert a AA-powered Buddha Machine to solar power.

The modification is incredibly simple: after replacing the disposable AA batteries with NiMH rechargeable, two wires are swapped connecting the battery compartment with the main PCB and the box is sealed up again. Now, whenever one of [Phil]‘s solar panels is connected to the power jack the batteries begin charging. [Phil] says he can get two days worth of runtime with a full 8-hour charge, so he shouldn’t need any batteries for his Buddha Machine anytime soon.

PVC Magnetometer to measure magnetic storms

In the hopes of getting a heads up on when the aurora borealis will be visible from his back yard, [Alex] built a magnetometer to measure disruptions in Earth’s magnetic field. The build is extremely simple, too. It’s amazing what you can build with a few components and a trip to the dollar store.

The design or [Alex]‘s project is called a torsion magnetometers. In this setup, two mirrors are affixed to a permanent magnet connected to a string. A laser is shone onto the mirror and is reflected back to an array of sensors. In [Alex]‘s case he used a simple laser pointer and a pair of photoresistors encased in a PVC tube.

[Alex] has been running his magnetometer in his back yard for over a month now and has the data to prove it. Luckily for [Alex], those graphs he has been generating may get a little more interesting. A coronal mass ejection is coming our way and is expected to hit today around 22:30 UTC. We’ll go outside to look for an aurora, but we’re sure [Alex] will be glued to his laptop tonight.

Check out the CGI visualization of [Alex]‘s magnetometer after the break

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DIY Fresnel reflector

Just like destroying an ant colony with a magnifying glass, there’s nothing like cooking hot dogs and roasting marshmallows with a nice parabolic reflector. Of course covering an old satellite dish with mylar or aluminum tape doesn’t take much skill, however cool it is. [Uwe] came up with a much more technical means of building a Fresnel reflector that will cook your hot dogs in seconds, but only on sunny days.

[Uwe] channeled a little bit of [Apollonius] when he realized that a flat cardboard ring with a section removed could be joined together into a conic section. The resulting section looks just like one concentric ring in a Fresnel reflector. [Uwe] wrote a small program in Visual Basic to calculate the necessary diameter and angle of his conic sections.

A bit of cardboard was cut out and pieced together with some very reflective aluminum tape. The resulting Fresnel reflector concentrates 117 times the normal solar radiation onto a small point. It’s more than enough to burn holes in construction paper, but we’ll be using a microwave for our lunch today.

DIY shade finder tool takes the tedium out of solar surveys


[Steven Dufresne] does a lot of tinkering with solar-powered applications, a hobby which can be very time consuming if done right. One process he carries out whenever building a solar installation is creating a sun chart to determine how much (or little) sun the target area will get.

The process requires [Steven] to take elevation and Azimuth measurements of many different points, which often consumes about half an hour of his time. While taking measurements recently, he started thinking about how he could improve the process, and came up with a stellar solution that reduces the process down to a one-minute task.

In short, his shade finder tool uses a pulley, a pair of rollerblade wheels, and a pencil to accomplish a full shade survey in under a minute. The science behind the tool is best explained by [Steven], so be sure to check out his site for plenty of details and diagrams.

We have to say that we’re extremely impressed by his shade finder – hopefully his work can help others maximize the efficiency of their solar solutions.

Stick around after the jump to see a short video of the shade finder in action.

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