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.

Solar charger for Occupy Boston

As soon as the team at Revolt Labs heard Occupy Wall Street was coming to Boston, they decided to pick up their soldering irons in support of the throngs of protestors. They came up with a Solar charging USB box to keep those cell phones and digital cameras charged.

The case came direct from an Army surplus store. Originally, the box was used by the Dutch military to test the air for poison gas and signal when it was safe to remove a gas mask – hopefully not a portent of things to come.

On top of the box is five solar panels that output two watts each. A bit of breadboard holds a 7805 voltage regulator, a few caps and a diode. This regulated output goes to a USB hub and provides power for recharging.

For a cheap and easy project for our brothers without arms, we couldn’t think of a better project for the Occupy Boston tent city. Of course heating units will be needed at the Occupy protests this winter, but at least now the protesters have the means to power their communications equipment.

 

update: Once again, this has devolved into political argument and name calling. We, as hackaday, really couldn’t care less which party you are for or what your political beliefs are. We want to talk about the project, in this case a portable solar charger. We go to other sites to argue politics. Maybe you should try here.

eReader battery never goes flat (in the sun)

solar_powered_kobo

Instructables user [flapke] has a Kobo eReader and wanted to add some solar cells to it in order to charge the battery for free. The modification is similar to others we have seen recently, though his work was done so well that it almost looks stock.

He started out by sourcing a pair of solar panels from DealExtreme that purported to supply 5.5v @ 80mA. Like most of us are inclined to do, he tested them before use and found that they actually put out around 50mA instead. While the performance was a bit off, they still fit his needs pretty well, as the charge current needed to be at or less than 100mA to avoid damaging the battery.

He opened the Kobo’s case, and carefully removed a section of the back panel to make room for the solar panels. Once they were soldered together in parallel, he wired them to the eReader’s battery through a Schottky diode to prevent the battery from draining.

While we think his solar modification is a great way to ensure that he never runs out of juice while reading by the pool, we would certainly add a bit of extra charge circuitry to ours to prevent damage to the battery. What do you think?

Fixing the Rovio battery charging circuit

[Chris] was unhappy with the battery performance of his Rovio. It seems that he’s not alone, so he set out to reverse engineer the battery charging circuit to see if there was a fix. Boy is there, what he found is the diode above, apparently installed backwards when compared to the silk screen diode symbol. Now it’s entirely possible that the silk screen is wrong and this was fixed during assembly. We think that’s unlikely because if the closer of the two diodes was supposed to have the same polarity as the one next to it there should have been room to install them both in exactly the same orientation. [Chris] pulled out a soldering iron and changed the diode to match the silk screen. That fixed his problem and he’s now getting better performance than he ever has.

[From our comments section]

Intelligent battery charging

[Razor] shares with us the plans for an intelligent battery charging circuit. Instead of blindly charging your battery into oblivion, this one shuts off once  the battery is fully charged. It is a nice clean circuit that can be adjusted and fine tuned to your specific needs via some trim pots and dip switches.

[via HackedGadgets]

Nintendo DS mini USB plug

DSCompare

Noting that so many of his electronics are using the mini USB plug for charging, [Xavier] decided to modify his Nintendo DS to charge via the same adapter. It looks like the existing adapter is basically a proprietary mini USB plug, so replacing it was actually almost a perfectly clean swap job. He has nice pictures of the process and some helpful tips as well. If you’re thinking of consolidating your charging devices, this looks like a step in the right direction.

Willow Garage’s PR2 robot

We would like you to meet PR2. Made by Willow Garage, PR2 is a platform for research into robotic programming.  The bot itself is simple compared to some of the humanoid bots we see, but its behavior is quite complex. In the video above, you see PR2 completing milestone 2 of its development. This includes navigating an office with closed doors and plugging itself into a standard wall outlet for a charge.  We’re especially fond of the “wiggle”. You can hear some of the developers talk more about PR2 and its completion of milestone 2 in the video after the break.

[Read more...]

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