solar powered lantern

The MOONLIGHT, a solar powered lantern, is built and was designed in collaboration with the rural Cambodians it is made to serve. Over 70% of the country has no access to the power grid, so as a result they have traditionally relied on kerosene lamps after dark for tasks like cooking, eating and reading. Those lamps pose a great fire risk, as most rural homes are built from wood and straw. The MOONLIGHT can be rented in rural areas for less than $.08/day, the same amount traditionally spent on kerosene. These photos were taken in villages around Kandal Province, near the Mekong River, the first area to adapt the MOONLIGHT for everyday use.

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innovations: changing world one little at a time.



Solight Solarpuff - Solar-Powered Lantern

Ìnspired by the principles of origami and wanting to help the people in need, Alice Min Soo Chun created a lightweight lantern. The main material this lantern uses is recyclable PET, which is durable in all sort of weather conditions. It’s environmentally-friendly and weighs only 2.3 ounces. The Solight Solarpuff is water resistant and doesn’t need extra batteries because it’s recharged with a solar panel.

“I’ve been to South Sudan to volunteer. When I saw the children dressing, eating, and living, I couldn’t help but cry. You should actually see what’s going on there. Seeing people live like that, I realized I was actually living a very fortunate life. We get so used to what we have and take it for granted. Their medical and education systems are all so poor. They had no electricity, so I brought a solar-powered lantern to the night school. Despite the poor environment, so many kids joined the class because they really wanted to study. Their textbooks were totally worn; even the covers were gone. They didn’t even have any writing tools, so I brought a bunch of pencils to give to them, expecting they would like it. However, they kind of didn’t like it. Do you know why that is?”
“No, why?”
“They didn’t have any knives. There were no pencil sharpeners. Each house should have at least one knife, right? I thought they would for sure have one, but that was just my thought. They preferred a pen to a pencil, because they didn’t even have any knives.”

“제가 아프리카 남수단에 봉사활동을 하러 자원해서 가봤는데, 애들 옷 입고, 먹고, 생활하는 거 보면서, 그냥 눈물이 났어요. 정말 아무 말이 필요 없더라구요. 눈으로 봐야해요. 봉사활동을 하면 거꾸로 ‘저렇게 사는 사람도 있는데 난 너무 행복한 거잖아’ 하고 오히려 깨달아요. 우리가 너무 안일하게 우리에게 주어진 걸 모르고 살거든요. 거긴 의료 시설도 너무 열악하고 교육시설도 너무 열악해요. 전기가 없어서 야학 할 때 쓸 태양광 랜턴을 가져갔어요. 그렇게 야학을 하는데 공부를 하고 싶다고 애들이 엄청 와요. 이 애들이 가지고 온 책을 보면 겉표지도 없고 다 찢어져 있어요. 필기구도 없어요. 그래서 연필을 나눠주면 엄청 좋아할 거라고 생각해서 연필을 준비해서 가져갔는데 별로 안 좋아하는 거에요. 그게 왜 그런지 알아요?”

“왜 그렇죠?”
“칼이 없어서요. 연필 깎을 칼이 없는 거에요. 집집마다 칼이 하나씩은 있어야 하잖아요. 당연히 있을거라고 생각했지만 그건 우리 생각일 뿐이에요. 오히려 볼펜을 더 좋아해요. 연필 깎을 칼이 없으니까.”

Reverse Engineering: Solar Lantern Circuit Part II

So now we need to know what the inductor is and what the diodes are.  The only definitive way to determine what the diodes are - is to unsolder them and read the labels.

So D1 is the plastic-y one and it has 1N5817.  And the glass diode is D2 - 1N4148.  Annoyingly, depending on how you look at it, it also looks like 1N4146.

The inductor is a bit harder to figure out, honestly.  I’d get an inductance meter if you can, but if you can’t and want to be masochistic…the way we essentially did it (thanks to @mgburr and @apexys) is by finding the resonant frequency that the inductor works at.

So we tried a Clapps oscillator:

Which didn’t give me much of anything.  The line on the scope moved upwards, but I didn’t see any waveform.

So then Apexys suggested a 555 wave generating circuit.  To be honest, I’m not completely certain what it does.  But what I did was once the circuit was made, I tapped my scope’s probe off of pin 7 and got a rough estimate of the frequency of the wave.

Note, the chip did get hot to the touch with this circuit, even though it worked.

Waveform on scope:

And we estimated a frequency of 15-18kHz for the triangle-ish pulse.  Based on that estimation and the tank circuit equation.  

For 15kHz, the inductor would be 1.125 mH

For 18kHz, the inductor would be 0.7818 mH

But wait….it seems like the actual frequency that we want is actually hidden in the waves inside of the triangle shape there.  So……per Apexys, the frequency is much higher than 15-18kHz.

@_@ *googles for inductance meter*