Nocturnal Solar Light Bulb Saves Your Lungs

Solar nightlight

India has a bit of a problem with electricity. In fact, over 74 million rural households live without power altogether. Instead they rely on burning fuel for light — and coincidentally, inhaling harmful smoke. Not to mention fuel isn’t cheap. [Debasish Dutta] wants to change this — so he came up with yet another solar powered light that is a low-cost alternative.

It’s a very simple light made out of a cheap Tupperware container, a 2V solar panel, a white LED, a rechargeable AA or AAA battery, a photo diode and a Joule thief (voltage boosting IC). One day of charging can provide approximately 20-22 lumens for the entire night of operation. While it doesn’t seem like much, a typical kerosene lamp puts out less than half that brightness.

And with the photo diode, it automatically turns on at night, and off during the day. A coat hanger doubles as both a stand for charging, and a hook for hanging it at night.

[Dabasish] says this is just the beginning and has a website dedicated to creating green energy and sharing it with the world. Video below.

43 thoughts on “Nocturnal Solar Light Bulb Saves Your Lungs

  1. I like it! A switch wouldn’t add much to the cost, and could allow brighter light for the 3-4 hours it’s actually used, but whatever. There are also mass-produced lights already around – a friend of mine went on a little campaign and managed to source hundreds for an old-age home that had had two fires due to people trying to read by candle-light during power cuts. If more people like her or [Debasish Dutta] were around, we’d live in a much nicer world :)

  2. Thank you James Hobson for posting it.
    I did not use any LDR for auto cut in and cut out.The IC QX5252F has inbuilt function.So the cost is reduced,
    Can you please edit it.

  3. A standard bike generator can source 300 mA at enough voltage for a few watt LED With no regulation needed just diode bridge. Try using a gravity bucket of soil or water and the only high tech part, gearing (bike parts) to the generator with the slow rotation of the pulley in the hoist. This would make hundreds of lumins instantly for the time to haul the weight up again.
    No chemical cells are used at all.
    NiCd’s are nasty and on their way out if not already.
    Li requires that charging is picky hence more circuits to support the modern cell tech.
    This is done somewhere in the third world in a similar project, I don’t remember where.

    1. Light hous used to use a “falling” weight to , wowver they used clockworks to regulate how fast the weight would fall. Otherwise it would simply fall in an uncontrolled fashion without doing useful work. Even the act of regulating the rate of fall looks likely to waste the energy input to raise the weight. Not saying it couldn’t be useful, but it may not be as straight forward as it would seem

  4. howabout using the suns energy during the day to lift a gravity bucket really high, top of your highest tree or a flagpole or something. Like a gravity bucket but upscaled and automated.

    actually better than going up would be to go down into the earth, something like a well or a cliff face. Might even be able to bring up a lot of water for the next day then still be heavy enough to produce elec on the way down

    1. That’s horribly inefficient. You are converting the already low efficiency solar energy to a motor, which translates to mechanical energy, then reverse the direction at night. That’s a lot of losses. Just convert the solar to a battery.

      And this has been done… thousands of times. There’s an instructable almost every week on something like this. Hardly hackaday worthy. But then again, hackaday reports on almost everything.

      1. are you kidding me?! this is a great robust and thrifty build that is perfect for the impoverished people of the world! you obviously won’t realize the importance of having light until you don’t have access to it.

        1. I hate to be a negative Nelly….. but there is a common theme in many projects designed to use technological means in order to improve the lives of people who live in very impoverished situations: that you can throw some tech at them and suddenly things will be OK……. One laptop per child is a good example of this kind of thinking.

          You try to give a kid a laptop when they don’t have running water in their household. There’s not an infrastructure of internet connectivity for them to work with, and while teaching a child to read or speak another language can certainly “increase their odds of success” in life, there’s something missing in the perspective that this magical tech is going to fix their lives or really help them out in the long term when really they don’t have anything to eat today or a way to bathe etc etc etc.

          Don’t get me wrong, I have lived for years of my life where we traveled by foot to a well that the villagers dug in order to bale water by hand and carry it back to the “house”….. There was only moonlight or a candle for light at night.

          You get torn up by bugs. You stay very dirty all the time and are constantly nursing sores and other health problems that wouldn’t be an issue if you had running water.

          And then there’s the socio-political/economic instability that always makes you worry when a gunfight will break out.

          The problem is that in these kinds of situations, saying ‘Hey, this light only costs 2$ USD’ is not really congruent with the fact that many people are living outside of the cash economy almost entirely and that this level of needing parts that they don’t have that cost money that they don’t have isn’t really helping……. In other words, if this light would be helpful to you, chances are that you won’t be able to acquire it anyway.

          1. @hmmmmmmmmmmm
            This is a Good Post. Being poor in the less developed parts of the world is fundamentally different from being poor in the first world in ways that a lot of people have trouble wrapping their heads around. Folks have a tendency to think of it as being a matter of too little money, like if you just get the dollar value of a thing down low enough people in a village in the middle of nowhere will be able to mosey down to the nearest Walmart and buy it.

  5. Nice work. I’ve been thinking of something similar with a 5v output for phone charging as well. Lithuim ion seems to be a bit cheaper – around 50c/Wh vs 80c for NiMh. The compound solar cells are also more than the standard 156mm 0.5v cells.

  6. After looking at the qx5252 datasheet and solar cell specs, I think a 1.5V cell would be a better choice. A typical 17% efficient multicrystalline solar cell has a MMPT voltage of 520mV and still provides ~90% of peak power at 560mV. So a nominal 2V cell will output 2.24V at close to full power. The internal Schottky diode in the qx5252 will drop that by about 0.25V, so the charging voltage will be well over 1.6V, shortening the life of the battery. With a 1.5V cell, the charge voltage will be around 1.43V, close to the optimum for a NiMH cell. As the charge nears completion, current will drop, Vf on the schottky will drop, and solar cell voltage will increase. Voltage to the battery should peak at around 1.6V with minimal current.

    1. And you won’t get 17% efficiency from the cheap “B” grade polycrystalline solar cells found in solar lawn lamps. They are in the 10-14% efficiency range. A perfect polycrystalline “research cell” can be 17% or higher though.

        1. Don’t believe the listings of Chinese suppliers. 19% from a mono-crystalline cell is realistic though. But as long as they are cheap, that is what really matters in this application.

    2. Thanks for the suggestion.
      Can you suggest the solar panel current rating? I know higher the current quicker will be charging.
      The aim is to single day charge and give light up to 4- 6hrs.

      1. The higher current the better. It will charge the battery faster. If you need light for a longer time you should use a battery with higher capacity to store more energy. Something like a “D” cell would give you 3 or 4 times more run time on the LED.

      2. You can also use two or more solar cells in parallel, but you will need to add a Schottky diode to each solar cell to prevent them from trying to charge each other.

        Also, using multiple rechargeable batteries in parallel is possible, but you would need to add a small value (1 or 2 ohm) resistor on each battery so they share current evenly. But this is tricky to do, and will only work if all the batteries are exactly the same.

      3. The QX5252F has a maximum charge current of 300mA, so you probably don’t need a solar cell that produces more current than that.
        Also, you could try a slightly higher Inductor value (maybe 47uH), and you should get light for a longer time with only a small change in the brightness of the light. The lower the inductance, the higher the current flow through the LED.

      4. Compound solar cells in an epoxy encapsulation are difficult to find cheap with high current. Bare cells are the cheapest, but a bit too high current; over 3A for a 78x156mm cell.
        I’ve seen some circuits using the 5252f just as a boost controller. A few b-grade cells direct connected to the battery would charge quickly and would avoid the 15% losses through the schottky diode.

    1. Assuming that this device is made for people who have little to no access to electricity,
      I doubt that a crowd funding campaign will be able to reach them.
      Furthermore a quick search on reveals a solar lamp for $7.81 with similar specifications as your lamp. Depending on whether your costs exceed that price it would probably be a better option to sell your lamp directly to the locals or resell cheaper ones from the internet if your main interest is in providing everyone with a ‘cheap’ and solarpowered light solution.

      Regardless, I like the project and suggest everyone to also have a look at your MPPT project which might be a more suitable candidate for crowd funding or a kit.

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