I made a short video of the LTC3108 energy harvesting board with a solar cell. The test is done indoors, it was completely dark outside. Light source is a single 23W CFL bulb, around meter away. The breakout board has 1:20 transformer ratio and 470uF VOUT capacitor. The supercap was pretty charged already, I included it to show how it really helps recover from a pulse load.
Needless to say that at daylight (not direct sunlight, shadowy indoor corner), this is a monster; recovery from a pulse load is within 5 seconds.
Martin,
nice video. You can do this with the new LTC3129 using a solar panel about the size of a postage stamp. Check it out! (although it doesn’t have a storage pin.)
I had a look at the datasheet and don’t think it will work with such a small cell; You need to consider the output voltage under load and also the current the cell can provide. The “solar cell build” of the LTC3108 breakout board starts working as low as 100mV and 3-4mA of current; The “Peltier element” build will start up at 20mV, roghly same mA’s. The lack of storage is a serious draw-back as well, since a supercap there can provide enough juice to last during the night without input
On second thought (second datasheet read), it may be a good choice too; Dave – do you have experience with that particular chip?
Hi Martin,
Do you plan to sell this module?
Yes,
it is already available in the shop
What happens to the harvesting chip if you use a solar cell (such as the 6X6 you suggest on the breakout board page), if, say, you take the unit outside into direct sunlight… Does it fry the chip? I want to use the harvester in just such a situation, but I have not found where the chip disconnects or is protected during an over-voltage situation.
Hi,
There is no over voltage situation: the solar cell will will still produce 0.5V on direct sunlight, the amps will be higher. The LTC 3108 handles them nicely;
For outdoors usage you can really go with a smaller cell