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Garden Light
Posted on 2012/05/29 by celem
NOTE: Some updates are at the end of the article.
Recently I purchased a couple of Solar powered LED garden path lights at the local
Dollar Tree store for $1 each. Ever since I read TalkingElectronics.com‘s writeup on
converting such garden lights into 5-volt solar power supplies, I have wanted to tinker
with one. The one dollar light intrigued me because it was so amazing that one could be
sold for that price.
The one-dollar LED garden path light reduced the parts count and that is probably a big
part of their ability to sell it so cheaply.
I reverse engineered the circuit. It matches, quite closely, the example circuit for the
Shiningic YX8018 specification sheet. My schematic is shown below:
While the Shiningic YX8018 specification sheet does not show the internal schematic of
the YX8018 integrated circuit, It would, most likely, be a charge pump similar to those
shown by TalkingElectronics.com‘s writeup on the older type of garden lights that
use discrete components. I did a Rube Goldberg conversion of one of these lamps into a
solar 5-volt power supply, similar to what was described by TalkingElectronics.com‘s
writeup. I have had an ultimate plan to use one of these to power an Arduino (really an
ATmel ATtiny84 or 85) in a remote installation but I suspect that current limitations
may preclude this. I may try a 3.3-Volt converter suspecting that it will yield a little
more current but I still doubt that the current will be enough to do anything meaningful.
Posted research by Radio-GHE’s website hints that I’ll never get anything more than a
few milliamps. My circuit modifications are shown in the schematic below:
Modified Lamp Circuit
Conversion to 5V Power Supply
As you can see from the photo above, my circuit yields 5.1 Volts. I did a load test, of
sorts. Using two meters, I measured the voltage while simultaneously measuring the
current through a 10k-ohm potentiometer that served as a load. Adjusting the
potentiometer I found that the circuit provided .424 ma at 4-volts (yes, 4/10s of a
milliamp!). This was rather disappointing – only 0.001696 Watts! The load resistance
was 9.4kΩ I am abandoning any thought of using these lights for anything other than
their intended purpose – illuminating a single LED. However, these lights are
interesting little packages of rather clever engineering.
UPDATES:
Check out THIS-POST for some interesting information on this chip.
Reader “Peter” posted a good comment and referenced a blog named “Tom’s
Projects” wherein he describes his successfully modified a similar garden light
to power a thermometer with Morse code output on an LED as well as providing
the 3.3V supply for its ATtiny25 controller. I assume that Peter and Tom are
actually the same person. In any case, he has successfully achieved my
objective, at least at the 3.3V level. His series of three posts are excellent and I
encourage you to read them. They are Part1, Part2 and Part3.
An anonymous commenter to “Tom’s Projects” references a good Russian
article about how to make a YX8018 stabilized power supply. The Google
translation version is at THIS-LINK or the original Russian version is HERE.
