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Project Page: Solar Night Light


A Traveling  Night Light

BottleI built this solar night light thinking that it would be good to bring camping. The light was build using a recycled plastic peanut jar with the surface sanded to help diffuse the light.

A single white LED, powered by one AA NiMH batter, provides the light. The solar panel trickle charges the battery when the sun is out. This means that the solar panel acts as an on/off switch. If the light is placed in a window it will always charge in the day and come on at night with no intervention required.

Joule Thief

I learned the circuit, which is similar to ones used in solar landscaping lights, from Evil Mad Scientist Laboratories. Using the Joule Thief circuit allows the LED to be powered by a single 1.5 volt battery.

BottleThe biggest stumbling block in building the circuit was winding the inductor by hand. The size requirement for the ferrite core was not clear to me, so I was forced to use the Goldilocks Method. The first core that I bought was too small and the next one was just right. At least I think think the first one was too small, all all I know for sure is that it didn't work.

BottleThe wire used to warp the inductor is 30 AWG wrapping wire. In the EMSL Joule Thief video they solder everything together straight off and press the appropriate leads onto a battery. BottleIn order to use the circuit on a breadboard I wire wrapped the leads from the inductor onto cut component legs saved from other projects.

Circuit on a Jar Lid

BottleVelcro attaches the solar panel to the top of the jar lid and the battery to the underside. The circuit is built on a small round circuit board. I used a piece of plastic tube to mount the circuit board to the lid. The tube was the packaging for glow necklaces.

 

BottleI'm not entirely satisfied with the jar, but since all the electronics are contained in the lid, the light can easily be moved to any jar with the same size thread. The tube holding the circuit is glued to the lid and a standoff attaches the board to the tube. There is plenty of extra wire running to the LED, so the light can be positioned lower in the jar if desired.

BottleWhen the light was finished I put it in the front window to catch the sun. It was satisfying to see it begin to glow just after dusk. The energy harvesting nature of it really hit home when I went to bed and realized that there was no need to shut off the glowing light in the window. Sure, this is using solar energy on a very small scale, but it really makes one consider wider possibilities.

Parts Bin

Parts Bin

4.5 volt solar cell

from BG Micro

Round PCB Kit (5-Pack)

from RadioShack

2100mAh NiMH battery

from BG Micro

 

AA battery holder

from RadioShack