Introduction: Upgraded Garden-Variety Solar Night Light
Here's something quick and easy that you can whip up in less than an hour, using parts that you may already have lying around. It makes a neat gift for friends and family!
Yes, I'm sure you've seen a zillion solar garden lights stuffed in a mason jar before, and this one is certainly similar. I've changed a few things this time around though, that boost performance and change the look a little. The performance-altering steps are not necessary of course, but they will help the LED stay lit for much longer.
Here's what you'll need:
A dirt-cheap solar garden light - I bought the one I used for a dollar.
A mason jar or some other container with a transparent lid.
A decent solar cell - it should fit inside the lid of the jar. 4V at 80mA is perfect.
One 2xAAA battery holder with leads
Two AAA NiMH batteries
A few bags of small, clear marbles - Cateyes or spiders look best.
And just a few basic tools:
A soldering iron
A glue gun
Step 1: Disassemble the Garden Light
If you're not planning to upgrade your garden light, then you can skip ahead to the assembly steps. Just take apart the garden light until you're left with a solar cell, the LED and the circuitry, which should all still be functioning.
If you're going to be upgrading, then read on! Continue taking apart your solar light until you're left with nothing but the bare circuit board. In my case, it was a tiny sliver of PCB with some battery terminals and an LED sticking out. Pretty basic, eh? This little board basically contains a Joule Thief, all neatly mounted and ready to use. Not bad for a dollar - and in many cases cheaper than making your own.
But we're not done yet! Oh no! Get out your soldering iron and remove the battery tabs from the board, they will not be needed. If you want to change the colour of the LED (which I do not recommend in this case, because white looks best), then go ahead and do it now. Be sure to observe polarity.
Step 2: Mount the New Battery Holder and Insulation
The new solar panel is much more powerful than the old one, capable of charging two AAAs instead of one, and in less time. I used a 4V, 80mA solar cell I found on dealextreme.com for about $5. Don't use anything bigger than 4V if you're only charging two batteries!
The bottom of this solar cell is basically two huge power rails, ground and positive. Glue the battery holder to the ground side with hot glue, about 5mm from the edge.
Now, cut off a bit of the black wire from the battery holder and strip off about 5mm of insulation from the end. Solder the wire onto the ground side of the solar panel close to the edge, and out of the way. Leave the red wire for now, it will not be soldered just yet.
The PCB from the garden light will be mounted about in the middle of the back of the solar panel, so that the LED is close to the center. Cut a piece of some sort of insulating material (I used craft foam) to the same size as the bottom of the garden light PCB, and glue it with hot glue onto the back of the solar panel. Do not glue the garden light PCB yet.
Step 3: Solder the Garden Light PCB
Hold the garden light PCB in place on top of the insulation, so the LED is in the very middle. Using its position as a reference, cut the red wire from the battery holder so that it will reach the "BAT+" location on the PCB. This is where one of the battery terminals used to be soldered. Strip off a bit of insulation, and solder the wire in place.
Now, you should have two pieces of wire left, that were cut from the battery holder: red, and black. If you don't have any wire, or they're too short, it doesn't matter, just use any insulated wire you've got.
There are two more wires left to add. Take the leftover red wire and cut it to size to run between the solar panel's positive terminal and the "SOL+" hole on the garden light PCB. Strip the ends of the wire and solder them in place.
Take the leftover black wire and solder it between the "GND" hole on the garden light PCB and the ground rail on the solar panel.
TIP: To solder on the solar panel, it helps to put a blob of solder on the copper first, then reheat the solder as you push the wire end in.
Step 4: Finish the Upgraded Light
Before gluing everything together, it's a good idea to test it to see if it still works. Pop two rechargeable batteries into the battery holder and cover the solar panel with your hand. Does the LED light up? Good! Then you may continue. If not, hold the solar panel under a light for 30 seconds then cover it back up. The LED should light (though dimly). If it still doesn't work, go back and check your work. Pull out the batteries first, then go and look for short circuits and wires in wrong places.
With your light now working, you can glue the garden light PCB in place. Put a few small blobs of hot glue on the insulator and stick down the PCB, with the LED in the center of the solar panel.
Step 5: Finish the Jar
I decided to use marbles to fill this jar. They look much better than simply frosting the glass, and look great both in the daylight and when lit from behind with the LED.
I had some marbles left over from childhood that I used up, but I didn't have quite enough to fill the jar. I bought four small bags of marbles from a dollar store to fill it up to the neck. Be sure to use marbles that are transparent, so the light can shine through. I used mostly Cateyes and Spiders (the names I recall from when I was a kid), because they are clear with just a splash of colour. Mix them up inside the jar for even distribution.
Now, just make a small "hole" in the center of the marbles which the LED will fit into. They should push aside just enough that you can slip in the LED. The solar panel and garden light PCB simply sit on top of the marbles, there's no need to glue anything down. The lid should close on the solar panel and hold it in place without it being crushed or rattling around too much. Add or remove some marbles for a perfect fit.
And that's it! Place the jar on a window sill where it will get light during the day and cast a happy glow all night. With an extra battery and a more powerful solar panel, the light should easily last longer than the night, and will charge up even on cloudy days.
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