Introduction: Solar Tree Lights

This Instructable shows how to turn solar powered pathway lights into solar powered tree lights. It's not always convenient or safe to to run AC extension cords all over the garden to power lighted decorations. Solar powered lights carry their own power source with them and can be hung anywhere they will receive sunshine during the day to recharge. The project was also a way to re-inforce solar energy concepts for one of my children. As basic as they seem, pathway lights demonstrate the storage of solar energy by charging a battery during the day time, and then using the stored energy to provide light at night.

The multi-color pathway lights we used have a small PCB that controls the battery charging function as well as the "random" color changing function of the LED. You can use clear pathway lights as well - whether to use color or clear is a personal preference. All the "tech" is provided by the pathway light. What we are going to do is to disassemble the light, relocate the LED to an ornamental glass ball and attach a wire hanger to the solar module so that the solar light can be hung from tree.

Step 1: Bits and Pieces

Solar pathway lights came from Walmart. The glass balls came from AC Moore craft store and are readily available elsewhere. The paint is Krylon Frosted Glass spray paint which will diffuse the light from the LED to create a uniform glow. The paint is recommended for internal use only. Over time we found that the paint started cracking and sliding but that created even more visual appeal in a way that is difficult to do by intent. You could use glass etching chemicals or sandpaper as an alternative to achieve the same effect as the paint. You can also spray the paint on the inside of the ball which should keep it in perfect condition for a long long time!
All told, cost for a single light will be roughly $5 each which the major cost from the pathway light. The balls work out to about $0.80 each.

Tools you will need are drill with 1/16" and 1/4" drill bits, pliers, side cutters, hot glue gun, sharp knife, Phillips screwdriver and a soldering iron.

Step 2: Making the Solar Module

Cut the connectors off the Ethernet cable with the side cutters and remove the protective plastic sheath by using a sharp knife to start a small section, and then pulling (ripping) the rest by hand. This will expose 4 twisted wire pairs. You will need one length of twisted pair wire per light. Cut the wires to a length of about 3 feet. You can use more or less length - this is largely personal preference and does not affect performance due to the low current needed to illuminate the LED.  You can of course use any small gauge (28 gauge is good) electrical insulated wire for this - Ethernet cable was just convenient as I have a bunch of spares in my electrical bin. 

Unscrew the screws on the bottom of the solar module to expose the battery, LED and PCB. For these lights, the PCB was held in place with a melted plastic rivet and hot glue. It was easy to remove with a gentle upward pull. There is a variation on the PCB color and mounting even for the same solar lights. Seemed odd but it would appear that the internals come from different factories - some have green PCBs others are brown. Since we made up 6 lights in one day some pictures will have green, some brown.... just depends on which pictures were taken when!

Remove the LED from the PCB. The easiest way is to first mark one leg of the LED with a black sharpie, and then mark the same hole on the PCB with a black sharpie, then cut the legs of the LED to free the LED from the board. If you have a solder sucker, you can unsolder the LED from the board. The goal is to free the LED with long enough legs for you to solder wires to the LED.

Solder the twisted pair to the PCB. Tie a knot in the wire so that the ball will eventually hang putting strain on the know and not on the solder connections. This is called strain-relief. Basically allow two inches of wire between the PCB and the knot. Do not pull the know tight.

Use a 1/16 drill (or larger if your hanger wire is thicker) to make holes on either side of the solar panel. Then form your wire hanger and press through the holes. Bend small feet on the back side and then hot glue them. Add a little hot glue to the top as well to prevent water from running into your solar module.

Feed the wire through the hole in the base plate and then use hot glue to secure the PCB to the base plate. You can now re attach the base plate and fasten the 3 screws that you removed earlier.

Solder the LED to the far end of the wire. Use electrical insulation tape or heatshrink to make sure that the negative and positive leads do not touch each other or your LED will not light up. It is important to connect your LED the same way as you marked when you cut it free. LED is polarity sensitive and will only work in one electrical orientation. 

Step 3: Making the Ball

Paint the ball with the Krylon Frosted Glass paint and leave it to dry. You can try and paint the inside of the ball for better durability.

The glass balls come with a flimsy silver cap. Enlarge the hole in the top with a 1/4" drill bit. Work carefully because it is easy to unintentionally destroy the cap. The hole needs to be big enough for the LED to go through it.

Trim the wire clips that hold the cap onto the ball shorter. This makes it harder to assemble the ball but avoids the clip showing a shadow down the surface of the ball when it is illuminated.

Feed the LED through the hole so that the wire side of the LED is about 1/4" into the silver cap and then hot glue the back end. This will seal water out and provide support for the wires. 

Finally, once the glass ball has dried, run a bead of hot glue around the top rim of the glass ball and quickly install the cap/LED assembly to complete the ball. You need to work quickly before the hot glue sets. The glue will help support the clip function of keeping the cap and ball together. In the last picture with the unpainted ball, you can see how everything should look after this final assembly step.

Step 4: Hanging Them Up

All that's left to do now is to find a tree to hang them. We made 6 lights in one day. The tree lights have weathered over the last 3 months but that has given them a rather unique look. 

Since we had a lot of pathway light scraps, we glued two of the cones back to back to make a hanging pendant as shown in the last picture. 

And that is that! Enjoy the "free energy" light show.
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