Solar-Powered Jack-O'-Lanterns*

Do you ever have a location where you'd like an illuminated Jack-o'-Lantern but there was no easy way to get electricity to it? I don't have much faith in battery powered decorations, so I wanted to find a different solution for the 'no AC available' location.

Why not use solar cells to power my Jack-o'-Lantern? And to make it halfway easy (I complicated things so it's not full-on easy) I decided to use solar garden lights (<$1 from Walmart) to make it. I get the impression that these lights don't get fully charged on some days and I get some shade, so I decided to double up the solar cells (partially complicating) and decided the cells should be mounted ideally at the right angle so the sun's rays hit the cells at a 90 degree angle for maximum output (more complicating).

I want an illuminated Jack-o'-Lantern under my mailbox. My 'no AC location'. Let's tackle the challenge....

As a fun side note take a look at how Jack-o'-Lanterns got their name courtesy of the History Channel: https://www.history.com/news/history-of-the-jack-o...

*Note that the title, "Solar-Powered Jack-O'-Lanterns" is plural. There are two methods of creating a solar powered Jack-O'-Lantern described. Two Instructables in One!

Supplies

Plastic Blow-molded Jack-o'-Lantern

2 - Solar Garden Lights ($<1 each at Walmart)

A paper clip (for my mounting situation)

22 AWG Black Jacketed 2 Conductor Wire, 3.5mm Dia

30 AWG Flexible Silicone Wire; Red and Black

Screw Eyes

Phillips Screw Driver

Razor Knife

Mounting Screws

Silicone Caulk

Oral Syringe

Epoxy Glue

Heat-Shrink Tubing

Electrical Tape

PLA Filament and 3D Printer

Orange Paint (Pumpkin colored)

Soldering Iron and Solder

Drill Motor and drills

Heat gun or other heat source for the heat-shrink tubing

Mini Zip Ties

Step 1: Scope Out Your Location

Here is the mailbox I wanted to hang the Jack-O'-Lantern under. I had already installed mini screw eyes previously for other decorations.

This mailbox faces North so the Jack-O'-Lantern would be in the shadow of the mailbox's post. Not ideal for a solar powered Jack-O'-Lantern.

But behind the mailbox is a nice decorative post piece sticking out just begging for a solar panel!

Step 2: Figure Out How to Mount Your Jack-O'-Lantern

Since the blowmolded Jack-O'-Lantern is very light I thought I could hang it from its stem. All I had to do was drill a hole horizontally through the stem. A straightened paper clip fits and was bent to form hooks that snagged my preexisting screw eyes perfectly.

Jack is now mounted.... Now onto the Solar stuff!

Step 3: Design Your Solar Array and 3D Print It

As I mentioned, I wanted my solar panels to be perpendicular to the sun's rays. So what angle is that?

I didn't want some rough estimate or average angle like what a large commercial solar panel would use. No, I wanted to know what the angle to use TODAY, in Mid-October, Halloween Season Time!

Well to figure this out I took a digital protractor (angle gauge) and taped a short length of drinking straw to it. I then adjusted the angle gauge until the shadow cast by the straw was only the wall thickness of the straw; in other words the sunlight was shooting directly down the straw. I now knew the angle (55 degrees; you would have asked if I had not mentioned this) the sunshine was coming in at and could design my solar array holder at the proper angle.... for Halloween Season!

The solar array would use solar cells from the solar garden lights so it would need to have recesses to mount them into. There also has to be holes in the bottom of those recesses to pass the solar cell wires through to the control circuit.

The array would need to have a place for the battery and circuit board that was removed from the garden lights. Originally I was just going to mount the 'guts' of the solar light (battery & electronics) in the base of the array but it got cramped so I copied over the battery and electronics holders into my 3D design. They needed to be mounted horizontally and since 3D printers don't like to print into air, I created a separate subassembly that could be printed in the correct orientation, facing up. This subassembly was to be glued into place on the inside back wall.

The 3D design was also set up so all the walls where either vertical or angled such that a 3D printer could print them without any trouble. So no supports needed here. I also used the same angle printing concept to add some brackets with holes for zip ties to dress the wires.

Step 4: Disassemble the Solar Garden Light

Remove the clear diffuser from the main light by twisting. Use a screwdriver to remove the screws holding the light together and pry it apart. Inside you can see the battery and a small circuit board. Prominent are the two wires connected to the solar cell in the top of the light. You are going to remove these solar cells so cut the solar cell wires.

Step 5: Remove the Solar Cell. Careful It's Glass

To remove the solar cell you need to remove the rubbery caulk sealing the area behind the solar cell where the wires emerge. To do this you need to take a razor knife and cut a rectangle around the wire. If you look closely you can see where the plastic has ridges that show where the opening in the top is located, where you need to cut to free the solar cell.

After cutting the caulk, take a screwdriver and carefully push down on the rubbery caulk next to the wire, inside the area you have cut loose. Be very careful as the glass solar cell is glued to the top of the housing. Apply gentle firm pressure and the solar cell should come loose. You should be able to remove the solar cell completely.

You might want to have spare solar garden lights. I cracked a cell trying this. Hey, at less than a dollar why not get a few and reduce the anxiety of this step?

Step 6: Remove the Battery, Battery Holder Contacts, Circuit Board and LED

Carefully remove all the parts from the bottom assembly of the solar garden light. Remove the battery. These garden lights are nice in that they use a Nickel-Metal Hydride (NiMH) battery instead of an ecologically harmful Nickel Cadmium (NiCd) type. Cut the wires to the battery holder tabs and pull them out from their plastic slots. Cut the remaining wires and un-solder them from the circuit board.

Step 7: Lengthen the Solar Cell Wires

You will need to add some length to the solar cell wires. Splice on about an inch of wire. Red for positive onto the white wire. Black for negative onto the back wire. Solder and insulate with heat-shrink tubing. Do this for both solar cells. Now those wires will get you to where you need to go!

Step 8: Connect All the Wires Back to the Circuit Board. Remote the LED

Hook all the wires back onto the circuit board. You can see the labels on the circuit board in Step 6 and the photo above. The solar panels are connected in parallel. Both positive (white/red) wires are twisted together and connected where the S+ (solar +) is marked and both negative (black) wires are twisted together and are connected to SB- (solar & battery -). Connecting the solar cells in parallel keeps the voltage output from the cells into the circuit board the same as the original voltage, but doubles the current into the board and battery. So, in theory, the battery should charge faster and hopefully more fully.

Extend the LED. It has to find its way into the Jack-O'-Lantern. I needed about 16 inches of jacketed two-conductor wire to get the LED where it needed to be. Remember to thread the wire to the LED through the hole in the side of the solar array box before soldering on the LED. [ I can't tell you how many times as an electronics enthusiast I soldered wires to a jack before sliding the sleeve/body over the wire resulting in having to un-solder the wires and put the sleeve over the wire and then re-solder.] Solder the extension wires to the LED. If you look into the clear base of the LED you can see that one lead wire is wider, this is the negative lead wire. Dress up the splices with heat-shrink tubing.

Solder a red wire from the B+ to the flat battery contact. Solder a black wire from the SB- to the spring battery terminal.

Step 9: Mount the New Electronics Assembly

After connecting all the wires back onto the circuit board (in the right locations, mind you!) you can mount the circuit board into its plastic holding slots. The battery holder contacts can be slid into their respective slots (the spring is negative). Battery polarity marks are recessed into the plastic base of the electronics assembly where the battery will be installed.

The mounting brackets can be used with zip ties to secure the wires. I don't think they really need this but I can be neat and tidy somewhere in my life (where it really does not matter).

The new electronics assembly can then be glued in place with epoxy (or silicone if you like something not quite as permanent as epoxy). There is a slight recess in the back wall just waiting for it. I can hear it calling, can you? (I hope not!)

Wait to install the battery until after the electronics assembly is glued in place. The spring force on the battery can flex the electronics assembly base and cause it to bow a small amount, not great for gluing to a flat surface.

Install the battery, noting the correct polarity.

Step 10: Silicone the Solar Cells in Place

Time to mount the solar cells. I took an oral syringe and filled it with silicone caulk. This gave me a small bead of silicone and much better control. I applied silicone around the perimeter of the solar cell recesses and pressed the cells into place. Silicone is messy so be sure to wear disposable gloves and have plenty of paper towels available.

Step 11: Make the LED Holder for the Jack-O'-Lantern

Take the bottom plastic assembly of the garden light that had all the electronics in it and cut off all the plastic that protrudes; the plastic parts that would have extended up inside the solar garden light housing. You want to cut off all the battery holder tabs and slots so that the plastic bottom of the housing is just a flat disk. The tube that extends out the bottom of the housing where the LED was located should be saved. This tube will hold the LED inside the Jack-O'-Lantern.

Now paint this disk lovely pumpkin orange.

After dry, apply silicone around the perimeter of the disk or (for those of you that like bigger targets) in the recess around the light bulb hole in the back of the Jack-O'-Lantern.

Mount the orange disk over the light bulb hole in the Jack-O'-Lantern.

Step 12: Mount All the Parts in Their Places

Hang the Jack-O'-Lantern in place under the mailbox using the paper clip wire hooks.

Use two screws (the ones left over from disassembling the solar garden light) to mount the solar cell array to the mailbox post. Insert the LED into the holder in the back of the Jack-O'-Lantern. You may have to wrap the wires with some electrical tape to get them to fit snugly.

Now wait until dark and take in that beautiful grinning Jack-O'-Lantern that glows every night without external electrical power - What an achievement!

Enjoy!

But wait, there is a much less complex alternate approach described in the next step!

There are two Instructables in ONE!