Miniature Lighthouse for Pre-Recycling Coin Cell Batteries

Artists and makers are often the gleaners of a disposable society, making use of the waste we wish didn’t exist. This means that we have an inherently complicated relationship with batteries. Sure, most batteries can be recycled, and I implore you to do so, but what if we could breathe new life into them whilst they wait to be recycled? I might just be impatient, but I was compelled to develop a specific use case for the box of stale CR2032 batteries sitting on my desk.  

My specific scenario might not apply to the general audience of this article, but I hope it inspires similar projects using stale batteries, because they are just that –stale. Why do I have a growing collection of CR2032 batteries on my desk? The parasitic 3V vultures found on all the headstocks of my student’s instruments –the clip-on tuner.  

Manufacturer’s guarantees aside, the batteries in these tuners never seem to last an entire semester. This could be due to teenagers ‘’forgetting’’ to turn them off after using them, for days on end, but I digress. Bottom line is I go through CR2032s as if they were literally little silver proverbial hotcakes. It goes without saying that I’m forced to buy them in bulk not only due to their rate of consumption but also due to their individual cost.

So, what ridiculous solution did I come up with to pre-recycle those batteries? A miniature lighthouse to serve as a gleaner beacon on my desk that would simultaneously suck the remaining life out of those stale 3V coin cells before being recycled.  

• 3D printed lighthouse parts (.stl files below)
• Conductive thread or tape
• CA glue (super glue)
• Bus wire (uncoated thin gauge wire)
• An LED (colour of your choice)
• Small spring (pulled from the battery compartment of a defunct television remote in my case)
• Scissors
• Soldering iron
• Hot glue gun
• A pile of stale coin cell batteries

As a proof of concept, I taped a stacked pile of CR2032s together to see if their combined power was anywhere close to 3V, it was! Then I tested whether they had enough combined amperage to power an LED, they did! With this confirmation, I immediately started 3D modeling.   

The 3D modeling was pretty straight forward as the lighthouse is made from basic geometric shapes using Tinkercad. Feel free to download the .stl files below or have a go at making your own lighthouse design! After modeling and slicing, print your design and start thinking about colour schemes while you wait!

When choosing an LED, I opted for a non-diffused transparent yellow one to get that lighthouse look I was after. Once an LED has been selected, start modifying it for our purposes by bending the negative (short) leg and trimming it to about 1cm long.

Then, insert the long (positive) leg of the LED into the hole in the center of the lantern room of the lighthouse and align the short bent leg with its matching slot. Set aside.

If you're unfamiliar with conductive thread, it’s great for incorporating circuits in textile projects or for lighting up miniature lighthouses! Feed the conductive thread through the tower of the lighthouse and tie a knot to keep the string taut on the inside of the tower. Then, add a few dabs of CA glue to keep it in place. Next, cut just below the knot that you made with scissors, keeping the end connected to the top of the lighthouse tower long. Trim the excess thread at the base of the lighthouse tower flush as it doesn't need to be connected to anything.

*(Conductive tape can be used as an alternative to conductive thread.)

This step is a bit fiddly but is simple enough. Bend the end of the bus wire into a curve and feed it through the holes in the lighthouse base. Once the wire is threaded, wrap the end coming out of the center of the base around the small spring and affix it with a bead of solder. Next, pull on the wire until the spring's base aligns with the small protrusion in the center of the lighthouse base. Use a dab of hot glue to keep it in place

Now that the spring is glued in place, feed the other end of the bus wire through the tube in the lighthouse tower. Next, slide the tower onto the base and use some CA glue to lock it in place.

Now for the fiddliest bit. Thread the remaining length of bus wire through tube of the lantern room so that it comes out the middle of the lantern room. Bend the long leg of the LED (positive) to match the contour of the underside of the lantern room, leaving the excess protrude out from under it (a small groove is allotted for this). Then, wire the bus wire to the short bent leg of the LED (negative) and make the connection permanent with a bit of solder. Trim the excess wire.

Next, glue the lantern room to the lighthouse tower with CA glue, being sure to properly align everything before the glue sets. Then, take the excess length of conductive thread coming out from under the lantern room and wrap it tightly around the protruding leg of the LED (positive). Secure it in place with some CA glue and trim the excess wire flush with the tower. Lastly, glue on the roof of the lantern room with a conservative application of CA glue. Assembly is now complete!

Testing should be done throughout the assembly process but it's good practice to do a final test once everything is assembled to ensure everything works as intended. With everything working as it should we can now turn our attention to aesthetics!

I modeled the lighthouse after some of our favourites out on the East Coast and took some aesthetic cues from them, such as horizontal stripes, and incorporated them into my design. As I couldn't decide what look I wanted for the tower I opted for a temporary solution, using black electrical tape to create bold horizontal black stripes. This way I can live with the design for a while and maybe try some alternatives before committing to a final design. I painted the roof and the trim of lantern room with black acrylic so that the light only shines through the lantern panes, selling the effect. Overall I'm pleased with the design and function of the lighthouse. I'm equally stoked to recycle the old cardboard battery recycling box cluttering my desk with this functional miniature lighthouse!

Cheers!

Mr. Ham