Creepy UV LED Sun Jar!




About: depotdevoid is short for The Depot Devoid of Thought, the place where you go when you lo...
Gaze in awe mere mortals, at my Creepy UV Sun Jar!  This new twist on an old idea is awesome, eye catching, and kind of spooky all at the same time. 

I'm the kind of instructabler who makes a lot of sun jars, as well as othersolar powered LED devices.  I've built several of these with UV LEDs in them, as I like the weird purplish glow, but they're very dim.  Now with the simple addition of some glow in the dark paint, the full power of the UV LED is revealed!

As with all of my instructables, if you make your own version of this, be sure to post a picture in the comments and I'll send you a digital patch!


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Step 1: SCIENCE!

If you're not interested in how this works, feel free to skip to the next step.  Stick around if you're awesome and want to learn about ultraviolet radiation, the visible electromagnetic spectrum, and fluorescence.

Human beings can see in a very narrow band of the electromagnetic spectrum, about 750nm (red) to 390nm (violet)--do you remember ROY G. BIV from gradeschool science class?  This is just a tiny chunk of the spectrum, which ranges from radio waves (longest wavelength) at the very bottom all the way up to gamma rays (shortest wavelength) at the very top.  Just below the human visible sprectrum is infrared light, far infrared being heat and near infrared is what people use for active nightvision and remote controls.  Here we're more concerned with the other end of the spectrum, ultraviolet light.  This is the stuff that gives you a tan (or skin cancer) if you get too much of it, though we're working with very safe levels so don't panic. 

An ultraviolet LED will put out most of it's light in the invisible near UV range, with it's major output around 375 nm, just outside of our range, but with a smaller output around 400 nm, or just within range.  For this reason, to the naked eye an UV LED or a blacklight looks pretty dim, but really they're pumping out quite a bit of light that you can't see.  Here's a chart from wikipedia to clarify.

So what good is a bright light that looks dim?  Well,  UV light has an interesting property, in that it causes a number of chemicals to fluoresce.  Fluorescence is when a chemical absorbs light of one spectrum and emits light of a lower spectrum.  In this specific case, the high energy UV photon strikes some glow in the dark paint, causing it to emit a spooky green glow (around 540nm, at a guess).  Thus, spooky sun jar!

Step 2: Gather Supplies

Here's the complete list of parts:
  • Solar Garden Light
  • Wire Bale Glass Jar
  • Glow-in-the-dark Paint
  • UV LED (I get mine from dealextreme)
  • Aluminum Foil
  • Epoxy

As to tools, you'll need:
  • Sandpaper
  • Wire Cutters
  • Soldering Iron
  • Sturdy Scissors
  • Screwdriver (maybe)
  • Paintbrush
  • Stirring stick
  • Hairdryer
  • Hot Glue Gun

I got very lucky, as I happened by the dollar store this summer when they had solar garden lights. I bought a couple dozen, figuring that they'd probably be crap but I could at least reuse the parts for other projects. Much to my surprise, they were actually quite good quality! I went back the next day to buy their complete stock, and I guess someone beat me to it! So anyway, I started checking back whenever I thought about it, and while I never got any more solar lights, they did get a big shipment of wire bail glass jars, which I promptly bought 40 or 50 of!

Step 3: Paint the Jar

Stir the paint thoroughly.  Make sure to scrape the bottom, a lot of the glowy stuff settles down there and hardens even with the lid closed.  You can still break it up and stir it back in though.

I used a brush like the one you see in the pictures below, I think it worked a lot better than a standard paintbrush would have.  I applied a coat, hit it with the hairdryer, and repeated, for three coats total.  Don't leave much settled at the bottom, it won't do any good down there.

Step 4: Prep the Electronics

If you've made these before, this will seem like old hat, but if this is your first sun jar, read on. 

First you'll need to dismantle the solar garden light.  Just keep in mind, you only need three things:  the battery and holder, the circuit board, and the solar panel.  Just make sure these are intact and all the connections are good, everything else can be cut away and discarded, or saved for future projects (that's what I do!).

It's a lot easier to get clear LEDs than diffused, so just get the clear ones.  Using a piece of sandpaper, scuff up the outside of the LED.  Instant diffusion!

With that done, snip the connections of the LED that came installed in the solar light.  Keep track of which side is positive and which is negative.  This is easy if they've marked it on the circuit board, but if not pay attention to the LED itself--they're almost always flat on the negative side.  Solder on the new UV LED in its place, making sure to get a good solid join.

Step 5: Install the Electronics

Clean both the surface of the solar panel and the inside of the jar's lid.  Anything obscuring the panel will make it less efficient. 

I've had a lot of practice making these, and I find that this is the best way to assemble them:
  1. Hot glue two corners of the panel to the lid
  2. Let it cool
  3. Hot glue the battery holder to the panel
  4. Let that cool
  5. Hot glue the circuit board to the battery holder
  6. Let it all cool for a few minutes
  7. Epoxy everything thoroughly--E6000 has worked best for me
I've tried just hot glue and four or five different epoxies, and this formula seems to hold up better than anything else.

Let the paint and the epoxy dry overnight before moving on to the next step.

Step 6: Install a Reflector

I do this to most of my sun jars, as much of the light is focused on the bottom of the jar where it won't do any good.

Get a piece of foil, fold it up until it's about the size and shape of the bottom of the jar, then press it into place.  This reflects a lot more light back up to the glow in the dark paint and makes it much brighter than it would be.

Close everything up and put it outside in the sun, you're done!

Step 7: Final Thoughts

This is a fun addition to all the other jars in my front yard.  It definitely stands out and glows as bright or brighter than most of the other jars.  Even after the LED runs out, it keeps the glow for a little while.

Thanks for viewing my instructable, I hope you liked it!  If you did, please take a moment to rate, subscribe, and comment!  Do you have any questions or recommendations?  Did I leave anything out?

As with all my instructables, if you make your own version of this, be sure to post a picture in the comments and I'll send you a digital patch!

Thanks for stopping by!
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    67 Discussions


    8 years ago on Step 2

    Just wanted to let you know the solar lights are back at my local dollar store so you might check for them at yours. They run out fast but they keep getting more in. I didn't have luck finding the jars though.

    2 replies

    7 years ago on Introduction

    Just wondering, since the solar unit has a 1.4 v power supply, how did you get the 3.5 v uv led to light? It's interesting. Good job on your project.

    4 replies

    Reply 7 years ago on Introduction

    Thanks sunspirit, and thanks for the patch!

    All the voltage change is handled by the electronics that came from the garden light--I've seen "Joule Thief" circuits that step up the voltage from a battery to run an LED, but I didn't build one of my own. The circuit board from the garden light does all that, while charging the battery at the same time!


    Reply 7 years ago on Introduction

    Thanks depotdevoid. That little piece of infio that circuits step up the voltage completes the circuit in my brain. Now to the workbench. **(:>))


    7 years ago on Step 2

    Never mind I didn't see the other post you left with this one...

    Thank you!!!! I want to make them for my son's spooky themed costume birthday party!!!


    Reply 7 years ago on Step 2

    Hi Jaime, I'm not sure exactly what you mean, could you be more specific?


    Reply 7 years ago on Step 2

    When I went on to find UV LED's the search results showed LED Emitters that look the same as in the picture. 10pk for $1.16 come in blue, green, red. Are those what I'm supposed to get?


    Reply 7 years ago on Step 2

    Can these work?


    Reply 8 years ago on Step 3

    What do you mean? The first picture at the very beginning of this instructable?


    9 years ago on Step 7

    Purely curious - might there be a way to use the same power as the LED to power a miniscule motor or something to cause the tinfoil to move a little, just to create an even more spooky appearance? No need for motor/'animator' to be active at any time other than when the LED is on. Can see where battery may need to be bigger to accomodate power for motion. Nice instructible!!

    2 replies

    Reply 8 years ago on Step 7

    How about some memory wire - just enough to wiggle it a tad?