Using UV LED strips to build a long wave fluorescent mineral display case
I recently noticed that relatively low-cost LED strips are now available with long wave UV LEDs. I thought that these LED strips might work nicely for a small fluorescent mineral display. LEDs use less power and should last for years even when on continuously. A display with LED lighting could be left on and even be small enough to hang on the wall like a picture.
Unfortunately, short wave LEDs are still very hard to find, expensive, and also burn out after a couple hundred hours of use. This means that the display must use only long wave fluorescent minerals. Leaving a short wave UV light turned on would also generate excess ozone and fade your room’s furnishings over time without an enclosed case with UV absorbent glass to filter out all of the UV going out into the room.
My local Fry’s electronics store had 12V DC one foot UV LED strip lights for $8 as seen below. These are used for glow in the dark effects by computer hackers inside PC cases. They don’t list the wavelength, but I would guess just a bit below 400nm – towards the high end of the long wave UV region. The color response of fluorescent minerals was just a bit different than my fluorescent tube-based long wave UV light. I had a spare 12VDC 2A AC wall adapter around from an old external hard drive and used it for power. Looking through my LW minerals with the UV LED light, the English fluorites did not have as bright of a blue UV response as one would expect, but some other minerals such as manganocalcite were even brighter. After trying out the UV LEDs, I decided to go ahead with the small LED-based display case idea. I also tried a cold cathode UV PC light. It seemed to have a lower wavelength, but was not bright at all compared to the LEDs. The yellow wire on the LED strip is 12VDC and the black wire is ground.
There are also more powerful and expensive flexible and cuttable UV LED strips lights available from internet LED lighting stores by the foot. It sounds like they might have shorter wavelength LEDs (385nm) nearer the wavelength of the typical long wave UV light and output a bit more light. I have not tried these yet. It is also possible to dim LEDs strip lighting using PWM (turns “on” and “off” very fast varying the “on” time). Ideally, one would want LEDs at 360nm to see a color response more like current mineral lights. They seem to be making these at least one place in China now according to a Google search, but no one seems to have them in the US yet.
Looking around at a couple local arts and crafts stores (Michaels and Hobby Lobby), I noticed that nice looking shadow boxes with a glass cover are available at a relatively low cost. I selected one of the deeper 10 by 14 inch shadow boxes to try the LED display idea. It was even on sale for 40% off. Some are only about one inch deep, but the larger ones can be a bit over three inches deep.
Since the case was already built, I only needed to add the LEDs and line the case using black craft foam sheets. I drilled a small hole to run the wires out the back to the 12V DC power supply. The LEDs were mounted using sticky Velcro squares that came with the LED strips. The results are seen in the picture below.
Shadow Box case with UV LED strip lights
Next, some selected long wave fluorescent minerals were added and the cover was closed as seen below. The colors look a bit better than the images below since my camera got a bit washed out by the long wave UV. This is with some room lights still on. In the last image, the lights are off. The longer wavelength seemed to make it harder to photograph, it appears the camera sensors pick up a lot of the longer wavelenth UV.
Minerals added and case closed
Display with room lights off
Result and Ideas for additional work
I now have a small low-cost display case for long wave fluorescent minerals using LED lighting. It can be hung on a wall like artwork and left on 24/7. Even during the day with lights on, you can see the UV color response. The other lighting strips might be a bit brighter and have a lower wavelength. A dimmer might also be worthwhile. At night, it is almost a bit too bright. A standard household AC dimmer will not work, but special dimmers are available for the LED strip lights. It might also be possible to add some clear plastic or glass shelves to hold a couple rows of smaller specimens since long wave UV is typically not filtered out by glass and some plastics. A long wave filter could help clean up the purple haze a bit, but with the hidden lights and case it is not bad.
Adding a Dimmer and IR Remote Control for the UV LEDs
Most LED strip lights operate off of 12VDC. I found a low cost white light LED strip light kit shown in the photo below that contained a power supply with a dimmer (uses PWM?) and a small IR remote. The connectors are not the same, but with a bit of soldering for the two 12V LED power connections, it was hooked up to the UV LED strip lights in the shadow box display case. The small white dimmer controller module can be hidden inside the shadow box case. The curved side of the small black IR sensor (second wire coming out of right side of controller module) needs to be facing out towards the room. The IR remote can be used to dim and turn the UV light on and off. It solves the problem of the light being a bit too bright at night and it is handy to have a remote. It would also be possible to use a second kit to add a white LED light inside the shadow box display case to view minerals in normal lighting.