Fluorescent Mineral Stand

Hello. This instructable describes the creation of a simple mineral stand with an ultraviolet light source. The phosphorescent mineral will rotate on the pedestal so that it can be seen from any angle. The mineral will be illuminated alternately with ultraviolet and warm white light.

Intro:

Some minerals have the ability to temporarily absorb light and release it in a form of a light with different wavelength. This property is called "fluorescence." It works on the following physical principle: A photon from the ultraviolet spectrum strikes a susceptible electron within the mineral. Impact energy then excites the electron and it temporarily jumps on a higher orbital. After a very short while, excited electron falls back to its ground state orbital and loses some of its stored energy by emitting a photon at a longer wavelength. This higher wavelength light is visible to the human eye, so we can observe this wonderful phenomenon :)

• Small engine with gearbox
• M3 screws and nuts
• small bearing
• threaded insert
• piece of black fabric
• Double-sided tape
• wooden sticks (2mm diameter)
• black matte paper
• UV LEDs warm LEDs
• buck converter (optional for the motor)
• 2x 20k ohm resistor
• 555 timer
• 100 uF capacitor
• small piece of universal PCB
• rubber band
• wires
• glue gun
• 3D printer
• soldering iron

The stand will consist of two parts:

• The lower part on which the motor, LEDs and electronics will be mounted
• Upper rotating part where the mineral will be placed

In the front part of the lower part there will be a sloping place for a sticker with a description of the mineral, on the inner circuit there are holes for LED diodes. At the rear, there are two holes for mounting the engine. For easier installation from below, I created holes on both sides.

I used Autodesk Fusion 360 for the design.

The rotating disk has a diameter of 80mm. A bearing is pressed into it from below and the disk is screwed to the bottom of the stand, into a threaded insert. Along the circumference of the inner - smaller disk there is a groove for catching the rubber band, which will be connected to the motor.

The engine originally had a gear, so I designed the pulley wheel as a replacement.

I first built the whole circuit on a breadboard. The 555 timer takes care of alternating colors in the interval of 1.4 seconds warm white and then 2.8 seconds ultraviolet and all around. The times can be extended by increasing the values of the resistors, or by changing the capacitor for a larger one. If the output of the integrated circuit (pin 3) is at the HIGH level (around 5V), the ultraviolet LEDs will light up. If the output is at the LOW state level, warm white LEDs light up. Adjust the currents flowing through the LEDs according to the required luminosity by changing their respective resistors.

The output of the buck converter is set to a value of approximately 3.3 V, at which the rotation speed is just right.

I chose 400 nm UV LEDs, but they are available from 270 nm and higher.

I printed both parts from PETG black filament. Threaded insert is suitable to be installed using a hot soldering iron, but it can also be done manually, using pliers. I inserted the bearing into place manually - the hole for it should be just tight, so no glue is needed.

It is important to test that the top rotates with minimal friction and without jerking. If necessary, lift them from the bottom using small metal pads.

Fasten the motor with the new belt pulley to the stand with two screws from below. If the belt pulley is not flush with the groove in the rotating disc, the motor (or disc) must be wound with washers.

Solder the cable leading to the motor terminals and pass it through the hole in the bottom to make installation easier. Connect the motor to the output of the buck converter. A buck converter is only required if the motor supply voltage is lower than the voltage required for the LEDs and the integrated circuit that will control them. In my case, the IC runs at the 5V level and the motor at a voltage of about 3V.

I inserted LEDs into the holes at the bottom of the stand, which I secured with a melting gun. Their order is alternately: UV, warm, UV, warm.

I tilted the slope slightly upwards to illuminate as much of the minerals as possible. In this step, I also connected the hot cathode cathodes together with the UV LEDS anodes

I soldered the control circuit to a small printed circuit board. The circuit is simple, consisting only of an ordinary ne555, two resistors and a capacitor.

I connected the buck converter to the control circuit and its output to four LEDs. I placed the printed circuit boards under the rotating disk and secured them with a gun. Make sure that the wires running along the bearing and near the saltpeter do not prevent the disc from moving smoothly.

I cut a circle out of a piece of black cloth. I then glued it with double-sided tape to the rotating disk. I think that the stove will hold and at the same time look better placed on a piece of fabric, but most of all it will not be damaged by direct contact with hard plastic.

First insert the rubber band into the bottom of the stand, then screw in the rotating part. The rubber band must be fitted with pliers or tweezers, first on the smaller (and only accessible from one side) pulley wheel of the motor, then on the disc wheel.

The matt black background emphasizes the colors of the mineral and at the same time gives the whole stand a more pleasant aesthetic appearance. As a background, I used a cut-out strip of black paper, which I fastened around the perimeter of the stand with wooden sticks.

The project is completed. The stand can be placed on a shelf or in a display case and enjoy the beauty of phosphorescent stones from different angles.

Thanks for reading. Stay safe and healthy :)