• 3cm x 7cm double-sided blank PCB [USD12 for 20pcs from eBay]
• 0.5W 30000mcd 8mm 5-chip straw hat UV LED [USD34 for 50pcs from eBay]
• Resistors 2.2kΩ 1/4W, 4.1Ω 1/4W, 100Ω 1/2W
• Capacitor 1.5mF 10V
• BC337 transistor
• 555-timer IC
• DIP8 IC socket
• N/O reed switch
• Strong rare-earth magnet
• 9V battery connector
• 9V battery
• Wires & soldering kit
• Wildfire’s Luminescent Water Dyes [USD28 for 5 0.2oz bottles from Blacklight.com]
• Frosted glass spray [from Home Depot]
• Gold spray paint [from Home Depot]
• Wide-mouth mason jar with 3-1/8" opening
• Ziploc freezer bag
With that long parts list, what you end up with is an innocent looking jar filled with a coloured liquid. No circuit or battery is visible since the liquid filling all the way to the top, along with the frosted glass coating, appear as opaque and completely hide the illuminating assembly. Since the jar is sealed, the on/off switch is our small rare-earth magnet, which you place on the metallic lid to get the spirits glowing. The fluorescing colour differs from the natural colour of the dyed water, so a beautiful gradient is formed when the jars glow.
I have yet to run out of battery on any of these. According to the math, a 9V battery would last about 5 hours, and it can be easily replaced. You can complete one of these jars in a day or two. However, some parts are easier purchased in bulk, so you may as well build a big family with all the different colours ;)
Step 1: Spray Painting
Fully cover the lids and the outside of the jar bottoms with the gold spray paint. Lightly spray patches of gold scattered around other glass surfaces as well. The gold-patches-on-frosted-glass effect makes the jars look great in daylight.
Let the jars sit for at least a day before any contact with water. You may spend the rest of the day building the circuit ;)
Step 2: Build Circuit
The circuit basically relies on the 555-timer to generate a periodic heartbeat, along with the BC337 transistor, control the amount of current flowing through the UV LED. The UV LED in turn goes from half brightness to full brightness, and then back to half brightness again, and so on. The resistors and capacitor values are chosen more or less by trial and error to provide the frequency and brightness that make the jars comfortable for viewing.
The layout of the circuit is important because it must be compact enough to be hidden in the mouth of the mason jars. The picture showing the bottom traces is drawn as if you are looking through the PCB from the top. When you actually make the traces at the bottom of the PCB, they will be inverted from the drawing, as shown in the last picture. Note that all circuit components are on one side of the PCB, except for the reed switch, which is on the same side with the traces.
The easiest way for me is to solder in all the components you see in the Top view, then flip the PCB over to form the traces by bridging adjacent solder points with solder. The second part may take some practice if you haven't done it before, but it will become much easier once you get used to it. Lastly, attach the reed switch at the back, and solder in the 9V battery connector.
At some point you will need to trim the PCB as shown in the pictures, so it will fit in the mouth of the mason jar. Normal scissors will do, no special tools needed. You can do this now or later.
Step 3: Test Circuit
If everything goes well, start mass producing the assembly for the number of jars you plan to make. If you plan on making a big family of jars, it may be worthwhile to adopt a pattern transfer + etching-based technique to fabricate custom PCBs.
Whichever way you create these circuits, make sure you test each one before proceeding.
Step 4: Fluorescence Water
Fill a mason jar with water almost all the way to the top as shown. Pick a colour of dye and put in 10 drops regardless of the size of your mason jar. When illuminated with UV light, the colour of fluorescence is not the same colour as what you see in daylight. For example, the jar that appears white in the photo will fluoresce in blue! So read the label to pick your colour.
Step 5: Circuit in the Jar
Trim your PCB such that the assembly fits inside the opening as shown, with the UV LED facing downward and reed switch upward, the trimmed PCB and 9V battery side-by-side with each other.
Press down such that the assembly is fully inside the mouth of the jar. Make sure there is still plenty of extra plastic sheet on each side, protecting the circuit from the overflowing water.
Step 6: Seal and Done!
Place the rare-earth magnet on the lid directly above the reed switch and watch the spirits glow!