Safe USB version of the Gillian's Diamonds lamp. (With PCB file.)

Probably the final version of this lamp, and a competition too (Patreon version already won.) It's a safe low voltage version of the PCB aimed at the small 2" (50mm) diameter glitter-lamp style bottles. It produces extremely good fluid movement when used with a 10 ohm resistor for a current of around 500mA for the total current draw is around 750mA. I recommend the use of a 2A USB power supply to allow continuous use.
The bottle is filled with common plastic wedding table scatter crystals available on eBay and from shops like Poundland in the UK. The crystals are a light plastic like hard polystyrene, and float in a solution of water and common table salt adjusted and fine tuned to make them flow well without gathering at the top of the bottle (too much salt) or the bottom (too little salt). A pinch of boric acid can be used to reduce the risk of mould growth in the liquid.
Fine tuning the solution is easier with a dropper bottle filled with a saturated salt solution.
By using silicone sealant to attach the resistor to the base of the lamp, all the power dissipated is put into the bottle, keeping the resistor cool and allowing very efficient operation. Allow the silicone to cure completely if it is the acid curing stuff (smells like vinegar) or use neutral curing silicone for fish tanks and mirrors.
The LEDs are connected as parallel pairs and identical LEDs (colour and batch) should be used in each pair to allow proper current sharing.
You can download the file for the PCB design and find a link to the viewing software here:- http://www.bigclive.com/freebies.htm

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