Magic ball light effect

Time taken: 15 hours.
Materials:  2x UV reactive acrylic glitter contact juggling balls, 32x ultrabright 5mm UV LEDs, 2x experimenter’s boards, 16 x 100 ohm resistors, hookup wire in red and black, 9v battery and connecting cap, switch, nail, brass tube, magnet, AT Tiny, voltage regulator, 2-wire connectors, solder, black 3.0mm leather, black 1.2mm leather, waxed thread, contact glue, leftover grey muslin from waist sash, hot glue.
Tools: Craft knife, scissors,  pliers, soldering iron, speedy stitcher.
Techniques: Basic electronics, soldering, leatherwork, fabrication.
Difficulty level: I’m going to say difficult because of the array of skills involved, and because making it all work together was complex.  But if you have any experience with electronics, it’s pretty straightforward.

When Saarebas attack in the game, they start by producing a ball of light in each hand.  They have a very specific hand movement they use to conjure them, a sort of aggressive wrist-flick.  I wanted to reproduce this as closely as I could, given the limitations of not actually being a mage, and within the constraints of cosplay competitions (which generally frown on flame and electrical arc effects a la tesla coils).


I happened to have a UV reactive acrylic contact juggling ball already, and when we placed it against a UV LED torch, it glowed in a suitably magicky looking way. OK, so if I could get some UV LEDs into the palms of my hands, I could get glowing balls of light. But how to make them turn on when I flick my wrists?

For this, I consulted my brother Grist, who likes inventing things in the realms of high voltage, prettyshiny, and blowing stuff up. He went away to think about that for a while, while I got on with making palm-lights.  To do this, first  I used this extremely handy wizard to enter the number of LEDs per array (16), the input voltage (9v), the forward current and forward voltage (which will be found on the specifications for whatever LEDs you buy). This wizard then produces potential circuit layouts, complete with resistors, and you can pick the one that works best for you. Because I was using a 9v battery and LEDs only want 5v, I ended up with this: 02Where each resistor was 100 ohms.  The next step was to put a circuit together.  I used a pre-punched experimenter’s board with the copper-printed side just a series of parallel lines joining the holes together. I scored with a craft knife to break the circuit where I didn’t want current to flow.  Working out where to score it bent my brain a bit, and I think it might be just as simple in the end to use a universal board and make the connections yourself.  However, I persisted and in the end it came out the way I wanted.  Then on to the soldering..

03 04I’m not a fan of soldering, the fumes make me feel sick (even with lead-free solder) so I have to do it with windows wide open and it’s winter here, so I was glad when that part was over.

The first time I got to this stage and hooked it up to the battery, four of the LEDs didn’t work.  I tested the circuit and everything was fine, so I concluded that I had a couple of dud LEDs.  Diodes only let current flow through them one way, and if one in a series is a dud, it’ll stop the others lighting too.  Unfortunately I wrecked the board trying to get the dud ones off and had to start again.  This time I tested all the LEDs (you can do this if your multimeter has a diode tester, the LEDs will light when you put the pins on their wee legs) before putting them in the board.  I found 7 more duds out of the 50 I’d bought.  Traps for young players.

Anyway, second time round everything went smoothly, and I ended up with this:

05I am not so experienced at electronics that I don’t still get a huge thrill when I turn something on for the first time and it actually works!

These then needed to be made suitable for holding in the palm of your hand.  First I coated the backs where all the solder and sharp cutoff bits of wire were with hot glue, and stuck a piece of 3mm thick cover strap leather to them to protect my palm.  Then I cut a couple of strips from the same leather, about 1.5cm wide and long enough to form a circle around the array of LEDs. This circle would form the cup that the ball would sit in, and direct the light up into the UV reactive acrylic.  I also cut a couple of rectangles to protect and encase the circuit and LEDs so they could handle being knocked around a bit, and stitched the whole thing together nice and firmly.

0607So that’s all well and good, but how would they sit in the palms of my hands?  I decided that my Saarebas needed some fingerless gloves with holes in them for the lights to poke through. These would not only hold the LEDs in place when I made my wrist flick, but they’d conceal all the wires connecting them to the battery in the cuffs.

I contemplated buying a pair of gloves and cutting the holes in them, but then I had one of those brainfart moments where I decided I’d made everything else for this costume, I needed to make these as well – even if it meant learning how to make gloves for the first time!  And then I thought it’d be clever to give them the same sewn-together chevron pattern as the skirt and collar have.  So off I went to look up how to make gloves, and then made a pattern and drew my chevron shape on it, cut it all out and then sewed it back together.

08 09 10I discovered that making gloves is not that hard, but it is kind of fiddly putting all the little gussets between the fingers, and the left one’s a bit tight so I made the right one a bit bigger.  Leather stretches though, so it will fit ok eventually, right?

I considered using buckles to hold them on, even going so far as to make the buckles, but in the end I decided that I’d get a better fit and more concealment of wires, along with being in keeping with the slightly run-down, dusty look of the rest of the costume, if I instead used wrist wraps made from the same grey-dyed muslin that the waist wrap is made of, tied on.

11Pretty pleased with these, I have to say.

Meanwhile, Grist had come back to me with an ingenious idea and a prototype he’d built for the switch.  Check this out:

 switchThe idea is that inside the brass tube is a short piece cut from a nail.  Most of the time it sits stuck to the magnet, but when I flick my wrist, it comes loose and slides to the other end, touching the contact.  That tells the ATTiny to switch the LEDs on, and leave them on for 15 seconds.  Ingenious!  There’s a voltage regulator in there because Tinys don’t like 9v either, and the two sets of connectors allow it all to be taken apart if necessary.

Next I had to carve chunks out of the cuffs in order to put all this gubbins in:

12I added a manual switch because there’ll be times when I want to turn it off manually, and times when I want the lights to stay off no matter how much I wave my arms around.  The final step was to make small pieces to cover the ends of the switch, attach the bracer and glove…

13.. and then put it all on and try it!


I am very happy with how well this worked, and I’ll post a video of it as soon as I can.  It was a lot of work to do, but worth it I think.

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