Lightning Staff
For Halloween of 2023, I wanted to be a lightning mage[1]. It would be simple to just make a lightning-themed costume, but what good is the empty threat of arcane lightning without the actual danger of arcane lightning?
After some fiddling, I quickly settled on the basic design concept. I would need a staff which could shoot lightning bolts (or, alas, more realistically, at least have real electrical sparks come off the top).
To do this, there would be a real Tesla coil up there. There would also be buttons in the middle, switches to control various options, and tons of LEDs everywhere to give the impression of magical and electrical power seething within. This would be my first major electronics project.
Design and Features
Schematic-wise, the concept, not starting particularly simple, grew organically into something very complex indeed over several design iterations.
A Raspberry Pi Pico controls everything, and recognizing my (then more limited) electronics knowledge, most of the circuitry is off-the-shelf parts, stitched together with tons of manually cut wires.
After a preliminary design exploration, I quickly decided to simply buy the Tesla coil complete[3]. The one I got seems to qualify as only mildly dangerous[4], and also conveniently came with a built-in battery, from which the rest of the staff is powered through Buck converters. The Tesla coil operates in some kind of pulsed mode, where you can trade off spark size vs. spark rapidity with a dial. Quite large sparks might be a second or so apart, while smaller ones end up sounding like a machine gun.
Figure 1
: Debugging an issue with RGB buttons[5].
Figure 2
: A black piece of construction paper with cutouts and packing tape windows produces a stencil (left). When assembled above an LED strip but below a layer of painted thin plastic, you get light-up rune effects. I drew all the symbols myself based on vibes; some are actual runes (though no message is conveyed).There are three buttons in the center of the staff (Figure 1). The bottom one simply closes the switch on the Tesla coil, activating it. The Tesla coil can also be activated electronically by a power relay. The middle button activates the Tesla coil through this relay, and also runs a light show. The top button does the same thing, but with a more extensive light show that involves a build-up period.
The light show consists mostly of three LED strips. Two are embedded into the staff sides, and show various patterns. The third is on the lower back of the staff and lights up symbols (Figure 2) through cotton-balls as diffusers. With the powerful Pico, quite complicated patterns can be programmed and updated. (There is also a speaker, which I intended to intensify the Tesla coil's noise, but ended up weak and a disappointment.)
The gist of the light show is that, when idle, the staff emits a low humming sound and shows slowly fading lights in friendly colors. When you hit the top button, there is an exhilarating 'charging' sequence where light races up the staff toward the Tesla coil. When the Tesla coil switches on, the symbols at the base show 'chords' of symbols together in an angry red, as if casting spells, and the lights continue to race up, periodically.
There is also a bank of switches and dials above. Lowest is a volume potentiometer for the speaker. Next, a switch to toggle the light effects. Then, a switch to switch the non-coil electronics between battery and USB power. Then, a master switch dedicated to the Tesla coil power, as a safety feature. And finally, the master power switch. They all have RGB status LEDs, but none of them are labeled, to make it just that bit more fun[6].
At the bottom, there is also an LED 'bar graph' which serves as a battery meter: push a button and it shows an animated sequence displaying the battery level. This is measured with some voltage divider network on the battery and one of the Pico's ADCs.
Figure 3
: Draft design for staff cross-section. There is an aluminum angle beam in the middle, forming the core and top face of the staff, a cut PVC pipe forming the rest of the hull, and bolts to hold it all together.And of course, there's tons of level-shifting and miscellaneous circuitry to make it all work, some of it not even used. I was also thoughtful enough to include dedicated lines for a RPi Debug Probe and dedicated charging lines to a socket for the Tesla coil battery.
Physical Build
The basic physical build (Figure 3) starts with an aluminum beam. Although a bit floppy, the readily available alternative was an iron beam, which was also a bit thicker, and therefore incredibly heavy. Still, the aluminum provides a good bit of stiffness and a satisfactory substrate upon which to mount the other hardware[7]. The electronics, including wires, were mostly mounted with hot glue, whose semi-permanent nature sometimes made for inconvenient fixes of inevitable mistakes. One face of the beam also forms the top face of the staff. I finished it with a rotary wire brush.
The remaining curved section of the body is a PVC pipe, which wraps around the beam and gives it shape and additional strength. There have to be a ton of cuts in this pipe for the LEDs, and a trench cut all the way lengthwise for the exposed face of the beam. Many tedious and absurdly messy sessions with the Dremel took care of this.
The final layer is a thin shell of plastic, also cut lengthwise. This is a protective tube for a fluorescent light. I opened it up and painted it with a finish that alleges itself to look like hammered copper, but the coating was a bit disappointing on this admittedly challenging base.
The whole thing—beam, pipe, shell—is bolted together in several places. The result is not fully rigid, but is quite sturdy. You wouldn't want to get into a proper melee battle with it, but if you did you could absolutely give someone a good clonk.
The LED strips on the sides proved particularly obnoxious. The required long channel cut into the PVC pipe resulted in two flimsy strips of PVC, which somehow had expanded slightly (relieved stress or thermal damage from cutting, who knows) and therefore were quite unruly. Worse, hot glue turns out not to stick to PVC very well.
The entire build is very space-constrained, and a lot of stuff is positively crammed into it.
Figure 4
: The royal mess of wires inside the staff during build, while debugging some issue with the LED light strips.
Figure 5
: Testing the side LED light strips.There were other other ideas that didn't make it into the build.
Foremost, there's supposed to be a knob at the bottom for the staff to rest on, but instead it's completely open. I also bought some ultra-bright LEDs, thinking I could add them to the light show, but I never really figured out a place to mount them.
I also designed some fins for the top. They would make the staff look scarier, but were actually a safety feature: the top of the staff is a metal spike at the top of the Tesla coil (spikes concentrate electric fields). You could hurt yourself mechanically on this, and fins might prevent you from accidentally stabbing yourself (or the ceiling). However, I couldn't see a good place to attach the fins that wouldn't interfere electrically (or look completely stupid; the Tesla coil body is already much wider than the staff).
I also got a large number of small wooden knobs, like for cabinets. I glued them together one on top of the other, forming four towers, which I painted a dull purple. This made some very convincing high-voltage ceramic-insulator lookalikes[8] for that sweet electrical engineering cargo-cult look. However, despite the effort, I couldn't find a place to put these, either.
Wireless Power
The powerful changing electric field of the Tesla coil can induce currents. The following video, taken during trick-or-treating, shows the effect on decorative lights at someone's house. The lights are wall-powered LEDs, but switched off.
(Epilepsy warning: flashing lights and sound ⚠️)
I don't know the physics here for sure, but my guess is that the changes in the electric field as the spark repeatedly charges and then discharges induce currents in the long wires.
Future Work
The physical build of the staff was always its worst aspect. This could have been improved, but I simply ran out of time. Already crunched for time on the physical build, they moved that year's Halloween festivities a few days earlier, to fall on a weekend or something, and so I had to throw together the only partially completed staff and hope for the best. The enclosure was so crammed full of wires, it didn't even fully close.
Unfortunately, in Halloween 2024, I dusted off the staff and went as a lightning mage again, but there was a light drizzle, and the staff appears to have partially shorted out. The Tesla coil still works, but the lights flicker or get stuck. I will have to tear it apart and try to fix it sometime.
I think the 'right' thing to do on the project would be to strip out all the electronics kluge and put in a custom PCB with a new circuit, maybe still outsourcing the MCU to the Pico. This was beyond my skills at the time, but is well within them now. It would be much smaller and more robust, fixing many of the problems with the current staff iteration, but could still probably be built with even THT.
The outer shell of the staff was cut a bit too small, and a bit unevenly. It also has an uneven coat of paint that is also too thick, so the LEDs, especially in the base, don't glow as much as I'd like. I have a new plastic tube, but haven't done anything with it yet.
If someone in the Portland, OR area would like to play around with the staff, I am prepared to sell it as-is, along with all designs, source code, and unused / spare parts, for say $300.
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