Arc Reactor Halloween Prop

The night before a Halloween party I was browsing [Hackaday] and came across a last minute arc reactor prop. Having spent the last couple of weeks working on a sonic screwdriver for a friend’s costume, I figured I had to at least have *something* the next night and a quick-and-dirty Tony Stark costume seemed like just the thing.

Planning:

Seeing as how [Evan's] rep rap is still being built and there was no time for drafting besides, I couldn’t go the 3D printer route. It was easy enough to start from scratch and I had some components lying around

I thought about a couple of lighting sources – discreet LEDs, a cellphone backlight, surface mount LEDs, and EL wire – but discrete LEDs seemed easiest given the timeframe. The backlight would have also been cool, but would have required a color gel. As for power, I was originally going to power the LEDs with a watch battery, but I wanted a way to switch them on and off and also to be able to replace the battery easily. A single watch battery was more than sufficient to light all the LEDs, though:

Construction:

Using PVC pipe for the case was an easy choice given my past success with sensor node enclosures. I cut a 0.75″ wide piece of 3″ PVC and painted it silver. The tube around the outside is a piece of 0.125″ ID vinyl hose. I bent a piece of brass rod to fasten then ends.

To light the prop, I used eight high-intensity blue LEDs with 1K resistors around the edges of the case just like the demo I made for OSHW ’11 back in September.

The silver paint did not stick very well at all to the PVC, so I had to re-glue several of the LEDs. Using primer would have been a good idea.

The positive leads were long enough to reach to the center, so I just soldered them together there. A piece of copper tape helped bridge the gaps. The ground bus was wire-wrapped.

To make the “arc tube,” I fastened magnet wire to the vinyl hose with copper tape and wrapped it around a few times. This was a perfect use for an old spool of wire that had come undone and gone all “rat’s nest.”

To diffuse the light, I glued a piece of printer paper to a lens cut from a scrap of polycarbonate(?) sheet.

I made the little center bit from a steel washer, driller alternating holes for decoration:

The back of the piece was corrugated carboard. I glued some aluminum foil to it to reflect light towards the front.

To wear it, I just glued to the piece to a shirt and poked it through a gap in the buttons of a top shirt. I had to pin the top shirt just underneath to add some extra support, but it worked pretty well:

The wires lead to a 3 AAA battery case in my front pocket. Popping out the middle battery was a perfect “switch”!

BOM:
The whole build was completed in less than 5 hours, with a minor re-glue after an hour of walking around with it. Out of pocket, I spent $1.20 on resistors at Radio Shack. The total bill of materials was less than $10.

• 3″ PVC x 0.75″ – $0.50
• 3″ strip of aluminum foil – $0.07
• 8x blue LEDs – $2.50
• 8x resistors – $2.00
• sheet of paper – $0.05
• magnet wire – $0.01 (?)
• copper tape – $0.01 (?)
• Battery case – $3.00