Wearable Arc Reactor

by MishaT, published

Wearable Arc Reactor by MishaT Oct 21, 2012
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Wearable Arc Reactor by MishaT is licensed under the Creative Commons - Attribution license.

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122775Views 16858Downloads Found in Costume


A printable, wearable arc reactor based on the Mark I movie version.

There are already some great arc reactors on here, but I wanted to take my own crack at it.

Update: I increased the clearance of the top ring, should be easier to assemble now. Also added source files.

Update: I uploaded the 9V battery holder you see in the pictures due to multiple requests, as a warning it is not an optimized part but a quick design to work with the switch I had on hand. I am sure there are better designs out there on Thingiverse if you look around.



5 M3x10 screws and nuts

14 White 5mm LEDs

10 Blue 5mm LEDs (optional)

Resistors (Depends on your configuration)

Print the crystal in clear PLA and the other parts in a dark color, metal or black are best. For best result print the crystal with a low rectilinear infill and no more than two shells.

Assemble everything except the base. I put some aluminum tape on the underside of everything that I did not want to be translucent, but this is optional.

Put white LEDs in holes that are not covered from above by the top piece (10 around the outside and four in the middle), optionally put blue LEDs in the other holes to give a nice bluish glow to the outer ring. I sanded the LEDs before wiring them in to give them a more diffused glow.

Wiring of the LEDs will depend on your particular LEDs and the power source you use. I am running off a 9v battery and have eight parallel rungs of 3 LEDs in series with a 68 Ohm resistor. My LEDs are a little under-powered and could be brighter with smaller resistors or if they were wired two in series instead of three, but they are bright enough. You can use this calculator to design your own circuit: http://led.linear1.org/led.wiz

Cut a hole in a t-shirt just big enough to fit the crystal, pin the edge of the cloth in the groove between the top and base pieces and secure with screws. Attach some sort of belt using the slots in the base to go around your chest so the arc reactor does not move around.

You will need to run a wire under your clothes down to your pocket to your power supply as there is no room to build a battery into the reactor itself.


P.S. I strongly recommend not trying to get on a plane with this on.

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Just a quick thanks... I wore this to NYC Comic Con and got some positive feedback. I deviated from your color scheme a little, and didn't have clear PLA so I used translucent white... it was plenty bright with 24 LEDs and one 9V lasted about 4 hours. I used the link for the wiring and it was spot on.. thanks again!

I noticed the final version of the crystal has holes for the resistors, yet the crystal STL doesn't. Would you still have the version with the holes for the resistors. Any help is appreciated! Thank you.

I took out the resistor holes so not to dictate wiring which can be done any number of ways. You don't really need them.

wiring did not work had to change it and then designed a power pack that hold 2 9v battery on my belt plus arc reactor too big so scaled it down to 95.27% looks right on my chest now...will send you pack design if you want it to add to this download..cward91279 gmail

Cool, feel free to upload your own thing!

Could you direct me towards the 9v battery case? it would really help, I couldn't find this on my own. Thanks for your time.

I uploaded the battery case model

Would it be too much to ask to have it as a solid part instead of an stl? Thanks!

I don't think I have that anymore, sorry

Okay, no worries

Where did you take the battery case from? My mail is [email protected] Send it if you can. Thanks

Could anyone point me in a direction for a step by step process (I know there is many ways to do this but anyway that works is fine with me)?

Do you have the file for the battery too? =)

Comments deleted.

In regards to the wiring on the back of the clear piece....#1 Im assuming the green insulated wire is the (+) and the resistors are the (-).
My question is why the negative, that connects to the battery, comes from the resistor in that place? Shouldnt the negative connect to the battery where the resistor is that comes off the left side. (The one that has one of the legs tucked under) Or does it matter???? I just dabble in electricity and electronics.

I did it like in the photo and it works perfectly.

So it basically doesnt matter which resistor leg touches the negative terminal on the battery?

No, The resistor can be on either leg but the + leg of the LED must go to the + side of the battery, Thru the resistor or not.
so + battery to resistor to + leg of LED then - leg of LED to - on battery

  • LED leg to + on battery then - leg of LED to resistor then other leg of resistor to - on battery.
    Note, Resistor legs can be swapped with each other, resistors are not polarized.
Comments deleted.

I am printing this right now for a friends birthday tomorrow (@voiceofthebigjb). He is a Robert Downey Jr impersonator so I'm sure he will love it. I'm printing the main parts in white colorFabb XT 20% infill 260c (to be painted) and the crystal in colorFabb XT clear 15% infill 0.4mm shell 220c. The video will be up in a few weeks on http://barnnerd.com when the part is assembled and finished. I'm @Barnacules on Twitter if any of you want to get in touch.

Did you ever make this?

with how much % infill did you print the LED part? why not solid?

Comments deleted.

I can only get it to consume power, not generate power like it does in the movie. What am I doing wrong here?

Thank you, thank you so much for updating the ring, and posting the CAD files. I truly appreciate it, and will be printing another.


Please let me know how it turns out! I increased tolerances by about half a mm in all directions, but have not test printed the update design.

I still had issues with clearance. Time to start sanding. For me the crystal will just not fit in the top. I think its the slots.

Great work Misha I was wondering if you do any other costume design?

Thanks! Haven't tried :) This was a halloween costume a couple years ago.

I have some designs that I have not uploaded to thingiverse and was wondering if you can give me some critics or advice since I'm trying to improve my techniques.

great work Misha T ! but can i ask idiot question... what type of resistor did you use ?

Thanks, please see the previous comments.


I would be truly grateful if you could update your files. The top simply doesn't fit the crystal at all.

I've busted 2 tops now trying to get this to work, in addition to butchering the crystal. It certainly is reasonable to expect some sanding, but I'l having to pull out the dremel with a cutting head.

I'm sure you can see the issues in your cad files.

If you don't have time to fix, at least consider posting your CAD files, so we can edit away. We'll certainly give you props.



I have put it on my to do list, I will update for better clearance and upload the original solidworks files.

First off, awesome design!! Looks great and very creative.

As a little bit of constructive criticism, the top and the crystal do not fit together without massive amounts of sanding and filing. It would greatly help if you could design a little bit of play in-between all of the press fit parts. Maybe an extra +/-1mm of space on the radii of the concentric circles that fit over the crystal, and an extra 0.5mm of width on each the slots on the outer and inner rims of the crystal.

Thanks! You are right, and some day I'll get around to revisiting this design, but I have a lot on my plate at the moment.

When you calculate the resistor values, do you use the maximum voltage of the battery or the nominal? For example a typical 9V battery has about 9.6V when fully-charged. Do you use the 9V figure or the 9.6V in your calculations?

I think I just used 9V, it won't make much of a difference.

Okay, thanks for the tip. BTW, what do you recommend as the infill for the crystal? Your instructions said "low". Are you thinking something like 0.1 or more like 0.3? Thanks.

I think I did .1 or .15. The lowest you can get away with while still having a nice top finish.

what did you use to enclose the battery and switch?

I just threw something together quickly, it wasn't very good. I'm sure if you search Thingiverse you will find lots of 9v battery holders.

I actually tried looking, but I didn't see anything I liked. Would you mind sharing it? I would like to print it out along with the arc reactor you designed.

PM me your email, but I doubt you'll find it useful. It is sized for whatever junk switch I had laying around.

Mind if I PM you too for the battery holder?

Has anyone got a bit better picture of how they've wired

You can use this easy calculator to design the circuit for you based on your battery, and the LEDs that you have: http://led.linear1.org/led.wizhttp://led.linear1.org/led.wiz

Thanks very much for the info. Ill let you know how I get on

Would I be able to get a copy of the crystal with slots? They would be handy!

Sorry, I've erased them from the original model long ago.

I have all the pieces perfect except the crystal (which seems to be 100%) is missing the slots for the resistors? Everything else is perfect any ideas?

I removed the resistor slots so people can wire it up as they want

Hi there, just wondering what printer you have? I'm using a replicator 2 and am wondering what settings and layouts i need to make this successful. will the top layer print face up with the slotted tops? Thanks!

I have a RepRap and have not had the opportunity to use a Replicator 2. Perhaps someone else on here can share their settings.

Hi MishaT,
Are you willing to sell me one? I don't have a 3d printer and I can't solder for the life of me. I would like to buy one so I can wear it on my sons birthday. He is having an Iron Man themed birthday party. Thanks, and let me know.

Hi! Unfortunately I'm in the middle of moving and my printer is not up and running. I'm sure if you find a hackerspace in your city someone would be happy to print one for you.

Just finished building mine, and it came out great. Thanks for adding it here.

A few suggestions, based on the issues I ran into. The crystal did not want to fit into the top. I'm assuming I was just outputting a little more plastic than you were when you designed it, but I had to spend a couple hours grinding away material with a dremel and files before the top could be squeezed on. It might be a good idea to update the model with a little more tolerance for printing inconsistencies, since a super-snug fit isn't really required anyway.

If I make another one, I might try increasing the space for the circuitry slightly by hollowing out the base a little bit more, or maybe also putting strategic holes for screws between the LEDs to act as terminals for electrical connections to reduce the amount of soldering required. And perhaps a second shelf that sits between the crystal and the base, which can isolate the negative (or positive) side of the circuit to reduce the necessity for insulated wires. After connecting all the positive sides of the LEDs to the main battery pack wire, you could stick a plastic plate on top, which would have holes for all the negative LED leads, and connect them all to each other without having to worry about shorting.

Certainly not necessary for an electrical pro with a decent soldering iron, but for someone (like me) doing this sort of project for the first time, changes like that would save a lot of time and frustration.

Anyway, thanks for saving me a lot of modeling time by uploading this. I'm very happy with the end result.

Thanks! Your copy looks really cool! Originally I had the whole circuit layed out in the plastic with connection channels and everything, but then decided to take it out so not to dictate how people should wire up their LEDs. This way people can set up their LEDs any way they want and account for variations in LEDs and power sources.

That makes sense. Case in point, I actually didn't use any resistors, since 8 rechargeable AA batteries provided the exact 9.6V I needed for 3 LEDs.

You still need a resistor unless you buy LEDs with a built in one. It is there for current limitation as an LED doesn't really have any internal resistance of its own.

Oh, I thought they were only needed if the voltage was too high for the LEDs. What happens if you don't use any? I ran mine pretty much constantly at a convention this past weekend and didn't have anything burn out.

An LED is just a diode, if you don't have any resistance in a circuit you essentially create a short. Some LEDs come with built in resistors, it is possible you have some of those.

So the only viable option for LEDs is to provide more voltage than is needed, and then use resistors to burn off the excess as heat? That seems very inefficient. I clearly have a lot to learn, so I'm trying to find information elsewhere, but much of it is conflicting.

LEDs will have a given rating, for example 3.3 forward voltage and 20 mA limit. Depending on what your voltage source is you need to add a proper resistor to limit the current below your LED's threshold to keep it from burning out. Look of Kirchhoff's circuit laws for help calculating your circuit.

I did the math and used batteries/LEDs that equated to 0 ohms of resistance needed (even while staying well below the LED's maximum voltage range). I assumed this meant I needed no resistors, but now I see that there are, in fact, 0 ohm resistors, which I guess is what I should be using for my setup.

Thanks for bearing with me on this.

I'm confused on how you got that number, can you sketch out your circuit?

Apart from the different voltages and lack of resistors, I have it laid out pretty much the same as yours. 8 parallel sets of 3 LEDs each, connected to 8 rechargeable AA batteries. The LEDs (http://www.taydaelectronics.com/leds/round-leds/3mm-leds/blue/led-3mm-blue-water-clear-ultra-bright.html)http://www.taydaelectronics.co... have a forward voltage rating of 3.2-3.4V, and the batteries are 1.2V each, for a total of 9.6.

When I enter it into the calculator at exactly 3.2, it suggests to use 12 series of 2 each, with 180 ohm resistors, (presumably because it's programmed to always use resistors), but if you change the LED voltage to 3.19999999, it suggests 8 series of 3 with 1 ohm resisters (presumably because it only uses integers and always rounds up).

But mathematically, assuming it went below 1, it should suggest a resistor at some infinitesimal fraction of an ohm.

Got it, looks like you are lucky in that between the resistance in the wires and internal resistance of the battery you are close enough to the required resistance to not burn out your LEDs. This will not always be the case depending on your circuit layout.

My son and I built one of these for his Halloween costume dance.  Printed great on our R2 with only minor cleanup required to fit everything together.  The LEDs pressed into the recepticles nicely.  Be prepared for sticker shock on the blue LEDs.  Might be a good idea to just print the clear part as transparent blue and stay with white LEDs.

That's great to hear! Check eBay for really cheap LEDs.

Instead of wiring up LEDs, I managed to find a small set of indoor battery powered 'light strings' from Noma. They're essentially a string of  24 tiny surface mount LEDs already wired together. I set them in place and hot glued them. 

They work great for the $8 I paid for them as Canadian Tire!

Thank you! now i don't have to design my own :)