Stepper Motor Arc Reactor

Written by: admin@makezilla

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Back in 2008 when Iron Man came out, the arc reactor was one of the most popular DIY builds on this site. A number of very talented, and often very involved, arc reactor builds were published. With the Iron Man 2 trailer just recently released, and the sequel slated for release in May, I predict that arc reactor builds will be on the rise again. In an effort to get a jump start on the rest, I present this build for the arc reactor. The idea of this build is to present an arc reactor that requires soldering, but doesn't require machining. In this way it falls in the middle of the quality-effort arc reactor continuum.

Step 1: Tools/Materials

Picture of Tools/Materials

For this project, the following tools and materials are required:

  • Soldering Iron
  • Solder
  • Desoldering Braid
  • Hemostats or SMD Tweezers
  • Wire strippers
  • Wire Cutters
  • Hot Glue Gun
  • Dremel Tool
  • Safety Glasses (wouldn't want to lose an eye, would you?)


  • Stepper Motor (Either purchased or preferably salvaged from old broken electronics. VCRs, Printers, and DVD players are particularly good sources for stepper motors)
  • Wire (22-26 gauge is ideal, instead of buying new wire, wire can also be harvested from existing cables. Old ethernet cables are particularly good sources for large amounts of wire.)
  • Blue SMD LEDs (my project uses 6, but feel free to use more)
  • Through Hole Resistors (I used some 150 ohm axials I had lying around, but depending on your led, you may want to size it accordingly. For those of you unfamiliar with electronics, this LED resistor calculator should help you figure out what resistance value to use.)

A quick note on safety: This project uses certain tools that could present a risk of injury. Eyeglasses are strongly recommended, and care and common sense is needed for safe operation of the dremel tool and soldering iron. The author of this instructable assumes no responsibility for injury or accident incurred while working on this project. Please, be safe and have fun.

Step 2: Remove Stepper Motor Rotor

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Stepper motors (and virtually every other rotary motor in existence) consist of 2 fundamentals parts: a rotor (the moving part of the motor in the center) and a stator. Once you either purchase or salvage a stepper motor, the first important step is to remove the rotor of the stepper motor (as we will not be using this). Having no luck attempting to pry at the rotor shaft with pliers, screwdrivers, and hammers, I turned to the ever-useful dremel tool and cut it off.  This will leave you with the casing (the backplate, if you will), and the stator (the part with all the coils of wire).

Step 3: Prep the Stator Coils

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The stator of the stepper motor consists of a number of coils of wire. The stepper motor I got my hands on was an 8-pole, 3-phase motor, meaning that there were 3 sets of 8 coils wired together in series around the stator. With the turns in a given coil touching each other, it is important that short-circuits do not occur in the coil turns. Therefore, the copper wire in the coils is coated in a thin layer of insulation that is meant to prevent electrical flow across turns of the coil.

When constructing our arc reactor, we will be soldering leds to the coils of the stepper motor. When soldering, depending on the insulation and heat of the iron, it is possible that the soldering process will burn away the insulation on the wires. Because of this, it is desirable to cut all the wires that link the led coils to any other coil, so as to not inadvertently short out an led or wire leds together incorrectly.

Once you have either of the 2 coils for a given led electrically isolated (all the wires connecting it to other coils removed), go ahead an add some solder to the coil (it will make applying the led much much easier down the road).

Once you have both coils electrically isolated and soldered, proceed to the next step, in which we will add an led to the coil.

Step 4: Wiring it Up

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Once you have a pair of coils electrically isolated with solder applied to them, go ahead and solder your led between them. If you are using a PLCC-2 led package (the leds only have 2 leads on them), then simply solder the 2 led leads to the coils. If, on the other hand, you are using a PLCC-4 package (package has 4 leads on it), you will want only want to solder some of the leads (consult the led datasheet to determine which leads to solder). For reference, a copy of the electrical schematic is included in the pictures below. From the schematic, I used 6 leds which I grouped into 3 pairs, with the anodes of each led pair facing one another (in other words, reverse the direction of every other led on your arc reactor).

Once you have soldered all the leds together, go ahead and solder on wires to connect all of the led cathodes together, and tie the anodes of each led pair together. Connect each pair of anodes to a current limiting resistor. At this point, power your circuit to test your led wiring, troubleshooting any failures. Once it works, I added on the backplate of the stepper motor (adding hot glue), and then made the final connections to the battery holder.

Step 5: The Finished Reactor

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With the electronics all wired up, feel free to walk about and show off your finished arc reactor. The reactor I built was not really designed to be wearable, but if you wanted a wearable reactor, feel free to glue on some straps and lengthen the device power cords to make the battery pack fit in your pocket.

I hope you enjoyed this project. If so, please feel free to rate and subscribe, and check out my website for more exciting builds!