Choreographed Iron Dust

For Students, Fair Volunteers, etc.

(Last updated February 5th, 2011)

Dear Reader,

We sometimes receive queries from students, science fair volunteers, etc., asking how the Dancing Trees display works, how they might reproduce it, or create simpler items based loosely on its design, etc. Such inquiries have come from students as young as 12 years in age, from under/non-funded fair volunteers, etc.

This page was posted in response to these queries.

(Note that we assume you have already read the Technical Description page here.)

Sincerely,

David Durlach, Founder/Director TechnoFrolics <david@technofrolics.com>

 

Preamble

To begin, please understand that the Dancing Trees science-artwork required a very significant commitment of TechnoFrolics resources to develop, continued resources to keep up-to-date, and that ongoing sales generate a portion of TechnoFrolics (quite modest) income. It is thus not an open source project where we are comfortable providing complete circuit board schematics, choreography code, etc.

In actual practice however, it is rare that the proprietary nature of our system is the main limiting factor. Rather, it is more often the student's/volunteer's lack of relevant technical knowledge, underestimate of the complexity and cost of the system, or both.

Notwithstanding the above, we would very much like to help interested persons become more involved in science-art, learn about magnets and magnetism, design and build their own creations using our artworks as inspiration, etc. It is from that perspective that we offer this document.

 

Complexity and cost of actual system

The Dancing Trees display has many complex parts requiring detailed knowledge of electronics, computer programming, magnetic fields, and more. For reference, just one of several system elements is shown below. Constructing such a thing is well beyond the expertise, and budget, of the typical student/volunteer contacting us.

 

Warnings (provided for those people planning to do their own projects)

  1. High voltage (e.g., the 120VAC present on standard USA outlets, 230VAC on many International ones) is potentially lethal if used/handled incorrectly. Only trained electrical/electronic personnel should work with such.
  2. The power levels used to generate magnetic fields similar to those present in the Dancing Trees system can cause a fire if incorrectly designed and cooled.
  3. Inductors such as electromagnets, when spontaneously disconnected from their voltage/current drive, can generate voltages on their leads up to tens of thousands of volts. If sufficiently large (in terms of their stored energy), this behavior has the potential to be lethal.
  4. Fine iron powder is flammable in the form used in the Dancing Trees display, and explosive if in aerated form (such as if vacuumed up).

Taking into account the above, we strongly recommend:

  1. Experimenting only with low voltage systems. One option is purchase a commercial power supply that plugs into a standard wall outlet, outputs no more than 12VDC, is internally protected against shorts, and is certified by a safety agency (UL, CSA, VDE etc.). How much current you will need will depend on what you are doing. 2-4 amps, for a single electromagnet, is not a bad starting place. A low voltage DC bench top supply with adjustable voltage and current limits can be ideal for experimentation.
  2. Soldering across each electromagnet's two leads (in "parallel" in other words) a bidirectional voltage clamp, to prevent high voltage surges when the electromagnet leads are disconnected from the power supply. For a DC supply up to 16V, we recommend the P6KE20CA. (Note that if you turn the power supply voltage up to a point where the voltage clamp begins to conduct, it will get very hot and potentially fracture explosively, presenting a hazard to eyes etc.)
  3. Using iron filings, rather than fine iron powder, as fire and explosions hazards are dramatically reduced.
  4. Being aware that magnetic field have the ability to erase computer hard drives, credit/debit cards, and in unusual circumstances, adversely affect heart pacemakers and other medical devices.
  5. Engaging a trained supervisor, should you not yourself be a trained engineer.

In no event should the warnings above be considered complete, or a substitute for proper training in the relevant engineering fields and/or close supervision by trained professionals.

Readings and Experiments

  1. If you are planning to use iron filing and a permanent magnet moved by hand, simply get a few permanent magnets, a jar of iron filings, and play!
  2. If you are imaging experimenting with electromagnets, at a minimum, we recommend reading about:
    1. The relationship between voltage, current, resistance (DC), and dissipated power.
    2. Electromagnets, including topics discussing magnetic field strength as a function of number of ampere-turns (Current x NumberWindings).
    3. (And if you are more advanced, inductance and related time constants, as they relate to the speed/frequency at which one can change a magnetic field.)
  3. Get insulated copper wire, ideally enamel coated (vs. thick plastic/rubber coating, which takes up valuable space), and say in the 18-24AWG size depending on what you are doing.
  4. Get some iron or soft steel bars (big nails, studs, or bolts can be a good starting point), and wind the wire around them.
  5. Try putting different currents through the wire, different numbers of turns, etc., and see what happens. (You may wish to add a surge protector as above. Otherwise, take care to avoid touching the magnet leads during the moment when they are disconnected from the power supply!)
  6. To "choreograph" an electromagnet in a simple OnPositive - Off - OnNegative kind of way, you might wish to use a switching mechanism such as shown below.

 

And for those persons interested in developing electronic controls for electromagnets, we recommend reading about PWM (Pulse Width Modulation) theory and devices. These allow essentially continuous, rather than discrete, bidirectional control of magnetic fields. "H Bridge" is the name for one type of standard bidirectional controller employing PWM principles.

And of course familiarity with micro-controllers, programming languages, analog and digital electronics, and user interface design would help too.

Good Luck!