Spring 2013- MMAE 433- Academic project

Sofia is an electromagnetic levitation clock capable of making small objects float in thin air. Like a regular clock, Sofia keeps track of time, but instead of having revolving hands, she orbits the object under her glow. Perhaps a metaphor for time, space and gravity.

Over the centuries, mankind has always been fascinated by the idea of tracking time. From looking into the stars to state of the art atomic clocks time keeps captivating our attention. In modern days, timepieces are transforming, adapting their functionality, serving less as time tracking mechanisms and more as ways to express ourselves.

**A little theory**

The following formula is one of my favorite ways to introduce the system:

We can closely approximate the force applied on the levitating magnet by the electromagnet. Notice how the driving factor in the equation is the distance (*d^4*), meaning that a small change in distance will cause incredible changes in the current (*i*) required to levitate the same load (*f*). K being a constant dependent of the geometry of the system.

In other words, levitating a magnet more than a few centimeters is extremely challenging, not only because the electromagnet has to be powerful enough, furthermore, the system has to be fast enough to react to small disturbances.

The diagram below illustrates the system, *R* is the resistance through the electromagnet, *L* is the inductance of the coil, *v* is the voltage through it; mg is the mass of the magnet and gravity, *d* is the distance from the coil to the magnet and *e* is the voltage across the hall effect system.

**So How does it actually work?**

In simple terms, the hall effect sensor between the magnet and the coil is constantly measuring the magnetic field. If it detects the magnet getting too close it will reduce the voltage to the electromagnet, if it detects the magnet getting too far, the controller will increase the voltage to the electromagnet. This loop happens at a very high frequency, so fast that the magnet appears to float statically.

**Process**

The process was elaborated, starting by laser cutting the body of the clock and the sanding it until it was perfectly smooth. Priming then painting, we used an automotive class primer to prepare the surface for our stainless steel paint.

**In the end**

Time is much more than the numbers on a phone’s screen, sometimes we seem to forget that. With Sofia we wanted to step back and communicate time in a different way. No screens, no overloads of data. Look up as our ancestors did, discover time.

This project was originally a final capstone design project for the Mechanical Engineering Undergraduate Degree at the Illinois Institute of Technology.

Participants: Sebastian Morales, Pablo Criado-Perez, Ahamad Khalil, Brandon Slack, Christopher Anene, Eizaaz Zakaria and Haochen Wang.

Special thanks to:

Mathew Spenko Ph.D.

The class of 2013

**References:**

Lilienkamp, K., Lundberg, K. Low-cost magnetic levitation project kits for teaching feedback system design. American Control Conference, 2004. 0-7803-8335-4

Wiboonjaroen, W., Sujitjorn, S. Real Time Implementation of the State-PI Feedback Control Scheme for a Magnetic Levitation System, International Journal of Mathematical Models and Methods in Applied Sciences 978-1-61804-164-7

Zeltom, 2009. Electromagnetic Levitation System. Available online: http://www.zeltom.com/documents/emls_md.pdf

Zschokke, S. 1996. Early stages of orb web construction in Araneus diadematus Clerck. REVUE SUISSE DE ZOOLOGIE, vo!. hors serie: 709-720; aoilt 1996