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Description This section contains information about the progress of the oscillator.

See top for progress navigation.

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Voice Coil We ultimately decided to use the voice coil oscillator type because it has several advantages over other options. Its performance will not degrade in cold temperatures, which allowed us to achieve our entire goal frequency ranges while still using a small countermass. We had originally shied away from the voice coil because we anticipated problems with the high impedance wires that NASA currently has installed in their system and the higher current that a voice coil requires to function. However, we found that we could work around these problems. We decided to purchase the Non-Commutated Direct Current Moving Magnet Linear Actuator from H2W Technologies. This voice coil offered a large range of travel, sufficient force output, small size, and previous favorable performance in cryogenic temperatures. To utilize this product, we needed to provide centering springs, which we obtained from Century Spring Corporation. In addition, to make our wiring compatible with NASA's setup, we purchased transformers from Radio Shack and designed an amplifier circuit that would drive the voice coil. The amplifier is a current driven op-amp circuit that receives signals from the computer through the computer's audio output.

H2W Moving Magnet Voice Coil

Piezoelectrics Before deciding on the voice coil, we initially pursued the possibility of using a piezoelectric stack or actuator. Originally, we were thinking that a piezoelectric crystal would provide the oscillation we needed because of its small size and ability to output large forces with the application of relatively little power-dissipating current. However, as we researched products we found that as piezoelectrics are cooled to 4 Kelvin, they lose as much as 90 to 95 percent of their efficiency. This meant that the piezoelectrics that would only barely work for our purposes were pushing the boundaries of our size constraints. In addition, there was an issue of the minimum frequency at which we would be able to operate a piezoelectric while still using a feasible countermass. We spent a few weeks researching several possibilities, including the Piezosystem Jena N Series and the Cedrat Super Amplified Piezo Actuator 400M, almost purchasing the latter of the two. We ended up having communication issues with the people at Cedrat that turned out to be fortunate, as in the time in which we were negotiating with them we found another solution that worked even better.

Cedrat 400M

Calculations To determine what product would best serve our purposes, we derived a simple formula regarding minimum frequency output by a force driven oscillator that can be found here.

We implemented this formula in the form of an Excel spreadsheet that will calculate both minimum frequency and necessary countermass. The spreadsheet can be found here.

We also calculated the necessary k value for the centering springs. This can be found here. Our calculated k value was found to be inaccurate. We suspect that we did not calculate the normal value N properly. After experimenting trial and error style, we found an appropriate spring from Century Spring with a k value of 1.1 N/m (192 lb/in).

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