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Photovoltaic Cells

Suna Kang

Chris Maguire

Paul Pskorn

As their name implies (photo = light, voltaic = electricity,) photovoltaic cells convert sunlight directly into electricity. Once used almost exclusively in space, photovoltaics are used more and more in less exotic ways.

Photovoltaic cells can be used in the place of traditional power sources, such as batteries and electrical sockets. Breakthroughs in photovoltaics have made solar energy a viable alternative to traditional coal and oil power sources.

In our project, we sought to discover the uses and the possbile applications of the photovoltaic cell. The cell we used came packaged with a motor in a kit from Radio Shack. You can access the support site for our cell here. The specifications of the cell are as follows:

Solar Project Fun Kit

Solar Cell Material: ................... Single (mono) Crystalline Silicon

Voltage:
Maximum: ...................................................... 0.595 V
Under Load: ................................................... 0.484 V

Wattage:
Maximum: ...................................................... 0.238 W
Under Load: .................................................. 0.1452 W

Current:
Maximum: ....................................................... 400 mA
Under Load: .................................................... 300 mA

Life Expectancy of Solar Cell: .................................. Infinite

Life Expectancy of Motor: ..................... Approx. 130 Hrs. w/no load

Motor Current: ....................................... 220 mA @ 12,400 RPM

Our cell is extremely low-voltage (just over half a volt,) which limits its usability. We had to place the light source very close to the cell to generate a usable charge of any kind. With a sufficient light source, however, the cell more than adequetly powered the packed-in motor.

The success of the packed-in motor was a good start, but we wanted to see if the cell would work in other applications. We connected it to a higher-voltage motor, and it operated just as well as it did with the original motor.

We have also discovered that the cell can be used as a sort of variable resistor. Connecting the power line to a pin on the BX-24 and the ground line to the BX-24's ground, we were able to read in analogue values. These values were directly proportional to the amount of light hitting the solar cell.

Through some experimentation, we found that the cell was incredibly sensitive and reliable. It returned values ranging from 0 - 112.

This is demonstrated through our Director movie, which resizes an animation with respect to the amount of light the photocell absorbs.