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How to Convert Optical Power to DC Voltage

Light is energy. When light is absorbed by matter, it transfers its energy to the matter. Photodetectors channel that energy in a way that can be measured. A specific subset of photodetector is called a photovoltaic cell. A photovoltaic cell can be configured to measure the intensity of the light that strikes it, but it can also be configured to harvest the optical power carried in the light. Configurations that harvest energy are used for photovoltaic solar cells and also for specialized applications where electronic noise needs to be minimized.

Things You'll Need

Photovoltaic cell
Variable resistor
Multimeter
Optical power meter

Instructions

- 1
  Illuminate the photovoltaic cell with a source of constant illumination, that is, a source that supplies a constant level of optical power. If desired, quantify the light intensity by measuring the optical power with the power meter.
- 2
  Hook up the variable resistor to the output of the photovoltaic cell. Vary the resistor from an open circuit to a short circuit and record the resistance, voltage and current at every setting. Note that the DC voltage will change, even though the optical power stays the same.
- 3
  Determine the maximum power point of the photovoltaic cell. The power at any point is the product of current and voltage. Make note of the resistance at the maximum power point. The maximum power point represents the DC voltage and current generated at the most efficient operating point of the photovoltaic cell.
- 4
  Extract the power with a circuit matched to the resistance at the maximum power point. The circuit will be perfectly matched at the same optical power at which you made the initial measurements, and close to perfect for optical power levels close to that level. There are no general guidelines for doing this, because there are so many different types of circuits.

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