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If you are considering building your
own solar panel, you might try building the solar cell tester shown below. When
constructing a solar panel it is important to make sure that all the solar cells used in
the panel be closely matched for their short circuit current. One weak cell will lower
the efficiency of the whole panel. The system shown allows individual solar cells to be
tested for their short circuit current under a constant light intensity condition. The
system uses a low voltage 25 - 50 watt halogen spot light to simulate the light from the
sun. A small PIN photodiode is placed in the path of the light from the lamp and is
connected to a circuit, which converts the light intensity collected by the diode into a
voltage. Another circuit compares that voltage to a reference. The error signal is fed
to a pulse width modulation circuit, which controls the amount of power fed to the lamp.
The result is a uniform light source, whose intensity remains fixed. The system can be
calibrated to produce a light intensity equal to one sun. |
