Individual solar cells are wired
together in series-parallel arrangements
to create the voltages and currents
necessary for the solar panel’s
application. This requires creating a grid
of wires and supporting metallic traces
for the interconnections which add to
the area and also contribute electrical
losses like any wires do in a DC circuit.
The wires and traces also block light.
Modern solar panels incorporate
protective diodes that help prevent
heavy current overloads if a portion of
the panel is shaded. While effective, the
diodes create their own electrical losses
in terms of normal voltage drop and
Solar cell and solar panel images
This value is generally 0.01 to
0.05 ohms — 10 to 50
milliohms — hardly anything in
terms of adding to the load
resistance. However, with such a
small sense resistor the voltage
drop is also small. To compensate,
the multimeter adds a voltage
amplifier across the sense resistor
to boost the voltage to a
measureable quantity for the A/D
The gain of the voltage
amplifier is used in calculating the
voltage drop and resulting current
value. So, if the voltage drop
across a 0.01 resistor is
one millivolt and the gain of the
voltage amplifier is set at 100, the
Now, let’s get started on two of the solar panel
experiments. You can find complete details on these
and the other experiments including background
information, equipment setup, and experiment
procedures at www.learnonline.com. Just click on the
Experimenter Kits menu selection. Then click on the
selected experiment for your chosen processor.
Solar Experiment #1:
Sunlight versus Artificial Light
This experiment demonstrates the difference
between sunlight and artificial light as it strikes a solar
panel. It shows that sunlight provides a constant source
of voltage and current while artificial light produces
“ripples” due to its AC nature. The ripples are a result of
the 60 Hz AC that powers the incandescent light bulbs
and fluorescent lights.
Aim the solar panel at an open window with the
sun shining (Figure 7). Notice the steadiness of the
voltage output. Now expose the solar panel to artificial
light from an incandescent bulb or overhead fluorescent
light. Notice the ripples on the panel’s output. This is
due to the 60 Hz AC that powers the artificial light.
Go back to the window for another look at the steady
Now, expose the solar panel to a higher intensity
of artificial light by moving it closer to the light source
(Figure 8). Note the expected increase in voltage, as
well as the increase in ripples. This is a simple experiment, but few people have ever seen artificial light and
sunlight measured this way — this may include you, too.
Figure 7. Solar Panel Output for Sun and Artificial Light.
Figure 8. Expanded View of Solar Panel Output.