Instructions

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SOLAR EGG

Using the sun's energy is exciting and environmentally friendly. It is

part of the Energy Harvesting task area because it "harvests" more

freely usable energy.

There are indeed many solar lights that turn on at night. But for these

completely different circuits are used, with completely different char-

acteristics. Using a storage capacitor instead of the usual battery is

indeed innovative. And in the end, everyone can build their own personal

solar lamp and adapt their properties to their individual needs.

SOLAR POWER

Experiment 1

In the first experiment, a green LED is connected directly to the solar

cell. The longer wire of the LED is the anode (A) and belongs to the posi-

tive pole (red) of the solar cell. The short wire is the cathode (K), which

must be connected to the negative pole (black) of the solar cell. The

brightness of the LED depends on the ambient light.

Caption: LED and solar cell

Experiment 2

In full sunlight, the solar cell delivers a current of about 20 milliamperes

(20 mA), which the LED can still tolerates well. Therefore the LED may be

connected directly.

For a series connection with two LEDs you need two double terminals. It

only works in bright light, otherwise the required voltage for both LEDs

will not be reached. Each LED requires a voltage of at least 2 volts (2 V).

Caption: Series connection

SOLAR EGG

Build your own everlasting solar light

Discover the basics of photovoltaics

Exciting experiments with solar energy

Cathode Anode

Summary of content (4 pages)

PAGE 1
SOLAR EGG Build your own everlasting solar light Discover the basics of photovoltaics Exciting experiments with solar energy Caption: LED and solar cell Experiment 2 SOLAR EGG Using the sun's energy is exciting and environmentally friendly. It is part of the Energy Harvesting task area because it "harvests" more freely usable energy. There are indeed many solar lights that turn on at night. But for these completely different circuits are used, with completely different characteristics.
PAGE 2
BATTERY SUPPLY For a battery supply with three cells and a total voltage of 4.5 V, a resistor must be installed in series with the LED. The resistance of one kilo ohm (1 kΩ, colour rings brown, black, red) adjusts the current to about 2 mA. The LED can withstand up to 20 mA, but even at low currents, it delivers considerable brightness.
PAGE 3
WIRE PUSHBUTTON SWITCH STORED ENERGY Now we will build an additional push button switch made of wire. The bare wire should be bent so that it does not twist easily in the clamp. The storage capacitor works similar to a rechargeable battery, but has a much longer service life. It can be charged rather quickly and retains its charge for a long time. The correct polarity is important. The black wire is the negative pole, the red the positive pole. The capacitor has a capacitance of 0.47 Farad (0.47 F).
PAGE 4
ETERNAL SOLAR LIGHT The storage capacitor can also be charged directly from the solar cell. In addition, a diode is required so that the capacitor is not discharged via the solar cell when it is dark. In full sunlight, it takes a few minutes for the LED to light up. In darkness, the LED becomes weaker and weaker, but does not turn off completely until the next day. Because the eye adapts to the lighting conditions, the LED is always clearly visible: an eternal solar light.