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Measurements and analysis with the PC (not provided) 

Simple measuring tasks such as the polarity display or basic functional displays can be handled well 
with LEDs. If detailed measurements are desired, a multimeter is a good aid. In the educational kit, 
simple measurements and functional displays are carried out with LEDs and with the motor. 
 

 

The functioning of the solar module and a suitable light source 

Experimental set-up: solar module, patch panel, 100 Ω resistor, red LED 
 

This experiment also works with little light (cloudy sky); with a lot of light (full sun) the visible 
effects are more noticeable. 

 
Insert the connections of a red LED (light-emitting diode) and the 100 Ω series resistor in the patch 
panel. The longer connection of the LED is to be connected to the red “side” (+). Depending on the 
radiation intensity, the LED shines more or less brightly. If the LED does not shine, either there is too 
little “light energy” available or the LED was connected using the wrong polarity. If the LED flashes, 
you used the flashing red LED. 
 
Fig. 12: Simple functional test with a red LED 
 
Fig. 13: Patch panel set-up 
 
You can do the experiment with various light sources, e.g., with direct sunlight, a halogen lamp, an 
incandescent lamp, an electric torch, an energy-saving lamp, a fluorescent lamp, an LED torch, etc. If 
the LED shines brightly, the light source is suitable. 
 

3. 

Step: Determining the polarity of the solar current 

Experimental set-up: solar module, patch panel, 100 Ω resistor, red LED, orange LED or green LED 
 

You need a bright light source for the following experiment. 

 
The next thing we will do is set up a polarity checker with which you can comfortably determine the 
polarity (positive or negative pole) of the solar module and other voltage sources without having to 
unplug and/or plug in anything. From the upper bar the connection to the row of five is made with a 
100 Ω resistor and from there across to another row of five. From the lower bar two LEDs are 
connected to the rows of five. The LEDs indicate the polarity. As an example, the LEDs can be 
inserted so that the red LED lights up when the polarity is wrong and the orange-coloured one lights 
up when the polarity is correct. Instead of the orange-coloured LED, the green one can also be used, 
but its functioning is harder to see in daylight. 
 
The connection wires of the solar module can now be connected to the patch panel – without paying 
attention to the polarity. The LEDs signal what the polarities are. 
 
Fig. 14: Patch panel with polarity checker using LEDs 
 
Fig. 15: Detail of wiring 
 

If the polarity checker is to be used for higher battery voltages (e.g., 9 V), the series resistor is to be 
replaced by one with 1 K, so that the LEDs are not destroyed. 

 

4. 

Step: Using solar power directly with LEDs 

Experimental set-up: solar module, patch panel, 100 Ω series resistor, red, green, orange LED, 
flashing LED 
 

This experiment also works with little light (cloudy sky). 

 
Fig. 16: Insert the green, red, orange-coloured LEDs and the flashing LED one after the other in the 
patch panel. The longer connection wire of the LED is the positive pole. 
 
Fig. 17: The associated circuit diagram; first insert the green, the red and then the flashing LED in the 
patch panel to close the circuit.