Conrad Course material 10025 14 years and over 10025 Manual De Usuario

charge is still in the capacitor. The flashing LED shows little or no reaction. What happened? The 
electrolytic capacitor discharged “backwards” via the solar module. 

 

16.  Step: Stored energy and mechanical energy 

Experimental set-up: solar module, patch panel, 4,700 µF electrolytic capacitor, motor, flashing LED 
 

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

 
If you connect the motor directly to the solar module, it can be that the amount of energy coming from 
the solar module is not sufficient to make the motor start up automatically. 
 
Fig. 51: Circuit diagram – use the flashing LED as power indicator. First plug the 100 µF electrolytic 
capacitor in and then the 4,700 µF electrolytic capacitor parallel to the connections of the solar 
module.  
 
If the motor is connected to the capacitor, the motor shaft turns several revolutions. Under some 
conditions, the start-up held of the electrolytic capacitor is already sufficient, so that the motor can 
continue to run with the slight power of the solar module. 
 
Fig. 52: The motor is temporarily connected at the same contact points as the electrolytic capacitor. 
The motor turns a few revolutions, the LED does not flash anymore and it takes a few seconds until 
the LED starts to flash again if the motor is again disconnected. The motor completely discharged the 
electrolytic capacitor. 
 

17.  Step: Solar energy, charge monitoring and fuel gauge 

Experimental set-up: solar module, patch panel, flashing LED, red LED, 1N4148 diode, green LED, 
4,700 µF electrolytic capacitor, 1 K resistor, 2.2 K resistor, wire switch; additional experiment: 
rechargeable battery 
 

For the following experiments, you need a bright light source (or full, direct sunlight) for the solar 
module. 

 
Is the energy storage now empty, half-full or full? For this, we need a display, similar to a fuel gauge in 
an automobile. But the fuel gauge of a rechargeable battery is a lot more complicated. In order to get 
all the factors under control, there are clever monitoring electronics with microprocessors and 
elaborate software. 
 
In Fig. 53, you see the experimental set-up of a simple charge level indicator which you can assemble 
with the parts in your educational kit. The upper red LED indicates the charging current to the energy 
storage and shines as long as the electrolytic capacitor is being charged. The middle flashing LED 
begins to shine in connection with the diode and the green (or orange-coloured) LED when the 
electrolytic capacitor (or rechargeable battery) is completely charged. Due to the fact that D2, D3 and 
D4 are connected in series, the LED starts to flash only with a voltage of ca. 4 V. This voltage is 
suitable for the “battery full” display in the case of a lithium battery. If D3 is bypassed, the voltage is 
reduced at which D2 flashes. 
 
Fig. 53: Experimental set-up on the patch panel 
 
Fig. 54: Circuit diagram of the charge level indicator (test circuit whether solar module is suitable)  
 
The simple battery fuel gauge is implemented via voltage measurement of the battery. It would be an 
improvement to do the voltage measurement under load. The load ought to have a current 
consumption that is 10% of the battery’s capacity and could be activated at the moment of 
measurement by a button.  
 
Fig. 54a: Additional “load” with orange-coloured LED or Motor (sample circuit)  
  

18.  Step: Solar energy and non-return valve  

Experimental set-up: solar module, patch panel, electrolytic capacitor, button, silicon diode, series 
resistor, red LED