Conrad Course material 3964 14 years and over 3964 Manual De Usuario

 

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Fig. 48: Slow capacitor discharge (Schaltung19.jpg)

 

 

 

 
Fig. 49: The minute light (Aufbau19.jpg)

 

 

An LED flasher with smoothly swelling and ebbing brightness can, with a suitable frequency, help the viewer relax. 
The brightness follows a sinus wave. This circuit activates two LEDs precisely in phase opposition. The light thus 
continuously changes with smooth transitions between red and green.   

 

 

 

Fig. 50: A phase shifter oscillator (Schaltung20.jpg)

 

 
At the start of the circuit, the electrolytic capacitors are still discharged. Therefore the BS170 blocks and the NPN 
transistor conducts. At first only the red LED shines. Then the circuit tries to swing onto a middle current, but 
constantly overshoots and produces a sinusoidal signal at which first the one transistor conducts and then the other 
one conducts. 

 

 
 

green 

green           red