User manual

36
18 Four-color switch
Today we are using the purple glowing LED for the first time.
The housing is whitish, but in reality, the LED has a purple
glow. We use the RS flip-flop of the last experiment and ex-
pand it by four LEDs. Just like before, each transistor has one
LED in the collector line, but the other LED is installed into
the emitter line. That way red and yellow will always glow in
sync while at the other side we have purple and green.
In this experiment the two LEDs on the negative terminal
need to have similar voltages; that is only likely, if the colors
are located close to each other. The LED voltages at the same
current differ, whereby the order follows that of a rainbow:
red, yellow, green, blue, purple. Yellow and green are also
found close on the voltage scale. Try and change the places of
the LEDs and see how the circuit responds.