UP/DOWN FADING LED Circuit
These two circuits make a LED fade on and
off. The first circuit charges a 100u and the transistor amplifies the current entering the 100u and delivers
100 times this value to the LED via the collector-emitter pins. The
circuit needs 9v for operation since pin 2 of the 555 detects 2/3Vcc
before changing the state of the output so we only have a maximum of
5.5v via a 220R resistor to illuminate the LED. The second circuit
requires a very high value electrolytic to produce the same effect.
