analog fade in out RC

Basically I’ll be turning a 4071 style knight rider 8 led chaser and on each led I use this circuit to fade in and out… giving a more realistic version in led form… the alternative is bump up the cap size to 100uf… and use 1 transistor.

I figured this is the cheapest modification on a 4000 series logic night rider circuit…

You need resistors base - emitter for safe turn off. Also switch 1ohm and 10 ohm with each other. Or make 10 ohm to zero and 1 ohm to a value who don't fry the LED.


The first transistor has nothing to limit collector current - except the high value base resistor. This means the circuit may be very sensitive to manufacturing spread in transistor gain, some devices working and others burning up due to excessive power dissipation.