Elenco's PK-201 Experiment #18: Very slow Light Bulb

This experiment combines transistor basic principles and what was learned in experiment #8 (capacitor charge/discharge). When the switch is first turned on the current flows through the 100k ohm resistor (controls charge time of capacitor) to charge up the capacitor, the transistor and LED will be off. When the capacitor rises to 0.7V the transistor turns on first and than the LED will turn on. Current will increase as the capacitor voltage rises. When the switch is turned off the capacitor will discharge through the 470 ohm resistor and the transistor base (resistor controls discharge of capacitor), the LED will dim as this discharge current decreases. When the capacitor voltage drops below 0.7V the transistor will turn off.