Today in this video i have shown how to make simple circuit using general purpose transistor. All the transistors used in this video are NPN transistor. But you can use PNP transistor with little changes in the circuit diagram.
How the 1 TRANSISTOR LED FLASHER WORKS, ok here go, actually the circuit abuses the negative resistance factor in all transistor to produce the blinking effect. Here a common NPN transistor is used. When Switched On the 1K resistor charges the 100uf capacitor until the voltage become high enough to get emitter-base junction to avalanche. At this moment the transistor turned on quickly and the capacitor discharged by led through 100ohm resistor, and when voltage across the leads fall, the current stops, then the capacitor again starts to charge through 1k resistor. I have done a mistake drawing the circuit diagram the transistor's lead should be fliped.
For Circuit diagram of automatic night light click the link below