turn on and off a led with resitance, capacitor and diod

[iurelectr]

This is important to me bacause I'm going to do some toys with this and start building new circuits...we can exchange ideas and experiences

 

[tcmtech]

This can also be done with a single UJT (Uni Junction Transistor). It has only a few resistors and a capacitor to work.

 

[audioguru]

I have done the circuit with two transistors...but it doesn't work...
Why?

I'm using 12 Volts being the positive connected to the resisitor 330 ohm and the negative
to the capacitor (negative part) and to the negative of the led.

Your circuit is missing the important 10k and 120 ohm resistors.