I was watching the video on Forever Flasher circuit in Advent Calendar of Circuits 2011 series by vk2zay. Below is the circuit I am talking about. However, there are some things I understand and most things I do not understand about the working of the circuit.
Things I understand and do not understand:
When the circuit is powered up, Q2 is turned on a little through R1 and R2 which turns on Q3. When Q3 is turned on, Q2 is turned on more with the current coming from the collector of Q3, through C2 and R5. So they are complimentary pair as vk2zay said in the video. When Q3 is on, it turns Q1 on through R4. When Q1 is turned on, base current that were supplied to Q2 through R1 and R2 is no longer supplied because bottom end of R1 is in the ground potential.
In this position, where Q1, Q2 & Q3 are on, currents flowing are: from Q3:C to R7 to GND, from Q3:C to C2 to R5 to (Q2:B & (R2 to Q1:C to GND) ), Q3:C to R4 to Q1:B to GND. These are the ones I understand but I do not not how C1's current flows and comes from where and goes to where. But here, I think the voltage at "out" and Q3:C which is supply voltage, adds up.
After some point Vc2 goes up to about 0.9 volts which turns Q2 off. So it turns Q3 off. What happens to the charge and voltage at C2? How and to where it discharges? At this point, how and from where to where will Ic1 go?
I just added QTLP690C as a high forward voltage LED. Assume the forward voltage of the LED is 2 to 2.5 volts.
Sorry if I sounded complicated. I would appreciate any detailed information on this. Also, any tips on how to understand how these kind of circuits work?