Hi,
I just finished my first soldering project. I'm such a newbie. It's a JAMECO 3-D Christmas Tree. It all works fine but I don't understand how it all works. Here's the schematic for it.
https://www.jameco.com/Jameco/Products/ProdDS/211781.pdf
I can see it's an oscillator but can somebody explain the details of its operation?
I'm interested both in the operation and the numbers. I.e., what currents flow where. The LEDs are the tiny kind, I'm not sure what their voltage drop -- I should have measured yesterday, but was too tired.
So, R1 and R2 are current limiting resistors. R5 through and R8 are there to properly bias the bases of the transistors. R4, R6 control T2, T4 and R7, R8 control T1, T3.
The base current of T2, T4 is:
(9V - 0.7) / 82000 = 0.1mA
The base current of T1, T3:
(9V - 0.7) / 100000 = 0.83mA
It's hard to say according to the datasheet what the typical DC current gain is for this transistor because in the column where it should be listed, a "-" is put. But I assume the transistors will be fully open at 0.7 on the base.
The part I don't get is:
1) why would the transistors ever close (must have something to do with the caps but I don't get how it works)
2) why do R5, R6 and R7, R8 have different resistor values?
Many thanks in advance. And please remember, I'm new to electronics. So, if my calculations or analysis or questions evoke a fury of emotions, gently point out to me where I'm mistaken. That will be sufficient.
I just finished my first soldering project. I'm such a newbie. It's a JAMECO 3-D Christmas Tree. It all works fine but I don't understand how it all works. Here's the schematic for it.
https://www.jameco.com/Jameco/Products/ProdDS/211781.pdf
I can see it's an oscillator but can somebody explain the details of its operation?
I'm interested both in the operation and the numbers. I.e., what currents flow where. The LEDs are the tiny kind, I'm not sure what their voltage drop -- I should have measured yesterday, but was too tired.
So, R1 and R2 are current limiting resistors. R5 through and R8 are there to properly bias the bases of the transistors. R4, R6 control T2, T4 and R7, R8 control T1, T3.
The base current of T2, T4 is:
(9V - 0.7) / 82000 = 0.1mA
The base current of T1, T3:
(9V - 0.7) / 100000 = 0.83mA
It's hard to say according to the datasheet what the typical DC current gain is for this transistor because in the column where it should be listed, a "-" is put. But I assume the transistors will be fully open at 0.7 on the base.
The part I don't get is:
1) why would the transistors ever close (must have something to do with the caps but I don't get how it works)
2) why do R5, R6 and R7, R8 have different resistor values?
Many thanks in advance. And please remember, I'm new to electronics. So, if my calculations or analysis or questions evoke a fury of emotions, gently point out to me where I'm mistaken. That will be sufficient.