View attachment 263723
the circuit photo uploaded is blur. is it because of low resolution?where can I make resolution higher?

Mod: Adjusted the image.

 

hi xljin,
Do you have a question about the circuit.?
E

 

Instead of copying the blurry schematic, I found the same clear circuit in Google.
Your base resistor values are way too low so I increased them 10 times and reduced the capacitor values 10 times so that the timing is the same.

 

hi xljin,
Do you have a question about the circuit.?
E

yes

 

So what is your question about the circuit?

Ron

 

Instead of copying the blurry schematic, I found the same clear circuit in Google.
Your base resistor values are way too low so I increased them 10 times and reduced the capacitor values 10 times so that the timing is the same.

I use your pic. still blur.

 

I use your pic. still blur.

I think it's low resolution problem.

 

So what is your question about the circuit?

Ron

hi ,ron

my question is about shortly after the beginning of adding vcc, how it comes one transistor go saturation, and the other one go cut-off(right word?).

here is how I think: as vcc is added,
both transistor start to open by base resistance, but the transistors, base resistances，and collectors between are not the same exactly, so the two collector voltage are not the same.

assume left transistor's(v1) collector voltage go down faster, by coupleing of the left capacitor(c1),the voltage of the base of right transistor (v2) goes low, so v2 starts to cut off. the collector voltage stars to go up. and this voltage is coupled to v1's base, which make v1 goes to saturation.

I have two questions:
1. as I analysed before, the posative feedback happened to v1, we can also analyse v2 the same way. the difference is which one is quicker. my question is: what makes transistor go saturation or cut off. the collector goes quicker is the key?and why?
2.in this circuit, is collector voltage make sense or the voltage change make sense?I think is the second,because capacitor coupleing voltage change ,not voltage.

 

Hello there very good questions. If you read this thread in its entirety you'll find your answer it's a very common question and a very good read.
https://forum.allaboutcircuits.com/threads/oscillator-circuit-explanation.151221/

 

Hello there very good questions. If you read this thread in its entirety you'll find your answer it's a very common question and a very good read.
https://forum.allaboutcircuits.com/threads/oscillator-circuit-explanation.151221/

hi, delta

i guess the osilation circuit you recommended is different with mine.

 

Try this online simulator: https://www.falstad.com/circuit/

There is an example of your circuit under the menu "Circuits" - "Transistors" - "-Multivibrators" - "Astable multivibrator".

It's a common circuit, expect to see variations though the concept is the same.

 

"hi, delta

i guess the osilation circuit you recommended is different with mine"

On the contrary!
The component values may be different, the 330Ω resistors and the LEDs are positioned differently. The function is identical.
If you take the time and read the entire thread as I suggested
It will answer every single one of your questions.
Although it is not as personal as I am talking to you right now .I will only be repeating what has already been stated.With that said... if you have any other questions please feel free to ask. And the schematic in the other thread wiggles.

 

View attachment 263723
the circuit photo uploaded is blur. is it because of low resolution?where can I make resolution higher?

Mod: Adjusted the image.

View attachment 263729

how mod adjusted the image?

View attachment 263723
the circuit photo uploaded is blur. is it because of low resolution?where can I make resolution higher?

Mod: Adjusted the image.

View attachment 263729

"hi, delta

i guess the osilation circuit you recommended is different with mine"

On the contrary!
The component values may be different, the 330Ω resistors and the LEDs are positioned differently. The function is identical.
If you take the time and read the entire thread as I suggested
It will answer every single one of your questions.
Although it is not as personal as I am talking to you right now .I will only be repeating what has already been stated.With that said... if you have any other questions please feel free to ask. And the schematic in the other thread wiggles.
View attachment 263776

this is the circuit you give

this is the circuit you give me , maybe wrong link.

 

Xljin, your first schematic does not have a PNP transistor.
Doors open or close, transistors turn on or turn off.

 

Xljin, your first schematic does not have a PNP transistor.
Doors open or close, transistors turn on or turn off.

what's wrong with not having a PNP transistor?

 

Your base resistor values are way too low

No, they are not.

I increased them 10 times and reduced the capacitor values 10 times so that the timing is the same.

Now the base resistors are way too large. Assuming the Vf of the LEDs is approx 2.0 V, the ratio of collector current to base current is now 80:1. I'm not a huge fan of the 10:1 rule, but 80:1 is way too high, even for me. With the original resistor value it was 7.4:1. I suggest you increase the base resistors to 10 K and decrease the capacitors to 100 uF. The net change in frequency is 3%.


ak

 

Your first circuit has two NPN transistors. You can make it with two PNP transistors if you reverse the polarity of the battery and the capacitors.