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Help needed: is my circuit functioning?

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Hi,

I constructed my own astable multivibrator circuit with the resistors 2x 360 ohms and 2 x 36K ohms (these are on the bases of both transistors). Transistors: 2x PNP CS9012. The caps are 47 micro farads.

By right it should oscililate, but the whole circuit is dead - so could it be my new breadboard's fault? I tried that combination in a terminal block, and it worked.

Or could it be my connections?

Here's the pic - I tried reconnecting it but still it didn't work. Ooooh. :confused:
 

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littletransistor said:
Hi,

I constructed my own astable multivibrator circuit with the resistors 2x 360 ohms and 2 x 36K ohms (these are on the bases of both transistors). Transistors: 2x PNP CS9012. The caps are 47 micro farads.

By right it should oscililate, but the whole circuit is dead - so could it be my new breadboard's fault? I tried that combination in a terminal block, and it worked.

Or could it be my connections?

Here's the pic - I tried reconnecting it but still it didn't work. Ooooh. :confused:
hi,
Can you post a circuit drawing, its difficult see details on the picture>
 
Sorry man for the blurry picture.

Hmm... I need a breadboard drawing for this - any breadboard simulating software? I searched around, but all I get is for the logic gates chips.:p
 
littletransistor said:
Sorry man for the blurry picture.

Hmm... I need a breadboard drawing for this - any breadboard simulating software? I searched around, but all I get is for the logic gates chips.:p

hi,
If you post your circuit drawing it will help.:)

I dont use that type of software, have you tried Google?
 
It is a very low frequency oscillator.
Why not add two red LEDs so you can see what it is doing?
 

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audioguru said:
It is a very low frequency oscillator.
Why not add two red LEDs so you can see what it is doing?

Thanks for the help - I think I might have the capacitors in the wrong polarity - let me try flipping the cap over. :rolleyes:

edit: okay - here's the picture, it's a little bit weird, but you can see that the red semi-rectangular are the transistors. The green arrows pointing upwards are to +5V, and the another facing left is to the negative terminal of the battery. The red circular thing is capacitor, and the lines indicate that the their legs has been extended. The output is the LED and I couldn't get anything even I modified the circuit over and over again... :(
 

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1) Your capacitors are backwards.
2) Your transistors don't show which way they are connected, maybe they are also backwards.
3) Your circuit doesn't have a supply voltage. 3V? 9V? 12V?
4) You don't show how you connected an LED to the output. It might be shorting the output or maybe it is burnt out.
 
audioguru said:
1) Your capacitors are backwards.
2) Your transistors don't show which way they are connected, maybe they are also backwards.
3) Your circuit doesn't have a supply voltage. 3V? 9V? 12V?
4) You don't show how you connected an LED to the output. It might be shorting the output or maybe it is burnt out.

Thanks. Here's the revised circuit - the supply voltage is 9V by the way. Also, I directly connect the LED onto the circuit - but i have to test it using an LED before I put this device on the other parts. :)
 

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9V is probably high enough to cause the transistors to break down?, as you don't have any reverse Vbe protection. 6V would be OK, but 9V is probably too high.
 
Nigel Goodwin said:
Have you also seen protection diodes on the transistors as well?. 9V is fairly risky on the transistors otherwise.

Nope - that's a common 9V battery LED flasher. Will show you the original diagram and even the picture later - a company* in my place is supplying thousands of them every year to high schools, for the "Home Science" (please note: I'm not in America) studies. I'll see about trying other transistors in the meantime - my CS9012s are very old and it's really old.

Now I gonna get some new normal switching BJTs as well too. :rolleyes:

edit: *Here's the link: 2-LED flasher

I have that thing in my hands (now broken, dunno why?!) and the transistors are 2x CS9013s, 2x 47k and the other I forgot.
 
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The LED's in the collectors effectively lower the voltage that the capacitors charge to - this probably makes the circuit viable at 9V? - don't try 12V though.
 
The LED on your breadboard circuit has both its wires connected to the same spot so no current flows in it.

Your first circuit on the breadboard uses CS9012 PNP transistors.
The kit circuit uses CS9013 NPN transistors and the battery, LEDs and capacitor polarities are the opposite.
 
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