Astable multivibrator gets 'stuck'

I've built this circuit:


Source

It works great, and I'm getting some nice sparks :smiley:

But when I turn it on, usually it doesn't do anything at first. I have to push that button to get it going. According to the instructable, the circuit sometimes gets stuck and the button discharges the capacitor to unstick it. There is no stated way in the 'ible or the comments to fix the problem.

Is there any bug in the circuit that could be causing the problem? I've never had a circuit with that problem. I don't like having to push the button every time I want some ozone :stuck_out_tongue:

(If all else fails I might be able to make something to simulate a button push but I really don't want to)

Yeah, i'd put my bet's on the capacitors used to switch on the base of the transistor..

Simply change 1 of the capacitors to a higher capacitance value...

You may want to investigate a TLC555 timer Astable circuit.

wiring/circuit error
see attached DWG revision

pwmfdredo.JPG

That's the the same thing without the button ?

cjdelphi:
That's the the same thing without the button ?

No.
Compare, discriminate.

Other than the button and the bases of the transistors swapped around for the caps ..?

and what effect changing them around have?

Thank you all so much for your replies. I will try Runaway Pancake's answer and get back to you.

EDIT! It worked! I plugged and unplugged it a bunch of times, and every time it worked. Thank you thank you thank you!

I'm going to post a comment on the Instructable to hopefully save other people the trouble.

And there it is.

The modification suggested by RP merely swaps which pot/resistor is connected to which transistor base. As the pots and resistor have identical values, the difference must be to do with how you have the two pots adjusted.

The comment I was about to make is that with the power mosfet gate connected directly to one of the collectors, the input capacitance of mosfet will tend to damp the feedback, and that might account for the original problem.