Groovy 555 WebLink Re: [sdiy] 555 Timer VCO problem

[Cynthia Webster]

> Is there a way anyone could give me an clear explanation about each part of
> the circuit. For instance, what each op-amp does, what is actually happening
> at the 555 timer (how this waveform is actually being produced), what each
> capacitor does. I think this would be the best solution to solve this
> problem. By understanding the circuit better, I can troubleshoot it better.
 
Hi Jimmy!

Here's a link that explains a lot about the 555 very clearly.

http://www.poptronics.com/interactive/FreeProjects/555/555-P1.html

I've spent some time at this Poptronics site recently, and think it's very
well done. There are other examples,  and I've even learned a few things
here that I never knew simply about caps, & resistors & LEDs.

Hope this works as well for you!

Cynthia




on 4/19/02 9:28 PM, Jimmy Gogas at toothpick_77 at hotmail.com wrote:

> Hey guys,
> 
> I just recently finished building a Littleman (found at
> http://www.itn.liu.se/~nikro/diy/littleman/littleman.pdf). After a couple of
> days of testing and debugging, I got every module to work (seperately).When
> time came to join everything together, everything was working for a split
> second, until the VCO went down. I lost complete signal from it.
> 
> I spent yesterday trying to figure out why, but I couldn't get it
> working.I even tried rebuilding it on another board, but it still didn't
> work. The problem that I think, is that the 555 timer is not trigerring
> itself, as it is supposed to. In that configuration (pin2 connected to
> pin6), it should start oscillating right away when the power is turned on. I
> tested the 555 separately, following the guidelines for astable operation,
> and guess what, it worked perfectly. So the problem is not a defective
> timer. I replaced the op amps, but this didn't help either. I found that
> when the power is turned on, there is a positive spike followed by a
> negative spike really quickly. I think the problem is the circuit
> configuration, it's not stable.
> 
> I was wondering if anyone had any tips I should follow. The circuit is good
> when it works (and it has already worked... three days ago it was working
> perfectly), but recently it hasn't been working for me.
> 
> Is there a way anyone could give me an clear explanation about each part of
> the circuit. For instance, what each op-amp does, what is actually happening
> at the 555 timer (how this waveform is actually being produced), what each
> capacitor does. I think this would be the best solution to solve this
> problem. By understanding the circuit better, I can troubleshoot it better.
> 
> Thank you in advance.
> 
> 
> 
> 
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