Hi g0aqi,

If you use a different chip you can do it much easier. just one chip one
capacitor and three resistors and you are in business.

The chip is an LM358

It will totally flip it for you.

Take care,
V


> Hello everyone.
>
> Sorry to be a pain but, in spite of Bg's efforts to put some photo's
> in the group files, I'm having trouble getting my head around it
> all. I want to be able to flip the polarity of various voltages,
> (all low..) and a simple miniature relay change-over timer circuit
> would enable me to do this, rather than what I see featured in the
> files.
> I need to find a simple schematic using a 555 timer chip which will
> do this.
> The 555 switches on for a while then switches off for a while I
> understand the 555 won't flip polarity on it's own, hence the relay -
> A minature Double pole changeover relay, driven by the timer WILL do
> this.

> I've looked at various sites featuring the 555 timer but can't quite
> get my head around the various terminology and can't see a simple
> enough circuit.
>
> Can anyone give me a hand on this?
>
> This seems really fundamental to group experiments in this area and
> I'm sure that there will be others wanting something similar.

> Having a relay there with totally independent contacts means that one
> can use any voltage and not rely on the timer chip circuit.
>
> Cheers.
>
> Ed




--