[VoIP] Coin relay controller

[Donald Froula]

Sorry, I should have read more carefully. I was using
two 120VAC:18VAC transformers with their secondaries
connected together for isolation and current limiting.
That provided the 170 VDC after filtering.

Don

--- Mark Rudholm <mark at rudholm.com> wrote:

> Are you sure you're using a 2:1 transformer?
> I would expect to see 170 VDC if I was using
> a 1:1 transformer.
> 
> The 2:1 should halve your incoming 120 VAC
> down to 60 VAC, so with the filter cap, you
> should get about 75-80 VDC.
> 
> My experiments bear this out.
> 
> Donald Froula wrote:
> > It sounds like some kind of coupling or overload
> is
> > going on with the transformers. I use the exact
> same
> > arrangement to make a power suppply for a Nixie
> tube
> > clock I built. I get 170 VDC, unloaded. I did use
> an
> > extra winding to boost the voltage a few volts to
> > overcome droop under load.
> > 
> > Don
> > 
> > --- Mark Rudholm <mark at rudholm.com> wrote:
> > 
> >> Donald Froula wrote:
> >>> ...only if you cap filter it. Wouldn't
> unfiltered,
> >>> bridge rectified have about the same RMS as sine
> >> AC?
> >>> The frequency is doubled, of course.
> >> I find line AC through a 2:1 transformer then
> full-
> >> wave rectified and filtered with a 220µF cap
> yields
> >> about 78VDC, which is just about perfect since
> it's
> >> enough to power the higher voltage coin-relays
> but
> >> not excessive for the lower voltage ones.
> >>
> >> Oh, and thanks for the Bellcore, etc
> documentation.
> >> Very helpful stuff.
> >>
> >> So helpful, I'm toying with the idea of
> supporting
> >> the Stuck Coin and Initial Rate tests...
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