[GreenKeys] Loop supply options

[Steve Garrison]

I do that all the time!

Steve G./N4TTY

-----Original Message-----
From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net>
On Behalf Of epvgk at limpoc.com
Sent: Monday, September 9, 2019 1:03 PM
To: Paul Heller <paul0926 at comcast.net>
Cc: Jeff G <jeffg at junknet.net>; greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] Loop supply options

On Mon, Sep 09, 2019 at 10:16:08AM -0600, Paul Heller wrote:
> Does anyone use a rheostat to fine tune the loop current, or is that a
silly idea and close is good enough? 
> 
> Paul
> W2TTY

I have a big fat wirewound one in there because if I connect a bunch of
machines the current drops quite a bit and I might want to reduce the
resistance to bring it back up.

> 
> ITTY:			HTTP://INTERNET-TTY.NET:8000/ITTY
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> 
> > On Sep 9, 2019, at 9:10 AM, Ralph Irish <w8roi at wowway.com> wrote:
> > 
> > This transformer is  EXACTLY  what is needed for a trouble-free loop 
> > supply.  With a bridge rectifier and a healthy cap, it will provide 
> > fairly clean 170VDC at one amp.  This is not an unheard of voltage 
> > for a loop supply.  Several experimenters in past decades used 
> > voltages up to 250VDC for test purposes and found no ill effects to 
> > selector magnets, etc.  No matter what the 'supply voltage' is, the
voltage applied to the actual magnets will be less due to the dropping
resistor and hopefully, an adjustable resistor to set the loop current at
idle to 60ma.
> > 
> > The external resistors carry the extra voltage and if properly sized 
> > wattage wise will easily dissipate the heat from I squared R losses.
> > 
> > If I were going to build a loop supply, that would be my first 
> > purchase.  Price is reasonable and ratings seem conservative for long
life.
> > 
> > Good luck to all who are going to build a loop supply for some machine
or system.
> > 
> > Ralph - W8ROI
> > 
> > -   -   -   -   -   -   -   -
> > 
> > 
> >> On Sep 9, 2019, at 10:21 AM, Jeff G wrote:
> >> 
> >> When I first saw this thread, I had the exact thought of just a 1:1
transformer with a bridge and cap.
> >> 
> >> FYI - 1:1 transformers are readily available yet, I work on arcade
games and nearly every game has one, both for safety reasons as well as
being required by the open frame monitors. You can still buy them new.
> >> 
> >> I'm sure you can find them on Amazon, etc, but here's an example 
> >> from one of the popular vendors: 
> >> http://www.arcadeshop.com/i/1346/monitor-isolation-transformer.htm
> >> 
> >> These are usually good for an amp or two, as they generally run
everything on the game through it. Add a bridge, a cap, and a couple fuses
and you're there, for much less than $100.
> >> 
> >> Jeff
> >> 
> >> 
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