[GreenKeys] Loop supply options

[Ralph Irish]

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

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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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