[GreenKeys] Loop supply options

[Paul Heller]

Does anyone use a rheostat to fine tune the loop current, or is that a silly idea and close is good enough? 

Paul
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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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