[GreenKeys] my simple little loop supply ERIC AND GIL CONFER?

Thu Jun 30 00:38:10 EDT 2016

Eric and Gil... 

ok I want to use the power supply  gill mentions here  looks  good  but  
want to use  with Eric's  board which  as one resistor on board?  Ok is it 
ready to fly or  do I need to  change resistance  value.

Thanks   in advance  for shared  wisdom!

Ed#   www.smecc.org

In a message dated 6/28/2016 2:20:51 P.M. US Mountain Standard Time,  
greenkeys at mailman.qth.net writes:

In a message dated 6/28/2016 2:14:02 P.M. US Mountain Standard Time,  
gil at baudot.net writes:

So I went to test my M15 yesterday, but left my tty-connect at the  office. 
 Needed a quick loop supply.

I had picked up a dandy little 48V switching supply and 800-ohm 5W  
resistor some time ago, but had not tried it out yet.  Dug out those  parts, found 
a Bud case that was lying around, cut the end off an extension  cord (poked 
it through a cut-out), and found a 1/4" mono jack on a cable  (poked that 
through a hole), and the entire thing is isolated in a plastic  box with no 
need for line ground.  Resistor burns about 3 watts,  switcher pretty 
negligible,  so no need for cooling holes really.   No AC jack or switch, or even a 
light -- about as simple as it gets. 

The switcher has a trimpot to adjust from about 40V to 56V, so setting  
60mA for various setups should be no problem.  Could add a hole in the  end 
panel for a diddle-stick.

I think just 48VDC is plenty for most machines (provided you keep your  
keyboard contacts clean).  Seems to work very well (you could use two  for 96V).

48V supply (< $14 each for a little enclosed 48VDC, 0.57A switcher  that 
does 115/230-in):
http://www.mouser.com/Search/ProductDetail.aspx?R=RS-25-48

800-ohm 5W resistor (just over a buck) for 60 mA loop:

http://www.mouser.com/Search/ProductDetail.aspx?R=25J800E

gil

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