[GreenKeys] my simple little loop supply

[COURYHOUSE at aol.com]

good  to know! and  even part source listing  thx!
Ed#
 
 
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




gil smith, AF7EZ
greenkeys moderator
_gil at baudot.net_ (mailto:gil at baudot.net) 


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