[GreenKeys] inexpensive loop supply transformer wanted

[Cory Heisterkamp]

The Loop Supply el Cheapo...

Digikey: 
Transformer $9.95 + SH

That e place:
Proj box: <$5 including s/h
6 Super cheap insulated jacks <$5 inc s/h
mA meter $3.50 including s/h

Junk box or surplus:
Bridge, cap, fixed resistor $1
Wirewound adjustable $1
AC cord (who pays for an AC cord?)
Switch(es) $1

Total: ~$30 and an opportunity to "make the shipping worthwhile" ; )

-Cory




On Dec 22, 2013, at 3:02 PM, COURYHOUSE at aol.com wrote:

> Jim -   yes. transformers are still cheap in the junk  boxes at  ham  fests  or sometimes  free if they do  not   want to  take them home afterwards!  <grin!>
>  
> Ed#  Kf7RWW
>  
> In a message dated 12/21/2013 8:54:03 A.M. Mountain Standard Time, w0eb at cox.net writes:
> These are getting harder and harder to find.  One solution I've used in the past was to pick up a couple of 120 to 12 volt, 2 amp filament or power supply transformers.  Connect the 12 volt secondaries of the two transformers together.  T1 will step down to 12 volts from 120 and T2 will take that 12 volts back up to 120.  AC in to one primary and take the 120 out for the loop supply from the other primary.  Kinda hokey but it does work and 120:12 volt transformers are still pretty cheap from lots of places.
> 
> One in particular I use a lot is Marlin P. Jones associates out of Florida someplace.  Their website is www.mpja.com
> 
> Jim - W0EB
> 
> > I'm working on a small project to have a Single Board Computer such
> > as a Raspberry Pi or Arduino drive my TTYs (Model 15 at 45 WPM and
> > a 28 RO at 75 WPM) with some canned messages from memory.  As part
> > of that effort I'd it to have it's own loop supply (120VAC to
> > 120VAC isolation transformer, bridge rectifier, filter cap, 2800
> > ohm 20 watt limiting resistor).  Does anyone have suggestions on
> > where I might find a low cost isolation transformer for this
> > purpose?
> >
> >
> > Paul Newland, ad7i
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