[GreenKeys] Loop supplies

[Jeffrey D Angus]

Here's a transformer that will work just fine.
<http://www.mouser.com/ProductDetail/Pulse/DST5-120B39/?qs=sGAEpiMZZMvwUzoUXIIvyU3kfM2h%252b089EV3piJz8kJE%3d>
Data sheet on page 7
<http://www.mouser.com/ds/2/336/LT2012[1]-334898.pdf>

PC board mount.
Primary: 115/230
Secondary: 120/60
Current handling: 120 V CT at 0.10 amps, 60 V at 0.20 amps.
And it's ONLY $11.54.

And some additional thoughts on TTY loop supplies.
Ripple isn't an issue. It wasn't in 1930 and it still isn't now.
A 120 vdc supply with a 2K resistor in series with is is basically a current
source. The relative term used are "compliance" which mean how much
voltage is available to make the current happen.
Which, as has been pointed out, is critical when driving inductive loads.

This has been modeled repeatedly with LTSpice and other analysis
programs watching the voltage source being switched on and the
resulting rise of current through the inductor.

Equally important is the use of a series resistor and capacitor across
the switch contacts to limit the excursion of the inductive "kick" when
the switch opens.

What you want, and need to have happen, is for the current to rise to
60 mA within 3-5 mS of the switch closure so that the "distortion" (i.e.,
rise time delay) is minimal.






-- 
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20160518/3461849d/attachment.html>