Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!newstop!jaytee!vergil!gsteckel
From: gsteckel@vergil.East.Sun.COM (Geoff Steckel - Sun BOS Software)
Newsgroups: sci.electronics
Subject: Re: Ring signal generation (was DTMF Decoder IC)
Summary: old fashioned tech
Keywords: resonance
Message-ID: <2876@jaytee.East.Sun.COM>
Date: 11 Oct 90 17:41:38 GMT
References: <14793@mentor.cc.purdue.edu> <27114b84-483.1sci.electronics-1@vpnet.chi.il.us> <14913@mentor.cc.purdue.edu> <9770@uhccux.uhcc.Hawaii.Edu> <1990Oct10.151422.6001@zoo.toronto.edu>
Sender: news@jaytee.East.Sun.COM
Reply-To: gsteckel@east.sun.com (Geoff Steckel - Sun BOS Software)
Distribution: na
Organization: Omnivore Technology, Newton, Mass. (617)969-3448
Lines: 18

It's fairly easy (:-) to generate quasi-sort-of-sine-looking-things at
more-or-less 60-80VAC 20HZ by taking a filament transformer (remember them?)
and running it backwards, resonating the primary with a large NONpolarized
capaicitor, and using robust transistors (2n3055 or power FETs) in a multivibrator
configuration.  Using feedback from the resonant load eliminates needing to tune
a separate oscillator.

I'd recommend a 300 mA 12VCT filament transformer driven off 5 volts.  Use
an L/C/R bridge and 1/2pi sqrt(L * C) to determine the C value (don't be surprised
if it's several hundred microfarads or larger!), or just play around with a scope.

This can generate a LARGE jolt on its output, and remarkably large reflected voltages
on the driver transistors.  Be careful & have fun!
	regards,
	geoff steckel (gwes@wjh12.harvard.EDU)
			(...!husc6!wjh12!omnivore!gws)
Disclaimer: I am not affiliated with Sun Microsystems, despite the From: line.
This posting is entirely the author's responsibility.