[GreenKeys] To snub or not.

[Jeffrey D Angus]

Image 1: this is the reverse EMF kickback when you open the
contacts. A negative spike close to 120 v. This will usually kill
a keying transistor.
Image 2: Putting a reverse diode across the coil, clamps the
spike to near zero volts, but the reverse current through the
coil is long enough to miss the Spacing signal.
Image 3: Using a series RC snubber will cut down the reverse
spike, but still allows the coil to correctly act like there is a
Space signal. It also cuts way down on arcing on mechanical
contacts.

Oddly enough, Western Union had all this figured out over
a hundred years ago. ;-)


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



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