[GreenKeys] Snubbing of selector magnet

[Ken Schwieker]

How about a combination of a RC snubber and a TVS diode to limit the 
higher voltage part of the spike?  On ebay there are both P6KE200CA 
and P6KE400CA  (200 and 400 volt  600 watt bidirectional) for $1 to 
$2 and a 1500 watt ones for a little more).  The small size of the 
TVS diodes (about the size of a 1/2 to 1 watt resistor) make them 
easy to mount.

Ken S

At 10:37 PM 7/21/2013, you wrote:
>On 7/21/2013 7:55 PM, greenkeys-request at mailman.qth.net wrote:
> >> > Mostly the snubber affects what happens on the transition from Mark to
> >> > Space. And quite frankly, unless you've put an enormous value 
> of C in the
> >> > snubber, the Selector magnet is going to pretty much going to 
> let go when
> >> > the loop opens up.
> >> >
> >> > However, with too small a value, the over shoot and ringing 
> issues are going
> >> > to beat the hell out of the loop keying circuit.
>
>    Right.  Fortunately, modern optoisolators like the Omron G3VM-401B/E
>can handle sizable voltages, like 320V.  Enough snubbing to get the
>spikes down into that range isn't hard.
>
>    There's an argument for an R/C snubber instead of a diode.  A diode
>effectively shorts the selector magnet during the MARK/SPACE transition,
>so the current drops more slowly than merely opening the circuit.
>
>                                 John Nagle
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