[GreenKeys] LTSpice

[Jim Haynes]

On Sun, 21 Jul 2013, Jeffrey D Angus wrote:

> On 7/21/2013 9:23 PM, Jim Haynes wrote:
>> What if you put a 2K resistors in series with the diode?
> It cleans up the fall time of the selector magnet. Cutting the spacing
> distortion down to 2 mS or so, but the result is a very nasty fast spike
> across the contacts up to 213 volts. 93 v above the 120 v supply.
>
That's about what I expected to happen, because the spike could 
theoretically go to twice the loop supply voltage, or 240V.  With the
rise and fall time being about the same.  Which is OK because we have
loop keyer transistors and solid state relays that are good for 300V or
more.

Perhaps with a solid state relay, hence opto-isolated and a bit of
cleverness you could use the same 2K resistor for setting the loop
current and for snubbing - put the diode outside the 2K resistor.