[GreenKeys] Snubbing of selector magnet

[Ralph Mowery]

Thanks to Jeff for sending me the file on the Spice program.  Very instering 
to play with.

I did some simulations and one interisting thing is if you go to some of the 
values is not to look at the spike in voltage, but to look at the current in 
the circuit.

If you put in a larger value of capacitor the spike looks like it has been 
greatly reduced and would be beter.  However in looking at the current in 
the circuit, it seems to hold up for a longer time.  By reducing the 
capacitor you get a much large spike, but the current flow drops out much 
quicker.  This helps eliminate some of the bias distortion of the loop 
circuit.

Just as most things, it is a trade off as to what is needed, what you 
want,and what will work when it is built.

I did change some of Jeff's values to match what I am using.  It is a model 
19 set with pulling coils and about .9 Henrys of coil.  Also 160 volts of 
loop voltage and a 2600 ohm resistor.

----- Original Message ----- 
From: "Jeffrey D Angus" <jdangus at att.net>
To: <greenkeys at mailman.qth.net>
Sent: Monday, July 22, 2013 11:54 AM
Subject: Re: [GreenKeys] Snubbing of selector magnet


> On 7/22/2013 10:34 AM, Jim Haynes wrote:
>> On Mon, 22 Jul 2013, Chris Elmquist wrote:
>>>
>>> yes-- so if we choose an opto that can handle anything as big as the
>>> spike, we probably don't have to snub it at all.
>>>
>> Well, unless the turnoff is at least a little bit slow, the spike will
>> rise in voltage until something stops it, whether by snubbing or by
>> breaking down.
> And, that's why I've been playing with the LT Spice program. To look
> at various methods of snubbing and to see what they really do, instead
> of the "Well, we've always just used..."
>
> Earlier some keying circuits were posted using the HSR312 coupler.
> That doesn't seem to be available anymore, so I've decided to use a
> Toshiba TLP227GA instead.
>
> Jeff-1.0
> wa6fwi
>
>