I having to use Lt spice to input the circuit below. There appears to be a double switch but I cannot find it in the library. However, I did try to use the single switch in a configuration but cannot get it to run correctly. I am thinking I am almost there.

I am not sure if you can use the switch I have selected in that configuration.



thanks for any input anyone can give me.

 

Is the intent that each switch has a "make-before-break" form-C contact? If so, you need to account for a short period where node V(a) is momentarily grounded as the switch wiper moves from one end to the other.

Here is how to do that:

 

Looks like each switch has three states.

 

Looks like each switch has three states.

Yes, but is it A, both open, B (break before make)
or is it A, AB, B (make before break)?

 

I think I see how you did it. I am assuming you set this up in a logic format. I never understood it until I wrote each condition out. Is that how you come about that solution?

 

When modeling something, you first have to understand the reality. The question is, how does the switch work?

Here is the opposite case: break before make. A complication is that if you open-circuit a current-source, the voltage goes infinite. To get the simulation to run, I added a Zener across the current-source so that the voltage is limited to the break-down voltage of the Zener (100V) during the 20ms while the current-source would otherwise be open-circuited.