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Making a DPDT Switch
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You may have noticed that Micro-Cap has a SPST, SPDT, and a DPST. Is there a DPDT? No. It was
left out. So what do you do if you need one? Well, it's pretty easy to construct.
First of all let us review what the terms mean. The two terms most relevant are Throw and Pole.
THROWS: This is the number of separate wiring paths, other than open, that the switch can provide
for each pole.
POLES: This is the number of electrically separate switches controlled by a single physical actuator.
So for a DPDT we need two poles (switches) and two throws (paths) per switch. How do we do
that? Well we start with SPST and double it. Here is the SPST.
Next we change its GROUP so that when it changes state another switch with the same GROUP
name will do the same. The GROUP attribute can be changed in the Attribute dialog box. Double
click on the switch and change the GROUP attribute to Double_Throw (or any name you prefer).
The screen should now look like this:
Click the OK button and then while holding down the CTRL key, click and drag on the switch. This
creates a duplicate of the original switch including the GROUP attribute. When two switches use the
same GROUP attribute then any action (such as clicking on it) will be duplicated at the other switch.
If you add a battery to each switch and some LEDs to easily show the states, the circuit should look
like this.
If you click on either switch, the other switch behaves the same. Essentially this means that the combination
of two DPST switches have the same actuator, and as a result the combination of the two
makes a DPDT switch.
You can easily make a 3P2T (three pole double throw) switch using this method. It would look like
this:
You can make an n-pole switch but it must be a 1-throw or 2-throw variety. That's because there are
only 1-throw and 2-throw animated switch primitives to use. Perhaps in a future version. Hmm.
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