|A Few Words on Plastic Rotary Switches|
Plastic rotary switches are supplied in various forms and when properly used, are highly reliable. Typically these switches are supplied in single pole 12 position, 2 pole 6 position, 3 pole 4 position, and 4 pole 3 position types.
However, these are only the basic forms, and a clever travel limiting mechanism allows each of these basic forms to be varied to suit the user. This detent arrangement can be seen in the photos, and consists of a metallic collar with a protuding stop (B), which can be fitted into a series of holes (C) in the switch body.
Taking a single pole 12 position rotary as an example, this mechanism allows the user to select any number of switch positions from 2 to 12. Further, by placing the stop into the appropriate hole, switch rotation can start clockwise from pin 1, or anticlockwise from pin 12. So for example, if the user wants a single pole 4 position switch, it is simple to elect to use switch pins 1-4 or alternatively pins 9-12 to suit a front panel layout and a particular knob.
As a final comment, DO NOT overexpose these switches to soldering heat. Plastic has a memory. It started life as a moulding pellet, and will return to this form if overheated. Make your soldering quick and clean with a short cooling off period between joints on the pins. Holding a pin at soldering temperature for more than 15 seconds almost guarantees an open circuit switch.