Interesting rotary switch properties

[Mark Hammer]

Now I know why my 4T switch keeps clicking all of the way around!  I need to find that washer I threw in my parts bin and install it!  It thought I was just buying crappy switches. Thanks!

That's pretty much how I found out about it.  I had the washers and nut off a 4P3T, and the darn thing just kept turning and turning, clicking and clicking, and I'm thinking "When the heck did I order a 4P12T switch!!?" 

[duck_arse]

I'd love to try the search function to collect up all those thread references to the switch stop washer, but anyone who has used search will know why I'm not doing it.

the best fun with the stop washer is when you pull it out and then absent-mindedly clik the switch, as we all do, then put the washer the wrong side of the rotor. now youv'e got the stop in pos 8, but have only 3 cliks. I'm surprised you've never done similar, mark.

[Ice-9]

I'd love to try the search function to collect up all those thread references to the switch stop washer, but anyone who has used search will know why I'm not doing it.

the best fun with the stop washer is when you pull it out and then absent-mindedly clik the switch, as we all do, then put the washer the wrong side of the rotor. now youv'e got the stop in pos 8, but have only 3 cliks. I'm surprised you've never done similar, mark.

Yeah, been there and had plenty head scratching wondering why my logic is messed up, since then I always remember to return the switch to position 1 before fitting the tab washer. 

[electrosonic]

Raising the thread from the dead...

I have been playing around with these.

I have here a 3 pole 4 postion rotary switch and figured out that you can adjust the number of stops (as Mark has explained).

Playing around a with my multimeter I have a feel for how the internals connect,

The poles are labelled A, B, and C and the other contacts are labelled 1 to 12 and are arranged in a circle like a clock.

In the stock configuration

Position 1:  A ->1  B->5  C->9
Position 2:  A ->2  B->6  C->10
Position 3:  A ->3  B->7  C->11
Position 4:  A ->4  B->8  C->12

If you move the stop washer you can get up to 12 positions, but they just repeat

Position 5 is identical to Position 1
Position 6 is identical to Position 2
Position 7 is identical to Position 3
Position 8 is identical to Position 4
Position 9 is identical to Position 1
Position 10 is identical to Position 2
Position 11 is identical to Position 3
Position 12 is identical to Position 4

(I picture the internals like a clock with 3 hands with 120 degrees between each)

I can see moving the stop washer to eliminate a stop if you don't need a position, but trying to extend positions results in duplication so I can't see the use of that.

[armdnrdy]

I can see moving the stop washer to eliminate a stop if you don't need a position, but trying to extend positions results in duplication so I can't see the use of that.

That is exactly what the stop is for.
Let's say you need a single pole five position switch. You can use a single pole 12 position, (and have seven non functional positions) or you can use a 2 pole six position, (and have one non functional position)
Or you can adjust one of these rotary switches to the exact amount to where there are no "dead" positions.

[electrosonic]

My point was that you can eliminate stops, but you can't adjust the stop washer to get (for example) a fifth position out of a 3P4T rotary.


Well not exactly, you can get a fifth position, but it would duplicate the first position. Maybe that's obvious to some, but it wasn't to me.

[armdnrdy]

No you can not.

Even though you have 12 pins, the switch is still set up internally as a 1 pole, 2pole, etc.

[PRR]

> fifth position out of a 3P4T

It's 30 degrees per click, 12 positions.

They make the stator with (usually) 12 contacts.

But there are different rotors.

With a 1-wiper rotor you can select 1 of 12.

With a 2-wiper rotor you get two 1-of-6 selections.

With a 3-wiper rotor you get three 1-of-4 selections.

With a 4-wiper rotor you get four 1-of-3 selections.

With a 6-wiper rotor you get six 1-of-2 selections.

If you set the stop for more positions it overlaps. The A wiper becomes the B wiper and goes through the same sequence. Generally pointless. (Gotta be some use but I can't imagine what.)

You could change your 3P4T switch to another configuration "simply" by replacing the rotor. Simple at the factory. YOU can't get a naked rotor cheaper than you can get another switch; and some switch types can't be put-together again in the field.

[tubegeek]