Selector switches often throw me for a loop when I'm looking at drawings. Just as soon as I think I know what the symbols are, I find a new one, or I find out that I've probably been dead wrong all along. I attribute most of this to my own uneducated state, but at the same time, I don't think everybody is on the same page; I think some of the people making the drawings aren't using the proper symbols or there just aren't universally accepted symbols to convey every possible scenario.
Selectors really are (or can be) a lot more complex than one would think; consider if someone handed you a single selector switch with 4 contact blocks attached. By the time you multiply all the different configurations of:
(2 pos, 3pos, 4pos, joystick, etc.)
X
(spring return from right, spring return from left, maintained, etc.)
X
(operator cam style A, operator cam style B, ..., operator cam style Z)
X
(are the contact blocks arranged left>right or up>down?)
X
(contact block #1 style: NO, NC, dual, etc.) (X contact block #2, 3, 4 style)
X
(what SIDE is each contact block mounted on?)
X
(make before break, break before make, etc.)
...there are literally thousands of combinations; one of thousands of possible switches is in your hand.
Now, what if you had to bring a machine back from the boneyard, and someone's gone in and cannibalized the selector switches and contact blocks? Could you reconstruct the switches based on the prints? I don't think I could; at least not without a healthy dose of weeping and gnashing of teeth. So that's what I'm after: a reference that will educate me about selector switch contacts to the point that I could.
A web resource would be nice, but I'm pretty sure if it were out there, I would have found it by now. Everything I've encountered on the web is basic. A book is even better, if you can recommend a good buy. It would be nice if it included American symbols and European also, and maybe even compare/contrast the two. Also if it talked about timer relay contact symbols that would be cool. But I'm getting picky now; I'll take whatever I can get.
Thank you.
Selectors really are (or can be) a lot more complex than one would think; consider if someone handed you a single selector switch with 4 contact blocks attached. By the time you multiply all the different configurations of:
(2 pos, 3pos, 4pos, joystick, etc.)
X
(spring return from right, spring return from left, maintained, etc.)
X
(operator cam style A, operator cam style B, ..., operator cam style Z)
X
(are the contact blocks arranged left>right or up>down?)
X
(contact block #1 style: NO, NC, dual, etc.) (X contact block #2, 3, 4 style)
X
(what SIDE is each contact block mounted on?)
X
(make before break, break before make, etc.)
...there are literally thousands of combinations; one of thousands of possible switches is in your hand.
Now, what if you had to bring a machine back from the boneyard, and someone's gone in and cannibalized the selector switches and contact blocks? Could you reconstruct the switches based on the prints? I don't think I could; at least not without a healthy dose of weeping and gnashing of teeth. So that's what I'm after: a reference that will educate me about selector switch contacts to the point that I could.
A web resource would be nice, but I'm pretty sure if it were out there, I would have found it by now. Everything I've encountered on the web is basic. A book is even better, if you can recommend a good buy. It would be nice if it included American symbols and European also, and maybe even compare/contrast the two. Also if it talked about timer relay contact symbols that would be cool. But I'm getting picky now; I'll take whatever I can get.
Thank you.
