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I'm looking at some switches (here) and the description reads:

Small PC mounting slide switch features SPDT contacts and white positive action slide lever. Size about 0.56"L x 0.25"W x 0.34"H (excluding lever). Pins are on 0.17" centers.

What does "centers" mean in this context? Will I be able to mount the switch on a standard breadboard?

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  • \$\begingroup\$ FYI the switches which naturally mount in a breadboard are DIP switches - however they tend to be SPST. \$\endgroup\$
    – Chris Stratton
    Commented Jan 5, 2012 at 4:28
  • \$\begingroup\$ Unfortunately they're too small for this application. \$\endgroup\$
    – japreiss
    Commented Jan 5, 2012 at 15:20
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    \$\begingroup\$ I would avoid these switches; there's no datasheet provided. You couldn't construct a PCB layout for this switch without measuring one, and there are no tolerances published. Stick with something from a more reputable manufacturer like C&K Components or TE Connectivity, and a more reputable distributor like Digikey or Mouser. Something like this (6A at 125V, is that big enough?) will be better than a no-name switch from a distributor that doesn't provide datasheets. \$\endgroup\$
    – Kevin Vermeer
    Commented Jan 5, 2012 at 15:21
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    \$\begingroup\$ @KevinVermeer - such unconditional bias against surplus components is uncalled for, as the decision depends on intended use. If it's a design that is intended to be put into full-price commercial production or even a one-off in a critical application, you have a point. But if it's for an experiment, or for a limited run of hobbyist kits where unit cost is critical, surplus can play an important role. Additionally, vendors are sometimes chosen not because they are best for that part but because they are the only choice for some other part, and buying minor parts elsewhere would add overhead. \$\endgroup\$
    – Chris Stratton
    Commented Jan 5, 2012 at 15:37
  • \$\begingroup\$ The project is for a one-off DIY synthesizer sequencer. I need 64 switches per unit, so pricing is the biggest factor. The current through the switches will be negligible. I'm building on stripboard so I was hoping for an easy way to mount them. \$\endgroup\$
    – japreiss
    Commented Jan 5, 2012 at 16:32

2 Answers 2

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No.

Centers, in this context, means that the pins are spaced at 0.17" intervals.

Basically, the "center" of each pin is 0.17" from the previous pin's center.

As such, "on x" centers" can be translated as "the center of each pin is x from the center of the previous pin"

For a component to work in a common solderless breadboard, the pins have to be spaced 0.100" apart, in other words, they have to be on 0.100 centers (or some integer multiple of 0.100", such as 0.200" or 0.500" centers).

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  • \$\begingroup\$ Thanks. Unfortunate that they would make these switches in an odd size. \$\endgroup\$
    – japreiss
    Commented Jan 5, 2012 at 4:22
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    \$\begingroup\$ @japreiss - Not really. Switches like that are intended for PCBs, where spacing being a multiple of a value is not critical. The board can accomodate any spacing with the right footprint. As such, they're probably spaced for the minimum size capable of supporting their rated current and voltage. \$\endgroup\$
    – Connor Wolf
    Commented Jan 5, 2012 at 4:27
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It is telling you how far apart the pins are. The reason they specifically use "centers" is to avoid ambiguity. Suppose I had pins made of .025" square posts and told you they were .1" apart. Does that mean .1" between them, or .1" repeating pitch? In the first case the pins would occur every .125" due to their width. In the second case, there is only .075" between pins, but you don't really know which case you have from what I said.

Saying something occurs "on xxx centers" specifically says the centers of the things are xxx apart. In other words, that is their repeating pitch as in the second example above.

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  • \$\begingroup\$ Another point that may be worthy of mention, though probably not as an answer in and of itself, is that in many cases center-to-center pitch does not have an associated tolerance. If a part is specified as having 25 pins with a 1.00mm center-to-center spacing, and the placement tolerance is 0.10mm, then the first two pins are guaranteed to be between 0.90mm and 1.10mm center-to-center, and the first and last pins are guaranteed to be between 23.90mm and 24.10mm center-to-center. In some cases, though, there may be a center-to-center tolerance. For example... \$\endgroup\$
    – supercat
    Commented Jan 5, 2012 at 15:55
  • \$\begingroup\$ ...if there were 25 pins, with a center-to-center spacing of 1.00mm+/-0.005mm, and there was also a 0.10mm tolerance on pin placement, then the first two pins would be between 0.895mm-1.105mm center-to-center, while the first and last would be between 23.78mm and 24.22mm center-to-center. Although nearly all materials are subject to thermal expansion and contraction, which would affect distant points more than nearby ones, when dealing with rigid materials, the absolute deviation from ideal position is often more important than the relative deviation from ideal distance. \$\endgroup\$
    – supercat
    Commented Jan 5, 2012 at 16:01

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