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Author Topic: Why do some toggle switches have two pins per point in the circuit ?  (Read 683 times)
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For instance, that kind of switch one encounters often : https://www.sparkfun.com/products/97

Edited: inappropriate e-mail link replaced by an url link.
« Last Edit: February 24, 2013, 02:18:29 am by amundsen » Logged

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For instance, that kind of switch one encounters often : https://www.sparkfun.com/products/97

To make it harder to figure out how to wire it up of course.  smiley-wink

 Actually the most likely reason is mostly for more mechanical strength as the switch is going to be pressed a lot and two connections would not be nearly as stable as four.

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Also the legs act as an anchor while the circuit is being wave soldered.
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Why is that link a "mailto:" link?!

The reason is a combination of:

2 pins is mechanically weak, 4 pins means more options for routing traces past / through the PCB
real-estate under the switch, some switches with the same footprint will be SPDT and need at
least 3 pins anyway.   There is a cultural bias in favour of rectangles over triangles/hexagons in
engineering too (for instance the standard QWERTY keyboard can be more logically made from
hexagonal keys rather than square, yet hexagonal key switches are never seen)
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Quote
Why is that link a "mailto:" link?!

Because the mailto: link button is right next to the hyperlink button.

The pic attached is a good reminder of how those pesky little switches need to get wired.



* switch2.jpg (21.11 KB, 382x442 - viewed 24 times.)
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Yet another reason to have two pins per terminal is that the switch can then double as two jumpers.  This can allow a single-sided PC board design and thus save money over a two-sided design.  Traces traveling one way can use the switches to jump over traces running perpendicular to that direction.
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Thanks everyone !
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