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Topic: Why do some toggle switches have two pins per point in the circuit ? (Read 1 time) previous topic - next topic


Feb 23, 2013, 09:28 pm Last Edit: Feb 24, 2013, 08:18 am by amundsen Reason: 1
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.


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.  ;)

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.



Also the legs act as an anchor while the circuit is being wave soldered.


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)
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]


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.

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Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0


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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