Using 3PDT Switches Instead of DPDT

[fogwolf]

Hi,

I am a complete beginner working on my first project, an A/B/Y box:

http://www.generalguitargadgets.com/pdf/ggg_amp_aby.pdf

The problem is that this project calls for and shows you how to wire 2 DPDT bypass switches but I supidly purchased 2 3PDT bypass switches instead. I'm assuming I could still use these but am not sure how to wire them, since the spec shows DPDTs - would I just lay the 3PDT switches out in the same orientation as the DPDTs in the wiring diagram and ignore the middle column of 3 connectors on my switches?

Thanks!

[dschwartz]

yes, you can do that..

also, you can use the middle switch to activate a led.

[Mark Hammer]

The switches come with sets of 3 contacts, either two such sets in the case of DPDT, or three sets in the case of 3PDT.  The "P" stands for "pole", and the first character tells you how many.  So, 4PDT means four sets of three contacts.  If it were DPST (S for "single") there would be two sets of 2 contacts.

Were there are huge gulf in price between the different switch configurations, then paying attention to how many contacts they have might be worth doing, but in the present climate there is so little difference in price between 9-lug, 6-lug, 3-lug, 4-lug switches, that it is simply more convenient to have a bunch of 3PDTs on hand and only use the lugs you need.  A 3PDT can serve as a SPST if you want, or a DPST, or an SPDT, or whatever.  As long as there are enough lugs to do the needed task, you're fine.

The one tiny problem you'll have with a 3PDT is that when the lugs are laid out in a 3 x 3 matrix, it can be easy for the beginner to lose their place and forget which direction the contacts run in and which 3 lugs make a set of contacts.  With a DPDT, where the lugs are arranged in 2 columns of 3, it's easy, but 3 x 3 is a little more confusing to the novice.  What you will generally find is that the lugs "face" the direction the contacts run in.  That is, if you see a column of 3 lugs that are flat and facing each other, that group of 3 constitutes a set of contacts.  In the example below, the contacts are organized inside the switch as three columns not three rows.
__  __  __
__  __  __
__  __  __

[fogwolf]

Thanks for the replies - very helpful!!!

The switches come with sets of 3 contacts, either two such sets in the case of DPDT, or three sets in the case of 3PDT.  The "P" stands for "pole", and the first character tells you how many.  So, 4PDT means four sets of three contacts.  If it were DPST (S for "single") there would be two sets of 2 contacts.

Were there are huge gulf in price between the different switch configurations, then paying attention to how many contacts they have might be worth doing, but in the present climate there is so little difference in price between 9-lug, 6-lug, 3-lug, 4-lug switches, that it is simply more convenient to have a bunch of 3PDTs on hand and only use the lugs you need.  A 3PDT can serve as a SPST if you want, or a DPST, or an SPDT, or whatever.  As long as there are enough lugs to do the needed task, you're fine.

The one tiny problem you'll have with a 3PDT is that when the lugs are laid out in a 3 x 3 matrix, it can be easy for the beginner to lose their place and forget which direction the contacts run in and which 3 lugs make a set of contacts.  With a DPDT, where the lugs are arranged in 2 columns of 3, it's easy, but 3 x 3 is a little more confusing to the novice.  What you will generally find is that the lugs "face" the direction the contacts run in.  That is, if you see a column of 3 lugs that are flat and facing each other, that group of 3 constitutes a set of contacts.  In the example below, the contacts are organized inside the switch as three columns not three rows.
__  __  __
__  __  __
__  __  __

[AceLuby]

The one tiny problem you'll have with a 3PDT is that when the lugs are laid out in a 3 x 3 matrix, it can be easy for the beginner to lose their place and forget which direction the contacts run in and which 3 lugs make a set of contacts.

Ha ha... this was what I did on my first build w/ 3PDT switching... what a pain   

[Mark Hammer]

For those folks who started out with DPDT switches, adding another column of contacts was a no-brainer.  They would see it the right way.  For those getting their bearing in the world of easily obtainable 3PDTs, the signs are a little less obvious.