# momentary switch wiring



## ezcomes (Jul 28, 2008)

I bought a momentary foot switch to installed on a pedal from Mammoth...


the schematic I'm following says pay attention to the orientation of C NO NC but these switches don't have any writing/markings


how do I determine the orientation?


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## greco (Jul 15, 2007)

Normally Open (NO) and Normally Closed (NC) switch configuration can be determine by using a continuity test on a multimeter. If the meter buzzes (or shows continuity on the display) when you touch the switch terminals, you have a "NC" switch that will open (not conduct) momentarily while you push on it and close again when you "let go" 

NO is the reverse. 

Does his make sense?

Cheers

Dave


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## mhammer (Nov 30, 2007)

If you have any pic posted, I can't see it at the moment.

With that qualification, I will simply say that if the switch has only two solder lugs, then there is a 98% likelihood that it is a NO (normally open) type. That is, there is no continuity between the two contacts until you depress the switch actuator (i.e., stomp). There is a v_ery small l_ikelihood that it is of the NC type, which requires you to step in order to _break_ the contact. You would likely have needed to order it specially, from a place that has a huge inventory, since these are the much less commonly used type.

If there are *3* contacts, then internally it is set up to be both in one, and the function you give it will depend on the contacts you use. You will always use the center or "common", for either function, but use one of the outside lugs, depending on the function you wish. 

Let's call the contacts 1, 2, and 3. When the switch is minding its own business, 1 and 2 are connected, internally, but 3 is hanging on its own. If I connect wires to 2 and 3, then I have made a NO switch, since the switch is normally "open" until I step on it, at which point contacts 2 and 3 are joined. If I connect wires to 1 and 2, the same switch is NC, since 1 and 2 are connected until I step on it, at which point that contact is broken.

If you have a meter that beeps when there is continuity (usually anything below 200 ohms resistance), simply stick the probes on 1&2, or 2&3, and see which pair it beeps for. If you need NO for the pedal, then you want the pair where it doesn't beep until you press the actuator.

Personally, I've found that it is best to use either deliberate NO or NC 2-contact switches, since they tend to have a softer touch, and no discernible click. Momentary stompswitches of the SPDT or DPDT variety have a clear click, and require more force to actuate.


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## greco (Jul 15, 2007)

My answer was close....but mhammer gets the cigar.

He has far more experience with these switches....and I ALWAYS learn from his posts.

Cheers

Dave


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## ezcomes (Jul 28, 2008)

this is the switch...i realized something i should've understood...in this case...the centre two lugs are always the common...and the outer two are the ones its switching too...










i got confused...because the schematic i was following had the switch marked C NO NC...with the note, be careful to note which is which (NC vs C)
like this...but a DPDT instead...









is this case...its NO C NC...i just need to figure out which end is which...










multi-meter here i come


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## greco (Jul 15, 2007)

*ezcomes.*..*WARNING!!*.....I built a switching device for a friend using the style of switch similar to the one in your pic. The switches weren't momentary but that doesn't matter. 

*The terminals on this style of switch will not take much heat when soldering!!!.*..if you overheat them, they fall out... and you will be ....well...unhappy.

Cheers

Dave


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## mhammer (Nov 30, 2007)

I have some of those. Bought 'em by accident at Honson/Supremetronic on College several years ago.

This type does have a very obvious click (internally, they are actually identical to latching stompswitches, except for a slightly different curve to the contacts inside, that prevent them from latching), so they are the less-preferred type. But, that's what ya got, so that's what ya got.

As always, once you have the which-lugs-should-I-use challenge mastered, be careful when soldering. As I've repeated here many a time, the failure rate on these _for hobbyists_ is well beyond what would allow any manufacturer to remain in business very long. The chief hurdle is that folks will often apply too much heat for too long, resulting in the bit of damping grease inside the switch to melt, flow along the contacts, coat them, and turn into an insulator once they cool down.

So, some tips for happy and successful switch installation:

1) Folks like us often end up with switch whose lugs alren't gleaming shiny: i.e., they are slightly tarnished due to exposure. Before attempting to solder, scrape the contacts clean with an X-acto knife or equivalent, giving yourself enough of a nice shiny surface that the solder will tin the area and form a joint quickly.

2) If you can score some liquid flux, a dab on the contacts will speed things along.

3) Before applying the connecting wires, tin the stripped ends of the wires, and tin the surface of the lugs.

4) Let things cool off, so that heat does not build up. That can mean leaving a minute between tinning the lugs and soldering the wires to them. It can also mean soldering one wir, waiting a bit, then soldering the other wire.

All of this is undoubtedly overkill. Of course, I also thought it was overkill getting the extra insurance on a rental car...until I hit a porcupine driving the car back home late at night on the 416, and caused what would have been a $2k tab for a not-quite-so-new-looking-anymore bumper.

And, as always, a cordial invitation to watch this little video I made about the innards of stompswitches.

[video=youtube;6uhDKFhqYnw]http://www.youtube.com/watch?v=6uhDKFhqYnw[/video]


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## greco (Jul 15, 2007)

mhammer said:


> As always, once you have the which-lugs-should-I-use challenge mastered, be careful when soldering. As I've repeated here many a time, the failure rate on these _for hobbyists_ is well beyond what would allow any manufacturer to remain in business very long. The chief hurdle is that folks will often apply too much heat for too long, *resulting in the bit of damping grease inside the switch to melt, flow along the contacts, coat them, and turn into an insulator once they cool down*.
> 
> So, some tips for happy and successful switch installation:
> 
> ...


mhammer is giving excellent soldering advice here. 
Too bad I didn't know this when I was soldering this type of switch. I had to go out and buy another switch!

I not only melted the grease...I melted the while fricken area around the metal terminal!!

Count me in on the stats for "failure rates for hobbyists" soldering this switch...LOL

Cheers

Dave


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## mhammer (Nov 30, 2007)

I'm in those stats myself. That's precisely how I learned about what's inside those switches!


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## ezcomes (Jul 28, 2008)

i've been careful...i've melted stuff before...but i didn't imagine that these would be so easy to melt for almost $5 a pop

i'll keep watching what i'm doing! thanks for the help guys!

on a close side note...where are you getting 'non-popping' momentary switchs for pedals?


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## mhammer (Nov 30, 2007)

I generally get mine at Tayda. http://www.taydaelectronics.com/spst-momentary-soft-touch-push-button-stomp-foots-pedal-switch.html

They can take a couple of weeks to receive, but they're inexpensive and reliable.


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## ezcomes (Jul 28, 2008)

thx mark...but i need dpdt ones...


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## mhammer (Nov 30, 2007)

Can I ask for what application? That might clue me in to some viable choices I might be able to recommend.

In the interim, I'll simply put in a word for my buddy Steve Daniels and Small Bear Electronics: http://www.smallbearelec.com/servlet/StoreFront


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## ezcomes (Jul 28, 2008)

i looked at smallbear...i don't remember why i went with mammoth...i think that smallbear didn't have something i needed and wanted to order all in one shot...

Thanks though Mark...and pm sent...


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