DPDT on/on/on vs. on/off/on

[reluctant-builder]

Could someone please explain to me the difference between a DPDT switch that is On/On/On versus one that is On/Off/On? They really don't look any different, but I imagine they must have different applications.

However, can an On/On/On be wired to behave like an On/Off/On? I assume the opposite would not be possible...

Thanks.

 

[line6man]

These terms apply to three position switches. On/Off/On means that the center position disconnects the commons from both throws. On/On/On means that the common of the first pole makes contact with the normally open throw, while the common of the second pole makes contact with the normally closed throw.

More correctly, you might term a DPDT On/On/On switch a SP3T. If you were to add an external jumper across two of the terminals, the switching would become single pole, triple throw.

If you'll disregard the switch on the right side of this diagram, the left side shows the "On/On/On" switching pattern.

Note that "On/On/On" switching is distinct from "Center-on." DPDT center-on switches, in the middle switch position, will connect the commons to both the normally open and normally closed throws. This kind of switching is on the right of the above diagram.

DPDT On/On/On switches can be used as SPDT On/Off/On switches, but not DPDT On/Off/On switches.

 

[Cagey]

Could someone please explain to me the difference between a DPDT switch that is On/On/On versus one that is On/Off/On? They really don't look any different, but I imagine they must have different applications.

It's a little confusing, which is why a schematic of the switch's operation is critical when you're designing something. You can't rely on wiring diagrams. You also have to be careful whose describing what it is you're talking about. An On/On/On (or any combination of 3 on/off states) is not a DPDT switch.

DPDT = Double Pole, Double Throw

A "pole" is a common point. A "throw" is a switched point or position. The terms are slang from a long, long time ago. So, anyway, using the switch, you're throwing a pole around, or more accurately, moving a connection from one point to another.

In its simplest form, you have the SPST (Single Pole, Single Throw) switch. All it does is open and close. One pole, switches one point. Your house lighting is generally switched this way, although if you have any "three-way" switches, they're actually SPDT parts. I don't know why they call them "three-way". An electrician probably named them. Or a drummer <grin>

As you might imagine, there are numerous switching combinations possible with a toggle. Basically, you just have to remember S = Single, D = Double and T = Triple. They get more convoluted than that, but it's rare.

So, if you have an On/On/On switch that's actually two ganged switches internally, then it would be a DPTT (Double Pole, Triple Throw).

However, can an On/On/On be wired to behave like an On/Off/On? I assume the opposite would not be possible...

Toggle switch behavior is mechanically and electrically internal and intrinsic. It's not something you can modify. You buy the switch you need.

Here's where it gets ugly.

Because a toggle switch is a mechanical thing, there are all sorts of games you can play internally. You can arrange contacts, conductors, springs, pressure points, pivot points, etc. so that almost any combination of open/closed (on/off) states are possible. So, just looking at the switch, you have no idea how it works. I'm not even going to get into all the ramifications of that, or I'll be writing all night.

This is why I hate wiring diagrams. They tell you almost nothing about how something works. All they tell you is how they're connected. The behavior is a mystery. In order to know how it works, you need a schematic. A wiring diagram != a schematic. Totally different things. It's the difference between a picture of a house and the blueprints for it.

 

[reluctant-builder]

I don't know why they call them "three-way". An electrician probably named them. Or a drummer <grin>

Hey, now ... :icon_biggrin:

Thanks for the info, guys. I'll try and digest it tomorrow, after some much-needed sleep.

 

[line6man]

In its simplest form, you have the SPST (Single Pole, Single Throw) switch. All it does is open and close. One pole, switches one point. Your house lighting is generally switched this way, although if you have any "three-way" switches, they're actually SPDT parts. I don't know why they call them "three-way". An electrician probably named them. Or a drummer <grin>

Equally confusing are the "four way" switches. I never did figure out the logic behind naming them as such.  :tard:

 

[Cagey]

People have their own ideas about what makes sense.

For example, today I needed some lacquer and retarder, so I asked my roommate to give me ride to Woodcraft, which is about the only place you can buy that sort of thing on a Sunday. It's only a couple miles from here, but she'd never been to the place. She knows the area, though, so I told her it was north of 17 mile (an east/west road) on the southbound side of Van Dyke (a divided north/south road).

Her: So is it on the east side or the west side?
Him: Well, it's the southbound side, so that would be the west side of the road.
Her: Then it's not south, it's west.
Him: Well, it's the west side of the road, which is the southbound side.
Her: Van Dyke runs north and south!
Him: I know. That's what I'm saying. It's on the southbound side.
Her: Well, that's not west!
Him: (under his breath) Christ!
Her: I've never heard of anybody calling it northbound or southbound!
Him: Are you high? Have you ever been on a freeway? Or a boulevard? Or any divided road? The compass points never change!
Her: What's a compass got to do with it? We don't even have a compass! Do you know where you're going or not?

And I start to have flashbacks of being married...

 

[B3Guy]

so . . . what style of switch would be used to switch be tween P90/Humbucking/Rail on a Seymour P-rail? (specifically if I were to order 2 mini-togs from the big W)

 

[line6man]

so . . . what style of switch would be used to switch be tween P90/Humbucking/Rail on a Seymour P-rail? (specifically if I were to order 2 mini-togs from the big W)

Is your "humbucking" series coils or parallel coils?
For traditional series wiring, you would use a DPDT or SPDT On/Off/On switch. For parallel, you would use a DPDT On/On/On, or SPDT Center-on.

 

[Updown]

so . . . what style of switch would be used to switch be tween P90/Humbucking/Rail on a Seymour P-rail? (specifically if I were to order 2 mini-togs from the big W)

I've just built the Red Quilt Strat 'Redback' using these pickups  :toothy10:
Here http://www.unofficialwarmoth.com/index.php?topic=17451.0

Warmoth DON'T sell the ones you NEED !!
You NEED ..... ON / OFF / ON
These .... http://www.guitarpartsresource.com/electrical_miniswitches.htm
Or Here ... http://www.stewmac.com/shop/Electronics,_pickups/Components:_Switches_and_knobs/Mini_Toggle_Switches.html

To do the switching you asked for !!

 

[Cagey]

so . . . what style of switch would be used to switch be tween P90/Humbucking/Rail on a Seymour P-rail? (specifically if I were to order 2 mini-togs from the big W)

Well, the purple ones are the best, if I must say!​

 

[B3Guy]

interesting. good to know that the W ones are not correct.

 

[reluctant-builder]

Would any of you fine folks care to explain how this switch works / what type it is? And the purposes for which it could be used?

It's a mock-up of the "tone filter" switch in my Hagstrom. It looks a lot like an LP pickup toggle, but it has more terminals. In my guitar it was wired as follows:

Common from pup switch to top left lug, jumper wire from same lug to top right lug, output to jack from joined center top lugs. 0.01 uF cap on bottom left lug, 4940 pF cap on bottom right lugs. Grounds all soldered to center bottom ground lug.

Thanks.

Edit: I just attached a version that's a facsimile of how it was wired in my guitar.

 

[Cagey]

Would any of you fine folks care to explain how this switch works / what type it is? And the purposes for which it could be used?

I'm not gonna try it. You try it!
I'm not gonna try it. Hey! Let's get Line6man!​

 

[line6man]

Would any of you fine folks care to explain how this switch works / what type it is? And the purposes for which it could be used?

I'm not gonna try it. You try it!
I'm not gonna try it. Hey! Let's get Line6man!​

I have no idea. The physical construction appears to be DPDT, but we don't have any idea whatsoever as to how the switching works in each position.
You need an Ohm meter or continuity tester here. You can pick up a cheap meter for as little as $4, and I recall Home Depot used to sell a cheap continuity tester which was basically two batteries and a light bulb. It would take 30 seconds with an Ohm meter and a piece of paper to figure it out.

 

[Cagey]

I think I might spend more than 30 seconds at it, but you're right. Without a schematic or a meter, all bets are off. Need a truth table.

 

[SustainerPlayer]

Edit: I just attached a version that's a facsimile of how it was wired in my guitar.

Which model is it?

Maybe some help here:

http://www.hagstrom.org.uk/Schematics/HagstromSchematics.htm

 

[Cagey]

I'll be damned. Real schematics. Hardly ever see those for the guitar/bass. Most of the time it's paint-by-numbers.

 

[reluctant-builder]

This would be the schematic, which I shared on a different thread and Joe responded with a wiring diagram that reflected his interpretation.

 

[line6man]

I'll be damned. Real schematics. Hardly ever see those for the guitar/bass. Most of the time it's paint-by-numbers.

Cagey, that is exactly the point. People that want wiring diagrams want "paint-by-numbers." They neither understand, nor care how the circuit works, they just want to know which wire goes where to get their guitar to work the way they want. That is why wiring diagrams are common for guitars and basses, and schematics are not.

 

[line6man]

This would be the schematic, which I shared on a different thread and Joe responded with a wiring diagram that reflected his interpretation.

This schematic appears to contradict your switch. You have two capacitors joined to the same spot (Which is very likely to be a ground, as the center terminal of Gibson style toggle switches almost always are, but I better not make that assumption.), but the schematic does not indicate for the capacitors to be connected.