Bobbo
Memphis, TN
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I know what an SPST switch is. I know what an SPDT switch is, I have always heard it called a "3 way switch" because it can be ON/UP, ON/DOWN, or OFF. What is the correct name for a "4 way switch", you know, the one that goes between 2 SPDT (3 way) switches to give another place where the power can be turned on or off. A DPDT switch doesn't seem right since it seems that it would switch both hot and neutral rather than just crossing the 2 output lines across the 2 input lines.
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MudChucker
Winnipeg Manitoba
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Well... where to start...
First, your answer depends on what school your from.
a common 3 way switch is SPDT, or SPCO for either "Single Pole Change over" or, Single Pole Center Off"
a 4 way switch is often refered to as, DPCO.
Double pole changeover or Double pole, Center off. This switch is equivalent to DPDT. DPCO is a term used for switches with a stable off position in the center and DPDT for those switches without a stable center off.
There is also one more type of 4 way switch typically found in DC applications, a DPDT switch internally wired for polarity-reversal applications.
Hope that helps.
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MudChucker
Winnipeg Manitoba
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one more point to note, some 4 way switches (usually the polarity reversal units) are refered to as "Intermediate Switches"
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hemi-kz
Eastern PA
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A 3-way switch is called 3-way in electrician nomenclature because it has 3 connections (the ground screw doesn't count). In electronics it's called a SPDT.
A 4-way has 4 connections. It is not a DPDT (which would have 6 connections).
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enblethen
Moses Lake, WA USA
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A three way switch used in a residential, is a 2 position switch. The black scre is a common the two silver screws are what are called travelers to another 3-way switch.
A 4-way switch used in residential is a 2 position switch with three silver screws for the travels to the 2 3-way switches used in the circuit.
A double pole/double throw switch used in some 120/240 volt applications, opens both sides of a circuit, such as a motor or water heater.
Don't get these confused with DC application switches. Double pole/ double throw switches as MudChucker stated is used for reversing power in such applications as jacks.
There is in both applications a three position switch. These can have many different applications in DC circuitry. They can be on/off/on, they could be on/off/on momentary.
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MudChucker
Winnipeg Manitoba
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hemi-kz wrote:A 3-way switch is called 3-way in electrician nomenclature because it has 3 connections (the ground screw doesn't count). In electronics it's called a SPDT.
A 4-way has 4 connections. It is not a DPDT (which would have 6 connections).
true in terms of nomenclature...
the poles are not always on the outside of the switch.. some are internal
here are IEC 60617 Graphical symbols for 4-way DPDT/DPCO and Crossed.
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MudChucker
Winnipeg Manitoba
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enblethen wrote:A three way switch used in a residential, is a 2 position switch. The black scre is a common the two silver screws are what are called travelers to another 3-way switch.
A 4-way switch used in residential is a 2 position switch with three silver screws for the travels to the 2 3-way switches used in the circuit.
A double pole/double throw switch used in some 120/240 volt applications, opens both sides of a circuit, such as a motor or water heater.
Don't get these confused with DC application switches. Double pole/ double throw switches as MudChucker stated is used for reversing power in such applications as jacks.
There is in both applications a three position switch. These can have many different applications in DC circuitry. They can be on/off/on, they could be on/off/on momentary.
very good post... I should have been more clear on that crossed switch for DC applications, thanx for point that out a little more clearly.
One point I see you gently touched on that I also forgot to mention is that these switches also all come in, make-before-break, break-before-make configurations as well.
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enblethen
Moses Lake, WA USA
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Configurations can get really confusing is why I left some go.
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djevans
Tennessee
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This site might help "graphically" demonstrate what's going on in these circuits.
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hemi-kz
Eastern PA
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MudChucker wrote:the poles are not always on the outside of the switch.. some are internal
You're right. I stand corrected.
A 4-way could be (and probably is) made by cross strapping the switched poles of a DPDT internally.
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