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# Difference Between Switch and Contact?

09/28/2017 12:50 AM

What is the operational difference between switches and contacts used in Auxiliary power and control circuits? Can anyone explain with example or Circuit diagram?

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#1

### Re: Difference between Switch and Contact?

09/28/2017 2:24 AM

Contactor is used when there is need switch often and quickly. Motor control circuit

Motor control circuit

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#2

### Re: Difference between Switch and Contact?

09/28/2017 2:34 AM

If manually operated, usually called a switch.
If electrically operated, usually called a contact.

----||--- = contact (normally open)

___o---o___ = switch (or one way of showing one)

(In both of these, pretend that the dashed lines are solid.)

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#3

### Re: Difference between Switch and Contact?

09/28/2017 6:38 AM
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#4

### Re: Difference Between Switch and Contact?

09/28/2017 8:55 AM

It will probably mostly depend on context and the local dialect on what the differences are. For me difference is whether a direct or indirect mechanical action changes the current to flow. A person throws a switch to turn a light on. A relay gets energized by one circuit to close the contacts of another circuit.

This is not a hard and fast rule. A network switch has no mechanical action outside of its power switch.

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#5

### Re: Difference Between Switch and Contact?

09/28/2017 9:51 AM

Contactor have principal difference. His contacts designed for frequent switching. It are more arc-resistant.

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#6

### Re: Difference Between Switch and Contact?

09/28/2017 9:56 AM

The OP asked about contacts, not a contactor. They may have meant contactor but that is not what they asked.

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#7

### Re: Difference Between Switch and Contact?

09/28/2017 10:04 AM

Maybe. Then I apologize. Sorry my english

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#8

### Re: Difference Between Switch and Contact?

09/28/2017 11:39 AM

Your apology was not needed but it is gratefully accepted.

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#11

### Re: Difference Between Switch and Contact?

09/28/2017 4:45 PM

Unfortunately the question is not entirely clear. About what contacts are spoken.

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#12

### Re: Difference Between Switch and Contact?

09/28/2017 4:59 PM

Still, is interesting to make "contact" with you. Happy Thursday!

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#14

### Re: Difference Between Switch and Contact?

09/29/2017 1:32 AM

Thank you! It is very easy. Write me. Happy Friday!

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#16

### Re: Difference Between Switch and Contact?

09/29/2017 12:18 PM

Red Fred:

I always wondered about this : is cr4 only shown in English to other countries where English is not the native language ? In other words : is there a software discrepancy in Google translator that prevents a correction in word for word translations ?

I've noticed that in several answer's & queries from a foreign specialist, they are often followed by a request for an apology.

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#17

### Re: Difference Between Switch and Contact?

09/29/2017 12:56 PM

I suspect CR4 appears in English in other countries unless the user has their browser set to automatically translate all text to another language. Translating to another language is difficult enough with common human conditions. Technical (jargon) information is easily fraught with misunderstandings when both parties write in English. Translating jargon laden English into another language can quickly confuse a message. It might be a good idea for CR4 administration to expand rule #2 of the Rules of Conduct to warn those using a translation application of technical limitations decoding jargon.

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#9

### Re: Difference Between Switch and Contact?

09/28/2017 11:56 AM

When I think switch, it could something operating on low power transmitted, such as internet switch, or even a manual toggle switch to start power up of a small circuit.

When I think contact, I think of a relay with significant current carrying capacity.

When used in context of PLC, contacts are involved in most of the logic rungs, and usually have to do with valve actuation, motor starting, etc.

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#10

### Re: Difference Between Switch and Contact?

09/28/2017 4:32 PM

Let me give this a shot, as I have come to understand this:

Contacts are a pair of conductive surfaces when contacting each other allow the flow of current (closed) and when separated, prevent the flow of current (open).

A switch is a device to mechanically open or close one or more pairs of contacts. A switch may be operated manually, as with a push button, or selector switch, etc., or mechanically as with a limit switch.

A relay is a special type of switch which uses a electro-magnetic coil to open or close one or more pairs of contacts. Typically they are used to allow a low voltage and current signal to switch a higher voltage or current.

Contactors are a type of relay used to switch high voltage and current loads, for example, motor starters.

Note that not all switches have contacts. Solid state switches use transistors rather than contacts

In the world of PLCs, contacts are virtual, rather than physical. They are just bits of memory that have a value of 1 for closed or 0 for open.

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#13

### Re: Difference Between Switch and Contact?

09/28/2017 8:31 PM

Like the old saying;

"All squares are rectangles, but not all rectangles are square."

All switches have contacts, but not all contacts are switches.

Sometimes contacts are used solely for isolation, meaning they cannot actually "switch" a live circuit open or closed under load, but when there is no load, they can be opened to isolate something. Such is often the case with Medium Voltage switches; Load-Break rated switches are used to turn (switch) power on and off to a load directly or Non Load-Break rated isolation switches are used in conjunction with something like a vacuum switch that itself cannot guarantee isolation. So the vacuum switch opens and closes under load, but when open, an isolation device has contacts that then provide an "air gap" for isolation from the main power to ensure worker safety. It's also true at the other end of the spectrum, extremely low energy devices where contacts are used for isolation, not for switching.

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#15

### Re: Difference Between Switch and Contact?

09/29/2017 1:55 AM

Hold on one second!!! Read BT's question. "What is the operational difference between switches and contacts used in Auxiliary power and control circuits? Can anyone explain with example or Circuit diagram?"

The answer is that a switch is a mechanism to open or close a circuit and a contact is one of the points of a switch, relay or contactor.

Not unless I'm missing something, I think this is the answer to problem #7 of EE 101.

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