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-   -   Can someone please help me figure out what switch this is? (http://www.diychatroom.com/f18/can-someone-please-help-me-figure-out-what-switch-151114/)

javskies 07-22-2012 03:08 AM

Can someone please help me figure out what switch this is?
 
so im looking for a switch like this:

http://img37.imageshack.us/img37/8083/switchx.png

the red is the current while the blue is a wire where while no electricity is running through, the switch is open and current can flow. now when electric is ran through the blue wire the switch is closed and the current is cut off. does anyone know if this switch exist or if i can make it? thank you!

wirenut1110 07-22-2012 05:06 AM

Sounds like you're describing a 3-way switch.

dmxtothemax 07-22-2012 05:20 AM

Quote:

Originally Posted by javskies (Post 971444)
so im looking for a switch like this:

http://img37.imageshack.us/img37/8083/switchx.png

the red is the current while the blue is a wire where while no electricity is running through, the switch is open and current can flow.

I am confussed !
if switch is open !
how can current flow ?

zappa 07-22-2012 05:48 AM

Sounds like a simple single pole double throw switch. If so, you would swap a red with the blue.

Is this a project with a small toggle switch, house electrical wiring, generator transfer switch? Knowing the application would be a big help for us.

wirenut1110 07-22-2012 06:11 AM

After reading your terminology 20 times, I'm thinking you need a relay or a contactor or both(depending on the application).

Definitely not a single pole switch though.

joed 07-22-2012 08:08 AM

I think you want a remote controlled switch. The blue wire turns the switch off and on, correct?
A relay or contactor will work.

javskies 07-22-2012 09:08 AM

sorry for the confusion, im a noob at this lol. it would be a normal open switch and when electricity runs through the blue wire the switch is turned off. this is for automotive applications. i want to power one fuse system by a second fuse system that gets power right when the car turns on, and then i would tap into my headlight fuse so wen they are turned on the switch would turn offf

kwilcox 07-22-2012 09:21 AM

that would be a single pole nc (normally closed) relay. When power is applied to the secondary (blue) the switch opens.

These are used all the time in automotive applications where a small current is used to switch a large current load. You will need to determine the power flow through the primary (red wires) and the current available to the secondary before sizing your 12v relay. Then mouser electronics/digikey electronics will have the part.

javskies 07-22-2012 09:38 AM

Quote:

Originally Posted by kwilcox (Post 971574)
that would be a single pole nc (normally closed) relay. When power is applied to the secondary (blue) the switch opens.

These are used all the time in automotive applications where a small current is used to switch a large current load. You will need to determine the power flow through the primary (red wires) and the current available to the secondary before sizing your 12v relay. Then mouser electronics/digikey electronics will have the part.

thank you very much! so i should take a volt gauge and find the voltage coming out of both spots and that will determine the kind i need?

Billy_Bob 07-22-2012 11:15 AM

In general, all "voltages" on a car will be 12 volts DC or "Direct Current".

A relay is just an electrically operated switch.

Most automotive relays are designed to make contact when power is applied. Like a horn relay. You press on the horn and that activates a relay, which in turn connects two switch contacts and allows the horn to sound.

Other relays turn off when power is applied.

And yet other relays have three switch connections. There is a "common" and then an off connection and an on connection.

The connections are called N.O. for normally open. And N.C. for normally closed.

A "two switch connection" relay would be called SPST for Single Pole Single Throw.

A "three switch connection" relay would be called SPDT for Single Pole Double Throw. (The kind you should get. One of the connections is on when power applied, the other connection is off when power is applied.)

In addition to the switch connections on a relay, there are two "coil" connections. These are the connections which operate the relay. For some automotive relays (also called solenoids in the automotive world), the - [minus] or ground connection is the metal mounting bracket which would be screwed to a metal body part and in turn be connected to the - terminal of the battery via that.

Note relays which are always on can get to be VERY hot. They also make "clicking" sounds when activated. For these reasons, automotive relays are typically mounted in the engine compartment of a car. They get good air circulation there and keep the clicking noise outside of the passenger compartment.

Also there are two different types of relays for automotive use. One is called "continuous duty". The other is called "intermittent duty". The first type is designed to be on for long periods of time - like for headlights. The other is designed to only be on for brief periods of time like for a horn. If you keep an intermittent duty relay on for long periods of time, it may overheat or burn out.

Then automotive parts generally don't have these "specifications" included in the packaging or anywhere else. They usually just have a part number! Other relays like for electronic or electrical use come with detailed specifications and have "data sheets" on the manufacturer's web site. Like this...
http://www.grainger.com/Grainger/OMR...E17?Pid=search

Data Sheet...
http://www.ia.omron.com/data_pdf/dat...s_ds_csm42.pdf

The other thing you need to be concerned with is the "load" or what you are connecting this to...

What are you connecting this to?

(This will determine the "current rating" or amperage the "contacts" will be able to handle.)

How relays work...
http://www.mp3car.com/the-faq-empori...ire-it-up.html


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