Magnetic Switches: Open Loop vs Closed Loop

[awsmsrv]

Need some help. Anyone here know the difference between these 2 switches? I'm trying to install some LED lighting in my trunk so that when I open the trunk, the lights come on & when I close the trunk, the lights go out. Just testing the switches with the lights attached, I hooked up to my truck battery, but both switches turn the lights on & when the other side of the switch comes in contact, the lights don't go out. Regardless of the switch (open loop or closed loop), the lights are on whether in contact with the other half of the switch or not. What am I missing? Thanks.

[Dano]

Got some pics there?

 

Only 2 types of switches, Normally Open and Normally Closed. The description is of a switch in it's normal position with the contacts either open or closed. You need a Normally Closed momentary contact switch for the trunk lid. Sounds like you might have a maintained contact switch. Try pushing the button and hear if it clicks. If it does, it's probably maintained.

Here's a pic of one like you need.

 

Dan

Edited June 3, 2009 by Dano

[awsmsrv]

Got some pics there?

 

Only 2 types of switches, Normally Open and Normally Closed. The description is of a switch in it's normal position with the contacts either open or closed. You need a Normally Open momentary contact switch for the trunk lid. Sounds like you might have a maintained contact switch. Try pushing the button and hear if it clicks. If it does, it's probably maintained.

Here's a pic of one like you need.

 

Dan

Yes, I understand. I have 1 of each type because I didn't know which I needed. They are in 2 parts: 1 with the screws to attach the wires & 1 that is the other magnet (I assume). These are typically used for windows or doors with a security system that is set off by opening the window or door. Here's a picture of the switch: http://cache3.smarthome.com/images/7113.jpg. The far left part I don't think I need. Is that correct?

[Dano]

You want it to be a normally closed switch, so the contacts are made when you remove the magnet, and open when the magnet is attached. Run the + wire thru the switch, and they should work.

No, you don't need that shim.

 

Dan

[mbrood]

Technically, anything in basic electronics is a closed loop... current flows out one side of the battery, through all series elements and back to the other side of the battery.

 

As Danob11 said, you want to use a normally closed type magnetic switch...

so when the magnet gets close, the switch opens.

 

http://www.bergall.org/temp/venture/magnet.jpg

[awsmsrv]

Technically, anything in basic electronics is a closed loop... current flows out one side of the battery, through all series elements and back to the other side of the battery.

 

As Danob11 said, you want to use a normally closed type magnetic switch...

so when the magnet gets close, the switch opens.

 

http://www.bergall.org/temp/venture/magnet.jpg

OK. According to your diagram I must splice in a ground wire off the negative wire to the battery?

[Phil Gigliotti]

In a alarm circuit N/C means magnet close the spacer is used to keep the magnet away from steel casings

 

 

 

have a good day Phil

 

 

 

 

 

 

c

[Dano]

In a alarm circuit N/C means magnet close the spacer is used to keep the magnet away from steel casings

 

 

 

have a good day Phil

 

 

 

 

Thanks for the correction Phil, I didn't know that about alarm switches. So then he needs a normally open magnet switch?

 

Dan

[awsmsrv]

OK. I'm still confused. I can't get it to work correctly. When I attach the wires to the switch from the light & then attach the other end of the wires to the battery, the light comes on. When the magnet half of the switch comes in contact with the half that has the wires attached, there is no change. The light is still on. What must I do to get the light to turn off when the magnet half contacts the wired half of the switch? Do I need to have a separate wire to ground?

[Squeeze]

You should run the fused + Wire from the Bike to the Light and connect it to the + Wire or +Contact.

 

Then you run a ground Wire to one Lead of the Switch and the other Side of the Switch to the Ground Wire or Ground Contact of the Light.

 

Once the Magnet is near the NC Switch, the Contact is operated and the Light goes off. Remove the Magent from the Switch Area, the Contact goes in unactuated Postion which closes the Contact and connects the Circuit, the Light will lit.

[awsmsrv]

You should run the fused + Wire from the Bike to the Light and connect it to the + Wire or +Contact.

 

Then you run a ground Wire to one Lead of the Switch and the other Side of the Switch to the Ground Wire or Ground Contact of the Light.

 

Once the Magnet is near the NC Switch, the Contact is operated and the Light goes off. Remove the Magent from the Switch Area, the Contact goes in unactuated Postion which closes the Contact and connects the Circuit, the Light will lit.

So, does that mean I have a separate ground wire attached to the negative wire that goes to the battery?

[Squeeze]

So, does that mean I have a separate ground wire attached to the negative wire that goes to the battery?

 

Not a seperate Wire, but the Ground Wire

 

....

 

Then you run the ground Wire from the Battery to one Lead of the Switch and the other Side of the Switch to the Ground Wire or Ground Contact of the Light....

[awsmsrv]

OK. I've tried it wired one way, didn't work correctly: always on regardless of magnetic contact. Wired it the opposite way, didn't work correctly: always on regardless of magnetic contact. Tried to run a separate ground off of the negative wire that goes back to battery, also with both ways of wiring it. I just don't get it. The light is always on, no matter what.

[MiCarl]

So, does that mean I have a separate ground wire attached to the negative wire that goes to the battery?

 

No. awsmsrv drew his picture a bit different than convention. Normally the (-) on the battery is shown to the ground symbol, and the ground on the device is connected to another ground symbol. This merely indicates that it's a common leg for many circuits and is usually the chassis of the larger assembly.

 

Clearly you have ground or the light wouldn't come on.

 

Those magnetic reed switches usually only work with the magnet in proximity to the correct face. I believe all the ones I have seen have an arrow that points toward the magnet.

 

It's also possible you have a defective switch. Another thing I wonder is if the lamps draw more current than the switch is rated for and has welded the contacts together.

 

The stock switch is a momentary normally closed (NC) switch. What this means is that it completes the circuit when the plunger is not depressed. It's the opposite of a doorbell switch which is a momentary normally open (NO) switch. A doorbell switch completes the circuit when the plunger is depressed.

 

If you're making your own bracketry these switches would work http://www.radioshack.com/product/index.jsp?productId=2062540.

 

If you're using stock brackets you might get this switch to workhttp://www.radioshack.com/product/index.jsp?productId=2062540

 

It's very similar to the original switch. You might want to break the lever off (not hard). It has an extra connector - one is NO and the other is NC. You would use the NC for your application.

[awsmsrv]

No. awsmsrv drew his picture a bit different than convention. Normally the (-) on the battery is shown to the ground symbol, and the ground on the device is connected to another ground symbol. This merely indicates that it's a common leg for many circuits and is usually the chassis of the larger assembly.

 

Clearly you have ground or the light wouldn't come on.

 

Those magnetic reed switches usually only work with the magnet in proximity to the correct face. I believe all the ones I have seen have an arrow that points toward the magnet.

 

It's also possible you have a defective switch. Another thing I wonder is if the lamps draw more current than the switch is rated for and has welded the contacts together.

 

The stock switch is a momentary normally closed (NC) switch. What this means is that it completes the circuit when the plunger is not depressed. It's the opposite of a doorbell switch which is a momentary normally open (NO) switch. A doorbell switch completes the circuit when the plunger is depressed.

 

If you're making your own bracketry these switches would work http://www.radioshack.com/product/index.jsp?productId=2062540.

 

If you're using stock brackets you might get this switch to workhttp://www.radioshack.com/product/index.jsp?productId=2062540

 

It's very similar to the original switch. You might want to break the lever off (not hard). It has an extra connector - one is NO and the other is NC. You would use the NC for your application.

I can hear the switch move when the magnet comes close to the switch, so I don't think it's defective. I have both types of switch (NO & NC) & get the same results with both switches: the lights are always on whether or not the magnet is in contact. They are LEDs, so there shouldn't be much draw to turn them on.

 

I appreciate you guys trying to help me, but, I guess I'm not smart enough to understand what's wrong. It's very frustrating.