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Understanding Limit Switch NO, NC, COM (ON-ON) for LED Lighting: Wiring, Functions, & Usage

DonAndress 96585 26
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  • #1 17150587
    DonAndress
    Level 14  
    Hi.

    I need to install a few limit switches for LED lighting, but I am not sure how they work.
    The best solution for me would be if the limit switches were pressed in on one pin and released on the other.

    In the descriptions of the auctions on the known auction site you can read, for example:
    Quote:
    Contact configuration: NO + NC
    Switching method: ON- (ON)

    or
    Quote:
    Three pins: CN NC COM.


    And the question is following - if the limit switch is not pressed, does the voltage follow one pin, and when it is pressed, then the other?
    In some variant, does it completely cut off?
    How to decode these markings at auctions?

    We are talking about something like in the attached picture:
    Understanding Limit Switch NO, NC, COM (ON-ON) for LED Lighting: Wiring, Functions, & Usage
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  • #2 17150609
    maly_ninja
    Level 14  
    So in short:

    NO - normally open - open by default, closes after pressing the buttons.
    NC - normally closed - by default it is closed (closed), it disconnects after pressing the button.
    COM - common - common pin.

    So the NC pin is shorted by default with the common COM pin. If you press the button, the default pin (NO) connects to the COM pin and the NC pin disconnects.
  • #3 17150650
    DonAndress
    Level 14  
    Ok, then I should get what I mean, right?
    What about this description:
    Quote:
    Switching method: ON- (ON)

    Does this mean that either one or the other pin is short-circuited?

    Added after 15 [hours] 8 [minutes]:

    And one more thing came to me - if the switch is designed for 120-250V, it will work equally well with 12V for LEDs?
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  • #4 17152124
    Justyniunia
    Level 36  
    It will work, look at the currents it can switch.
  • #5 17152142
    tos18
    Level 42  
    DonAndress wrote:
    Does this mean that either one or the other pin is short-circuited?

    means that it switches once and twice and that it returns to its original position (it has a spring) when released.
  • #6 17152226
    zybex
    Helpful for users  
    Most often, the limit switches have three outputs. One is common (COM), one closed (NC) and one open (NO). As soon as the lever is depressed, the switch will take place. What was shorted will open, and vice versa what was open will shorten.
    There are also limit switches with four terminals, and the mentioned NC and NO are electrically independent of each other, i.e. they do not have a common COM terminal. Of course, if we want, we connect the two pins from both contacts and we have a common part (as if there were three pins).

    Here is an example of one without the lever.

    Understanding Limit Switch NO, NC, COM (ON-ON) for LED Lighting: Wiring, Functions, & Usage

    The levers also have different lengths and, if necessary, they are finished with a circle.
    These types of switches can also be combined. There are two mounted side by side with a common lever.
  • #7 17152230
    krzysiek_krm
    Level 40  
    Hello,
    DonAndress wrote:
    Does this mean that either one or the other pin is short-circuited?

    you can imagine this switch as a railway switch: when it is released, the current "goes" on the COM - NC route, when pressed, on the COM - NO route.
    DonAndress wrote:
    And one more thing came to me - if the switch is designed for 120-250V, it will work equally well with 12V for LEDs?

    It's hard to say, if your LEDs work with DC, you need to check the switch documentation for its DC switching capacity.

    best regards
  • #8 17152235
    zybex
    Helpful for users  
    It can always control indirectly, i.e. when the switch has a low current capacity, an additional relay or transistor can be used.
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  • #9 17158026
    DonAndress
    Level 14  
    krzysiek_krm wrote:
    It's hard to say, if your LEDs work with DC, you need to check the switch documentation for its DC switching capacity.

    And what should it be for it to work with DC 12V?
  • #10 17158066
    zybex
    Helpful for users  
    Most often, the maximum current is given on such a limit switch. For example, in the picture I have posted, you can see that it is 2.5A AC 250V.
  • #11 17158098
    krzysiek_krm
    Level 40  
    DonAndress wrote:
    krzysiek_krm wrote:
    It's hard to say, if your LEDs work with DC, you need to check the switch documentation for its DC switching capacity.

    And what should it be for it to work with DC 12V?

    I would check the documentation, more "decent" manufacturers declare compliance with various standards (for example IEC), the descriptions of which are quite easily available on the network.
    The switching capacity is a certain current-voltage relationship during switching.
  • #12 17159451
    DonAndress
    Level 14  
    Sellers on the Allegro are not able to give me such a parameter.
    It is not in the description either on the store's websites. It is only up to 5A and 250V AC.
    I think I will have to risk (PLN 1.50), it will burn at most or it will not switch, because I do not find an alternative too much.
  • #13 17160868
    zybex
    Helpful for users  
    We still don't know what kind of LEDs you have, i.e. how much electricity do they need? So far, we are talking only about a supply voltage of 12V.
    In fact, we do not know what you are going to achieve with these limit switches. Perhaps a bistable relay and a few buttons would be enough for you.
  • #14 17161644
    DonAndress
    Level 14  
    Really. Well let's go.
    I want to make interior lighting for a fairly large wardrobe. There will be a total of 11 such limit switches. The light is to turn on when the door is opened, with the limit switch closed, it lets go. So there will be a maximum of 4 limit switches "connected", the rest either have their own line or 2.
    The leds I am going to buy are a led strip based on 2835 diodes, 60 diodes per meter, 4.8W / m, about 0.4A / m.
    A maximum of about 13.5W and 1.2A can pass through one limit switch (this is the first limit switch in this configuration of 4 limit switches in a series).
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  • #15 17161669
    zybex
    Helpful for users  
    DonAndress wrote:
    The light should go on when the door is opened

    So it is supposed to work like a refrigerator lighting. I will tell you right away that it can be done with the use of a motion detector (s). Of course, the limit switches will also do the job, but you need to distribute a bit more cables in this cabinet. It is best to draw a schematic (or assembly) diagram of the arrangement of individual elements of the whole. We will check it and possibly advise something.
  • #16 17161778
    DonAndress
    Level 14  
    A bit like in a refrigerator, in fact.
    And motion detectors are not more expensive?

    Below is a "very ideological" diagram ;)
    Hope it makes sense.
    The part on the right, separated by dashed lines, is only marked so that you know what I'm talking about, and more specifically, I mean that this part of the wardrobe has two doors and the same piece of led strip must be turned on when opening only one or only second door.
    Understanding Limit Switch NO, NC, COM (ON-ON) for LED Lighting: Wiring, Functions, & Usage
  • #17 17161898
    tos18
    Level 42  
    The diagram is very illustrative but logical.
    5A switches should do the job.
    Pay attention to the total currents that can flow through the individual wires with all the stripes on. Select the appropriate cross-sections of the cables.
  • #18 17161977
    DonAndress
    Level 14  
    Will the 0.75mm line be ok?
  • #19 17161995
    tos18
    Level 42  
    Yes, if you break it down into two circuits.
  • #20 17162064
    AdrianHDmaxxx
    Level 13  
    Same as above. If it is split into two circuits, this line makes perfect sense.
  • #21 17162077
    zybex
    Helpful for users  
    DonAndress wrote:
    The light is to turn on when the door is opened, and when the limit switch is closed, it lets go

    This is a bit unclear. What does it mean that when the door is closed it lets go?
    After all, you can open any door, or even several of them, at any time. In my opinion, he has no idea that a given limit switch is on. The power supply goes everywhere and the limit switch is simply the switch of a given led (tape section).
  • #23 17162737
    DonAndress
    Level 14  
    zybex wrote:
    This is a bit unclear. What does it mean that when the door is closed it lets go?
    After all, you can open any door, or even several of them, at any time.

    In this quasi-diagram of mine, the second part from the right is drawers. The plan is that when I open the lowest drawer, its backlight will turn on, but when I open any drawer above, the lowest one should go out, because it will be covered anyway. Similarly with the next drawers.

    Added after 14 [minutes]:

    Ok, which is two circuits.
    Understood, thank you :-)

    Added after 16 [hours] 55 [minutes]:

    One more question came to me.
    I have to supply power to this lighting, to the switch.

    Should I add the currents in such a system?
    If so, will the 3-core cable, 1mm, pull the wire 3-3.5A and will not heat up excessively?

    I will lead it inside the wardrobe, the switch will be on the wardrobe.
  • #24 17164430
    tos18
    Level 42  
    The switch is in front of the power supply on the 230V side or on the power supply on the 12V side?
  • #25 17164489
    DonAndress
    Level 14  
    Before, because I don't want the power supply to warm up.
  • Helpful post
    #26 17164538
    tos18
    Level 42  
    3x 1 is enough.
    It is supposed to be in double isolation.
    The switch is to disconnect the phase.
    Remember to keep the colors of the wires.
    Remember about the protective conductor.
    Remember to protect the connections against touching - additional power supply housing.
    It would be good if your work was watched by an electrician before starting it.
  • #27 17164571
    DonAndress
    Level 14  
    OK, thank you very much! :)
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Topic summary

The discussion revolves around the functionality and wiring of limit switches (NO, NC, COM) for LED lighting applications. Users seek clarification on how these switches operate, particularly in terms of voltage flow when pressed or released. It is explained that NO (Normally Open) switches are open by default and close when activated, while NC (Normally Closed) switches are closed by default and open when activated. The common (COM) pin serves as a reference point. Users inquire about compatibility with different voltages, specifically whether a switch rated for 120-250V can work with 12V for LED applications. The importance of checking the switch's current capacity and documentation is emphasized, especially for DC applications. The conversation also touches on practical applications, such as using limit switches for wardrobe lighting, and considerations for wiring and current ratings. Suggestions include using motion detectors as an alternative and ensuring proper cable sizing to handle the expected load.
Summary generated by the language model.
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