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How to short-circuit the circuit and light the LED when the cabinet is opened? Detector needed.

Shibaka24 957 14
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  • #1 19887162
    Shibaka24
    Level 5  
    Posts: 11
    Rate: 4
    I would need a contractron or other detector that when the cabinet is opened would short-circuit the circuit and turn on the LEDs.
    I've been thinking about the satellite k1, but I'm not sure if this is the right type because every now and then they write something different about what it's for
    Please advise
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  • #2 19887309
    sosarek

    Level 43  
    Posts: 83875
    Help: 9318
    Rate: 15435
    Well, and what lighting will be powered, there are also mechanical stops.
    Company Account:
    Z
    Pka, Poznań, 60-850
    Helpful post? Buy me a coffee.
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  • #4 19887362
    gkwiatkowski
    CCTV and Stationary Alarms specialist  
    Posts: 4633
    Help: 646
    Rate: 1210
    Shibaka24 wrote:
    I would need a contractron or other detector that when the cabinet is opened would short out the circuit and turn on the LEDs.
    I was thinking about the satellite k1, but I am not sure if this is the right type because every now and then they write something different for what it is used for.
    Please advise
    .

    Satel K1 parameters:
    Maximum switchable voltage of the reed switch 20 [V].
    Maximum switchable current 0.02 [A].

    In the best case you can power 2 small signalling LEDs through it.
    Controlling something more powerful requires a relay capable of switching a large current of LED lighting.
  • #5 19887422
    Shibaka24
    Level 5  
    Posts: 11
    Rate: 4
    12v leds will be 24w
  • #6 19887521
    juan cabrillo
    Level 27  
    Posts: 737
    Help: 125
    Rate: 239
    That is, the reed switch is out for at least two reasons.
    The best would be a "fridge" switch. It works as it should (it short-circuits the contacts when the door is opened) and has sufficient current carrying capacity.
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  • #8 19887535
    Grzegorz740
    Level 37  
    Posts: 4135
    Help: 313
    Rate: 551
    With these LED parameters, the current drawn is 2A. So using the Satel K1 reed switch alone will be impossible. You need to use a relay to switch the LEDs with it.

    Added after 11 [minutes]: .

    As if you wanted to make the LED power supply yourself using a reed switch then you can make the connection according to a diagram like this.

    How to short-circuit the circuit and light the LED when the cabinet is opened? Detector needed. .
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  • #9 19887569
    bhtom
    Level 39  
    Posts: 4480
    Help: 444
    Rate: 600
    Welcome,

    Shibaka24 wrote:
    I would need a contractron or other detector that when the cabinet is opened would short circuit and light up the leds
    .

    A such sensor would work best.

    Greetings.
  • #10 19887581
    sosarek

    Level 43  
    Posts: 83875
    Help: 9318
    Rate: 15435
    @bhtom I would still go for a limit switch, even one like this https://sklep.avt.pl/wlacznik-krancowy-drzwiowy-hy06.html or as written by
    juan cabrillo wrote:
    A "fridge" switch would be best. It works as it should (when the door is opened it short-circuits the contacts) and has sufficient current carrying capacity.
    Company Account:
    Z
    Pka, Poznań, 60-850
    Helpful post? Buy me a coffee.
  • #11 19887615
    alster1
    CCTV and Stationary Alarms specialist  
    Posts: 2094
    Help: 352
    Rate: 535
    Grzegorz740 wrote:
    If you wanted to make the LED power supply yourself using a reed switch then you could make the connection according to a diagram like this.
    .
    Probably not too much, the reed switch is NC, in which case it will be powered all the time when the door is closed.

    sosarek wrote:
    I would nevertheless go for an end switch, even one such as https://sklep.avt.pl/wlacznik-krancowy-drzwiowy-hy06.html or as written
    .

    This is also NC :) it will light up when closed.
  • #12 19887620
    sosarek

    Level 43  
    Posts: 83875
    Help: 9318
    Rate: 15435
    alster1 wrote:
    This is also NC will light up when closed.

    Well what is the problem of adding a relay? ;)
    Company Account:
    Z
    Pka, Poznań, 60-850
    Helpful post? Buy me a coffee.
  • #13 19887634
    janek_wro
    Level 29  
    Posts: 1281
    Help: 123
    Rate: 290
    alster1 wrote:
    This is also the NC it will light when closed.

    As a remedy for NC/NO at the wrong time -.
    you can make two magnets, one in the door classically, the other behind the reed switch. So that the fields cancel each other out when the door is closed.
    The rest depends on implementation, power of diodes, supply voltage etc.
  • #14 19887921
    homo_sapiens
    Level 24  
    Posts: 525
    Help: 67
    Rate: 128
    Shibaka24 wrote:
    lead 12v will be 24w
    .
    Unfortunately, most of the reasonably priced models are on contact, for loads up to 2A. Examples:
    - mechanical: https://allegro.pl/oferta/wylacznik-wlacznik-krancowy-do-mebli-szaf-240v-2a-11777761891 (you can see a description of the assembly in another auction, but the electrical parameters are not given there)
    - electronic: https://www.oswietleniemeblowe.pl/pl/p/Wlaczn...enia-do-szafy%2C-bezdotykowy-LED-DOOR-12V/630
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Topic summary

✨ The discussion revolves around the need for a detector that can short-circuit a circuit to light LEDs when a cabinet is opened. The user initially considers the Satel K1 reed switch but is advised against it due to its low current capacity (0.02 A) and voltage limit (20 V), which are insufficient for the user's 12V, 24W LED setup requiring 2A. Alternatives suggested include using a "fridge" switch or limit switches, which can handle higher currents. The use of a relay is recommended to control the LED lighting effectively. Several links to products and diagrams for implementation are provided, emphasizing the importance of selecting a suitable switch for the application.
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FAQ

TL;DR: 24 W at 12 V draws 2 A—"With these LED parameters, the current drawn is 2A"—so a reed alone won’t do; switch the LEDs with a relay. This FAQ guides DIY cabinet-lighting choices and wiring to avoid undersized contacts. [Elektroda, Grzegorz740, post #19887535]

Why it matters: It helps DIYers pick the correct door detector and switch 12 V cabinet LEDs safely without burning contacts.

Quick Facts

How do I light a 12 V, 24 W LED strip when the cabinet opens?

Switch the 2 A load with a relay controlled by your door sensor. A bare reed switch cannot carry 2 A. Select a relay with contacts rated for at least your LED current and voltage. Wire the relay so the LEDs receive power only when the door opens. This approach protects the reed and ensures reliable switching. [Elektroda, Grzegorz740, post #19887535]

Can a Satel K1 reed switch power my LEDs directly?

No. Satel K1 is rated 20 V and 0.02 A, suitable only for tiny signal LEDs. Use it as a control input instead. Drive a relay with the K1, and let the relay contacts switch the 12 V LED power. That keeps current off the delicate reed contacts. [Elektroda, gkwiatkowski, post #19887362]

What switch should I use if I want simple, direct wiring?

Use a mechanical door-activated “fridge” switch. "A 'fridge' switch would be best." It closes when the door opens and has adequate current capacity for cabinet lighting. This avoids overstressing a small reed switch. Choose a model with contacts rated for your LED load. [Elektroda, juan cabrillo, post #19887521]

Are off-the-shelf furniture door sensors enough for a 2 A load?

Often yes, but confirm the rating. Many reasonably priced units handle up to about 2 A. Check the label or datasheet before buying. Mechanical door switches and electronic LED DOOR 12 V modules are common options. Match the current rating to your 12 V LED strip’s draw. [Elektroda, homo_sapiens, post #19887921]

How do I wire a reed switch with a relay for 24 W at 12 V?

Typical wiring:
  1. Put the reed switch in series with the relay coil supply.
  2. Use the relay’s contacts to switch 12 V to the LED strip.
  3. Pick relay contacts rated for at least 2 A at 12 V. [Elektroda, Grzegorz740, post #19887535]

Will a 12 V PIR motion sensor work inside a cabinet?

Yes. A compact 12 V PIR module can detect door opening motion and switch your LEDs. Select a PIR specified for 12 V operation and install it where it sees the intended area. This removes the need for a mechanical door switch. [Elektroda, bhtom, post #19887569]

My switch is NC and the light stays on when the door is closed—what happened?

You used an NC device, which closes contacts when the door is closed. That feeds the LEDs all the time with the door shut. Use an NO device for door-open lighting, or change the control logic. This is a common wiring pitfall. [Elektroda, alster1, post #19887615]

How can I invert NC to NO without rewiring the light?

Add a relay to invert the logic. Drive the relay coil from the NC switch. Wire the relay contacts so power reaches the LEDs only when the door opens. "Well what is the problem of adding a relay?" [Elektroda, sosarek, post #19887620]

Can two magnets fix a reed switch that triggers in the wrong state?

Yes. Place a second magnet behind the reed so magnetic fields cancel when the door is closed. The reed then stays open with the door shut and closes only when the door magnet moves away. Adjust positions for reliable operation. [Elektroda, janek_wro, post #19887634]

I don’t want to DIY—what ready-made options can I use?

Use a prebuilt LED cabinet/wardrobe light kit, such as IKEA Norrfly. A ready-made, tested product saves time and money versus building the switching from scratch. Confirm it fits your cabinet and brightness needs. [Elektroda, rgb, post #19887523]

What current should I budget for a 24 W, 12 V LED strip?

Plan for 2 A. That is 24 W divided by 12 V. Choose switches or relays and wiring that can handle at least this current. This ensures safe and reliable operation when the cabinet opens. [Elektroda, Grzegorz740, post #19887535]

I only need a tiny indicator—can I skip the relay?

Yes. A K1-class reed can drive only small indicator LEDs, not lighting strips. If you only need a couple of tiny LEDs, you can power them directly. For anything larger, use the reed to control a relay that feeds the LEDs. [Elektroda, gkwiatkowski, post #19887362]

Where can I buy a proper cabinet door switch?

Browse door switches at major distributors, such as TME’s “door switches” category. You can choose form factor and ratings to match your cabinet and LED load. Verify current and voltage specs before buying. [Elektroda, alster1, post #19887948]

Mechanical vs electronic door switch—what should I pick?

Both are viable. Mechanical contact switches and electronic no-contact LED DOOR 12 V sensors are common. Many budget options are rated up to 2 A. Pick the style you prefer, but ensure its current rating matches your 12 V LED load. [Elektroda, homo_sapiens, post #19887921]
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