Hello! I am hoping someone can help me with a wiring issue. I have created a string of LED lights, and I have a 12V power source. Hooking those up will not be a problem, but I want to mount the lighting into a small compartment that has 3 different (small) doors. Is it possible to attach the light strand to three different momentary switches (one to each door) so that the string of lights will light up if any one of the three doors are open? I don't have a circuit board, and would prefer to keep it as simple (analog?) as possible. My only prior experience with LED lighting/wiring is for little miniature house kits that I assembled as a pandemic hobby.

 

You need NC (normally closed) micro-switches wired in parallel. If you buy micro-switches with NO-COM-NC terminals, use the COM and NC terminals. When any door is open, the closed switch will conduct current to the string of LEDs.



You can also use magnetic reed switches.

 

Certainly "Mr C" has it right. Smaller and less expensive than the microswitches shown would be some of the switches created for exactly that application, controlling enclosure lights, such as refrigerator door light switches.

 

@MrChips suggestion:

@MisterBill2's suggestion:

Both do what you're looking for. When any single door opens the LED will light. When any combination of 2 or 3 doors the LED will light.

You can also use magnetic reed switches.

Oh - and Welcome to AAC.

 

Thank you for the specificity and diagrams! I think I am going to use reed switches; there isn't enough of a price difference compared to other options for me to worry about, since I'm only doing 3.

The contacts on the reed switches are exposed; any recommendations for protecting them from a dirty and humid environment? I was already planning to wrap the wiring and lights in clear water-resistent heat-shrink tubing as a precaution. The point at which the roof of my engine compartment is underwater, I have bigger concerns than my LEDs shorting out.

EDIT: Also, thank you for the very warm welcome.

 

The contacts on the reed switches are exposed; any recommendations for protecting them from a dirty and humid environment? I was already planning to wrap the wiring and lights in clear water-resistent heat-shrink tubing as a precaution.

As long as water/dirt/humidity can't get into the wire connections - shrink tubing (clear or otherwise) should protect.

Could you clear up some confusion? You were talking about three doors. What three doors might that be?
Also equally important: What sort of LED's are you using? How much current do they draw? Reed switches might not be robust enough to handle the load.

 

So, this is for an engine compartment in a marine situation, i.e. a boat?
You should always state up front the whole situation. This could give us a clearer idea and could make a difference in the solutions offered.

 

Sorry, I am a hobbyist and not an engineer so I wasn't clear enough. I intend to create this circuit to light the engine compartment of a Catalina 30. There are three doors: one at the stern (rear), one on starboard (right as you face front of boat), and top. The top is a lift-off panel while the other 2 look like cabinet doors that open from the bottom. I've already identified some waterproof heat-shrink tubing to run the home-made LED strip through. As they will be mounted to the top of the engine compartment (far enough from the engine that I don't worry too much about the heat either), I find it unlikely they will ever be submerged, or even splashed much. If they do, then the whole boat is going down at that point. I intended to mount them with heavy-duty double-sided tape to avoid drilling holes into the fiberglass. If you think marine adhesive or silicone is a better option, I can do that, but I thought something easy to remove if it is messed up would be better for a first-time project.

I need to take some more measurements, to confirm how many I will need, but I am not using more than 25 3mm LEDs (that's how many I have). The entire thing is probably going to be like 2ft long, maybe longer just to keep the lights themselves further from the engine itself.

I hope this is an improvement in the descriptive department.

 

you could use industrial sensors - either reed switches or inductive proximity switches.
they can be obtained with options like cable or cable with connector, completely molded. they have no moving parts so they are completely water proof (usually IP67 rated, which means submersion). to activate them they will need a flag. reed switches can be triggered by a magnet. inductive proximity sensors can be triggered by piece of metal.

typical form factors are something like this:



note, they are sensors so their job is to sense things, not to drive large loads. one could use them to drive a relay or mosfet that control lights.

 

Tell us more about the LED's. 3mm LED's running at what voltage? How many amps (or milli-amps) are you planning? What configuration are the LED's in (3 in series with 8 3 series parallel for example). It depends on the supply voltage and the configuration as well as the current. You could run 5 in series and 5 of those series strings in parallel. I'm not good at verbal description. I can draw a picture more quickly but I'm not on my drafting computer.

 

Marine environment is a different thing. Cabling doesn't have to be submerged in water. It is the humidity that will get you.
I had to completely rewire a MacGregor 26. Even though the cabling was double insulated, moisture had penetrated along the full length of the stranded conductor. You have to use marine grade cable.

Heat shrink tubing will not keep out the moisture. You need marine grade silicone.
I would go with the magnetic reed switches because they are sealed in glass.

 

For me; a picture paints a thousand words. And if I used 1,000 words - I doubt I could be any clearer:

[major edit] I can't reconcile my numbers. Nevertheless, six parallel strings of four LED's in series should work. But again, my numbers are a mess. Don't trust my math please. [end edit]

 

If the reed switch current capacity is not sufficient for the LED current, then the switches could be used to control a sealed/waterproof relay (be sure and add a suppression across the relay coil, cathode to +, to protect the switch contacts).

 

You might consider using LED tape, similar to the picture (first example I came to – a little research should be done). Tape like this has surface mount LEDs and the required resistors, in a adhesive-backed, silicon-sealed strip and is available in 12VDC versions – look for varieties listed for using in cars, with a waterproof rating.

This would save you mucking about soldering LEDs and resistors together, putting them in heatshrink, somehow adhesively mounting the strip, etc., and likely would be a more robust solution. This strips can be cut to length at specified locations, usually an inch or two apart.

Quality strips will specify the current used per foot, which is needed to specify switches.

 

Okay, a lot to address here; let's hope I can do it all without forgetting anyone. (I am typing on my phone at the moment).

LED specs: 9V-12V 3mm Clear/White. They came pre-wired and already have resistors.

If anyone can recommend something to seal the lights and wires in (if "waterproof" heat-shrink tubing isn't good enough), let me know. I was planning to get 4' of it and run the whole thing through there. Adhering the completed strip with marine silicone won't be any trouble.

I opted not to buy waterproof LED strips online because I'd need to cut into them to put the momentary switches in anyway. A lot of the ones available come with remotes, and are meant to be plugged into a wall outlet. I have a 12V rechargeable lithium ion battery pack I can use, as well as 9V batteries (also rechargeable via USBC).

I do have several strings of those LED strips aboard that I am already using as cabin lighting and I love them.

Given the rating on the LEDs, I figure I can use either one. As I don't intend to be fooling around in the engine compartment a lot (and the lights will primarily be off), I'd rather use the 9V and save my nifty 12V battery pack for another project. I just don't want to go through all the trouble, slap a battery into it, come back in 3 months and have the battery dead despite the lights not being used.

Clarification: I intend to mount the power supply outside of the engine compartment.

I hope I didn't forget to address anyone.

 

The contacts on the reed switches are exposed;

Really? When we say "reed switch", that usually means that the switch contacts are hermetically sealed inside a glass tube. Please post photos of your switch and the exposed contacts.

Unless you mean that the wiring contacts are exposed . . . ?

ak

 

Really? When we say "reed switch", that usually means that the switch contacts are hermetically sealed inside a glass tube. Please post photos of your switch and the exposed contacts.

Unless you mean that the wiring contacts are exposed . . . ?

ak

This as suggested above in the thread, but black. I got a 4-pack for like $12. There are glass tube ones, but the videos online are all of the "apply magnet, light turns on" variety. I need the opposite.

Also: On the advice of MrChips, I did get 8ft of marine-grade waterproof heat-shrink tubing instead of the standard stuff.

 

Unless you mean that the wiring contacts are exposed . . . ?

I think that's what he means. I've never seen a reed switch that wasn't sealed in a glass blister.

 

There are glass tube ones, but the videos online are all of the "apply magnet, light turns on" variety. I need the opposite.

Those are the most common types. But if you look at my drawing you see there is the type you're looking for. In fact, the ones you pictured have glass bulbs in them that have the same sort of contacts as pictured in my drawing: C, NC & NO leads.

Here's one now:
https://www.amazon.com/Gebildet-Normally-Magnetic-Induction-2-5mm×14mm/dp/B083TC1XR4/ref=sr_1_4

 

Those are the most common types. But if you look at my drawing you see there is the type you're looking for. In fact, the ones you pictured have glass bulbs in them that have the same sort of contacts as pictured in my drawing: C, NC & NO leads.

If I am understanding you correctly, you mean this? With these, would I then just put a magnet in each of the doors?

Aside from the switches, I either have or have ordered all the parts for the project! I should be able to start working on it on Monday. Given the use-case I've given (sitting OFF most of the time), do you recommend the 9V or the 12V power supply? Like I said, it would be a shame to put a battery in, admire my work, close up the compartment, then come back in 6 months to check the engine and have the battery dead just from sitting. I'm going to take some measurements of the compartment later to figure out how many (or rather, how few) LEDs I can use to get the job done. Based on my eyeballs and my memory, it will probably be 8-10 LEDs.