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Question for the people who actually know how to diy electrical stuff (not me)

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(@bjomag)
Posts: 4
Active Member
Topic starter
 

Hey everyone, and thank you for taking the time to read my post.

For a long time I have been wanting to add some light to my ongoing custom DIY 3D printer enclosure project.
However, it's my first time playing with LED lights and creating completely new "electric loops" if that makes sense..?

So I was wondering if anyone could help check my idea for potential fire hazards 🙂

Now, disclaimer: I am by no means an electrical genius, and nor do I know how to properly map out anything in a professional way, so I hope you understand my drawing and idea.

I purchased a 3-pos switch, so I could have two presets or levels of illumination controlled by two PWM units or whatever the right word for them is. However, I'm not sure if I've thought it out correctly. I am scared of burning something or shorting the PWM controllers as I obviously don't have an infinite supply of them.

I guess my question is: Is my concern valid (marked with green pencil) and if so, how do I fix it?
I have a decent length of LED strip, so the alternative is obviously two separate loops, even though it isn't a very sustainable solution...

Thank you for reading it means a lot <3

(And sorry if this is posted in the wrong thread. I wasn't sure where to post)

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This topic was modified 10 months ago by bjomag
 
Posted : 06/08/2023 3:45 pm
marcdraco
(@marcdraco)
Posts: 476
Member
 

Hi @bjomag first of all, welcome to DIY Perks. I'm just a regular joe like you so let's take a look at what you got.

I'm assuming when you say "regular" LED strip you mean the type that plugs into a USB port and lights up? There are quite a few alternatives, some require 5V others 12V, some with controllers and some without. These days there's a lot of interest in "smart" LEDs which aren't really that smart but they do respond to control signals from a microcontroller like an Arduino. I've used the 5V versions with excellent effect in a full-scale replica of the Ghostbusters Proton Pack. The strips can be cut and soldered to length and offer a staggering range of colour and controllability as each one contains 3 different LEDs: blue, red, and green.

Perfect if you want to make a fancy light show but rather over the top for what you're doing here.

In fact, PWM (pulse width modulation) is overly complex too. All you need to control the brightness of an LED strip is a current limiting resistor. The value is harder to pin down but we'll get to that.

I've run out of attachments today (silly me) but it's pretty easy to do since I talk far too much.

The switch is a single pole changeover but it's easier to wire it so the centre terminal is "common" (not the 0V).

Looking at the switch side on, you'll have three terminals (six if it's DPDT but they're just a parallel pair of SPSTs) and they can do the same job.

If we number them I, O, and II you can think of "O" your "common" terminal as you have it here. The great thing is, the way that switches work is they work the other way around. We can take an output voltage from "O" and put the supply on I and II - so you select either.

If you were using a PWM you'd only put it in series with the connection the either I or II if that makes sense so flipping the switch selects either the direct or the PWM supply. The negative terminal goes right back to the negative terminal on the supply.

PWM is used for simple dimming and it's highly effective, but if you just want two brightness levels that's far simpler (and waaaaay cheaper) with a simple resistor.

If you can give me some idea of which LED strip you have I can take a better stab at the resistor value, but if you'd rather use PWM that's fine too.

TL;DR:

A REALLY quick way to to this without all the chew is to nip to your local B&M store (in the UK) or Amazon outside of that and find a pre-made one with a USB plug and remote control ready to glue into place. These come with that wide variety of colours and start from about £10.

There is some pride in making your own though so I'm happy to assist.

 

 


Take everything I say with a pinch of salt, I might be wrong!

 
Posted : 06/08/2023 9:35 pm
(@bjomag)
Posts: 4
Active Member
Topic starter
 

Hey @marcdraco thank you so much for your very comprehensive rundown of options! Much appreciated! 

First off. The practical stuff:
I decided on using a 12V white COB LED (also since I have a 12v PSU) strip that is labeled 6000k white, as they were pretty reasonably priced and are going to be visible. I'm actually just now fearing, that the connection (shown below) is needed to keep that 6000k white setting as it also works as the controller..? I was planning on just cutting to length and soldering to wires connected to the two different PWM boards. 

I chose to go with PWM, as my original plan was to use a single controller to run the lights from, so I could still adjust light levels (Which would have been cheaper and easier). However I got a pack of four for 8 euros and I thought that was a good deal, since I am probably gonna blow one (As this is my first time using them). And I've always wanted to try a 3pos switch, so idk I just got it. 

SO. Long story short: I decided to bite the bullet and pay for what I dreamt of lol.

And so my new question is:
If I'm reading your point on switches working the other way around correctly (then please ignore my question below) - Then this means I should have my PWM boards connected directly to the PSU, and rather have the pos side (of the PWM managed side of the loop) running into either I or II, and then the O will be off, when in middle position, but the O connection on the back will be the output, going to pos on the LED strip? Then have two neg wires going to one PWM board each to complete the loop?

And if not:

And granted, this is if you can actually understand my hobbyist wiring-diagram... Is it possible to wire things up as I have sketched (Picture shown in original post), or will the positive connection to the LED strip run back through the positive side of the idle or inactive PWM board, and fry it? Or does it turn off completely when not given any current, and therefore not make any connection to the other part of the LED strip, making the current go only the right way?

Please tell me if this doesn't make sense, then I'll try to draw it again.

And yeah, I might have just ordered the parts before actually realizing my idea in detail and looking for flaws lol. It made sense back then okay xD

And yeah, it's not the DPDT type 3pos switch... Just made it as easy as possible for myself.  Even though I didn't, but you get what I mean.

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This post was modified 10 months ago by bjomag
 
Posted : 07/08/2023 1:29 pm
marcdraco
(@marcdraco)
Posts: 476
Member
 

This is the easy way. Batt is the 12V in from your supply, the switch selects either the "pure" 12V DC or the output from your PWM module. That's literally all there is to it.

image


Take everything I say with a pinch of salt, I might be wrong!

 
Posted : 07/08/2023 5:31 pm
(@bjomag)
Posts: 4
Active Member
Topic starter
 

Ahh, yes, okay I get it now. Thank you so much for your help marcdraco!

You might just have saved my project 🙂

 
Posted : 08/08/2023 5:51 am
marcdraco reacted
marcdraco
(@marcdraco)
Posts: 476
Member
 

No worries! Lights on 3D printers can be really handy - even for making sure your print is coming out right and hasn't shifted off by 1mm that won't become obvious until you get it off the table and it falls apart (waves hand...)


Take everything I say with a pinch of salt, I might be wrong!

 
Posted : 08/08/2023 3:19 pm
(@bjomag)
Posts: 4
Active Member
Topic starter
 

Yeah, you don't say lol. Been using my phone as a flashlight to see if my black filament was being put down correctly.. Can't wait to have a legit setup for that situation. 

 
Posted : 08/08/2023 6:50 pm
marcdraco reacted