Question about RGB LED strips and the Forum itself - Page 1
Forum section: electronics / beginners

author: DW1961
author_rank: Frequent Contributor
timestamp: July 07, 2020, 05:50:53 pm
content: Hi there. Second post.I can't find my "watched" threads or "Threads I've started" or "bookmarks" as they are called on some forums. Does eev have that option?This conversation has come to an end, as far as how RGB lights are connected, but the more important question is what happened to my motherboard. So, please feel free to add to any RGB knowledge here, but use the other thread that is focused on how the MB riser FETS fried.The only thread is located here:https://www.eevblog.com/forum/repair/motherboard-rgb-header-smoked-using-rgb-strip/msg3123416/#msg3123416Second, I'm trying to test an RGB 12V light strip using continuity. I'm not having much luck figuring out the wiring logic for the LED aspect of it, and the 12V sometimes baffles me too. The strip is your common Chinese made non-addressable RGB 12V strip you can get on Amazon. I'm trying to figure out what happened with this strip and my motherboard RGB header getting smoked. I don't want to repeat that when I get my board back from repair (It may of well been a bad RGB motherboard circuit too. I just don't know.)I posted a video here at eev (link to it) showing the confusing aspect of it.Here is a link to the video:https://1drv.ms/v/s!AqQihxjVvPuLhdsknab_EyctprcFMAThe entire post is here:https://www.eevblog.com/forum/repair/motherboard-rgb-header-smoked-using-rgb-strip/new/?topicseen#newAt firs I thought the strip was horribly shorted out, but I bought a different brand, and it does the same thing when testing 12+ and RGB circuits.I can get polarity on the pads of the strip, but when I use the 12+ circuit to test the LEDs themselves, sometimes, yes, it makes sense and the LED comes on, and sometimes it doesn't. For instance, sometimes I can connect the 12V pad that connects to the LED anode side of the pad (or I would think it does) and the common RGB cathode side of individual LEDs in the 5050 SMD, and nothing happens. However, the light strip works when plugged in.Thanks, as this is driving me crazy.

author: MK14
author_rank: Super Contributor
timestamp: July 07, 2020, 11:45:25 pm
content: This link seems to explain, that the Leds, are wired up in series (per 3 Leds), then in parallel (sets of 3 Leds, per bit of parallel section).So, that would seem to explain why they lit up that way, on your video.https://behindthesciences.com/electronics/rgb-led-strip-tutorial/I.e. They are in a set of 3 (Leds in series).You seem to think they are wired up separately from each other (I guess), from how you seemed to be testing it.Also, the "Show new replies to your posts." button, in/near the top left hand corner, shows the forum post results, you might be looking for.

author: DW1961
author_rank: Frequent Contributor
timestamp: July 08, 2020, 12:25:33 am
content: Quote from: MK14 on July 07, 2020, 11:45:25 pmHey thanks for that. I really appreciate that.I can't really make sense of that schematic. I'm very new at this.However, to answer your comment about how they are wired up, no, I thought all of the 12V sides would be connected to each 5050 chips individual LED anode side. If so, I should be able to touch any of the 5050 chips 12V sides and get continuity? The power only comes from one direction, which is the start of the 12V side of the strip.This is how I envisioned it:Light strip: 12V+ -->5050 chip 3 connections one to each anode side of the, then next 5050 chip and so on. The power only comes from one direction, which is the start of the 12V side of the strip. So I stil don;t understand why I can;t get continuity.You've given me some focus with your comment. So, for now, if possible logically, let's just leave out the RGB aspect of it and focus on power only. Once I get that straight, maybe I can understand the next part.As far as the forum goes I was looking for a section where I can see a list of specific threads I started/am subscribed to.

author: MK14
author_rank: Super Contributor
timestamp: July 08, 2020, 12:34:55 am
content: Quote from: DW1961 on July 08, 2020, 12:25:33 amTo partly answer the last (forum related question) bit, at least as regards threads YOU made/started.Via a number of menu/button clicks, you get to:https://www.eevblog.com/forum/profile/?area=showposts;sa=topics;u=686532Quote from: DW1961 on July 08, 2020, 12:25:33 amEach Led, drops around 2 or 3 volts across it, depending on colour. So, 12 Volts, powers 3 Leds in series, and the current limiting resistor, rather well and efficiently.So, the schematic (I linked to earlier)), shows the 12 volts, going through each of 3 Leds, and then a current limiting resistor.E.g. Look at Led10, Led11, Led12 and the resistor, on the schematic, below.

author: DW1961
author_rank: Frequent Contributor
timestamp: July 08, 2020, 03:06:11 am
content: Quote from: MK14 on July 08, 2020, 12:34:55 am"Via a number of menu/button clicks, you get to:" LOL yes thanks exactly what I was looking for! Your comment made me laugh.OK, I didn't means series. I meant parallel actually where the light strip has a copper circuit going the length of the LED strip, and then the 5050 chip taps into the main 12v+ circuit all the way down the strip, so that would be parallel and series? Also, just to clear things up, when the schematic says three LEDS, that would be one 5050 chip with 3 LEDS on it? I think I understand your explanation. The strip is wired in series, with 3 LEDS in parallel and so on? So, using my own graphics:12V+|Anode|---L1--L2--L3 all RED|Cathode|resistor|12V?So many more questions, but I want to take it slow and make sure I have the logic understood.Also, thanks so much for helping. So much appreciation.

author: MK14
author_rank: Super Contributor
timestamp: July 08, 2020, 04:21:49 pm
content: Quote from: DW1961 on July 08, 2020, 03:06:11 amSpecifically "when the schematic says three LEDS, that would be one 5050 chip with 3 LEDS on it?"No.Using/changing, your "text" schematic, it goes...12V+|Anode|---L1 of Led chip 1 of 3 (5050)|---L2 of Led chip 2 of 3 (5050)|---L3 of Led chip 3 of 3 (5050){I.e.} all RED|Cathode|resistor|12VAn output device, such as a transistor, which can pull this down towards Ground, and hence light up, all 3 Leds (5050's), of a particular colour. As well as all the other 'paralleled up', sets of 3 5050 Leds, depending on how long the Led strip is, such as 33 Inches.?I.e. There are 3 (R or G or B) common lines, which can be pulled towards ground, to light up in either R, G or B (Red, Green or Blue).E.g. Pulling the G/Green one towards ground, would light up all 3 5050 Leds, in Green. Or even the entire chain of 33 Inches (or whatever), all in Green.

author: DW1961
author_rank: Frequent Contributor
timestamp: July 08, 2020, 05:26:48 pm
content: Quote from: MK14 on July 08, 2020, 04:21:49 pmYes, looking back at my schematic, I meant it just like you did it, but didn't know about the grounding process. Thanks for that. However, why are the red LEDs in each chip assigned a different LED #, as in your diagram? My mind wants to say that each chips' Red LED, just using that color as an example, would be LED #1, again just using #1 as an example. When you say L1, L2, L3, I assume you mean the LED on the chip itself. So, to clarify my question, why would on chip's red LED be L1 and another be L2? I know I'm jsut confusing things, so I apologize for that.

author: MK14
author_rank: Super Contributor
timestamp: July 08, 2020, 05:32:15 pm
content: Quote from: DW1961 on July 08, 2020, 05:26:48 pmYou're right, I agree.If the first 5050 Led is called IC1, the second IC2 and the third IC3 (ignoring that they aren't actually ICs, but trying to avoid calling them Led1/Led2 etc, to minimise confusion here).Then it would beR/Red pin/connection of IC1.|R/Red pin/connection of IC2.|R/Red pin/connection of IC3.The schematic was drawn by someone else, so I followed their conventions, in my earlier posts.

author: DW1961
author_rank: Frequent Contributor
timestamp: July 08, 2020, 05:35:51 pm
content: Quote from: MK14 on July 08, 2020, 05:32:15 pmWhew! I was thinking, "Oh F*** I'll never get this logic!"So with that out of the way, and I just asked this question, which is pretty much why I posted about the LEDs in the first place--with the caveat that I am learning good stuff--how could a 12V LED strip fry the motherboard's FETs like mine got fried? I don't want to do that again.

author: MK14
author_rank: Super Contributor
timestamp: July 08, 2020, 05:51:27 pm
content: Quote from: DW1961 on July 08, 2020, 05:35:51 pmIt's not immediately obvious to me, if the 2 Amp rating, is PER colour, i.e. it could supply up to 6 amps, since RGB x 2 Amps = 6 Amps. Or do they mean a total of 2 amps, across all 3 colour lines (RGB) ?I think you said it was 60ma per Led colour section. So how many sections were there all together ?(Really it should be ONE thread, as I'm recalling the details from your other thread).As to faults.Either the motherboard was faulty, and you always met all its specifications/requirementsOr, the total Led units x current per unit x max colours on at same time, overloaded it.Or, the Led chains you connected were/are faulty, and used too much current.E.g. Current limiting resistor(s), wrong value (too low), or current limit resistor(s) shorted out or other RGB chain faults, such as mis-wiring etc. So that it exceeded the 2 amps limit, overloaded the motherboard and caused the drivers to over-heat and burn out.I would presume, there isn't any current limiting/protection on the motherboard, for the RGB chains.Because of the parallel connection nature of the Led chain(s), it would just take one section to be faulty, to overload the motherboard.Were all the colours lighting up as expected initially, or did one or more colours fail or be dim, right at the beginning ?If so, then the motherboard output drivers (probably fets/transistors), would/could over-heat and break.(The other thread may have the details, but I'm sticking to this thread at the moment, trying to combine lots of threads, gets too complicated/confusing).But, maybe I should start posting in the other (motherboard) thread, and leave this one ?

author: DW1961
author_rank: Frequent Contributor
timestamp: July 08, 2020, 07:07:54 pm
content: Quote from: MK14 on July 08, 2020, 05:51:27 pmWell, I emailed Gigabyte and asked how many amps the riser can handle, and the response was "2 amps.""(Really it should be ONE thread, as I'm recalling the details from your other thread)." I agree. Let's head on over there! This image is also posted there.

author: Jurlilane
author_rank: Newbie
timestamp: July 05, 2022, 11:05:34 pm
content: That's weird that it wasn't shown how many amps it had, I couldn't find it anywhere.