Help Testing LED RGB 4 pin Light Strip with Multimeter

DWD1961

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Nov 30, 2019
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If anyone has any electronics experience and knowledge of how LED light strips work, I'd really appreciate some help testing some strips I have for shorts etc. I just ordered a controller and power brick and my mulitimter will be here tonight. Before I plug in the power and controller, I want to test the strips.

I've researched how the strips work as best I can, and this is what I came up with:

What I'm testing:
12V RGB 4 pin strip lights

Please correct where wrong:
  1. If the system is 12V and 5 Amps, if you reverse the polarity, nothing happens bad, the lights just don't come on.
  2. The 12V black is positive and the RGB are cosidered negative, since the LEDS are all wired to the same 12V circuit.
  3. Given #2, I can test the amps by putting the multimeter inbetween the power source (12V wire) and the RGB wires?
  4. Testing continuity using the 12V wire will show a fault in any of the LEDs/wiring, whereas testing continuity on the RGB wires will only show a fault with the specific color of each LED, but a; LEDS of that color on the strip (so I could find a fault in the green, but not red )?
  5. What happens if you bridge the 12V wire with one of the RGB wires?

Thanks.
 

sinisterDei

[H]ard|Gawd
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Messages
1,221
My experience is exclusively with 5v strips of WS2812b LEDs, so I'm not gong to be able to answer all your questions or even most of them. I do have some inputs though.

You probably don't need a multimeter for this. I tested my strips by lighting them up and making sure all the LEDs responded to their programming. I used an arduino nano to control them, using the FastLED library.

Regarding #5, just don't do that?

Lastly, I don't know much about the 12v strips because I picked the 5v ones over them. I would have liked the 12v strips, except in general the ones I saw the LEDs were controlled in batches of three; if I instructed a 12v strip to turn on its first LED, the first three would turn on. Enabling the second LED would turn on 4-6, and so on and so forth. Since I was primarily using my strips to build my own ambilight I wanted individual LED control, hence 5v was chosen.
 

DWD1961

Gawd
Joined
Nov 30, 2019
Messages
653
My experience is exclusively with 5v strips of WS2812b LEDs, so I'm not gong to be able to answer all your questions or even most of them. I do have some inputs though.

You probably don't need a multimeter for this. I tested my strips by lighting them up and making sure all the LEDs responded to their programming. I used an arduino nano to control them, using the FastLED library.

Regarding #5, just don't do that?

Lastly, I don't know much about the 12v strips because I picked the 5v ones over them. I would have liked the 12v strips, except in general the ones I saw the LEDs were controlled in batches of three; if I instructed a 12v strip to turn on its first LED, the first three would turn on. Enabling the second LED would turn on 4-6, and so on and so forth. Since I was primarily using my strips to build my own ambilight I wanted individual LED control, hence 5v was chosen.
"You probably don't need a multimeter for this. I tested my strips by lighting them up and making sure all the LEDs responded to their programming. I used an arduino nano to control them, using the FastLED library."

What hapens if your light strip has a direct short in it and you pour teh volts to it? I need to test my strips after I solder them to make sure they don't have a short. I'm using them in my computer, and a direct short is probably not too good.
 

sinisterDei

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Do you mean a short *you* caused with your soldering, or a short caused in manufacturing?

In either case, I did my soldering to get the leads set to the arduino. Eyeballing the solder points was pretty easy, since there were just four solder pads to worry about and just making sure the solder beads didn't cross the streams or whatnot. I'm 100% amateur at soldering, so I figure if I can do it basically anyone can. Once everything looked good and tested good, I coated the solder joints in black liquid tape to permanently insulate them electrically.

Presumably if there was a short, when I did the test it would fry the strip at the worst case. 5v or 12v isn't likely to burn the house down or anything.
 

DWD1961

Gawd
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Nov 30, 2019
Messages
653
Do you mean a short *you* caused with your soldering, or a short caused in manufacturing?

In either case, I did my soldering to get the leads set to the arduino. Eyeballing the solder points was pretty easy, since there were just four solder pads to worry about and just making sure the solder beads didn't cross the streams or whatnot. I'm 100% amateur at soldering, so I figure if I can do it basically anyone can. Once everything looked good and tested good, I coated the solder joints in black liquid tape to permanently insulate them electrically.

Presumably if there was a short, when I did the test it would fry the strip at the worst case. 5v or 12v isn't likely to burn the house down or anything.
I wanted to check the strips from the factory and my own joints to see if there is a short. My motherboard smoked it's RGB chips caps and melted them, so it was either a bad MB or the strips shorted out.
 

DWD1961

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Anyone out there willing to guide me on this project? My new DMM gets here tonight!
 

sinisterDei

[H]ard|Gawd
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Good luck :) You're outside my expertise for sure. I've never been big on RGB for my case, so I've never used one of the headers on a mobo. Mine were always arduino driven for external applications, so I'm not sure what I know even translates.
 

DWD1961

Gawd
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Nov 30, 2019
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OK, so I think this strip is all fucked up. Just wanted to post my videos to see if I have erred in some way testing. If anyone cares to comment, please do.

This is a test of a piece right off the reel. It's never been used. I just pulled off the waerproofing so I could test it:
 
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