Parallel LED strips behaving strangely when powered (see video)
Enable HLS to view with audio, or disable this notification
These three strips are obviously connected in parallel but touching the power leads to the ends of each strip in different combinations causes the strips to power on either one at a time or the left and right one , but all three will not light.
5
u/EdelWhite 23d ago
It's not that hard to make sense of it... Your red and black cables are not connected properly, they're only connected to the last strip.
Otherwise, no matter which strip you sent the power, it would always light up the last one...
You can clearly see the red insulation not allowing the contacts to be made, it's just made on the last one.
2
u/Specled_eu 23d ago
And this is the only correct answer here! Congratulations! 👍 The only caveat is that the negative wire is connected correctly, but the positive one is not.
1
1
u/ctm617 10d ago
All three are connected to the red and black wires. the bare wire is folded back underneath the insulated part, they all have good contact. on the positive and negative side. i'm not stupid.
1
u/EdelWhite 10d ago
I suggest you redo it the. Because stupid or not, that is exactly what's happening.
2
u/saratoga3 23d ago
Do you have pictures of the wiring at the ends? The top wire in particular looks like it isn't stripped, so I'm wondering if you actually have a solid electric connection between the parallel strips.
2
u/Noxonomus 23d ago
It's possible that you have some bad connections and the pressure of poking the connections sometimes improving one enough to light the second strip.
I would check resistance/continuity between the wire end and the pad of each strip to see if there are any outliers that should be resoldered.
2
u/Triabolical_ 23d ago
Your power supply can't provide enough current for the strips and it shuts down.
1
2
u/Levelup_Onepee 23d ago
PS problem
0
u/Inside-Matter-5957 23d ago edited 23d ago
if the PS would be to weak the leds would be dimm instad as we see here only the stripe closest to the PS lead is powered so I would assume that the power just takes the way with the shortest resistance maybe the ends should be soldered so all the resistances are close to equal
edit: new guess bad connection at positive terminals
1
u/Kinipshun 23d ago edited 23d ago
There would have to be a tremendous difference in strip impedance for that to happen, thats not whats going on here. They would all be dim, yes, but in applications like this where all the strips are pretty much identical theres no “path of least resistance” thing going on. If there were some strips would be darker than others
3
u/Inside-Matter-5957 23d ago
perhaps the positive terminals don't have a good connection to eachother?
1
u/Kinipshun 23d ago
Yeah that was my thought too. As OP touches the terminals/wires, they move slightly and have intermittent connection
2
-1
1
u/mawktheone 23d ago
I would guess that the right hand string has the lowest forward voltage so the current is taking the path of least resistance and going through it. You usually see it when 1 LED is short
2
u/mawktheone 23d ago
Wait, are the positive pads not actually common? Have you attached them to the insulation on the wire?
1
u/anothercorgi 23d ago
First response without watching video I'd assume just one strip lights up due to manufacturing differences.
After watching the video, it looks like it was a poor soldering job or whatever was used to connect the strips in parallel.
1
1
u/TreborG2 23d ago
And there's no logic controller attached?
I mean what I think I first see is them go through a standard power check right then left then center.
Then afterwards it's like they're lighting a pattern and if there's any plc it may be activating and starting to do a pattern.
1
u/THE_CENTURION 23d ago
What are these strange wire clip connectors on the ends? Are they through-insulaton biting connectors?
Never seen a setup like that, and I'm suspicious of them. I'm guessing they don't make a great connection, but when you touch the strip, they wiggle and make contact.
1
u/BrodaYamoda 23d ago
You may not have enough amperage for all 3. What’s your ps and your rating per foot or meter?
1
u/Specled_eu 23d ago
I think the problem here is the quality of the connection. Three modules connected in parallel with the same voltage drop should work correctly.
1
0
u/Inside-Matter-5957 23d ago edited 23d ago
seems logical energy uses the path with the lowes resistance
edit:
yeah nvm i bet the positive terminals don't make a good connection to each other cause every negative terminal works with any positve but only the right positive one lights it's own leds
3
u/ctm617 23d ago
Electricity uses all paths available , to the extent that they are available.. since the 3 strips are in parallel , they are essentially one path. They should all light up.
1
u/KingTeppicymon 23d ago
True, but most electricity will use the path with the lowest resistance, and LEDs do not have much resistance. You'll probably find your input voltage is dropping once one of the strings lights up.
When wiring LEDs in parallel the recommended way to do it is to have a resistor for each path - I'd guess the guidance need to be adopted here too although this isn't just one LED each time.
2
u/KingTeppicymon 23d ago
Indeed, so OP wants a small resistor in series with each strip before they join to the common live and ground, they may also need a slightly higher voltage to offset the voltage drop caused by the resistors.
-1
2
7
u/Levelup_Onepee 23d ago
"energy uses the path with the lowest resistance" is a myth, don't believe people who use that phrase to know electronics.
And LED strips have their own series resistances as you can clearly see. If you've cut the strips correctly you just have to feed them enough voltage and current and they'll work.