Frustrated and Confused! No that’s not the tile of my dating profile (I don’t have) been married for 21 years…lol.
I’ve tried once again to get a 3 string (16.4’ each 32led/m) Christmas light setup working without a hitch. I’m not working with FastLED yet but I know you all know your LED’s.
What is happening is the first string works great. The second string once connected (and only with power off) works pretty good but might be a little dim. The third string is quite erratic in it’s patterns that it should be presenting.
I’ve tried connecting the GROUND wire to the end of the second string’s ground. I’ve tried injecting power (+ and -) at the second string and nothing seems to help.
The weird thing is some of the patterns work all the way to the end. They seem to be the ones that don’t use every single LED. So my guess is that it’s a power or data issue. But I have no idea what to do, as I’m brand new to this and don’t understand some of what’s going on. I’ve read and have been told that the data line should be able to go almost infinitely as each IC boosts the signal with power.
As I’m writing this maybe it needs power at the end of the first strip as well. Can I put a volt meter on any of these wires to help troubleshoot things? What should I look for. I only have a cheap one, not sure it would read what it needs to on the data line?
I’m using 2801’s with 5v/60a power supply. Every single LED is addressable not segments of 3 like some. They are actually great strips compared to the first 2812B’s I got for the price.
It would seem to be a power issue. I would even say it is likely a power distribution issue. I recommend using a volt meter, even cheap analog display (with a needle… ) should be alright. Start by checking at the PSU output and adjust it to 5Vdc.
It is hard to troubleshoot at a distance but here is how I would do it if I experienced what you are describing:
I would Individually check all the strips one by one to confirm they are 100% functional before assembling them or mounting them somewhere they are difficult to test again.
For each strip, set all LEDS to full brightness white with a simple sketch and using your voltmeter, check the furthest point away from the PSU connections for voltage drops. IE: That could be right in the middle of a 5 meter strip if you power it from both ends. Ideally no pixel has a voltage below 4.5 Vdc.
If all strips work fine, you are left with only a power distribution problem. Use the heaviest yet practical wire to carry the 5Vdc to all your strips. Coil them on a bench or table but do measure the exact distance required for you final installation power wiring. Again set all your pixels to full brightness white before again measuring at various points along your strips for a voltage drop of less than 0.5 Vdc.
If you are still stuck, send pictures or better still videos that show exactly your setup and the problem you are still getting. Detailed pictures of the wiring would help.
@JP_Roy Those are some great ideas. I was thinking of some others I did not. I really appreciate you jumping in every time I have a question. I will do some further checking tonight. I think you are right if indeed the IC’s do boost (if you will) the data from each to the next, that it must be the voltage is dropping too much on the first strip. I did not inject power there and by the time it gets to the second strip it’s probably if’y at best on what it’s carrying through to the next as it amplifies the data so to speak. Which is why on some patterns that do not use all led’s it’s better, because not as much voltage drop has occurred.
@Trey_Coursey you can also try dimming the LEDs. e.g. dim to 50% brightness and it won’t look THAT different to the eye, but will cut your voltage drop in half (theoretically… I think.)
@Ryan_Cush good point ! I tend to always aim for the worst case of power use but if you are sure that you will never use more than 50% brightness, it will certainly help with voltage drop and the need for heavy wiring.
@Ryan_Cush or @JP_Roy I’m sure I could look up what the threshold of a 2801 led pixel power input is but would it be a good idea to boost the 5V output a bit higher, I think my PS has that ability. Prob not over 6v but… thoughts?
@Trey_Coursey Not something I would do but… Typically these things are specified to have an operating range between 4.5 - 5.5 V so going 5.5 should be OK. But plz check the WS2801 specs before.
5.5 V at the PSU will work but here is why I personally do not like that idea…
If you then allow the voltage to sag somewhere to 4.5 Vdc, IE: still within operational range, you will most likely see a difference in brightness between the pixels powered at 5.5 V to those at 4.5 V
1.0 V difference is 20 % reduction on a 5V nominal, that’s a lot !!
@JP_Roy or @Ryan_Cush is there a preferred wire type for doing these injection runs? Solid core or stranded? I have some 14GA stranded but that seems way overkill. Almost as beefy as the led strip itself. I guess as long as the power doesn’t drop over the run I can use as small as that particular run needs? The first run to the second strand could be a smaller ga then the third strip may need. (although I’ll probably use the biggest needed throughout). Just curious if solid core would be any better for drop?
@JP_Roy Yea I think we are on the same page. I was going to check to make sure PS is a solid 5.5v and then begin to inject power at each strip. Hoping that fixes everything! Any preference on solid core or stranded? One better than another for volt drop?
@Trey_Coursey On a DC distribution, solid or stranded is ok.
Do not dismiss ‘overkill’ when doing power distribution.
Yes, as long as voltage does not drop too much, a smaller power wiring is ok. That is why I suggest you try it on a bench and measure it first and then you will see if that small wire is ok for you. But… if you have some 14GA… why not just use it !?
Solid vs stranded… 14GA is 14GA… it is the overall copper cross section and should have the same current carrying capacity ( I think !? )
I agree with JP – maximize power. I use 12/2 landscape lighting cable for doing mid-point injections. I’m starting to use 14/4 cable for jumper cable, especially if doing a large jumper like 30’. (Though you’ll need a “repeater” LED about every 6m.)
Regarding the @Scrat_The_Skeptic_Sq post – I’m curious what role the RGB amplifier serves, versus just directly injecting power from that other power supply into the 2nd strip?
On initial review it seems injecting power at every end of the 3 strips fixes most all of the issue. There are still some very slight flickering near the very end, where I also inject power but it may just be a loose connection. Tonight I will try soldering everything together and see how things look. I’d be pleased with what is shown now, only on a very few patterns does the last 1’-2’ have any issue at all. That can probably be adjusted by reducing the brightness as was mentioned above. Thanks so much for the help. I didn’t think that much power was being lost, but with the 5V system I can see why…
