@JP_Roy or @Ryan_Cush so I’m soldering my cables together to get everything more permanent. I was running a separate 16ga wire from PSU to end of segment one…I soldered that into the end fitting so that when I plug in my second string I would get the full 5.4v I have pushing. However when I meter it I am only getting 4.5 or so. Which I would expect from the drop THROUGH the first strand…but I have a separate cable running to this juncture. I’m sure this is electrician 101 and I get why it would do this because it’s all ONE CIRCUIT I guess…but the question is HOW do you INJECT voltage down the line then? Do I need to just POWER the second strand by this newly ran 16GA wire and only allow the clock and data pins to CONTINUE through? Thanks for any help.
What I do is I solder the secondary power directly onto the strip at one of the sets of solder pads – 5V and GND. Which sounds similar to your arrangement. So it’s feeding voltage in both directions up and down the strip. Are you positive your connections are good? You’re right, you should get 5.4V. Though, how long is your 16ga run? If it’s long, it’s possible that you’er getting voltage drop on that one. Here’s a handy voltage drop calculate that can help estimate: https://www.rapidtables.com/calc/wire/voltage-drop-calculator.html
@Ryan_Cush ok so I checked some things out. When I test from the PSU directly I get 5.4v when I check from the end of the first strand WITH the extra power injected I get 4.7v. If I unsolder the power injection I get 5.4v from the power injection 16ga wire and only 3.4v I think it was from the end of the first strand. So it would seem the additional 5.4V is bringing the power UP to a new average of 4.7 rather than a full 5.4.
When you inject the new power do you just run ONE injection wire that is soldered into each strand and continued to the next (bypassing the LED’s) or do you run a new injection wire from PSU to each new strand? So I’d have two or three injection wires depending on if I injected at the end of the third strand.
@Trey_Coursey I am getting a bit lost with your description. Can you post pictures or a drawing of your setup ?
If I understand, you are actually dropping 0,7 V in those wires injecting power. Seems like a lot even for 16 ga wiring. How long is that wiring ?
@JP_Roy So the simple description would be this.
PSU shows 5.4V at psu terminals.
End of Strand 1. 16.4ft 160 leds is 3.1v
If I connect 16ga wire from PSU to end of strand 1 I get 4.7v when connected.
I get 5.4v at end of 16ga wire if it’s not connected to end of strand. so no voltage drop through 16ga wire in 16’ length.
That help any?
@Trey_Coursey yes, it did clarify a bit more.
Are you using 2 wires to inject power, GND and 5V ?
How long is the 16 ga wire (s) ? 16,4 feet ??
@JP_Roy Yes 2 wires hooked up directly to PSU then at end of strip. Both ground and 5v (5.4v in my case) Two wire 16ga wire is just about 16.4’. There does not seem to be any voltage drop in this length, from what my meter shows. The calculator with default values of impedance (I don’t know mine) shows it would be maybe a 10th of a volt.
@Trey_Coursey OK 1st it is normal to see 5.4V at end of wires that are left unconnected. No current in wires mean no voltage drop.
I just used that tool that Ryan provided a link for and it seems that 0,7V drop is not totally unreasonable although it does seem a bit high to me.
Are you driving all the leds at full brightness ?
Also, would you want to chat directly now using Skype ? You can reach me at jpro56@hotmail.com
If you are running 160 LEDS at full brightness on white, I think it would take 60 mA per LED, or about 9 amps in total. Plug in 9A into the voltage calculator and you’ll see a 1.15A drop just in the power cable itself. As JP points out (and this was a learning for me too), the voltage drop is proportional to how much current is being pulled.
@Ryan_Cush yes I am running them in a pattern that would be pushing them pretty close to full. Not all white but a scrolling white, so probably 90%. I did not know about what @JP_Roy was saying about the voltage drop and current pulled formula. That would totally make sense when I hook those wires up to the “circuit” so to speak.
So I have two questions/thoughts regarding that information.
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Is it better to not run the entire 3 strands all together as far as power is concerned, meaning I’d hook up each strand independently to the PSU, rather than daisy chain them together.
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The bigger the strand series get’s (3 in my case) the more voltage drop that would occur since the amp draw continues to get bigger. This might make sense why just the last foot of leds on very few patterns were still doing some intermittent things when I had everything hooked up for my tests (power injecting) I bet the voltage drop for the entire circuit even at the end of the strand was marginally over 3V or so.
How would one get over that situation?
@Trey_Coursey Shorter power wiring AND Heavier power wiring.
@JP_Roy well shorter is not possible as I want all three strands on this one PSU. But bigger wire is possible. I do have some 12GA I will run some tests with that this afternoon. Id like to see at least 4.5v throughout the system, is that what I want 
??
@Trey_Coursey Yes, I mentioned that a few posts earlier. No matter how you achieve this, you should aim at having no less than 4.5 V anywhere along your strips. You may get a somewhat stable result even with only 4.0 V maybe even less but… that is not how I would do it !
Keep in mind that if you supply power at both ends of a long strip, the lowest voltage would be found somewhere down the middle of that strip ! Do check voltage at various points in the strips. 12 ga will definitely improve (IE: reduce…) the voltage drop. You could also just double-up or even triple-up on the 16 ga wiring if that is more practical for you.
Another suggestion would be to place the PSU somewhere close to the connection between the 1st and 2nd strip and not at the beginning of that 1st strip if that is possible. That would help shorten the overall length of the power wiring.
@JP_Roy some good thoughts. I’ll want to keep the ps near an end as I will have my controller in a weather safe box along with my ps. I will do some tests with my 12ga or double up my other wire to see what I can get. Now I know some things to do to help improve and learning alot along the way! Thanks again for your time.
Yeah, I use 12/2 cable and provide power at the very start and also about 2/3 of the way down the run. (That way, the 2nd power injection is feeding the final 1/3 and also the middle 1/3). But I also turn down the brightness significantly (and you really can’t tell that much, unless you’re comparing to another strip side-by-side.)
@Ryan_Cush Brightness may or may not be an issue for me. I’m putting the whole installation inside 1" PEX tubing. It looks great. I’ll def keep that in mind when I get everything pretty close to final. Really appreciate all you guys help. I have all the tubing put up today. It will be a year round installation as you can’t really tell it’s there on my white painted trim. So we will light it up on different occasions, big games, halloween, 4th etc.
@Trey_Coursey I am just hoping that you post the results here soon… 
I hope that wasn’t sarcastic @JP_Roy I do appreciate your willingness to jump in and help a poor soul like me that does lot’s of DIY but is not qualified in electricity…lol.
So I just ran the 12ga wire from PSU to end of first strand, before hooking it up the end volt drop was down to 3.1 ish. With the injection the end of strand 1 reads 5.1v So now only about .35v drop over the first strand. Need to figure out if I can continue from the end of this first stand with additional 12ga wire, or do I need to wire directly to the psu and then go to the end of the second strand…only testing will tell. I’m hoping I can just continue the 12ga from end of first strand. I’m very close! thanks again.
@Trey_Coursey For heaven’s sake… Sarcasm implies an intended meaning that is the opposite of what is seemingly expressed. Typically intended to hurt or wound someone.
Now, where do you see sarcasm here !?
Now I will admit to teasing you into posting your results but hey… there is no obligation… it is up to you…