nedaso:
This time I'm running only 30 LED's and I still have problems.
What I can see you still power it with flimsy wires. So the voltage at the first low is probably already low, let alone not all that stable.
Don't forget it's just 5V. If you lost 0,5V you already lost 10%! And the leds all have a chip in them that's not very tolerant to low (or spiky) voltages. And at 60mA max per led current goes up quick.
An yeah, get a multimeter. Don't bother with the current setting 
Thanks everyone for your replies, everyone has been very helpful!
As for the wiring, I'm using a 2.5mm^2 wire for everything, except the data wire (which is a jumper wire) and the arduino ground wire. Is there any improvements I could do?
nedaso:
(blue included, which draws the most amps)
Only if you use it more than the other colours.
HKJ-lygte:
For strips with separate power wires it is easy enough, you just connect the supply to the two power supply wires and the Arduino to the GND and data on the 3 data wires.
Actually, if you are powering the Arduino from the same 5 V, you connect it to all three of the wires on the three-pin "data" connector from the strip so that is how it derives its 5 V. This ensures there is no grounding problem.
Sorry for bringing the topic back, but I have an update.
I bought a multimeter, and checked the voltages. With all LED's off, the voltage measures at ~5V, but when I set all lights to white, the voltage shows ~3.5V (most of the leds are red, not white). So this indicates a voltage drop, however, using a 2.5mm^2 wire across the entire strip seems unpractical as the strip becomes more like a solid bar.
The ground and 5V rails on the LED strip should be a buss and the data line is a point to point.
I am curious if you were to ohm out each end of the 5V & Gnd buss what is the reading.
If you flex the strip whiles reading end to end resistance (5V & Gnd), does the reading flicker or jump?
What is the reading from the middle of the strip (Gnd & 5V) to each end (that's two readings)?
Nothing to be sorry about!
nedaso2:
I bought a multimeter, and checked the voltages. With all LED's off, the voltage measures at ~5V, but when I set all lights to white, the voltage shows ~3.5V (most of the leds are red, not white).
Hang on, where did you measure the voltage? Where your 5 V supply connects to the strip, or at the other end of the strip?
If the voltage is down where you feed the strip, it is obviously a problem with your wiring, not just the strip. If you have a proper 5 V feeding into the strip, then the LEDs closest will be perfectly white, but they will get yellower and redder along the strip to the end which is not connected properly to power. If you connect power to both ends, it will be yellow in the middle.
nedaso2:
So this indicates a voltage drop, however, using a 2.5mm^2 wire across the entire strip seems unpractical as the strip becomes more like a solid bar.
Well, that's just tough, isn't it? Either you have something that works, or you do not. 
But that also depends on whether you expect to light most of the strip. If you only ever run a few lights back and forth along the strip, the load will be minimal and it will work OK.
Paul__B:
Nothing to be sorry about!Hang on, where did you measure the voltage? Where your 5 V supply connects to the strip, or at the other end of the strip?If the voltage is down where you feed the strip, it is obviously a problem with your wiring, not just the strip. If you have a proper 5 V feeding into the strip, then the LEDs closest will be perfectly white, but they will get yellower and redder along the strip to the end which is not connected properly to power. If you connect power to both ends, it will be yellow in the middle.
Well, that's just tough, isn't it? Either you have something that works, or you do not.But that also depends on whether you expect to light most of the strip. If you only ever run a few lights back and forth along the strip, the load will be minimal and it will work OK.
I measured the voltage at the beginning of the strip, the middle and the end and the voltage seems the same, around 3.5V (probably I did something wrong?). The first 10-15 LED's are perfectly white but they go yellow and red at the end, just like you mentioned.
okay so If I really need to reconnect the voltage at each meter or so, does it really need to be a 2.5mm^2 wire? The amperage is pretty high because there are 300 LED's, but I believe 2.5mm is an overkill?
nedaso2:
I measured the voltage at the beginning of the strip, the middle and the end and the voltage seems the same, around 3.5V (probably I did something wrong?).
Is your LED strip a 5V LED strip? From what you have wrote, is that if you measured from the point of input voltage on the strip and got 3.5V. And so you expect a 5V LED strip to be working all grand and happy with 3.5V's? Explain, please how ~3.5V = 5V.
Idahowalker:
Is your LED strip a 5V LED strip? From what you have wrote, is that if you measured from the point of input voltage on the strip and got 3.5V. And so you expect a 5V LED strip to be working all grand and happy with 3.5V's? Explain, please how ~3.5V = 5V.
Well I'm sorry I'm kinda new at electronics, dont be too harsh.
I measured the voltage with all the LED's off and it showed 5V but as soon as I turned on some LED's the input voltage dropped to 3.5-4V. Is that a problem with my power supply?
Is that a problem with my power supply?
Yes, it looks like it can’t supply enough current. What is it rated for?
If the colours are indeed mutating along the strip then it is because the voltage is fading as you progress along the strip. You would have to measure between ground and "5 V" at each 50 cm or so along the strip at the "snip" points where they are exposed.
But if your voltage is 3.5 V at the start of the strip then you have already lost voltage before getting to the strip, which would indicate that either the power supply itself is not capable of the necessary current, or that the cable between the power supply and the strip has too much resistance (and would be getting warm, too!). So you must have measured the voltage across the power supply terminals as well.
In case it is not obvious, when I say you need something like 2.5 mm2 supply cable paralleling the strip, that is the sort of cable you must have between power supply and strip in the first place.
Grumpy_Mike:
Yes, it looks like it can’t supply enough current. What is it rated for?
That is the specification of the power supply. It says it can provide up to 18A of current which seems efficient. However, other computer components are connected to it, maybe it cannot provide 18A because of those connected components?
Paul__B:
If the colours are indeed mutating along the strip then it is because the voltage is fading as you progress along the strip. You would have to measure between ground and "5 V" at each 50 cm or so along the strip at the "snip" points where they are exposed.But if your voltage is 3.5 V at the start of the strip then you have already lost voltage before getting to the strip, which would indicate that either the power supply itself is not capable of the necessary current, or that the cable between the power supply and the strip has too much resistance (and would be getting warm, too!). So you must have measured the voltage across the power supply terminals as well.
In case it is not obvious, when I say you need something like 2.5 mm2 supply cable paralleling the strip, that is the sort of cable you must have between power supply and strip in the first place.
Thanks for a detailed answer!
I have the 2.5 mm2 cable connected all the way from the power supply terminals to the beginning of the strip (also there is a 1000uF capacitor between the positive and negative). However, the GND to ARDUINO is connected with a simple jumper wire, because I obviously can't plug a 2.5 mm2 cable into the arduino.
It says it can provide up to 18A of current which seems efficient
Is it a PC power supply? Because those are sometimes a bit funny, they only regulate on one of the rails. So yes I would be suspicious of that.
Grumpy_Mike:
Is it a PC power supply? Because those are sometimes a bit funny, they only regulate on one of the rails. So yes I would be suspicious of that.
Is it a PC power supply? Because those are sometimes a bit funny, they only regulate on one of the rails. So yes I would be suspicious of that.
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Yes, it is a PC power supply. Is there a power supply I could use for this project, besides the power supply that uses terminals for connecting everything?
Is there a power supply I could use for this project, besides the power supply that uses terminals for connecting everything?
I would have thought screw terminals are ideal for this sort of project. There is little danger in using them. All power supplies of this sort of specifications have short circuit protection on them.
So are you now confirming that the 3.5 V is at the start of the strip (and at the power supply itself)?
Exactly how do you have the heavier cable connected to the PC power supply? A PC power supply has multiple connections to the 5 V (red and black wires) so you would check the voltage across one of the other pairs of 5 V wires to know how secure your connections are.
Note again my comments in #22 about the data connection and its ground connection running as a pair, direct to the start of the strip and preferably powering the Arduino from that same point.
Thank you HKJ-lygte for your Help,
I had the same problem that was solved by connecting the GND of my LEDs to the Arduino GND. Indeed they have separate power supplies but the Arduino need to be connected to the ground for its signal to be transmitted.
Thanks for your help.
