Need help powering 10M of led strips.

Other Hardware LEDs and Multiplexing
1

Hey everyone,

I have 2 ws2812b led strip with 300 LEDs on each. The current draw is approx. 18A on each strip. I have a 5V 40A power supply that I would like to use to power both of the strips. I know that I have to inject power to the second strip, I just don't know the best way to do it.

The power supply has three outputs. The first output is going to the first strip and has a 1000uf capacitor attached to it. To inject power to the second strip, would I use the second output from the power supply? Also, do I use another capacitor?

Lastly, I would like to run the strips as 1 long strip and control it using the ESP8266 board, would I be able to power that from the power supply as well? Are there any precautions I should take?

ESP8266

Wire for power injection

LED Strip (have 2 of these)

Power Supply

2

Not only do you need to power the second strip, you would also need to power that first strip on multiple points. With 18A the voltage on the other side will be nowhere near 5V...

For best result, run a 2,5mm2 (or 1,5mm2 but that's a bit borderline) wire parallel with the strip. Connect every meter. Connect BOTH ENDS of that cable to the power supply. Do the same for the second. Don't forget to add a 470Ω ohm resistor at the start of both strips.

How you connect that to the supply, what about just connecting both cables? If you have two sets of connections on that supply, fine, use those. I think they will just be in parallel (but NO guarantee without details!)

And with 18A per strip, that piss pore 1000uF is completely useless...

Also note, with high currents like that fusing IS an issue. Even when you use 2,5mm2 the wire is the weakest point. Aka, if you make a short circuit things will get very very hot very very quick. Even without stressing that supply to much.

3

OK, so you wrote it for me.

The other point, is the "chain" connection for data from the end of the first strip to the start of the second. You need to connect the data out of the first to the data in of the second, and you also need to connect the ground (negative) adjacent to the data out of the first to ground adjacent to the data in of the second in order to protect the integrity of the data. The data and ground lines must be together as a pair.

Now if it happens to be convenient to drive data to the strips separately, then this may not be necessary as such but it also applies that the data input connection to each strip must be run together with the ground connection from the Arduino to that strip adjacent to the data input connection. You must then be careful that significant current is not carried on that ground connection or if it could be, that the ground connection at least is adequately specified for the current as septillion explains and in any case, none of the current powering the LED strips must pass through the Arduino PCB itself.

If there is a significant distance (what? More than 10 or 15 cm perhaps) between the source of the data, whether the Arduino or a Data Out terminal of a strip, and the Data In of another strip then not only must an adequately rated ground wire travel with the data connection, but you must provide the 470 Ohm resistor at the Data In terminal of the strip.

4

septillion:
Not only do you need to power the second strip, you would also need to power that first strip on multiple points. With 18A the voltage on the other side will be nowhere near 5V...

Sorry, I should have stated at that if all 600 LEDS are one at max brightness (white) the current pull in total should be 36A. (600LEDs *60mA/perbulb@max) I doubt I will ever be leaving it on in that state but I'd like to have the peace of mind knowinng if it is on that it'll be safe.

septillion:
For best result, run a 2,5mm2 (or 1,5mm2 but that's a bit borderline) wire parallel with the strip. Connect every meter. Connect BOTH ENDS of that cable to the power supply. Do the same for the second. Don't forget to add a 470Ω ohm resistor at the start of both strips.

I'm using 2.5 mm2 wire. My original plan was to inject it at the end of the second strip, so at 10m. So you're saying that's useless? I thought the 470 ohm resistor was only from the data pin out form the ESP to the data in on the strip?

septillion:
How you connect that to the supply, what about just connecting both cables? If you have two sets of connections on that supply, fine, use those. I think they will just be in parallel (but NO guarantee without details!)

Any downsides to wiring them in parallel?

septillion:
And with 18A per strip, that piss pore 1000uF is completely useless...

Also note, with high currents like that fusing IS an issue. Even when you use 2,5mm2 the wire is the weakest point. Aka, if you make a short circuit things will get very very hot very very quick. Even without stressing that supply to much.

Would you suggest me to use a larger one? It's really only there as a protection from the power supply peaking when powered on.

5

Paul__B:
OK, so you wrote it for me.

The other point, is the "chain" connection for data from the end of the first strip to the start of the second. You need to connect the data out of the first to the data in of the second, and you also need to connect the ground (negative) adjacent to the data out of the first to ground adjacent to the data in of the second in order to protect the integrity of the data. The data and ground lines must be together as a pair.

Now if it happens to be convenient to drive data to the strips separately, then this may not be necessary as such but it also applies that the data input connection to each strip must be run together with the ground connection from the Arduino to that strip adjacent to the data input connection. You must then be careful that significant current is not carried on that ground connection or if it could be, that the ground connection at least is adequately specified for the current as septillion explains and in any case, none of the current powering the LED strips must pass through the Arduino PCB itself.

If there is a significant distance (what? More than 10 or 15 cm perhaps) between the source of the data, whether the Arduino or a Data Out terminal of a strip, and the Data In of another strip then not only must an adequately rated ground wire travel with the data connection, but you must provide the 470 Ohm resistor at the Data In terminal of the strip.

Understood, I do plan on chaining the data pins together as you mentioned and sharing the ground. How can I power the ESP and ensure that the current form the strips never pass through it?

6

My ultimate goal is to have one long 10m strip that I can control through Home Assistant. The strip will be placed along the roof inside an aluminium channel with a diffuser on top. The goal is to fit all the wiring inside the channel and have the power supply and esp inside a box at the end of the wall with only one wire leaving the box, to be plugged into the wall.

7

malam04:
Sorry, I should have stated at that if all 600 LEDS are one at max brightness (white) the current pull in total should be 36A. (600LEDs *60mA/perbulb@max) I doubt I will ever be leaving it on in that state but I'd like to have the peace of mind knowinng if it is on that it'll be safe.

I'm using 2.5 mm2 wire. My original plan was to inject it at the end of the second strip, so at 10m. So you're saying that's useless?

I understood. But that is 18A per strip. Even when connected at both ends that's still flowing 9A into the tiny tracks of the strip which will result in significant voltage drops. And also, although it's save (aka, the heat isn't going to melt the cable) to use 2,5 mm2. It probably has a significant voltage drop. You have to remember you're only starting with just 5V. 0,5V already is 10% :wink: And that will probably reduce brightness by around 1/6th.

malam04:
I thought the 470 ohm resistor was only from the data pin out form the ESP to the data in on the strip?

It's used to protect the data pin in case there are voltage differences between the data line and the Vcc of the led receiving it. So it's useful everywhere you might have voltage differences. And between the two strips there is a bigger change.

Also, not really sure but just checking, doesn't the strip need 5V data? Which a 3V3 ESP cannot do (without a level converter).

malam04:
Any downsides to wiring them in parallel?

You don't have a choice.... You have a single 5V supply to feed multiple 5V devices. So yeah, parallel it is. But for the current I think I would have used two 20A supplies.

malam04:
Would you suggest me to use a larger one? It's really only there as a protection from the power supply peaking when powered on.

Should be fine without... The supply will just have a (low ESR) cap at the output.

malam04:
Understood, I do plan on chaining the data pins together as you mentioned and sharing the ground. How can I power the ESP and ensure that the current form the strips never pass through it?

Use thick cables. Note that connecting both ends of the cable running parallel to the strip effectively doubles the wire thickness. And I would go for a star ground aka only connect the GND of the two strips and the ESP at the supply. The resistor in line with the data line should protect the dataIn of the first led.

8

septillion:
Also, not really sure but just checking, doesn't the strip need 5V data? Which a 3V3 ESP cannot do (without a level converter).

Well, it can and does, but may not be reliable. A 74HC14 hex inverter, with two gates in series (or actually, one gate driving the other five gates in parallel) should do the job as level converter, though a 74HCT14 would be perfect. The level converter is also the "line driver" located at the ESP, the resistor at the other end at the LED strip itself.

septillion:
And I would go for a star ground AKA only connect the GND of the two strips and the ESP at the supply. The resistor in line with the data line should protect the data In of the first led.

It is never a good idea to run the data and reference (i.e., ground) lines separately - or indeed, any two power lines separately. Because the data line must run together from the ESP to the first LED string, the logical way to ensure the LED string power is not running along these lines, is to take the power feed for the ESP back from the junction with the first LED strip where the (first?) 1 mF capacitor is, along with the data wire - three wires together. The NodeMCU is isolated from fluctuations on the LED power terminals by its 3.3 V regulator.

9

Yeah, true. Star point at the GND of the first strip is even better. But that still leaves the second strip...

10

It appears the two strips are chained, so the second strip will be attached directly to the first, all three connections joined and a pair from the power supply also feeding that point (as well as all the other intermediate points).

11

If you want to link the power from the first strip to the second as well (aka make it one big strip) the 2,5mm2 isn't enough...

If you link GND from the first strip and from the supply you made a loop and defeated the star.

Or do I miss something?

12

septillion:
If you want to link the power from the first strip to the second as well (aka make it one big strip) the 2,5mm2 isn't enough.

If you link GND from the first strip and from the supply you made a loop and defeated the star.

There are two reasons for "star" bussing in this situation. One is to provide power to the strips uniformly and with minimum loss, the other is to prevent "ground loops" which is the situation where the current drawn by one part causes significant voltage differences between the ground used as a reference for signal at various parts of the assembly.

If cables are adequately specified, neither of these will be a concern in this case. It does not matter much whether you run a heavier cable alongside the strip and "tap" it across to the strip at regular intervals such as every one metre, or provide separate runs from the power supply to multiple points. The first of these will require a heavier cable, but the cable length will be much shorter in total and be neater in layout than the multiple cables of the second. As long as the first strip connects close to the second, and the ground but preferably both supply lines are connected between first and second by a reasonably heavy cable, this will prevent such a ground loop problem

13

Paul__B:
As long as the first strip connects close to the second, and the ground but preferably both supply lines are connected between first and second by a reasonably heavy cable, this will prevent such a ground loop problem

But that would require a thicker cable to handle the current of both strips... 2,5mm2 So yeah, neat but more unpractical...

(Or I'm I still missing something :p)

14

2 lengths of 10m of 2.5mm^2 wire has a total resistance of about 0.14 ohms, will drop 2.4V at 18A - don't think
its adequate if you are going to full brightness.

Though to be fair full brightless is probably way too bright(!)