12V LED Strips in series. - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: January 27, 2021, 03:34:47 pm
content: Correct me if I'm wrong, but if I connect 2 3amp 12V LED strips in series, I could run them on 24V and 3 Amps.The trouble would only come with the control signals. Assuming they are, say, WS2812s with a "DATA" signal of 5V. The first strip would work and the second would get a -7V data signal and not work... or worse.I'm trying to work out if it's feasible to step the data signal up with a mosfet gated on the more negative strip, but switching the upper strips 12V, dropping it to 5V all while maintaining the 1kHz data signal intact.Is it feasible to consider boosting the control voltage to 24V as well (or 10V rather) and dividing it sensibly at the first strip?

author: ledtester
author_rank: Super Contributor
timestamp: January 27, 2021, 04:01:23 pm
content: Please explain why you want to connect the LED strips in series rather than in parallel. That would help to understand your situation.I have a feeling using a DC/DC converter to convert 24V to 12V will work better for you.

author: paulca
author_rank: Super Contributor
timestamp: January 27, 2021, 04:20:12 pm
content: Basically I'm trying to find a way to lower the current on longer runs of RGB/RGBW LED strips, by using higher voltage along the run.An example strip I have is 12V, 5m, 30LED per meter. It realistically pulls 3A, though I think its theoretical is more like 5A. That's fine.But my living room is 4x4m. 16m+ to put cornice lights in. So we are looking at 9-15 Amps and the voltage drop (and heat) that comes with that over thin PCB traces. So it needs to be powered in multiple places along the length due to the high current.If I could find a realistic way to run multiple strips on series voltage, while maintaining and possibly repeating the 5V control signal I could keep it to one, possibly two cable drops around the room and still be able to uses fully addressable RGB LEDs.As the run it so long, it's not desirable to have cables running along the length, but ideally only where the two ends meet.24V double length strips are available, but have much lower resolution.

author: themadhippy
author_rank: Super Contributor
timestamp: January 27, 2021, 04:33:27 pm
content: Id put a power feed at each corner,each feed connected to 2 strips, the control line conected to the first strip and linked end to end ,but not linking the last strip to the first strip

author: Gyro
author_rank: Super Contributor
timestamp: January 27, 2021, 04:42:18 pm
content: Aside from the logic level shifting issue, the other problem is that, if one strip gets turned on without the other, the unlit strip will see something closer to 24V.It sounds like the arrangement is probably too susceptible to errors, given the cost of the strips.

author: Syntax Error
author_rank: Frequent Contributor
timestamp: January 27, 2021, 05:52:09 pm
content: What LED strips are you using? You say RGBW and addressable WS2812. They are not the same. RGBW use 5pins and run on 12V. WS2812s are 4pin and often require 5V. Running either from 24V will risk destroying the strip. Instead you will need 24V rated strips. As @themadhippy says, use extra power feed points to fan out the current, say at 4m poinrs, rather than drive all the current through the first LED on a 16m strip; which might become a fire hazard.Some hints on fan out/zoning here:https://www.instyleled.co.uk/support/how-to-install-led-tape-large-projects/

author: Terry Bites
author_rank: Super Contributor
timestamp: January 27, 2021, 05:54:00 pm
content: opto isolators?

author: madires
author_rank: Super Contributor
timestamp: January 27, 2021, 06:14:32 pm
content: If you want to use a higher power rail voltage you could simply power each strip via a buck converter.

author: gnuarm
author_rank: Super Contributor
timestamp: January 27, 2021, 07:43:06 pm
content: Quote from: Syntax Error on January 27, 2021, 05:52:09 pmYeah, what he said. 12 V strips imply something other than the chips you mention. The reason they use 12 V strips is because they are a convenient voltage for LEDs placed in series inside the strip. If the LEDs are controlled, they have to be controlled for all LEDs in a series string in the strip. So there will be a string of Red, a string of Green and a string of Blue, each controlled separately. It would not be practical to add another strip in series since the currents are controlled independently.To put them in series like you want you would need to use strips of LEDs without a controller and control them from the power head. I don't know if anyone makes them that way.

author: paulca
author_rank: Super Contributor
timestamp: January 29, 2021, 11:03:51 am
content: I am aware of the "fan out" and multiple power drops, that's exactly what I'm trying to avoid as it's costly and frankly annoying. Dropping it in every corner to 4 separate power supplies pretty much doubles or triples the cost. Those 5-10A DC power bricks aren't cheap. Nor is 16-18AWG wire and conduits.I was deliberately not totally specific to the exact type of LED, but I am referring to RGB addressable LEDs. I added RGBW as it's probably good to explore those, given that RGB strips produce a weird weak ethereal kind of "white" light, because the coloured LEDs have such narrow spectrums. I haven't looked into how they work in terms of addressability or if they do work addressably.WS2811 is the separate chip with 3 RGB LEDs in series. 1 pixel = 3 LEDs. They are 12V, at 30LEDpm, around 1Amp per meter theoretical, but in practice more like 0.6Amps per meter.WS2812 is the chip in the LED. 1 pixel = 1 LED. They also come in 30LEDpm, but consume more than twice the amps due to the lower voltage.The 24V strips, as I understand are just 6 LEDs in series.Looking at the resolution of these strips...30LEDpm with a 1:1 ratio, ie WS2812s, is 1/30th of a meter per pixel, about 3.3cm which is fine or even a bit overkill.30LEDpm with a 1:3 ratio, ie WS2811s, is 1/10th of a meter, 10cm, which is sort of okay for effect lighting.30LEDpm with a 1:6 ratio, ie 24V double length strips, is 1/5th meter, 20cm and getting a bit off spec if you want any kind of animated effect lighting.If you go looking for 15-20m LED strips for living room crown lighting, you most often find them to be series LEDs running on mains voltage. Though they are usually single warm white and non-addressable. But the obvious reason they do this is cost and lower current.I'm just trying to work out if there is a way to interconnect multiple strips in series to limit the total current to something sensible. If I have 4x4m strips, each pulling 3Amps, I could run 2 series sets on 24V. Or all 4 on 48VDC?The buck converter solution is interesting, but would that not require running power feed cables the whole length? To do that needs larger, more expensive and uglier aluminium mounting rails, with a back channel for the wires.

author: Syntax Error
author_rank: Frequent Contributor
timestamp: January 29, 2021, 12:22:01 pm
content: Addressable rgb or rgbw LED strips are often ~5V only.Neopixelis the Adafruit Industries brand of the WS2812. Read all about powering addressable neopixel strips:https://learn.adafruit.com/adafruit-neopixel-uberguide/powering-neopixels

author: themadhippy
author_rank: Super Contributor
timestamp: January 29, 2021, 01:23:29 pm
content: Quoteno need for multiple power supplies 1 large enough to run the entire tape run with 4 feeds taken from it,andno need for conduit,its an extra low voltage circuit .As for cable you can pick up 100 meters of 1mm2twin and earth for 30 quid ,if the power supply is in the center of the room your only gonna need 10 ish meters of cable ,only a tenner even from the diy sheds for 25 meters of the stuff

author: paulca
author_rank: Super Contributor
timestamp: January 29, 2021, 01:45:46 pm
content: Quote from: themadhippy on January 29, 2021, 01:23:29 pmAh. I was aiming on just plugging them into plug sockets with DC bricks and running the cables up the corner of the wall. The conduits were more for aesthetics.Unfortunately, due to the style of the house a whole side of the living room ceiling is inaccessible from above. Not just a matter of lifting a few boards to wire. So it would involve cutting holes in the ceiling, fishing wires etc. to mount it all in the ceiling. For something like that I'd get a spark in as they have tricks to make that type of thing easier. It's an option I suppose.I'm beginning to accept series isn't the best option. I'd need to run wires along with the LEDs anyway and I don't think there is a way to use the existing copper traces in series as obviously the strips them selves are parallel.It's just a shame though. The main issue with these strips is that they run on 5V. Meaning that any wattage of light at all starts to place you into high current and high voltage drop scenarios. Even the 12V compromise versions run into issues over 5 meters.If a single strip pulls 3A at 5V and has resistance so that the voltage drop is acceptible... I can't see a reason why you can't run 2 strips at 10V, 4 strips at 20V for the same voltage drop as 1 strip at 5V."Sum'it ought to be done I say!"

author: themadhippy
author_rank: Super Contributor
timestamp: January 29, 2021, 03:26:27 pm
content: QuoteAh ye its making sense,however it aint that difficult,and theirs no hidden tricks,just lift a board as close to the corner as you can get,hope the joists are going right the direction otherwise it really is ball ache time,cut a hole big enough to get your hand (a 3"-4" hole saw is perfect)close to the corner ,push a length of mini trunking lid from the hole to the lifted floor boards,attach the wire to the trunking lid and pull it in,As for repairing the holes in the ceiling

author: paulca
author_rank: Super Contributor
timestamp: January 29, 2021, 03:46:28 pm
content: Totally agree. Was thinking it through, the ceiling is papered in textured wall paper. EDIT: That texture would work awesomely with the lighting. The pain and struggle however are real. It would need stripped and repapered.I suffer engineers depression, I look for every reason not to do something until I forget the reasons I wanted to do it in the first place, so the effort outweighs the benefit and I procrastinate things away.

author: themadhippy
author_rank: Super Contributor
timestamp: January 29, 2021, 04:17:38 pm
content: Quotehow lucky do you feel? a "geko "http://www.super-rod.co.uk/products/coiled-systems/gekko-gripper/may work or small fiberglass rods