i following this layout, have a 24v 600w power supply attached to two 5meter 720led 24volt fcobs, two 5meter 60led 5volt ws2813, and one 5volt esp32
Can the two ws2813 led strips and the esp32 share a buck convertor tuned to 5v in any configuration at all? or must each have their own 5v tuned buck convertor?
what about the injection lines - can they share a 5v buck convertor with the main line or must each injection line have its own buck convertor?
Thanks
also, can the level shifter be shared between led strips or does each strip/pin have to have its own level shifter?
In theory, the 24V->5V converter could be shared as long as it is rated to provide the total current needed for all connections.
In reality, it makes far more sense to put the converter(s) you need right near their injection points on the strip. That way your longer injection lines only have to carry the 24V equivalent current to drive the 5V injection points of the converters. That current is a little more than 1/5th of the current needed at 5V so the voltage drop on the 24V line is 1/5 that of the same line if it was driving only 5V.
The levelshifter must have one channel per GPIO used.
If you connect 3 different strips to 3 GPIOs, you need a levellshifter with at least 3 channels.
Thanks!
Wait, so youâre saying⌠for example if i have one of these:
https://www.amazon.com/gp/product/B0BLSGDVHF/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&th=1
The amperage going from the power supply into the converter is âlittle more than1/5thâ the amperage going out of the converter to the strip. as an example, if the strip required 5v 15 amps that means it would draw roughly 3 amps from the power supply going in the convertor, and 15 amps going out of the convertor to the strip?
The way a buck converter (BC) works is to supply a maximum low voltage output power by taking the same amount of high voltage input power plus a little bit for efficiency losses.
Note I said power in both cases, which for these DC circuits is simply Volts x Amps. So if your LEDs need 8A of maximum power from a 5V injection point, your BC will need to be able to handle 5V x 8A = 40W of power. It will supply that by drawing 40W/24V=1.67A from the 24V bus (actually more like 1.9A due to conversion losses).
If you have more than one BC you have to add up their usages to get a total current for the 24V bus, but it will be much less than the totals for the 5V injections. Just remember, the total power out is the same as the total power in less the losses.
This has a big implication for voltage drop problems for at least 3 reasons:
-The voltage drops on the 24V are smaller because the total current needed is smaller.
-The 5V injection points can typically be very close to the actual strip, so thereâs little 5V drop at all.
Now lastly, one (potentially) bit of bad news:
The converters you posted are well recognized as probably the worst choice you can make for those type of devices. They have poor regulation and do not provide reliable power at all.
Pick something else (please).
Thanks for the heads up. I will test the convertors to see if its a YMMV issue and return it if it doesnt work.
If you havenât bough too many of these, Iâd just return it (or bite the bullet and put it in the trash).
This has proven itself to be a clear case of âvote with your feetâ.
Donât fight with a bad design, throw it out - life is too short 
if I use a convertor near an injection point, is a fuse required between the convertor and the led strip injection point, since it has been converted to a different volt/amp at the output?
can i mix convertor amperage on the same <5m 5v strip ? example: the start point on the led strip has a convertor that supplying 5v 7a and the injection point at the end has a different convertor that is maxed out at 3a?
As far as fusing, I keep my actual 5V injection points very short (usually < 5cm) and only fuse the input (HV side). By the time you overload the BC it either self-regulates itself down to 0V output or simply becomes a âfuseâ (and you replace it).
Mixing and matching can work as required, although I tend to try and come up with a maximum distance the strip will handle without injection and then try to evenly space BC throughout as required.
One thing to keep in mind when using BC for injection points (and really just in general), youâll get better results if you disperse your injection points evenly throughout the strip. Most people focus on the start and end of the strip, when in reality youâre better off starting in the middle of the strip. From one âmiddleâ injection point, your power line can service the same # of LEDs to the âleftâ and ârightâ. If one line is not enough, you go to 2 points at the 1/4 and 3/4 spots.
Using that general idea, youâll get more even power distribution and better colour results overall. Youâll probably be able to stick to a single type of BC as well. Note thereâs no real disadvantage to using a 8A converter even when you only need 4A (other than cost).
Thanks!
One question - â40W/24V=1.67A from the 24V bus (actually more like 1.9A due to conversion losses)â. How did you get 1.9a? What is the formula to calculate conversion loss?
Itâs very precise - you make a good guess based on the mfg specs and experience with the devices (I think the guess I quoted was 15%(?) ).
Seriously, a very good converter under exactly the right conditions might have an efficiency of 95%.
More likely, youâll see 85%-90%, so budget more for your power supply. Just remember those maximums are for the case where you run your display at full White & 100% brightness.
If I plan to never exceed 50% brightness on all my 720/m fcob, ws2813 and ws2812b strips. is it okay to use fuses for amperages rated at 50% brightness?
Or should I install fuses for 100% brightness? If I install fuses for only 50% brightness, could a scenario arise where WLED accidentially (through a bug or user error) signals 100% brightness and blow all my fuses?
Realistically, fuses are to protect your wires from dead shorts and such mishaps causing your wires to draw more power than theyâre rated for.
A fuse isnât going to protect electronics or save your power supply from an overload, theyâre typically much too slow for modern electronics.
Iâd fuse for 110% brightness (allowing for surges).
Manage the brightness you need for your effects/displays/preferences in your software (presets, etc.)
If you plan to never exceed 50% brightness, then setup the software so that happens.
The hardware and supplies should be designed so they can operate even if the software ends up going wrong.
