hi all, i have a cool art project to illuminate a load of big bottles hanging from the ceiling at a beach bar. i would like to illuminate them with (constant voltage) cob led strip inside the bottles and control them using a multichannel LED controller.

my problem is that the control circuitry almost certainly cannot be located remotely near the leds.

see attached image of (part of) the space..



there are 80 5litre bottles hanging up. i probably cannot illuminate them all (budget limitations) but id like to do as many as possible.

the client is quite clear he does not want to see "electronics"

i can feed cables to each bottle between/above the bamboo roof (there is a plastic sheeting above it for the rain)

the cables could be routed along the bamboo to the the black structure on the left and along that to a space for a control box.

going across/above the bamboo rather than along it with cabling is hard because i have to do everything from below.

i have a choice of either a 30 channel driver, or individual small drivers with 3 channels (designed for rgb originally) all controlled from a programmable controller. i could hypothetically mount the 3 channel drivers (they are only 30mm x 40mm) on the cieling and wire the 3 nearest bottles to a driver.

however this would be almost impossible to do without a real spiderweb of cabling from one driver to another, and the power cabling would need to be quite chunky (60 leds, 200 Ma each.. 12 amps at 24v.) the client will probably not accept this and it would take ages to plan and build nicely.

if possible id prefer to route a single slim twin core cable from each lamp, along the bamboo to the bar wall and mount the drivers there. either spaced along the bar wall in small boxes, or in a central box at the end of the bar. simpler and cleaner.

the problem is EMI. If i mount the controllers in a single location some of the cables could be 10 - 20m long. voltage drop wont be an issue i dont think, at 24v and 200ma, and 20m cable, awg17 gives a drop of only 0.15v

so my question is (finally) is there a way to mitigate emi from a cable with 24v 200ma pwm flowing through it?

for reference the 3 channel drivers have a pwm frequency of 10khz.. the 30 channel driver is 1.5khz. i can choose whichever is less likely to cause issues.

its a beach bar. there is a soundsystem in close proximity and the client/owner is a music lover who has famous dj's coming to play. if i make his speakers hum (or worse) il be in real trouble.

at a minimum the cable will be twisted ( ive found some nice cable that looks like twisted 2 core jute string so will blend in nicely)

but id also consider shielded cable, and/or some kind of snubber/rc network thingy (you can tell im an expert) or anything else that wont add much to cost and will allow this to work.

any advice most appreciated.

 

I would be a little nervous sitting underneath!
Bottle drops! , bamboo snaps!

 

I would be a little nervous sitting underneath!
Bottle drops! , bamboo snaps!

its actually more solid than it looks. the bamboo is quite thick as is the rope around the bottles. they are attached to the bamboo with fairly solid galvanised wire.

having said that its not my bar and i didnt hang the bottles up or have the idea of putting them there. ive just been asked to light them. so. in short, not my problem

 

I suggest series strings of an individual LED or two in each bottle. even or 8 LEDs in each string will allow a 24 volt feed with a small value resistor to limit the maximum current. then a 200HZ PWM driver will allow low voltage wiring rules to apply. With a maximum LED current of 100mA in each string 80 bottles would draw less than an amp.

 

I suggest series strings of an individual LED or two in each bottle. even or 8 LEDs in each string will allow a 24 volt feed with a small value resistor to limit the maximum current. then a 200HZ PWM driver will allow low voltage wiring rules to apply. With a maximum LED current of 100mA in each string 80 bottles would draw less than an amp.

i possibly dont understand your reply, but i think you are suggesting to have groups of bottles on a single driver with small leds?

the idea is to have the bottle/lamps individually addressable so i can do animated effects across the ceiling (waves/ripples of light, individual bottles flashing/turning off etc) i also need them to be bright enough to illuminate the space, some of them are quite dark glass. so im looking at at least 1 watt per bottle, ideally more (2-5 watts) so i can do some punchy effects when needed.

less than an amp at 24v means less than 24 watts of led lighting spread over 80 light sources, in an outdoor space 15m long and 6 m wide. it wouldnt be very noticeable.

edit: also 200hz pwm would play havoc with smartphone cameras and also possible be low enough to be visible when the lights were dim (most of the time) ive been advised to keep things above 1khz to avoid unpleasant side effects. plus the drivers i need (compatible with the controllers on the market and the associated software) dont exist with such low pwm frequencies. the newer ones are higher.. oldest ones about 400 hz, but also only 8 bit brightness and known for not providing a very pleasant effect. the dirvers i mentioned are either 1.5khz 12 bit (the 30 channel one) or 10khz 16 bit (the 3 channel ones)

 

I would try one strand of twisted wire and bring it close to the sound system to see if there's any interference.
If you get noise, than you may have to go to shielded twisted pair or small coax cable.

The 10kHz unit would seem less likely to cause interference, but no guarantee.

 

I would try one strand of twisted wire and bring it close to the sound system to see if there's any interference.
If you get noise, than you may have to go to shielded twisted pair or small coax cable.

The 10kHz unit would seem less likely to cause interference, but no guarantee.

i also wonder if there may be risk to the driver, ive read (but barely understood) some stuff talking about self induction, ringing, capacitance etc in longer cable lengths. id love to avoid having to purchase a single driver to test, they are cheap ($10 for the 3 channel one) but they are from a us supplier and shipping them to italy costs 2x the price of the product, plus it takes ages. however i am beginning to suspect its critical to test not just the led effect etc, but the whole thing including realistic cable lengths.

these are the two drivers im considering:

the 3 channel one (needs a seperate controller)

https://www.nledshop.com/downloads/datasheets/nled-ws2816fet-datasheet.pdf

the 30 channel one (in built controller and pattern storage)

https://www.nledshop.com/downloads/datasheets/nled-30chn-v1a-datasheet.pdf

 

An LC-Filter on the Output of each Channel will completely eliminate any broadcasted Noise,
and depending on how much Time and Money You were possibly contemplating spending on the Wiring,
it could end-up being cheaper and easier in the long run.

18-gauge "Zip-Cord" is cheap and easy.

I missed the Frequency You will be using in all the words.
.
.
.

 

An LC-Filter on the Output of each Channel will completely eliminate any broadcasted Noise,
and depending on how much Time and Money You were possibly contemplating spending on the Wiring,
it could end-up being cheaper and easier in the long run.

18-gauge "Zip-Cord" is cheap and easy.

I missed the Frequency You will be using in all the words.
.
.
.

sorry i have a habit of being wordy.

short version

10 Khz 16 bit pwm 24v circa 200mA

or

1.5Khz 12 bit pwm 24v circa 200mA

LC filter could be the answer but it must not interfere with reasonably rapid modulation of led brightness, it is for animated effects on leds.

driver datasheets in my last post.

 

maybe relevant re. driver selection. i read a quite technical page that covered pwm frequency and bit depth here:

https://codeinsecurity.wordpress.com/2023/07/17/the-problem-with-driving-leds-with-pwm/

and half understood some of it.

the part that jumped out at me was this:


"For 8-bit PWM at 1kHz, the minimum pulse time is 3.91μs. For 12-bit PWM at 1kHz, the minimum pulse time is 244ns. That’s quite a short time period – the equivalent pulse frequency jumped from 256kHz to 4.1MHz. At 16-bit you’ve got a pulse period of just 15.26ns, corresponding to 65.54MHz – a heck of a lot more than the 1kHz PWM rate.

A major challenge with higher bit depths is the rise and fall times (tr/tf) of the driver, especially on LEDs that pull more than a few milliamps. Consider the 12-bit 1kHz case mentioned above – a minimum pulse time of 244ns means that, in order to meet a timing accuracy of 20%, the rise and fall times of the driver cannot exceed 24ns. For a 3V / 50mA LED that’s a voltage slew rate of 245V/μs and a current slew rate of 4.1A/μs. This quickly enters the realm of having to carefully consider MOSFET gate charge, gate driver performance, and power delivery network impedance."

(emphasis mine)

this paragraph makes me think the higher frequency/bit depth driver might have more issues with long cable runs. no idea if my interpretation is valid.

 

The L and C values can be quite small.
All You have to accomplish is to "take-off-the-sharp-edges".
This won't affect any visual-effects.

With Filters on the Outputs,
Higher-Frequencies equate to smaller value Filter-Components.

Not complaining about words, although a Schematic would have been a bonus,
most folks provide the bare-minimum, or less,
and have to have the required-details pried out of them with a crowbar.
.
.
.

 

The L and C values can be quite small.
All You have to accomplish is to "take-off-the-sharp-edges".
This won't affect any visual-effects.

With Filters on the Outputs,
Higher-Frequencies equate to smaller value Filter-Components.

Not complaining about words, although a Schematic would have been a bonus,
most folks provide the bare-minimum, or less,
and have to have the required-details pried out of them with a crowbar.
.
.
.

unfortunately i dont have a schematic, i have an idea of an effect i wish to achieve, and researching has lead me to believe there may be issues, hence asking the lovely people here if what i am proposing (led separated from pwm driver by long cable) is doable or not. i have attempted to provide as much information as possible. thanks for the suggestions

 

What is wrong with letting " 200hz pwm would play havoc with smartphone cameras"??
Yes, I see that I did not understand that the intent was actual useful illumination. That does make a big difference. But if the LEDs were 100 milliamp devices THAT would be a lot more light.
I think my math lost something someplace. That would be over 300 milliwatts in each bottle. (100mA x 3.2 volts x 8 LEDs in each string.)

 

hi all, i have a cool art project to illuminate a load of big bottles hanging from the ceiling at a beach bar. i would like to illuminate them with (constant voltage) cob led strip inside the bottles and control them using a multichannel LED controller.

my problem is that the control circuitry almost certainly cannot be located remotely near the leds.

see attached image of (part of) the space..

View attachment 350110

there are 80 5litre bottles hanging up. i probably cannot illuminate them all (budget limitations) but id like to do as many as possible.

the client is quite clear he does not want to see "electronics"

i can feed cables to each bottle between/above the bamboo roof (there is a plastic sheeting above it for the rain)

the cables could be routed along the bamboo to the the black structure on the left and along that to a space for a control box.

going across/above the bamboo rather than along it with cabling is hard because i have to do everything from below.

i have a choice of either a 30 channel driver, or individual small drivers with 3 channels (designed for rgb originally) all controlled from a programmable controller. i could hypothetically mount the 3 channel drivers (they are only 30mm x 40mm) on the cieling and wire the 3 nearest bottles to a driver.

however this would be almost impossible to do without a real spiderweb of cabling from one driver to another, and the power cabling would need to be quite chunky (60 leds, 200 Ma each.. 12 amps at 24v.) the client will probably not accept this and it would take ages to plan and build nicely.

if possible id prefer to route a single slim twin core cable from each lamp, along the bamboo to the bar wall and mount the drivers there. either spaced along the bar wall in small boxes, or in a central box at the end of the bar. simpler and cleaner.

the problem is EMI. If i mount the controllers in a single location some of the cables could be 10 - 20m long. voltage drop wont be an issue i dont think, at 24v and 200ma, and 20m cable, awg17 gives a drop of only 0.15v

so my question is (finally) is there a way to mitigate emi from a cable with 24v 200ma pwm flowing through it?

for reference the 3 channel drivers have a pwm frequency of 10khz.. the 30 channel driver is 1.5khz. i can choose whichever is less likely to cause issues.

its a beach bar. there is a soundsystem in close proximity and the client/owner is a music lover who has famous dj's coming to play. if i make his speakers hum (or worse) il be in real trouble.

at a minimum the cable will be twisted ( ive found some nice cable that looks like twisted 2 core jute string so will blend in nicely)

but id also consider shielded cable, and/or some kind of snubber/rc network thingy (you can tell im an expert) or anything else that wont add much to cost and will allow this to work.

any advice most appreciated.

Interesting problem.

My thoughts

1. White or warm LED's are fine, the glass provides the color.
2. insert some standard LED assembly into the bottles.
3. Terminate the LED connection with a watertight seal (epoxy) and let each bottle be connectable, like it was a light bulb.
4. Install a wired setup allowing each "bulb" to be connected.
5. Make it variable intensity but nothing more, it'll look superb.

 

Interesting problem.

My thoughts

1. White or warm LED's are fine, the glass provides the color.
2. insert some standard LED assembly into the bottles.
3. Terminate the LED connection with a watertight seal (epoxy) and let each bottle be connectable, like it was a light bulb.
4. Install a wired setup allowing each "bulb" to be connected.
5. Make it variable intensity but nothing more, it'll look superb.

yes that's my plan, i'm going to design something "collapsible" that will fit through the neck of the bottle and open up inside to mimic the structure of an old filament lamp.

however i do wish for the lamps to be individually addressable, hence the original question.

 

Individual addressability for each assembly adds a whole lot to the complexity. It will require address decoding of each bottle assembly, or address decoding externally and a separate feed to each bottle assembly. And each address would need to include the dimmer portion. So suddenly it is a quite different project.
OR, it would require an 80 output controller and separate wiring to each bottle, which is more likely to be possible.

 

I am not worried about the addressability part I have experience controlling pixel arrays, and it's not a "whole different project" it IS the project, from the beginning. my only concern is the practicality of with the long cable runs between the (already specified) pwm drivers and the LEDs.

 

https://www.amazon.com/DOITOOL-Acce...=1748524980&sprefix=led+filam,aps,677&sr=8-28

 

https://www.amazon.com/dp/B0CX53V81...0?ie=UTF8&psc=1&pd_rd_plhdr=t&aref=wZgTK2jqrN

 

https://www.amazon.com/dp/B0CX53V81...0?ie=UTF8&psc=1&pd_rd_plhdr=t&aref=wZgTK2jqrN

yes those type of things are what i have in mind, or possibly some of this:

https://www.diffusioneshop.com/en/lampo-reel-cob-5mm-5mt-10wmt-24v

although it is single sided so the filaments are probably better.

i have ordered some of both already for testing. its all about if i can get enough light out of the short length i can put in the bottle sensibly.