Driving multiple white LEDs

[Electronics4you]

Hi there,

I want to control multiple white LEDs individually and the LEDs are separated several feets. They are to be used for lightning. I have some requirements:

• Limit the number of components for each LED
• Limit the number of signals between each LED
• Bus connection (ethernet, I2C, SPI) to enable the addition of new LED when needed
• LEDs may require 3W @ 12V
• Preferably components without programming for each LED circuit

I need some suggestions on what to use for this project, and my initial setup is something like this:

• Daisy chained LED/PWM drivers with SPI
• MOSFET from LED/PWM driver to handle high current to LED

I don't know if simple drivers exist for daisy chaining in this way, but suggestions are welcome

Thanks in advance

 

[Diver300]

There are multicolour LED lights that would work. You would just have to programme each colour to be the same brightness.

https://www.wholesaleledlights.co.u...x-5mm-7-2-watts-per-metre-165-510-lumens.html

 

[Electronics4you]

Diver300 : That I know, but I need to drive LEDs, which I already have, so the solution is not suitable for me

 

[AnalogKid]

What do you mean by "control"? Just changing the brightness individually? It sounds like a 6-wire bus, 4 wires for I2C, 1 wire for +12 V, and one wire for PWM. But only one PWM signal for the bus would mean all LEDs are at the same brightness. And, if you are sending I2C you will need a microcontroller (and programming) at each LED, so you would not have to send PWM. Can you clarify your question?

ak

 

[Dr_Doggy]

off the top of the hat:

1) an individual matrix for all leds, or "led Group", could use alot of wire, may need code
2)individual driver for each LED(or 2), as example shown above, will need separate code too for each chip address
3) I am doing small project that will replace hard wired bus with "IR rx & IR repeaters" eliminating travel wires, but then each LED component needs its own source power, plus IR limits distance between, plus components maybe costly if you have alot of leds, plus needs code, plus i can't verify if it works, as this project is still in the making.

 

[Flyback]

you will need microcontroller, and a signal wire which goes to all the leds and their circuitry. The micro (master) will send each led circuit a coded pulse train (eg 11011011) and which ever receiver has this address turns on , or off the respective led.
To drive the led (is it only one at each place) from 12v, and 3w , you will need to use a buck converter led driver...there are many off the shelf, eg diodes.com zxld1360, or the linear.com LTM family LTM8040
https://www.linear.com/product/LTM8040

THE ltm8040 is good as it has digital inputs which you can use to switch on or off the leds, and the switchgn stage is integrated in the chip, so you don't need to design anything...except you need to make the pcb...so you could use the eagle pcb software as it is the easiest to use.

 

[Electronics4you]

Sorry for the new years delay...

Using a daisy chain solution requires no additional microcontroller and the circuits can be created without programming of each single unit. However, there doesn't seem to exist a single LED IC to control e.g. brightness and also use daisy chaining. It may be a little overkill to use a multi-LED chip for this purpose.

I only need to control the brightness of the LEDs with as few wires as possible and the distance between them is around 3-5 feet.

Doesn't off-the-shelf solutions/IC's exist for this (I guess often used) kind of design?

 

[Dr_Doggy]

a pwm circuit will control brightness, a matrix will control multiple LED's, it would be difficult to combine the two without cpu. Personally I wouldnt even want to do matrix without cpu either.
if you wanted to dim them all the same 1 pwm would work, more pwm wires is more seperate control.
if you want to control each section individually on less wire then matrix works.

as far as i can think of anything else would require encoder & decoder which is the spi, or what i think you are calling daisy chain, and the 4 wire solution, but then you are talking about extra costs in circuits and again cpu's no matter how you choose to encode. thats why your shelf option is only in complete kits.

also if it is expandable we still need to consider power supply, if you are sourcing from main controller that source will have limit, btw how many leds are we starting with, and how many do we plan to expand to? also how/where are we planning to power them?

 

[ronv]

Just to make sure:
You want to be able to dim each LED individually?
Any limit to the number in the chain?
Spec for the LED?
Any ideas on the addressing of the LEDs?

 

[ronv]

Hmm,
There's an interface for this:
https://www.mouser.com/ds/2/75/DIM01-V12-542208.pdf
https://en.wikipedia.org/wiki/Digital_Addressable_Lighting_Interface

 

[KeepItSimpleStupid]

Have you heard about DALI? **broken link removed**

Not saying it's appropriate.

 

[Electronics4you]

• Current number of LEDfs: 10 pieces
• Possible number of LEDs: 20 pieces
• LED specs: 3W @ 12V

I want to be able to control the brightness of each individual LED.
I have no idea about the addressing of the LEDs though

ronv and KeepItSimpleStupid : The DALI interface looks interesting and just the thing I have been looking for. I will read some texts about it first