3.3V PWM signal from WS2811 to control other LED driver

Other Hardware Hardware Development
1

Hi,

I have 8 AEG Evyn LED RGB ceiling lights and they come with a RGB led strip around the light.

Schermafbeelding 2023-11-19 112011
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These lamps come with a proprietary 2.4GH RF controller with a matching remote control.
This controller is a little PCB that is mounted in the 24V LED driver.

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Of course I wanted to get rid of this as soon as possible :wink:

This controller is powered by 12V and sends out 5 times a 3.3V PWM signal to drive CC, CW, R, G and B to the 24V LED driver. I have tested and played with this and in the meantime successfully connected a IKEA Tradfri Zigbee controller, with it's 3.3V PWM signal to the CC CW channels.
It's hanging on my ceiling now and I'm controlling this with Zigbee2MQTT.

Now in my office I want to hang up 8 of these lamps and my idea was to control the RGB LED strip in them with 8 WS2411 modules. Most importantly so I can use WLED with all it's awesome effects but also because it's a one-wired signal.
The reason that I chose the WS2411 is because it says it uses PWM to drive the 3 RGB channels.

I bought a few WS2811 breakout boards:

WS2811-LED-Driver Pinout
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I have done some testing for myself (still in the learning curve of electronics) and hooked up 4 of these WS2811 breakout boards including some standard RGB LEDs to my ESP32 WROOM and everything is working great.

What I have figured out (and should have know before of course) are a few things:

  1. The voltage that the separate channels get is between 2V and 3V (2.7V to be exact for the Green LED at full power), because a LED on average needs around 2.5V. This is of course is not enough voltage for a 3.3V PWM signal.

  2. For this WS2811 module you need to buy RGB LEDs with a common anode. That means that the shared pin on the RGB led gets a positive voltage (5V in this case) and the 3 other RGB pins get a PWM signal that is pulled to/connected GND (ground).
    A standard clean 3.3V PWM signal most often has the positive PWM channel from 0 to 3.3V.
    In this case the 24V controller on the AEG Evyn light also need a positive PWM signal for the R, G and B channels.

My question now is of course how to get this to work?

  • I probably at least need a level shifter to shift the outgoing 2-3v to 3.3V. Also I probably need to add a resistor between the output of the WS2811 and the level shifter, because the output is around 18mA at full brightness, and that maybe is too much current for the level shifter.

  • I need to somehow reverse the voltage of the (negative) PWM signal, so the output to the 24V LED controller is between a (positive) 0 to 3.3V.

Or... Could there be a better way? Maybe by using a Optocoupler with some resistor (what value) between it and a fairly simple circuit behind it with some transistor?

Or... should I ditch the whole idea with the WS2811 and connect these 8 lights to my ESP32 WROOM somehow in a different way (direct PWM from ESP32?)?

Most importantly is that I definitely want to use WLED for these 8 RGB lights. I also like to use a one-wire signal to the light. And lastly it would be great that I can mostly use ready made modules, because that's more easy then to make 8 custom made circuits between the WS2811 and the 24V LED driver (however that will positive for my learning curve)

[It's awesome that you read this far :slightly_smiling_face:]

2

Can't you just connect the WS2811 directly up to the 24V controller?

A level shifter shouldn't be necessary, at least from my evaluation of your post.

3

I'm fiddling around with the WS2811 at the moment (for controlling small motor, EL strips, etc.). I'm feeding 5V from the Arduino, and measure the output PWM as 5V. For each channel, when the color value the PWM signal is constant 0, and at 255 it shows less than 100% PWM signal (it isn't constantly on). A multimeter wouldn't show any of this correctly.
ESP32 output is 3.3V, so that difference explains your measurements.

For the reverse polarity of the signal, it might be that a PNP BJT transistor on each channel would do the trick, except that you lose the current limiting protection. I'm also a noob, so I'm trying this out now.

4

Hi,

Thank you so much for your reply! :slightly_smiling_face:

I can say that I got my idea working for a regular light strip with a Logic level converter and a Mean Well LDB-350LW series.

The only problem is that you can clearly hear a high pitched sound coming from the Mean Well LDB-350LW. My guess this has something to do with the relatively low PWM signal (or refresh rate) of the WS2811 (800 KHz). I tried setting the operation frequency to low, connecting pin 7 to VDD, so it should be 400 Khz, but I still hear the high pitched sound.
Of course I don't want this high pitched sound.

What could be a solution?
Maybe I could use a capacitor? Although then the PWM signal would be totally ruiend, the voltage of course will change, but still maybe the Mean Well LDB-350LW series or some other controller will do something with the "voltage information"?

5

The LDB is a constant current LED driver but so is the WS2811.
The WS2811 needs a constant voltage NOT a constant current. That is your problem.
Exactly how do you have all the devices connected?

6

Hi,

Thank you for your reply!~ :slightly_smiling_face:

I think you are right. My plan to use the WS2811 chip to not directly drive single LED's, but to drive bigger LED's, that need more voltage and power.
So I'm trying to use the output from the WS2811 to driver other electronics, like for example other LED drivers

7

OK, so what is the problem?

8

I have everything working. It's nice that my idea apparently is working so far.
The only issue now is that I can clearly hear a high pitched sound coming from the Mean Well LDB-350LW in this case, as you can read in my other post from today.
I'm looking for a way to overcome that

9

What is connected to the LDB input?
What is connected to the LDB output?
What is generating the PWM signal?
What is the PWM frequency?
What is the PWM voltage?
Are the grounds of all components connected?
How is the LDB physically mounted?

How is all of this related to using the WS2811 output??
If you have a diagram of how you have everything connected please post it here.

10

Thank you for your effort and I will keep your input in mind.

11

You are welcome but I have not given you any input.

12

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