I’m planing the Event Lighting for a Sauna so i’d like to expand the Lighting while leaving room for further additions to the System in the Future. Since i haven’t found something ready to buy online or some similar topics in this community, i’m posting this.
Unfortunately i can’t use WS-xxxx LEDs everywhere because it simply gets too hot around some places. So i have to use special sauna LED spots or stripes. Those aren’t adressable, have common Ground instead of common Positive Terminal, run on 24 Volts and are not even the slightest bit compatible with en ESP32. So my plan is to design an adapter, which takes the WS2811 IC, sends the pwm signal through some optocouplers and amplifies it with three MOSFETS.
The expected benefits of such an Adapter would be to make the LED Spots adressable and really damn easy to control by WLED - which i think is the best System there is! Future plans include to build an DMX Like System but easier, more Custom and many more options.
My only problem is, that i’m not that familiar with designing such circuits so i hoped you could help me out with my circuitry. First i made the Schematic of what i think could maybe work. Any Professional here able to confirm or tell me what to do better?
Thanks for your reply!
The mentioned board is nearly what I plan to use. Unfortunately it’s common anode but I need a common cathode Driver board.
Sorry if I overlooked it but I didn’t find a Common cathode version of it.
I don’t believe your current schematic is going to work. You either need a gate voltage that is higher then the source voltage or need to switch to P-channel MOSFETs. An N-channel in the current configuration is not going to work.
What are you going to drive that needs the + side pulsed? General LED strip is all done on the negative side per channel. If you need the + side most often those devices are CC (Constant Current) and not CV (Constant Voltage) and for that you need a completely different setup all together. Can you link what you are planning to use as lighting devices?
Thanks for the reply!
So I’d just have to use P-Channel Mosfets and this would Work?
Edit: Found some IRF9540N P-Channel Mosfets in the basement. They’d work I Guess. In order to get them to run I’d need 24V in front of the Pull-Up resistor which should probably be around 10k, Right?
The lights I’m going to use are from EOS.
The product page is >here<
You can find the datasheet >here<
They’re doing sauna equipment and I already used those with Wled in another sauna, except the installation there was made with the ESP32 PWM going over three Mosfets for common anode and from there again three mosfets for common cathode conversation. This time the LEDs should be addressable. That’s why I want this converter board.
Well P-channel yes, but you need a different driving circuit you can’t just hook them up to a GPIO pin from an ESP. Also make sure to take the general 20v difference into account, so it can take quite a bit more circuitry to do it correctly!
Looked at the stuff you linked! I almost can’t imagine that the RGB version is wired up that way, never seen a light like that before unless they are doing CC and then you need a different kind of driver all together. But they also state 24v so that would mean CV.
Hard to say without stripping it open and taking a look.
Good luck with the board though, hopefully you can make it work for these lights!
Thanks for the help.
I’ve installed a circuit on a perf board to test if it works and it does!
The 24V from the power supply goes first into a step down buck converter to get the 5V for en ESP32, which is running Wled 0.15.b7 the data pin is connected to a breakout board like this one. Instead of an rgb LED I’ve connected three PC817 optocouplers (pin 2) to its output and pin 1 via 470ohm resistor to 5v like shown in the schematic earlier. The only difference is, that as MOSFETS I used IRF9540N P-Channel. And Pulled those up via 10K to 24V instead of 5V.
So now I could design some pcbs for each spotlight so they become ws2811 controlled and thereby compatible with Wled.
If you’re interested in the EOS spot, I opened an old one up and here is what it looks like.
Ah interesting! That’s quite the unique light, looks like it has some CC drivers right in the circuit hence why it works with CV 24v coming in. Seemingly they are able to handle PWM on their power input the allow for dimming too.
Awesome your board works! Regarding the P-Channel normally the gate and the source can have a difference of about 20v. In your configuration you are around the edge of this working and staying working.
You are pulling it to +24v (0v difference vs the source) then down to 0v, so for the gate -24v versus the source to activate it, if you want to do it correctly you could add a Zener in there to make sure it doesn’t exceed +10v or -10v in retrospect of the source voltage, otherwise you might blow up the MOSFET at some point.
@Quindor
Thanks for that hint. I don’t know much about Zener diodes, would a 1N4740A with 10V fit? It goes between gate and source, right? Would i have to replace the 10K pull up resistor with the Zener or does the Zener in combination with the resistor work? I’ve no idea how this works if both components are in the same place in the circuit.
So far the MOSFETs worked fine for over an hour without getting even slightly hot. Meanwhile the ESP32 was getting really warm by only driving this one LED light.
