# DMX Control - 50W COB LED

I have a DIY project, with the aim of building an (LED-based) stage/theatre light from scratch.

One of the challenges I've hit with this is getting DMX control to dim the LED. I spent some time looking for an 'out of the box' solution, but to no avail. This lead to researching some DIY options, and I've thought of three potential solutions. I'm unsure as to the feasibility of each, so your feedback would be much appreciated!

1: Using an LED Strip DMX Controller and then boosting the (12V max) PWM output signal to 32V max. Unsure if there is equipment to boost the PWM signal correctly to match the 50W (32V) LED dimmer curve.

2: Taking a 12V power source, stepping it up to 32V via a variable boost converter. Then can dim the LED via a potentiometer connected to the 'voltage adjuster' on the boost converter. Figure out a method to control the 'voltage adjuster' / potentiometer via DMX. Unsure as to this part of it.

3: Going full breadboard, building a controller from scratch. Something from the following documents. While I'm sure I could replicate the PCB designs shown, I would have absolutely no knowledge of what each component does.

If anyone has any suggestions as to which approach would be best (or a seperate approach), or any improvements that would be much appreciated!!!

• Welcome to EE.SE! "suggestions" and "best" are however for you frowned upon here. Can you narrow it down to some circuit specific question? – winny Nov 13 '18 at 7:58
• If you have experience with MCUs, option 3 isn't all that hard. I've done it with an MSP430 + RS485 transceiver IC. Then you could output whatever signal your LED driver of choice prefers. If you have any more specific questions about that approach I can try to answer them. – Nate Strickland Mar 14 at 18:20

Use the PWM signal from the DMX controller to drive a dimmable LED driver?

Just make sure you have a pull-up resistor if your DMX controller is open-drain, and that the frequencies and voltage levels are compatible with your LED driver.

Product recommendations are off-topic here, but there are plenty of commercial constant current drivers with analog and PWM input for dimming.

1 - Your boost converter won't like being driven by a PWM signal.

2 - That doesn't make sense as it is not even a full solution, you just delegated the issue to another design step.

3 - Building something from scratch is a decent option.

• Thanks heaps for that 4th Suggestion! The DMX decoder I linked in (1) outputs a 12V PWM signal (designed for LED strips), I think. So would this signal allow something like the (Mean Well HLG-40H-36B) (that @Misunderstood suggested) to be dimmed? – BaseThree Nov 13 '18 at 19:51
• @BaseThree - if its made for LED strips it is very likely that it is an open drain driver, so it won't necessarily output a 12V signal, unless you have something like a pull up resistor. – Wesley Lee Nov 13 '18 at 20:32

Using an LED Strip DMX Controller and then boosting the (12V max) PWM output signal to 32V max.

No the DC-DC boost converter is for a constant input voltage, not pulsed.

Taking a 12V power source, stepping it up to 32V via a variable boost converter. Then can dim the LED via a potentiometer connected to the 'voltage adjuster' on the boost converter.

LEDs are current driven. You need a constant current source with PWM dimming. Then you find a DMX512 with a PWM output. You need to understand that DMX dimmer modules can be constant voltage, constant current, or PWM signaling (typically 5V).

The LED you selected needs a constant current source. Many of the cheap DMX dimmers are made for use with 12V and 24V tape strips of LED that are powered with a constant voltage.

Going full breadboard, building a controller from scratch.

You would need to learn a lot more before taking on a DMX project.

To give you an idea what you need to learn see this Lighting Kit from Infineon.

You need EIA-485 communications for the PHY layer, you need to implement the USITT DMX 512/1990 protocols if addressed to your dimmer, and pass through the DMX commands not addressed to your dimmer.

There are multiple parts to dimming an LED with DMX if not using a complete off the shelf solution.

1. A constant current driver with a PWM dimmer input.

2. A DMX dimmer module with a 5V PWM signaling output.

3. A DMX controller.

The Infineon Lighting Kit @ $120 is one of the least expensive solutions. Most professional DMX dimmer modules are over$200.

If you can find a DMX dimmer that outputs a 5V PWM signal then use a $7 Mean Well LDD-1000H constant current driver with PWM dimmer input. You will also need a 36V DC power supply to power the LDD. It is possible the 4 CH dimmer you linked to will provide a 5V PWM signal if powered with 5V. If you do not need to use the DMX protocols, and just want to dim the LED, use a$28 Mean Well HLG-40H-36B which can be dimmed with a resistance, a 0-10V level, or 10V PWM.

If you need a programmable potentiometer use a Digital Potentiometer

• Thanks heaps for the suggestions! Using the DMX protocol is a necessity for this project. Your knowledge in the "full DIY" option is very cool to have! I've read the documents and approaches you suggested, but it does look quite difficult! #2.... Can I use a Constant Current Boost converter to make this work? #4 I will look at trying to find a DMX dimmer in the 5V PWM region! – BaseThree Nov 13 '18 at 20:04
• You cannot boost the output of the "4CH 4 channel RGBW Easy dmx512 DMX Decoder,Dimmer" because the output is pulsed (PWM). Many constant current LED drivers have a PWM dimmer input. That is likely the way you want to go using a 5V DMX PWM generator. The Mean Well LDD is about as inexpensive as it gets for a reliable driver with PWM input. – Misunderstood Nov 13 '18 at 22:03
• Great! Thanks for the heads up regards not being able to dim PWM. So I could use something like the LDD-1500L, which accepts a 5V PWM signal. All I need to do is find some kind of DMX to 5V PWM converter? – BaseThree Nov 15 '18 at 20:34