PWM LED fade with buck regulator LED driver [solved]

Hi everyone,

I’m currently working on a project in which I need to power and control the fade level of five LEDs running in parallel at 700mA/1.5W. I’ll be using an external 150-1500mA buck regulator LED Driver (PS-SP12144), powered by a 12v/1000mA PSU. The LED driver takes a PWM that can regulate the LED connect to the LED driver. Here’s a short description of the pin layout: Pin Description VIN Positive terminal for 9V -48V DC Power supply GND Power Ground LED+ Positive of LED terminal LED- Negative of LED terminal EN PWM terminal. When applied with ground or suspended, full amount of current will be output and when connected with +5v or VIN, output current will be 0.

I’ll be using an Arduino Uno (first revision) to control the pwm through the analogWrite function, but for whatever reason, nothing happens when I PWM the EN pin. Here's a picture of my setup:

I've also tried to use a special PWM frequency library (,117425.0.html) to change the PWM frequency to 1000Hz, but with no luck.

I've used PWM signals many times in arduino projects, but I just can't get my head around this issue. If I connect the LED driver en PIN to VCC, then the light turns off.

Product link:


The picture isn't very good. Your Uno has a small black wire to the GND pin and it's impossible to see where the other small black wire goes. Is it in a PWM pin at all ? Is the first wire from GND connected to that green wire, and where does that one go ?

Thanks for pointing that out! The green and black gnd wire doesn't matter, they aren't part of the circuit.

The black wire from the arduino is connected to PWM pin 9 and the LED driver EN pin.

So how did you connect the grounds, as in your many other projects ? See my signature below.

By the way, the description of that PWM input shows that is is reversed PWM. That means a larger duty cycle will lead to more dimming, not more illumination. You want to keep that in mind while creating your sketch.

Thanks for your answers. Seems like I was just too hung over to remember that the led driver should be grounded with the PWMing Arduino. Embarrassing :sweat_smile:

And thanks for the tip, I’ll keep that in mind.