I'm working on a circuit where that involves four 1W LEDS, controlled by an Arduino via a LED driver. I've tested the circuit and it works except I'm not sure how to proceed with the PWM part. The LED driver has PWM pins but it seems that it needs 20V and of course that's not possible directly with the Arduino. Based on what I've gathered, a MOSFET is the best way to control the PWM with an Arduino (3.3V). I've attached a drawing describing the circuit and an idea for how to use the MOSFET but I'd really appreciate some ideas there. Specifically I'm not sure if the selected MOSFET (2N7000) has the right characteristics and where I may need resistors. Would the PWM pins on the LED driver typically be high impedance such that I would not need to use resistors?
LED Chip is XL4001E1 no MOSFET needed. PWM dims with 5V
Come on, do you really expect us to know which LED driver from the description: "a LED driver"?
Full details of the hardware please. Not your description of it but something concrete: datasheet, product page, or at least part number and manufacturer.
rappa:
The PWM is inverted so 0V fully on and ~3V turns off
Which is normal.
Just connect LED(s) and LED power supply to the module.
LED supply voltage must be at least 2volt higher than Vf of the LEDs in series (typical ~3.3volt per white LED),
e.g. 12volt for a string of one to three LEDs, or 24volt for a string of four to six LEDs.
Connect PWM+ground to the Arduino.
A PWM value of 0 turns the LED off, and a PWM value of 255 is fully on.
analogWrite (PWMpin, 100); // is about half brightness
Leo..
