Hi Guys
I hope this is a good place for my question, even if it is perhaps not directly Arduino related.
I'm trying to dim a 12V LED strip using an Arduino and a N-channel mosfet.
Turning the LED strip on and off using the arduino works fine. But once I send a PWM signal through the mosfet the LED strip starts blinking instead of dimming, the PWM setting doesn't seem to matter much.
When I checked the PWM signal from the Arduino with an oscilloscope the PWM signal is fine, but when I check it at the LED I get the attached plot below (attached at different magnifications).
It's clearly PWM'ing, but for some reason the voltage drops over time...
Any ideas what I'm doing wrong?
Thanks
Jacob
Any ideas what I'm doing wrong?
Well no because you have not told us in any detail what you are doing.
Schematic with component values?
Software?
What sort of LED strip, what current does it need?
What is the current specification of your power supply?
Grumpy_Mike:
Well no because you have not told us in any detail what you are doing.
Schematic with component values?
Software?
What sort of LED strip, what current does it need?
What is the current specification of your power supply?
Fair points, sorry if my initial post was a bit on the thin side.
I've tried with two different mosfets, (this one: https://assets.nexperia.com/documents/data-sheet/PSMN2R7-30PL.pdf and another one I can't remember right now).
Not much in the way of a diagram, connected the PWM pin on the arduino to the gate, source to common ground and drain to LED strip.
I've tried with two different 12V LED strips and a 12V computer fan.
All exhibited the same problem.
with regard to software, on the arduino either the Fade example or just an analogwrite with any value not 0 or 255 will exhibit the issue. The oscilloscope is a Picoscope.
However, changing the power supply fixed the issue. The Cheap china brick seems to be the problem, although it is rated for 6A (much more than the LED strips and much much more than the computer fan will ever draw).
I'm not sure if there is anything I can do to make it work with the China brick or if is just easier to go out and buy a better quality psu.
-Jacob
Try putting a large capacitor, say 1000uF across the output and see if it improves. If not then get a new supply.
