Hey all.
I have this LED circut and dimming the LED with Arduino Uno. And the dimming works, but have one problem with the dimming. When dimming from PWM level 0 to PWM level 1 it starts with a burst (the led lights up really bright, then dims down to the set PWM level). Anyone knows what the problem might be?
Thanks for any help
Hi thastian,
Below is a bit from the AnalogWrite reference that may be relevent.
Notes and Known Issues
The PWM outputs generated on pins 5 and 6 will have higher-than-expected duty cycles. This is because of interactions with the millis() and delay() functions, which share the same internal timer used to generate those PWM outputs. This will be noticed mostly on low duty-cycle settings (e.g 0 - 10) and may result in a value of 0 not fully turning off the output on pins 5 and 6.
Depending on your driver this might be a problem of your circuitry and not the Arduino output. Have you checked the Arduino output with an oscilloscope? Usually it's not a good idea to cut the output of a constant current driver (many LED drivers are constant current). If possible you should always control the inputs to such a driver and not the output.
Hey Riva
Thanks for the reply and unfortunate its not pin 5 or 6 im using. tryed all of Arduino's uno's PWM outputs, no real difference 
Riva:
Hi thastian,Below is a bit from the AnalogWrite reference that may be relevent.
Notes and Known Issues
The PWM outputs generated on pins 5 and 6 will have higher-than-expected duty cycles. This is because of interactions with the millis() and delay() functions, which share the same internal timer used to generate those PWM outputs. This will be noticed mostly on low duty-cycle settings (e.g 0 - 10) and may result in a value of 0 not fully turning off the output on pins 5 and 6.
What are you using for an LED driver?
Hey Chagrin.
The LED driver followed with the LED downlight. So its a custom driver for the LED downlight. The only infomation that its says is this:
"
Dimmable LED driver
Power: (5-7) x 1W
Input: AC200-240V
Frequency: 60Hz
Output: 320 mA
"
The LED downlight spec says its a 6W LED. When opened its a whole lot of smalled LED's. Maybe 20-30 LED's inside the downlight.
Chagrin:
What are you using for an LED driver?
Hey Pylon
Thanks for your reply
Unforenate i dont have a oscilloscope.
And i rather save the option to controll the power before the driver as a last resort. Not to be difficult, but I don't realy like to play with 230v. And im not sure if the driver is gonna respond good to PWM. But i will keep it in mind
pylon:
Depending on your driver this might be a problem of your circuitry and not the Arduino output. Have you checked the Arduino output with an oscilloscope? Usually it's not a good idea to cut the output of a constant current driver (many LED drivers are constant current). If possible you should always control the inputs to such a driver and not the output.