10 wat LED Flood Light fading with TIP122, Why it is flickering??!

Hi ,
I am trying to fade 10 wat LED Flood light with TIP122.
everything is correct based on many tutorials on how to control LEDs With arduino and TIP122. However, when the fading amount is less than 100 which is between (0~255), the LED flickers!!, when i reduce the amount of delay it is fine. but i need smooth fading.
i used the power supply of the Flood light itself which is very small!!
i would really appreciate it if someone could help me.
Thanks.

Edit : the voltage across the LED pins when it is on, is 31 Vdc!

You need to smooth out the PWM. Grumpy_Mike posted a great little circuit on here for this.
Imgur

ashkan1637:
Hi ,
I am trying to fade 10 wat LED Flood light with TIP122.
everything is correct based on many tutorials on how to control LEDs With arduino and TIP122. However, when the fading amount is less than 100 which is between (0~255), the LED flickers!!, when i reduce the amount of delay it is fine. but i need smooth fading.

If the LED power supply is already sending PWM to the LED (very likely!) then adding another layer of PWM to that signal can cause all sorts of problems, including nasty flicker.

You probably need another LED driver, one with a PWM input.

thanks a lot ken , is well i am hoping for something simpler, do you know any other way?

thanks to you too fungus, well i attached a picture of the whole case, it doesn't seem that the power supply use PWM output.
would you look at it?

Thanks a gain

You could try just putting a largish Electrolytic capacitor in parallel with the LED.

ashkan1637:
thanks to you too fungus, well i attached a picture of the whole case, it doesn't seem that the power supply use PWM output.
would you look at it?

The only way to know for sure is to attach an oscilloscope to it.

OTOH we have some symptoms, ie. It goes crazy when you try to PWM the output. That strongly suggests it IS a PWM signal coming out of that little box.

Another way would be to feed the output into an Arduino pin (via a suitable voltage divider) and see if it goes HIGH/LOW.

well , at the moment i could enhanced it by using low pass filter ,
look at this site :

i used 10K R and 2.2uf C. however, there is still a very small fluctuation when the PWM signal is almost 255!!

have to tune it i think.

any suggestion?

Ken , i tried all capacitors i have at the moment , the response is the same,
how much capacity as an example would be good?
thanks

may anyone could explain the power supply of this type!!!
it is a small one which is shown on previous reply with attached picture.

when the LED is ON , the DC voltage is 31 Volts. also there is 68.7 AC voltage!!! i could not find any rectifier or diode. the amp is 0.14.
so considering 31 DC voltage >> 4.34 watt . the lable says 10w !!

ashkan1637:
may anyone could explain the power supply of this type!!!

a) It will have a feedback mechanism to give the right current to the LED (eg. it might measure "amps")

b) You are interfering in that mechanism (by rapidly making/breaking the circuit), the feedback isn't working.