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I'm trying to build an Arduino controlled LED panel, used for videography and a general worklight. Planning to use the PWM signal from Arduino and through a Mosfet in order to dim the 12V LED. However I'm afraid that the PWM signal may cause flickers on video, therefore not suitable for videography.

Initially I've thought of using a low pass filter in between the Arduino PWM Output and the MOSFET, which I then realize it wouldn't work as MOSFET can't be used that way. Is there a way I can smooth the PWM coming out of the MOSFET into the LEDs? The LEDs would most probably be 50W.

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  • \$\begingroup\$ Can you please provide more data about the LED's you are driving? Is it a module with its own internal power control, or is it just LED's? A link to a technical datasheet would be best. If it is a no-data Ebay special, it might not be possible to design anything ahead of time. You might just have to experiment with it. \$\endgroup\$
    – user57037
    Oct 2, 2016 at 16:34
  • \$\begingroup\$ @mkeith Thanks for helping me out. It's a no-data China made LED strips, only thing available is that it operates on 12V and is rated at 18W per meter. I've tried voltage dimming before using a boost/buck converter, and it works perfectly. However now I'd like to be able to dim it with an Arduino, with a smoothed PWM signal to prevent flickers. \$\endgroup\$
    – Infrasonic
    Oct 2, 2016 at 18:24
  • \$\begingroup\$ You can alter the PWM signal of the Arduino well into tens of kHz (I've done it for video and photo applications aswell). You lose a bit of resolution, but in my case it was acceptable. Take a look here. \$\endgroup\$
    – Wesley Lee
    Oct 2, 2016 at 19:27
  • \$\begingroup\$ @WesleyLee That might work, would do that as an alternative if I'm not able to build one with constant voltage. Thanks! \$\endgroup\$
    – Infrasonic
    Oct 3, 2016 at 6:02

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Make the PWM as close to 120 Hz ( 100 Hz in Europe) as you can by choosing an appropriate crystal for your Arduino and setting the PWM generator carefully. Even though your LEDs will not be precisely phase-synchronized to the video recording frame rate, your recordings will probably be OK.

I had some experience with this in a small video recorder project I worked on. Even though I expected the room fluorescent lights to cause a beating in the video brightness of the recording, they did not. I am unable to explain why.

If this doesn't work for your application, the next level of complexity is a big step: You will have to make a voltage-controlled constant current source ("VCCCS") to drive the LEDs with a pure, un-rippling DC current. Use the low-pass filtered PWM output you mentioned to drive the control input of the VCCCS. Try simple first!

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  • \$\begingroup\$ I think the reason fluorescent lights doesn't flicker on 120Hz (60 Hz here in Malaysia) is because there's residue light when it's turned off, where else the LED turns off instantly when no current is passing through it. Thanks for the suggestion though. \$\endgroup\$
    – Infrasonic
    Oct 3, 2016 at 6:04
  • \$\begingroup\$ Fluorescent lights definitely flicker. If you hook up a photocell to an oscilloscope, you can see a distinct 120 Hz flicker. Then try an incandescent lamp in the same set-up. Much less flicker. Also, some white LEDs have phosphors just like fluorescent bulbs, this might damp out the flickering a bit compared to a non-phosphor type LED. \$\endgroup\$
    – FiddyOhm
    Oct 3, 2016 at 11:53

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