Do I need anything in the circuit to stop the flickering?

Forum about LEDS, LED lights, DMX and other lights.

Moderator: Mversluis

Post Reply
Ashleee
Starting Member
Starting Member
Posts: 3
Joined: Wed Jan 11, 2017 11:59 am

Do I need anything in the circuit to stop the flickering?

Post by Ashleee »

I'm hoping someone here has some experience with the PCA9685 PWM controller (16 channel, I2c interface). So far everything is working pretty well after getting the circuit connected properly. I'm using a Picobuck LED driver to drive this high power RGB LED.

PCA9685 datasheet:http://www.kynix.com/uploadfiles/pdf65976/PCA9685BS2c118_658254.pdf

The PCA9685 allowed for a PWM frequency of between 40Hz and about 1500Hz. The default is 200Hz. After setting this frequency, I can choose the pulse on and pulse off interval anywhere from 0-4096 (which is the pulse resolution). So if I want the LED on full brightness, I can set On=0 and Off=4095. This works fine and I get a nice solid LED.


However if I start to dim one of the LEDs to say 25% of it's brightness, I'll set the On=0, Off=1000. This dims the LED but sometimes it starts to flicker. I've tried a lot of different combinations of On/Off times and PWM frequencies. Even at 1000Hz it is flickering, and it gets worse when I start to use all 3 RGB components.


I'm driving the Picobuck with a seperate 12V DC source, and it has a heatsink. Do I need a resistor or a capacitor somewhere in the circuit to stop the flickering? All I'm trying to do is get the LED dimmable from 0-100% without any flicker, so I can combine the red, green and blue colors.


Here is a picture of the setup, there are no extra components - just PCA9685 board, Picobuck and the RGB LED. The red/black wires off the Picobuck are going to a seperate 12V DC supply.
AuFSj.jpg
AuFSj.jpg (56.27 KiB) Viewed 5380 times
What am I doing wrong here?
Post Reply

Return to “LEDS, DMX & Lights Forum”