---------------------------------------------------------- Lightning-List Digest Archive --- Total Messages Posted Fri 01/13/17: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 10:07 AM - Re: Flickering on PCA9685 PWM controller with 3W RGB LED (Paul Bryant) ________________________________ Message 1 _____________________________________ Time: 10:07:08 AM PST US From: Paul Bryant Subject: Re: Lightning-List: Flickering on PCA9685 PWM controller with 3W RGB LED Chuoi, I do know too much about electronics, but a good friend of mine is an electrical engineer. I asked him if he had any ideas to help you. Here's what he said: Tell him. The way this works is to get the LED to "dim" your turning it on for 50 % of the time. Real dim= the LED is on for 25% of the time. What I think is happening is the 200 hz is too low for the DIM mode without flicker. Try 1000 hz. Using a cap on the LED side is a bad idea but it might help (prob not) on the 12V side. Also get a VHF handheld and scan the comm band for noise when you are running this. It is possible for these PWM switches to put out a lot of noise if not properly designed. You don't want to be dimming the lights to find out you got no comm receiver anymore! Mike Dwyer -----Original Message----- From: Chuoi Sent: Thu, Jan 12, 2017 3:34 am Subject: Lightning-List: Flickering on PCA9685 PWM controller with 3W RGB LED I'm hoping someone here has some experience with the PCA 9685 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. PCA 9685 datasheet: 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. here What am I doing wrong? Read this topic online here: http://forums.matronics.com/viewtopic.php?p=465002#465002 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message lightning-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Lightning-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/lightning-list Browse Digests http://www.matronics.com/digest/lightning-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.