Other NXP ProductsのトピックRe: PCA9685 LED driving

PCA9685 LED driving

JohnJohnny — Sat, 12 Dec 2020 11:19:06 GMT

Hello,

I would like to use the PCA9685 to drive bicolor LEDs (2-pin LEDs, color changes when the current in the LED is reversed).

I am thinking of connecting my LEDs between 2 pins of a PCA9685, let's say OUT1 and OUT2.

If OUT1 is set to HIGH, I can control the brightness of color 1 by applying PWM to OUT2.

If OUT2 is set to HIGH, I can control the brightness of color 2 by applying PWM to OUT1.

If OUT1 and OUT2 are LOW, LED is off.

Could you confirm me this is possible?

Re: PCA9685 LED driving

guoweisun — Mon, 14 Dec 2020 01:02:58 GMT

Could you please send us the application block diagram for better comprehend ?

Re: PCA9685 LED driving

JohnJohnny — Mon, 14 Dec 2020 09:10:01 GMT

Hey,

here is an example of what I intend to do. It features 3 push buttons that have internal bi-color LEDs. I've seen that PCA9685 outputs can source and sink current, this is why I imagine this is possible.

In the final application they would be 24 bi-color LEDs driven by 3 PCA9685.

Re: PCA9685 LED driving

guoweisun — Tue, 15 Dec 2020 01:45:13 GMT

Thanks for your feedback!
But I still can't fully understand!

Could you please give one channel complete circuit for example sent OUT1 high and generate PWM on OUT2?

Re: PCA9685 LED driving

JohnJohnny — Wed, 16 Dec 2020 11:34:47 GMT

Hello,

my question in a more general way would be:

can I drive 2-pin bi-color LEDs with the PCA9685, in a way that allow me to use both colors of the same LED (not at the same time) and control their brightness?

I'm thinking of configuring all the outputs in totem pole. Let's say LED1 is between OUT1 and OUT2 with a series resistor.
OUT1 PWM duty cycle = 100% and OUT2 PWM cycle = 0%, LED is red, full brightness
OUT1 PWM duty cycle = 50% and OUT2 PWM cycle = 0%, LED is red, medium brightness
OUT1 PWM duty cycle = 0% and OUT2 PWM cycle = 100%, LED is green, full brightness
OUT1 PWM duty cycle = 0% and OUT2 PWM cycle = 50%, LED is green, medium brightness

Does this work?

Re: PCA9685 LED driving

guoweisun — Wed, 23 Dec 2020 07:15:36 GMT

I am afraid that it doesn't work!