pca9685 - LED stripe PWM control

Other Hardware LEDs and Multiplexing
1

Hi everyone,

I've configured the Arduino UNO + pca9685 to fade in and out 16 LED's (16 channels), the effect is the one I like. Now I want to replicate the same effect with LED stripe, instead of one led to fade in and out, 1,5 M LED stripe.

I tried to use IRF520 module (https://www.lelong.com.my/mosfet-button-irf520-mosfet-driver-module-raspberry-pi-arduino-arm-nadieleczone-I5677355-2007-01-Sale-I.htm) but the effect is not the same.
I am thinking this is not the right transistor.
Can someone advise me what transistor ( or electrical schema) to use in order to replicate same PWM effect to RED stripe?

2

The IRF520 is not a logic level mosfet, so basically not suitable for Arduino's 5volt logic.

You didn't tell us what kind of LED strip(s) you are using. Post a link.
You also didn't post a connection diagam, and the code.
Leo..

3

but the effect is not the same.

In what way?

Using PWM is giving you only 256 levels of brightness, where as using the pca9685 is giving you 4096 levels of brightness. That is 8 bit resolution against 12 bit resolution.

4

Hi,

you are right PWM is not equal to PCA9685. I was referring to the fade in and out effect that I can achieve with PCA9685.

when using the IRF520, LED stripe is not so bright and also looks like no fade effect (just little). I've read somewhere that IRF520 needs 10v but my PCA9685 can provide from 0-> around 5v for diming effect.
is the IRF520"sensitive" enough to have from 0v to 12v output?
my understanding (maybe wrong) when having 0 v from PCA9685 will have 0 from IRF520and when having 5v from PCA9685 will have 12V ( or around) from IRF520. but the voltage grows ration will be similar to the output from PCA9685.

fell free to correct my judgment. Am I doing something wrong?

IRF520.PNG
IRF520.PNG491×537 180 KB

5

nd when having 5v from PCA9685 will have 12V ( or around) from IRF520.

Wrong.

As Wawa said the IRF520 will not turn on fully feeding it with 5V on the gate you need to feed that FET with 10V to fully turn it on.

If you use a logic level FET, that is one that turns on fully with 5V on the gate you will be able to switch 12V.

6

Hi,

thank you for your time, what transistor should I use or module to have 12V when input is 5V?

7

You need to know what current rating is required, it is not simply a matter of voltage. Look for a FET that describes itself as a "Logic Level" FET. These normally have a letter L in the part number, there are hundreds of these about.

Here is one :- N-channel power MOSFET [30V / 60A] : ID 355 : $2.25 : Adafruit Industries, Unique & fun DIY electronics and kits

8

5 m Led stripes need 6 A, so I need maximum 2A for 1,5 meter. can you advice me what to use?

9

My crystal ball tells me you live in Malaysia.

https://www.lelong.com.my/fqp30n06l-n-channel-logic-level-mosfet-60-v-32-35-m-937-surfnshopstore-I5665878-2007-01-Sale-I.htm

Leo..

10

:)) haha
no - I am living in Romania