Powering Arduino Nano and LEDs from 5V rail

[peter247]

@taconite
I would say at a guess , NO , the best way is use a buck converter off the main psu.

[Veti]

see this on how to do the wiring

https://www.blvprojects.com/blv-mgn-cube-3d-printer?pgid=k8hkwn62-f7fe97b7-2106-47ec-9a07-47b5b8c9a191

[dc42]

@taconite said in Powering Arduino Nano and LEDs from 5V rail:

Hey guys,

I want to power a Arduino Nano from the 5V Rail of a Duet 2 Wifi (v1.4) and controll LEDs with it (I don't have heater or fan outputs to spare).

I will use one remaining fan output to control the state of the LEDs

Is there enought power to drive the Arduino Nano and approx 30 LEDs of a (300 LED/5m WS2812b LED strip)?

Best Regards
Adrian

Arduino Nano: yes (although Arduino Pro Micro is a better one to use if it will take inputs directly from the Duet)
LED strip: 30 LEDs * up to 60mA per LED = up to 1.8A. That's more than we recommend drawing from the Duet's 5V supply; so no.

[taconite]

Thank you for your replies!

Why using a buck converter when I could just bi-pass the buck on the Nano. My concern is more about the current draw from the Duet.

As my fans are running on 24V I will use a optocoupler to convert it to 5V

[taconite]

Thank you @dc42

What is the recommended max current draw from the 5V supply?

[dc42]

@taconite said in Powering Arduino Nano and LEDs from 5V rail:

Thank you @dc42

What is the recommended max current draw from the 5V supply?

2A total, less 200mA for the Duet and any current drawn by LCDs, endstops and Z probes.

[taconite]

So I guess I will do it like that:

[peter247]

@taconite

Why the optocoupler ?
I can't see why you need one , if it is to switch the buck converter on you can find some buck converter which have a enabled pin.

[taconite]

@peter247 With the PWM output of the Fan I want to control the color of the LED. e.G. 10% dutycylce = green. My Fan Voltage is 24V but the Arduino can only take 5V

[peter247]

@taconite

So if I have got this right you are going to power your arduino and looks like spi controlled leds from a fan with pwm ?.

your diagram makes not sense to me !!!!

Are you use spi controlled leds like dotstar ?

[taconite]

So I kind of made it work with this scematic

Simulation show good results:

The Problem with that is, even if i just put on the Fan_PWM at 10% (S0.1) I get already 2.5V. Does anyone has an explanation of that? Because of that I am limited to less colors ("just 6").

This is the PCB I put together with an optocoupler, an DC/DC converter and an Arduino Nano.