request help for electronic F15e project

[Prayde]

hello everyone,

I started designing an F15e cockpit. my biggest gap remains electronics.

for the design of my MFDs I am inspired by the cougar thrustmaster MFDs and I will tell you how to make a dimmable backlite of 30 SMD LEDs without an external power supply. just with the 5v from the arduino card. I don't know what magic trick thrustmaster uses to get there without powersupply just the 5v from the usb...

my work in attached files

best regards

mfd.pdf

[No1sonuk]

My guess would be that the LED power comes direct from the USB, and the PWM brightness control uses a MOSFET.

[Prayde]

yes I was planning to do it like that. but will the arduino card support 30 LEDs in parallel at 5V?

[Vinc_Vega]

No, there is a limit in current drawing per pin, depending on which type of Arduino is in use.

Regards, Vinc 

Edited January 9, 2024 by Vinc_Vega

[No1sonuk]

4 hours ago, Prayde said:

yes I was planning to do it like that. but will the arduino card support 30 LEDs in parallel at 5V?

The point is that the Arduino doesn't HAVE TO support any number of LEDs.
The 5V supply for the LEDs comes from the USB before it gets to the Arduino.  The Arduino then turns on and off a MOSFET switch that turns the LEDs on and off.
The only problems with this are:
1) Tapping the USB power supply.
2) The USB source being able to drive the current - Ideally this should be a powered hub.

A better alternative, if you can do it, is to use 12V and a series-parallel circuit.  In this case, you have multiple chains of 3 LEDs in series with a resistor.
Have a look here:
https://rudysarduinoprojects.wordpress.com/2019/01/13/fun-with-arduino-05-connect-multiple-leds-with-a-relay-or-a-fet/

[Prayde]

Thank you for all your answers.
I'm thinking of using an arduino nano or equivalent (I'm looking for advice)

can I use the 5V PIN to power my 30 LEDs and control the DIM by a mofset using a digital PIN?

knowing that the arduino nano board will be supply by a powered USB hub.

 

[Vinc_Vega]

The 5V output bypasses the onboard regulator in case the Uno or Nano is supplied via USB alone. Regular USB ports (e.g. a computer output) have a current limit. Therefore, the developer decided to add a fuse to the Uno (maybe and to the Nano) to not draw more than 500mA. That should be the overall limit of these boards!

As you want to supply 30 LEDs in total, each with round about 20mA, that may be too much for an Arduino.

 @No1sonuk already proposed some elegant solutions.

Btw. the max current per I/O pin is limited to 40mA.

Regards, Vinc

Edited January 10, 2024 by Vinc_Vega