LED array with LEDs that require different amounts of mA

Other Hardware LEDs and Multiplexing
1

Hello everyone.
I am building an LED array for the first time and directly with different LEDs that require different amounts of mA.

I have a total of 81 LEDs. Of these, 48 require 20mA, 27 50mA and 6 100mA:
In addition, I used the Arduino Atmega 2560 which only supplies 5V.
I suspect that I need to use an external voltage source. I was also advised to use an LED driver. How can I limit the current for the different LEDs so that all LEDs are supplied with the appropriate current?

Now I have all this information, but I don't know exactly how to link everything together to build a working LED array. Can anyone give me a tip on the best way to go about this?

LED-Array mit LEDs, die unterschiedlich viel mA benötigen
2

You posted this LED-Array mit LEDs, die unterschiedlich viel mA benötigen

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Thank you.

Do you want to keep the post in German or the post here in English ?. You can’t have both.

3

The leds do not require 100mA
100mA is their max. current.
What do you want to schieve with this array?
100mA leds are blinding bright. So not a signal led or part of a screen, but like a light source.
You will hardly see the 20mA leds next to it.
Did you experiment with different resistors?
Do the leds all have the same color (around the same voltage)?

4

I would like to build an LED array that covers LEDs with wavelengths from 430 nm to 935 nm. The LEDs in the higher wavelength range are operated at 50 nm or 100 nm.

5

I thought I could take a large voltage source and then connect different sized resistors in front of the LEDs with different current requirements.

6

I want to keep the English post.

7

Yes that is the way to do it

8

ok but where exactly do the different resistors have to be positioned in the circuit if I use an LED driver?

9

A matrix driver or a constant current driver?
In case of matrix driver: in series with each and every led.
To reach the same current, red leds need higher resistor value than blue ones.
But it should not be about equal current, it should be about the eye's perception of equal brightness.

10

Yes, I mean a matrix driver. But isn't one resistor per row of LEDs enough? If I were to connect a resistor in front of each LED, I would need 81 resistors for my 81 LEDs.

11

You don't use an LED driver. Where the resisors go will depend on the position of the different LEDs in the matrix

12

What happens if more than one led per row is on?
Maybe 81 resistors is just about right...

13

OK I closed the post German.

14

do you want to be able to drive each individual led ?

15

Yes you can, but it is not about requirement, but about eye perception!

16

Yes, does this mean that I have to use 81 resistors?

17

Not necessarily, as i previously mentioned, it will depend on how the LED are arranged in the array

18

I’m not an electronics expert so I’ll let whoever is speak about that but my understanding is that it’s the safer option.

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