How would I safely connect 2 sets of 2-3 leds to a nano without using an external power source?

Other Hardware LEDs and Multiplexing
21

Connect the strips to the Nano's 5V and ground pins, like @camsysca described back in post #10.

23

Did you read this part on your Adafruit link?

Can NeoPixels be powered directly from the Arduinoā€™s 5V pin?

Sometimes. The Arduino can continuously supply only about 500 milliamps to the 5V pin. Each NeoPixel can draw up to 60 milliamps at full brightness. So yes, you can skip the separate DC supply and power directly off the Arduino as long as just a few pixels are used, more if the colors and overall brightness are low. When in doubt, give the pixels a separate power supply.

That is for an UNO, I am not sure if a NANO can supply that much. The Adafruit diagram at the link you provided shows an EXTERNAL PSU.

24

How much current are the strips pulling? just a dozen is something like 720 mA, which is way beyond a Nano. 400 to 450 mA is the max.

25

According to @olivia_ok8, 4 or 6 RGB LEDs, so 360mA at most.

26

Is the 5 mm or METRES? A photo of the entire roll/strip you want to use would be very helpfull.

27

Ok, that makes more sense, but I don't see a definitive statement that is the amount to be used. Let's hope they confirm @olivia_ok8

28

I am using 6 white squares total. After cutting each one off of the main thing, itā€™s not a very big prop.

29

The title says 2 sets of 2-3 LEDs
So that 2 x (2-3) = 2 x (-1) = -2 LEDs
Does that make it clear?

30

Also do I solder to the long or short side of the header?

31

Good thing I have an appointment for new glasses in a few weeks LOL!

32

Better to put female connectors on the end of the wires. These connect to the longer part of the Nano pins.

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33

I have NO idea what you are doing now, I will leave it to one of the other helpers to sort out.

34

Even with a low number of LEDs, omitting these steps can cause unexpected behavior, flickering, or fried data pins over time:

  • Data Inline Resistors (Crucial): Always place a 330Ī© to 470Ī© resistor inline between the Nano's digital output pin and the first NeoPixel's DIN pin. This suppresses voltage spikes on the data line that can easily destroy the first pixel's internal controller chip if the board is powered on/off dynamically.

  • Bulk Capacitor (Recommended): Place a 100ĀµF to 1000ĀµF capacitor (6.3V or higher) across the 5V and GND rails close to where the NeoPixels get their power. This smooths out any voltage sag when the LEDs suddenly change colors or flash.

  • Common Ground: Ensure all grounds are tied together perfectly.

  • Manage Software Brightness: In your setup function (using FastLED or Adafruit_NeoPixel), scale down the maximum brightness to save energy and protect your eyes:

    • C++,
      FastLED.setBrightness(128);
      // Limits power draw by half
      // OR
      pixels.setBrightness(100);

  • Always draw a schematic for your projects.

35

The short side. The longside is for connetion to a female jumper wire.

Be careful it's easy to melt the LED strip if you apply to much heat.

36

Iā€™m going to use the female connector

37

How should I connect the resistor

38

The "current limiting resistor" (to limit the current drawn from the output pin) is connected in series with the LED data input pin. It is a good habit to use all those words (current limiting resistor) so you get in the habit of including the resistor when you use LEDs.

39

I meant with what should I connect it with?

40

Connect like this...
UNO PIN >> RESISTOR >> DATA IN of WS2812

From the Uno male pin, use a female connector of a Dupont jumper wire... then cut the opposite end connector off the jumper, strip the insulation, solder it to the DIN of the WS2812.

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41

Iā€™m using a nano every doesnā€™t matter what digital port I use