I'm building a prop for a game. Its an Arduino Nano that runs some LEDs via a controller board, a small motor, and a mini MP3 board for sound. It's powered by a 9v battery. It runs great. I wanted to add some extra LEDs to it so a small analog meter that's attached to it could be seen at night, and wired some LEDs up to the battery in parallel with the arduino circuit. When it's turned on, the extra LEDs flicker and then die as the Arduino turns on and gets going. I'm obviously not understanding something about how the circuit works, voltage, etc. The Arduino is providing 5v that is enough to power a bunch of LEDs through an adafruit LED matrix board - why are 3 LEDs in parallel with the whole thing not getting enough power when the Arduino turns on? Here's an oversimplified circuit of how it's laid out:
Obviously I left out all the components attached to the Nano itself, but I wanted to show where the battery and power switch was and the 3 LEDs in parallel with the arduino circuit.
The 3 LEDs are white LEDs that are listed to have a voltage drop of 2.8v and pull 20mA. ledcalc.com said it needed a 30ohm resistor. Which works great when NOT also using the arduino.
So I'm not understanding something about how voltage works when powering different devices in parallel. Every search I do on google talks about LEDs in parallel vs series, but not much about parallel circuits. Any guidance here? Thanks.