I have written a simple Python program which runs on a RPi to make an LED blink. For that I connected my RPi using GPIO 23 with the anode of the LED, and before going back to ground, I added a resistor with 220 ohm. So far, this works.
Now I would like to make two LEDs blink, so I just thought to add a second LED and put them in series. Unfortunately, exactly nothing happened. So I have a number of questions:
- Why does nothing happen? Are the 3.3 volts of the RPi too little for two LEDs and a 220 ohm resistor?
- Is it even correct to put the LEDs one after the other, or would I need to put them in parallel?
- How do I calculate the correct resistor, if I don't know the data of the LEDs? What would happen if I simply remove the resistor? Would I risk damaging the RPi?