- Tue Aug 11, 2020 12:47 pm
Alright, thank you for the replies. My knowledge is indeed limited and i am learning as i go. As i said, the sole reason i was asking about leds in parallel was the fact that i need it in 2 weeks and aliexpress means 2 months, which is not an option. But in the meanwhile i found a local shop with resistors and will buy them there tomorrow, so i do plan to give each led its own resistor.
But as i really like experiments, i made a simple experiment with step-down. I plan to use 3 green LEDs but in this case i only used 2 to make things simpler. I used 4 multimeters: 1 for voltage and 3 for current: the far right measures current going into the step-down and the other 2 amps measure how much current goes into each LED. Sadly my multimeters are cheap so they only show as low as 10mA, so because usage of each LED is jumping between 0 and 10mA, i can assume its usage is somewhere under 10mA, which is good enough for me. Now as you see, there is no visual difference when i connect 1 or 2 LEDs. Another interesting thing, if you noticed .. when i connect the second LED, the voltage at the step-down output seems to rise very slightly and when only 1 LED is connected, it drops slightly.
One thing that i didn't remember when planning to use step-down is that in order to power the step-down i need to connect both ground and 3.3V to it. And that is a problem since i want the LEDs ground to be IO pins in sink mode. So that wouldn't work anyway.
What i am really interested in is how will the result differ when i use 1 resistor between 3.3V pin and + pins of all 3 LEDs and grounds from them going into a separate IO pins.
I know LEDs of same color can have different resistance and you have to match them as close as possible. Though since i am using such low current of 5mA, the difference between 2 LEDs of same color would have to be gigantic, to somehow draw deadly current of more than 20mA into 1 of them. But since its parts from aliexpress, you never know
Btw, the way i did things till now using step-down and LEDs ... i never bothered with what voltage the LED needs, i only kept in mind the max current it can handle. So i would start as low as 1.5V ... and if i wasn't happy with the current flowing, i would slowly raise the voltage value until i got 5-10mA per LED.
Now to clarify, in the end i plan to use a separate resistor for each LED, that is, 3 resistors together. But i am really interested how the thing would act with 1 resistor. I will include my findings here when i do them. For now, i included this interesting video. https://www.youtube.com/watch?v=mBhSICvAEzI