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2 LEDs in series with resistor at 3.3V won't light up, one LED works - Electrical Engineering Stack Exchange
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3.3v &3.3v LED how to connect 12V series circuit, how to calculate led series resistor, watts - YouTube
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Constant Current Adjustable Module, DC 3.3V 3.7V 5V LED Driver 30-1500mA Constant Current Adjustable Module for LED 18650 Li-ion: Amazon.com: Industrial & Scientific
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