Member #369454

Member Since: October 13, 2012

Country: United States

  • Tutorial - LED Current Limiting Resistors | about 2 years ago

    I have a science demonstration where I connect 4 equally-spaced two-lead bi-color LEDS (one red, one green inside the same LED) in parallel on a piece of regular lamp cord. When you connect these to an AC source they blink red and green alternately and appear yellow if you don’t move the bulb. I have always connected them in parallel on a piece of lamp cord and directly connected one end of the cord to a low voltage AC power supply and gradually increased the voltage until the bulbs light. When you swing the cord in a circle (holding the end near the power supply) the bulbs trace out little arcs during their on times and the colors are alternately red and green. My question: I have never used any limiting resistor and have done this dozens of times with set-ups that I have had workshop members construct. Does someone have a comment on why I have NEVER burned out a single LED? Luck (in which case I’d need 4 R’s)?? Thanks.

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