LED's

[last updated: 2025-09-15]

LED Light Strips
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Note: Some LED's that I have are mis-manufactured, and the flat is on the anode side (cheap clones = poor QC)
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• LED chip specs:
  • 5050:
    (3@ 3528's packaged as one)
    0.24 watts
    20 ma at 12v
    12 - 15 lumen
  • 3528:
    0.7 watts
    5 - 18 lumens, depending on "quality"

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• LED projects:
  • For mounting in 3d-printed things:
    5mm LED: hole diam 5.25, smooth fit, not snug
    3mm LED: hole diam 3.2, very snug

  • build an optocoupler with two LED's facing each other:
    Driving one LED with about 50ma, voltage generated on the facing LED measured about 30mv, clearly not enough to drive another LED or MCU input,
    but explains why instructible and other online projects use a gate or amplifier.
    OTOH that makes the level-shifting between 5v and 12v (which is why I was using the optocoupler in the first place) much more difficult....
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  • Monitor 120vac with LED:
    • simple, using LED in series with resistor across 120vac source:
      This worked, but the resistor needs to be high-wattage to dissipate the heat it generates
      in the process of dropping 120vac down to the 1 - 2 vdc used by the LED.
      Using a 10k, 2W resistor worked, but the resistor heated up more than I wanted inside my project box...
      Also, forum warnings say the LED could burn out for exceeding it's reverse breakdown voltage, but I didn't experience this.

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