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How many red 5mm leds i can power with a 12 V 1.5 A AC-Adapter?

Discussion in 'LEDs and Optoelectronics' started by ElectroMarco, Mar 18, 2018.

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  1. ElectroMarco

    ElectroMarco

    3
    0
    Mar 18, 2018
    Hi
    My friend gave me 5000 red leds like this one
    https://www.taydaelectronics.com/me...f78eab33525d08d6e5fb8d27136e95/a/-/a-1554.jpg
    that he found in a abbandonated storage unit that he bought...

    I would like to create a led sign or something , so i'm wondernig: How many red 5mm leds i can power with a 12 V 1.5 A AC-Adapter?
    Do i need resistors?
    If what i want to do is not possible, do you have some ideas on what can i do with 5000 leds?
     
  2. Alec_t

    Alec_t

    2,822
    754
    Jul 7, 2015
    Welcome to EP!
    The number you can drive will depend on how much current each LED draws. Most LEDs like that will take 20mA ok, but you can choose a lower current and hence increase the number of LEDs used.
    Yes, you will need some resistors.
    Does your mains adapter provide a DC output or an AC output?
    Is the output voltage regulated or not?
     
  3. ElectroMarco

    ElectroMarco

    3
    0
    Mar 18, 2018
  4. Alec_t

    Alec_t

    2,822
    754
    Jul 7, 2015
    This is how you could use the LEDs, arranged in strings of 5, each string having a resistor.
    LED-strings.PNG
    Only 2 strings are shown here.
    With the resistor value shown, the LED current would be about 17mA per string, so you would be able to have 1.5A/17mA = 88 strings in theory. In practice, allowing for some margin, 80 strings should be manageable, i.e. a total of 400 LEDs.
     
  5. ElectroMarco

    ElectroMarco

    3
    0
    Mar 18, 2018
    Thanks a lot for your help!
    i will follow your tips!
    Bye bye!
     
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