5 led circuit with switch

Discussion in 'Digital Circuit Design' started by Jason Barker, Feb 7, 2019.

  1. Jason Barker

    Thread Starter New Member

    Feb 7, 2019
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    Hi thanks for reading.

    Im looking to make a circuit thats simply 5 LED's and an on/off switch powerd by a low voltage high capacity lipo idealy.
    I'm not sure on how to set it out or what voltage/resistors i would need.

    Thanks for your time!
     
  2. danadak

    Distinguished Member

    Mar 10, 2018
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    783
    Then probably you will need a simple boost converter since a single LIPO
    cell V may not be high enough to drive the 5 LEDs in series. Or are you
    going to drive them paralleled ?

    Regards, Dana.
     
  3. Jason Barker

    Thread Starter New Member

    Feb 7, 2019
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    i would prefer parallel incase one of the LED's is damaged, i dont mind useing a stronger lipo, though i wouldnt want to go past 11.1V because size is an issue
     
  4. Jason Barker

    Thread Starter New Member

    Feb 7, 2019
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  5. iONic

    AAC Fanatic!

    Nov 16, 2007
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    Your LED's specs are If(forward current) 20mA, and Vf(forward voltage) 3.0-3.3V. Being that they are purchased from ebay I generally down-rate the specs for safety/longevity. I will calculate based on a If=17mA and Vf=3.0V. I actually do this for all my circuits containing LED's.
    With a single 3.7V Lipo, this is certainly doable.

    Calculations: (LINK)
    resistor.JPG

    In parallel, each LED needs a limiting resistor as seen in the wiring diagram above. 47 Ohm(1/4W) is a standard resistor value and should be easy to find.
     
  6. danadak

    Distinguished Member

    Mar 10, 2018
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    As Ionic has show with LEDs in parallel you do not need a boost converter,
    and your battery is fine.

    Regards, Dana.
     
  7. Jason Barker

    Thread Starter New Member

    Feb 7, 2019
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    thats ace! thanks!
     
  8. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,650
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    Note: With such a simple design there will be no way to know when your battery is discharged (3.0V) other than some dimming of the LEDs, so keep an eye on the battery so as to not shorten its expensive life!
     
    Jason Barker likes this.
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