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Led help?

bradnorwood

I have a simple project I need help with. It's a dual 10 LED light which hangs from my glasses to light the area I'm working on. It's nothing major but, I'm good at 3d printing but know very little in electronics. They are 3 mm LED's 3.2 volts 20 ma. Can someone help me with wiring this to an easy battery pack that I can attached to my belt etc. It needs to power 20 of them and last for 2-4 hours maybe. thx!

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    Hi there Tim

     

    You need limiting resistors in series with the LEDs, if you turned this on will a charged LION battery you would fry all the LEDs due to excessive current

     

    Charged LIPO is about 4.2V, a small series resistor for each LED of about 50 ohms would limit the current to 20mA when fully charged and a bit less as the battery discharges, a more efficient way would be to boost the voltage to say 16V and put the LEDs into groups of 5 in series, with a small 50R resistor , this overall would be more efficient

     

    Either way you absolutely should put in current limiting resistors

     

    and remember this is a LIPO, ensure it has protection circuitry built in or be aware of the discharge as you can damage the batter or worse if you dont treat it nicely

     

    Regards

     

    Peter

  • 0 in reply to Robert Peter Oakes

    Thanks Peter

     

    I new i forgot something!

    I will update the the schematic.

     

    Tim

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