0

This might be a very basic question but I am just starting out on my electrical engineering journey, and would like to check something.

I have a simple LED design running at 12V, currently I have 12 LED strips connected together with 8 LEDs on each strip for a combined total for 96 LEDs.

Each LED has a forward voltage of 3.2 (it's a blue LED) and a forward current of 20mA and a 470R resistor on each led, so I calculate I need 1.92A to run all 96 LEDs.

So if I buy a 12V 2A power supply will it happily run the LED strips even if I happen to remove some strips?

Sorry if this is just me being dumb I don't want to burn out any LEDs.

JYelton
  • 32,302
  • 33
  • 134
  • 249
Warranty_void
  • 41
  • 3
  • 1
    yes. an LED power supply can never really have too many amps, it can only have too few if you get one that's undersized. – dandavis May 11 '22 at 21:57
  • are you sure that it doesn't run 3 LEDs in series? you really should do that if not... In that case, you only need to size the resistor for 20ma at 12v-(3.2v*3); about 150 ohms. – dandavis May 11 '22 at 21:58
  • Requisite link to power supply basics: https://electronics.stackexchange.com/q/34745/2028 – JYelton May 11 '22 at 22:01
  • running chains of 3 LEDs, would only take 32 chains at 20ma each, or about 1amp... – dandavis May 11 '22 at 22:10
  • I agree it's a dumb way to drive LEDs drawing 64 mW=3.2*20mA while each resistor wastes I^2R=188 mW= .02^2*470 for an efficiency of 64/(64+188)=25%. Whereas 1 resistor shared between 3 LEDs would be a smarter way with 80% efficiency. , yet it was wise of you to ask. Although LED's have a wide tolerance for Vf from manufacturing tolerances so it will never burn out the LEDs with your method, but your 1/4W resistors might be operating around 100'C and operating near full supply capacity pushes operation to max temperature and this always reduces lifespan. Which is not a good thing. – Tony Stewart EE75 May 11 '22 at 23:47
  • Yes, if you are buying commercial LED strips (why wouldn't you?) they are 3 LEDs between the cut lines, and you have to cut them at the cut lines. 8 is awkward. Make it 9. – Harper - Reinstate Monica May 12 '22 at 00:15

0 Answers0