karthikeid Posted April 13, 2010 Report Share Posted April 13, 2010 hihow to drive led and supply constant current??circuit for driving 50led's in series/parallel @30mA per led. ??? Quote Link to comment Share on other sites More sharing options...
chromei386 Posted April 15, 2010 Report Share Posted April 15, 2010 From what voltage source? Batteries? Power supply unit? Wall wart?To get the right mA to your LEDs, use this formula: R = (Vs - Vl) / Iwhere R = resistanceVs = power supply voltageVl = sum of LED voltages (check, but probably 2v ea) I = LED mA = 30mAyou could hook them all up from a 12V DC source - having 5 LEDs per 'leg' and have 10 'legs' in parallel.... with some quick calculations that's R = (12 - (5x2)) / 0.030 = 67so you have 5 LEDs hooked up in series with a 67 ohm resistor....... then hook up 10 in parallel with power supply. the circuit draws 30mA x 10 = 300mA so you just need a 12V DC power supply capable of delivering 300mA (easy to buy, find or make!) Quote Link to comment Share on other sites More sharing options...
Hero999 Posted April 16, 2010 Report Share Posted April 16, 2010 What voltage are the LEDs?What voltage is the adaptor?It's more efficient to connect them as strings of many in series, in parallel. Quote Link to comment Share on other sites More sharing options...
karthikeid Posted April 17, 2010 Author Report Share Posted April 17, 2010 led's are 2v@10ma, i need to drive 50 leds, how do i connect in series or parallel ??? Quote Link to comment Share on other sites More sharing options...
Hero999 Posted April 17, 2010 Report Share Posted April 17, 2010 I thought you said they were 30mA?What voltage is the adaptor?Here's a site which explains the difference between series and parallel LED circuits.http://www.ngineering.com/led_circuits.htm Quote Link to comment Share on other sites More sharing options...
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