LEDs current in parallel string

Hello Gurus

Please clarify

I have LED with Vf 3 - 3.2v @60 ma each. If I put 3 LEDs in a series and 4 of such in parallel, total 12 LEDs, should the Output current from lm317 be 60 x 4 = 240ma for this calculator
http://www.reuk.co.uk/LM317-Current-Calculator.htm

Thanks

If you know basic circuit theory, then the answer is readily a yes. You can think of electrical current like water flowing in a pipe... except that its electrons flowing through a conductor (wire). If you have 3 devices in series, the same amount of water (current) will flow through the series parts. So you now know that each string of series devices will draw 60 mA. So, if you have multiple strings in parallel, each will draw 60 mA... so, 60+60+60+60 = 60*4 = 240 mA, total.

The easiest way to remember is that items in series see the same current (water flows through). When you have items in parallel, the current (water) divides and a portion goes down each parallel path. The amount of current going down each parallel path depends on the resistance/impedance of each path... less resistance, more water/current; more resistance, less water/current.

Thanks enjunear

One more clarification please. If I use lm317 For above 3 x 4 LED array in CC mode, whatever the input voltage will be ( of course greater than 9 + 3v lm317 drop) the output V will be 3.2 x 3 = 9.8v across each string and the rest will be dissipated as heat

Thanks

Yes, the heat will be dissipated in the voltage regulator and in the attached series resistor (which sets up the feedback voltage). Be sure to size the resistor properly for power handling, and heatsink the regulator sufficiently (depending on how much current it's sourcing).