LED STRIP LIGHT

[Rupesh]

i am new in designing so please go through this and help me .I want to make LED strip light using SMD 2835.The data sheet is provided below.The forward VI characteristics shows 75mA at 3.3 V.The relative luminesence intenisty at 75mA is 110%

12 V,1 Amps DC is used as the source .I have 3 LED's in a single strip, and a resistor to limit the current flow to 75mA.(but as per the available resistance 63.6mA flows through it)

http://ledcalc.com/#calc-LED resistor calculation
The resistor value is 28 Ohm and the nearest high rated resistor is 33 Ohms.

input power=12W
power abosrbed in single strip =(12*63.6=0.7632W)
The maximum parallel strip i can connect to 12V,1A DC supply =(12/.7632) =15 strips which means 48 LED and 15 resistors in total.

OR

from the economical point of view can i limit to 12 strips by allowing 80 mA current to flow through it by a 39 Ohm resistor

So anyone please go through these and guide me,

 

[KJ6EAD]

Try 3.1V, 60mA, 3 LEDs and a 47Ω resistor per series string; then parallel 10 such strings for a 60% loading of the power supply. This is a conservative design intended for long life of all components.

 

[Rupesh]

could you please explain why driving the LED with 3.1 V and 60 mA, when the forward characteristics shows, for 3.1 V, 45 mA current should flow?How you have taken those values 3.1 V and 60 mA?

 

[KJ6EAD]

I'll answer with questions. Why do the electro-optical characteristics get measured with a 60mA reference current; what ambient temperature will you operate the LEDs in; how long do you want the LEDs to operate before they start dimming or failing and what will happen if you draw the rated 1A from the power supply?