hi
Im about connecting a 12v 6.5a battery to 45 leds which are arranged in groups of 5 in seperate places about 12Meters apart.
the last time i did this with a resistor to 4 groups, the resistors got burned up due to heat generated
i even tried increasing the wattage of the resistor but the heat transrared to the leds.
How do i connect the leds and the batteries to prevent power loss due to heat?
The leds are white
hi
Im about connecting a 12v 6.5a battery to 45 leds which are arranged in groups of 5 in seperate places about 12Meters apart.
the last time i did this with a resistor to 4 groups, the resistors got burned up due to heat generated
i even tried increasing the wattage of the resistor but the heat transrared to the leds.
How do i connect the leds and the batteries to prevent power loss due to heat?
The leds are white
Mmmmm. A typical LED.Might not be yours. 20 mA, Vf=2.1 Volts. 5 LEDS * 2.1 = 10.5 V.
(12-10.5)/.020 = resistor value. Power rating > I^2 * R or (0.020^2) * Resistor value
So 5 strings of 5 with a resistor per string.
There's a problem with this approach. As the battery depletes, the LED's get dimmer and there is little or no battery voltage reserve.
What are the Vf and suggested If for your LED's or better yet, p/n and/or datasheet.
hi,
As your LED's are White, they have much higher voltage drop than 2.1V, look at this image.
White are shown as 3.5V, so you can only connect 3 in series across 12V, using a suitable series resistor.
So 3 * 3.5V = 10.5V this leaves 12V - 10.5V = 1.5V to drop across the resistor.
For a current of 0.02A this makes the resistor 75R.
EDIT:
So for 45 LED's you will require 45/3 = 15 sets of 3 LED's each set with their own 75R
i like that idea. im still afraid of short circuit on the line.
im using a pare of twisted copper wires for transformers. the worse is that the wires are quite small, I used it to make my connection so hidden.
i like that idea. im still afraid of short circuit on the line.
im using a pare of twisted copper wires for transformers. the worse is that the wires are quite small, I used it to make my connection so hidden. this is a rough diagram
Yes I got it sir
one more question, where will the resistors be located?
close to the source or close to the leds
and what wattage of resistors i will be using?
thanks allot
Yes I got it sir
one more question, where will the resistors be located?
close to the source or close to the leds
and what wattage of resistors i will be using?
thanks allot
You may be able to use a constant current source. There is an application of the LM317T here: https://www.electro-tech-online.com/custompdfs/2010/11/LM117.pdf The 1.2 ohm resistor is calculated from I = 1.2 V / (current in Amps). You really need about 3 V across the bregulator.
The LM1117T might work too. Haven't looked closely at the datasheet.