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Yes, a separate resistor for each led would generate significant heat. To miniminze this you can connect the leds in series to better match your supply voltage. The led voltages are then added together. For example if each led had a 3V drop at the rated current, you could use 3 in series to give a 9V drop (you need to leave some voltage for the current regulating resistor). Then pick a resistor value to drop the final 3V at the rated current. For example, if the current is 20mA the resistor would be 3V/20mA = 150 ohms and the resistor power would be 20mA x 3V = 60mW.svtiss said:I have a 12v power supply( its a 12 v battery) for the leds , if I use resistors for the current limit, that would be a lot heat , is that right ?
So for 125mA and the 2 leds in series, the resistor value would be (12.6-6.4)/125mA = 50 ohms. The resistor dissipation would be 125mA x 6.2V = .775W, thus you would need at least a 1W resistor.svtiss said:thanks
I have 2 leds and current around 100-150 ma for both , and the voltage ~3.2
You want to drive them in series. In parallel, one of the diodes may hog more current then the other.svtiss said:yes that was my question , use a v regulator or there are led drivers on the market ? and whats better to connect leds in series or parallel?
I dissagree, a switching regulator wouldn't be wasteful, it would save energy and increase the battery life.Regardless of the voltage you should use a current limiting resistor based on the forward voltage of the LED and the available voltage being monitored. A separate regulator just for the LED seems unecessary and wasteful. You might want to make a distinction between the input of your main regulator and the output of the main regulator.
Is there another likely interpretation for "power LED's". I'm not familiar with any other interpretation of the term. Perhaps that is the root of the confusion. How about it OP. What is the definition of a power LED per your original post?Have we established that the LEDs are only to indicate that the power is on?