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First of all, I don't have much electronic knowledge. I am having trouble connecting the LEDs in parallel.I have two types of LEDs which have different power.Here are some current measurements:

The red LED draws 1A when driven alone. red_alone

The blue LED draws 0.5A when driven alone.

blue_alone

When connecting two red LEDs in parallel: red_red

When connecting two red LEDs and 1 blue LED in parallel: blue_red_red

(1) Why did the 2 red LEDs not draw 2A?

(2) Why 2 red and 1 blue led did not draw 2.5A?

Note:My power supply is 30 volts and 50 amps.

bopele
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  • Can you put a link to the datasheets of the red and blue LED modules into the question. – Steve G Jul 01 '19 at 10:17
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    Never connect LEDs in parallel, as due to the I-V curve one LED can draw all the current, see https://electronics.stackexchange.com/a/174585/225159 – nyronium Jul 01 '19 at 10:20
  • Have you got the current limiting set to 1.58A on your power supply? – HandyHowie Jul 01 '19 at 10:59
  • Unless your LED modules have internal current limiters, your LEDs would burn instantly at 30 V 50 amps. It seems your LEDs are protected internally, please confirm by providing the specifications of the LED. You can definitely connect LEDs in parallel if they have identical specs, and/or protected with current limiter.. – Swagatam Majumdar Jul 01 '19 at 11:25
  • I actually bought the LEDs from Aliexpress and I don't have their datasheet.Also the power supply has no current limitation.If I do not connect the LEDs in parallel, how can I connect them in series? – bopele Jul 01 '19 at 11:26
  • You can add them in series by adding a resistor in series with the string. Use the following formula for calculating the resistor: R = supply - total LED FWD drop / LED current – Swagatam Majumdar Jul 01 '19 at 11:29
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    Usually, no data sheet means no answer = guessing = disappointment or unpredictability. Why buy something from a non-reputable supplier who also doesn't provide enough information to design the circuit properly? – Andy aka Jul 01 '19 at 11:56
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    @bopele if you don't have a datasheet, can you at least post a photo of the LED module so we have some idea what it is? Also, how are you measuring the current? What sort of meter? Does it read true RMS current? – Steve G Jul 02 '19 at 07:45
  • Your circuit is almost a short circuit, because a led is a diode and a diode in forward bias have pratically null resistance. Further, each color of led have a specific voltage drop. In your circuit, seems like the most of the current will pass through the led with less voltage drop, because it offer lower resistance, and the current ever prefer the way of lesser resistance. – Guilherme Oct 05 '21 at 14:57
  • how are you measuring the current? – jsotola Jun 03 '23 at 05:46

1 Answers1

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In absence of individual current regulation for each led, the total current of leds connected in parallel is unpredictable. One led may draw more current than another one, apparently identical. The difference between red and blue is even higher.

I imagine these are 12V leds. But you need to know the maximum current which can be used for each led and then, find a component to regulate this current. The easiest way is to add a resistor in serie with the led. But with 6W leds, it's not efficient because you will dissipate too much heat through the resistor. Ideally is to find a constant current supply for each led which will give the exact amount of ampere. But you must find such supply.

First find out how many amperes these led can take (you can/should use a little bit less). And then we can help further if you need to.

Fredled
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