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.


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.

  • \$\begingroup\$ Can you put a link to the datasheets of the red and blue LED modules into the question. \$\endgroup\$
    – Steve G
    Jul 1, 2019 at 10:17
  • 1
    \$\begingroup\$ Never connect LEDs in parallel, as due to the I-V curve one LED can draw all the current, see electronics.stackexchange.com/a/174585/225159 \$\endgroup\$
    – nyronium
    Jul 1, 2019 at 10:20
  • \$\begingroup\$ Have you got the current limiting set to 1.58A on your power supply? \$\endgroup\$
    – HandyHowie
    Jul 1, 2019 at 10:59
  • 2
    \$\begingroup\$ 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? \$\endgroup\$
    – Andy aka
    Jul 1, 2019 at 11:56
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    \$\begingroup\$ @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? \$\endgroup\$
    – Steve G
    Jul 2, 2019 at 7:45

1 Answer 1


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.


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