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Are there any special considerations I should pay attention to, when I wire multiple LEDs in Parallel?

I am doing a project with a 100 LEDs in parallel. Each LED could be a different color, and each LED is wired with a resistor (or should I not do this and group the LEDs with one resistor?)

I've calculated each resistor with regarding to the amount of current the LED will draw, and the power supply will come from a wall wart rated at 5v and 5A.

Sample diagram:

LED in Parallels

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  • \$\begingroup\$ Hmm... I see from the data sheet the forward voltage of this LED is 2 V. Then how can you supply it by only 1 V? \$\endgroup\$ – Circuit fantasist Jan 12 '15 at 23:27
  • \$\begingroup\$ In case you're not familiar with CircuitLab, all those values are the defaults. \$\endgroup\$ – Majenko Jan 12 '15 at 23:29
  • \$\begingroup\$ The important thing is to read the words, not look at the picture. He's using a 5V supply and a range of different LEDs, each with its own resistor calculated to suit. \$\endgroup\$ – Majenko Jan 12 '15 at 23:35
  • \$\begingroup\$ Regarding the circuit diagram, it should be still correct regardless of how it is prepared. \$\endgroup\$ – Circuit fantasist Jan 13 '15 at 8:03
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You have done that absolutely correctly.

People often fall into the trap of having just one resistor for a group of LEDs in parallel, which is completely wrong - doing so will cause uneven brightness in the LEDs at best, and at worst would lead to a cascade failure making the LEDs all fail, with some even exploding.

So one resistor per LED, or one resistor per chain of series-connected LEDs, is the right way to go.

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  • 1
    \$\begingroup\$ @Bill Keep in mind that different LEDs may have different currents and forward voltage drops. So, they may require different resistors. (But, you have already figured this out by yourself too, I think.) \$\endgroup\$ – Nick Alexeev Jan 12 '15 at 22:45
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If you've got different colors, then they will run at different voltage drops. (Red lowest, then green, blue.) Equal resistors would give red the most current... this may be what you want. The details depend on the leds.

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