I am currently making a shopping list for an LED light strip (link) and I am getting 3m of it. Now, my main problem is powering that beast.

By my calculations, (42W * 3m) / 5V = 25.2A, if that is correct, that seems like an insane amount of power for such a strip, and any power supply I could find that was > 15A is just a barebones transformer.

They have listed that 42W/m is the maximum power draw, which I am not extremely likely to do, so I am currently looking at this power supply. Would it be sufficient?

  • \$\begingroup\$ Do you mean, "I am not extremely likely to do", or do you mean "which I will not do, and I won't even try to draw 1/2 of that"? Unless you can unequivocally say it's the latter, you need a 25 amp power supply. \$\endgroup\$ Jun 11, 2016 at 20:13
  • \$\begingroup\$ @WhatRoughBeast Alright, I will start looking for some 25A supplies, thanks :) \$\endgroup\$
    – Vilsol
    Jun 11, 2016 at 20:23
  • \$\begingroup\$ If you broke the strip into 5 60cm lengths and wired them in series (with some level shifting magic for the control data) you could possibly use a 24V 5A power supply, 25A is like 12awg cable or a 2mm solid copper bar or something, how on earth are they pushing 8A/meter through that little flex pcb? Surely the voltage drop alone... \$\endgroup\$
    – Sam
    Jun 12, 2016 at 0:28
  • \$\begingroup\$ In addition to 'max' of 1W, the data mentions typical dissipation of each package as 0.2W; that suggests that 42 packaged lights per meter would typically draw 8.4W per meter, which might not be a bad typical-power estimate. 3 meters, 5A at 5V. \$\endgroup\$
    – Whit3rd
    Jun 12, 2016 at 1:24
  • \$\begingroup\$ @Tom On all the pages I could find, no one recommended higher than 24V otherwise it would kill the LED's. Also Each 1m segment has 144 LED's, so that's still 86.4W \$\endgroup\$
    – Vilsol
    Jun 12, 2016 at 23:06

1 Answer 1


If you choose to power a full 3 meter string from one end with one large power supply, you're going to have voltage drop problems I think at the other end and I think you're PCB traces will be hotter than you want if you drive them at full.

I suggest cutting the power and ground trace after each segment of 144 LEDs and powering each of the three segments with a separate 50W power supply. Just cut the PWR and GND traces of course...leave the data and clock lines intact.

The IRM-60-5ST from Meanwell is perfectly suited and you can buy from Mouser.

I have a feeling that the real world current draw from the APA102C is lower than the datasheet says when driving white (level 255 on all 3 colors).

Please post your real world current for driving 144 of these at full. Will be interesting to see. Maybe you can get by with a smaller power supply after all.

  • 1
    \$\begingroup\$ It's probably better to just disconnect the +V connection and leave the ground in place, you might have some signal integrity issues otherwise \$\endgroup\$
    – Sam
    Jun 13, 2016 at 1:55

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