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I'm working on a project and I need to power some RGB LED strips; three strips that need 12 V, 5 A each. The thing is that I have one switched-mode power supply of 12 V, 10 A and some 12 V, 5 A power supplies that came with the LED strips/ I assume these are linear supplies.

So the SMPS was already installed; can't I add one of those 12 V, 5 A LED supplies in parallel with the SMPS to get the 15 A needed for three RGB LED strips?

The RGB LED strips will be controlled by an Arduino and all will have a common ground.

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  • \$\begingroup\$ Can you specify if you mean "I power 2 strips from one supply and 1 from another" or "I want to join supplies' outputs and then feed all of that into LED strips"? \$\endgroup\$
    – Ilya
    Feb 25, 2022 at 23:50
  • \$\begingroup\$ @Ilya I want to join supplies output to feed everything \$\endgroup\$
    – Joe X
    Feb 26, 2022 at 0:02
  • \$\begingroup\$ Then Peter's correct. It's a bad idea. \$\endgroup\$
    – Ilya
    Feb 26, 2022 at 0:03
  • \$\begingroup\$ @Ilya so the RGB connection from all the led strips will be connected to the arduino and the 12V from 1 strip will be connected to a separate power supply? \$\endgroup\$
    – Joe X
    Feb 26, 2022 at 0:07
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    \$\begingroup\$ Feed the strips separately. Join grounds. Control signal may be the same, bring more information about strips. \$\endgroup\$
    – user263983
    Feb 26, 2022 at 0:09

1 Answer 1

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No, you shouldn't connect power supplies in parallel unless they are designed to work in parallel.

The two supplies will likely not be exactly the same voltage, so the higher voltage supply will supply all the current while the lower voltage supply delivers none.

In your application, you may be able to arrange for the 10 Amp supply to power two LED strips, while the 5 Amp supply powers the third strip.

The grounds of the two 12 volt supplies and the Arduino Ground should all be connected together.

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  • \$\begingroup\$ so does that mean that the 3rd led strip, which have R, G, B and 12V connection will have the RGB connection shared but the 12V? \$\endgroup\$
    – Joe X
    Feb 25, 2022 at 23:55
  • \$\begingroup\$ I mean all 3 led strips RGB connections will be connected to the Arduino and the 12V connection from 1 led strip will be connected to a separate Power Supply? \$\endgroup\$
    – Joe X
    Feb 26, 2022 at 0:09
  • \$\begingroup\$ Still unclear. Draw the schematic. Words don't cut it. \$\endgroup\$
    – Ilya
    Feb 26, 2022 at 0:15
  • \$\begingroup\$ ok, I'm downloading kicad, because circuito.io couldn't help me out for this... \$\endgroup\$
    – Joe X
    Feb 26, 2022 at 0:41
  • \$\begingroup\$ @JoeX use the schematic editor that is included in this webpage ... go to your question and click edit ... then click the circuit icon .... after drawing the schematic, click save and insert \$\endgroup\$
    – jsotola
    Feb 26, 2022 at 1:22

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