I'm using a 12v power supply with 12 meter cable ( 0.5mm ) to feed 4 small motors that use around 3A.

My problem is that when I turn all the motors the voltage goes to 7 volts. I need it t stay around 10-12V.

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I need to use the power suplly away from the motors 6 to 12 meters.

Any solutions to avoid this voltage drop on the cable?

  • \$\begingroup\$ Thicker cables. \$\endgroup\$
    – PlasmaHH
    Commented Feb 1, 2017 at 16:02
  • \$\begingroup\$ any other way?? \$\endgroup\$ Commented Feb 1, 2017 at 16:02
  • \$\begingroup\$ Firstly, paint nice schematic, otherwise it might be flagged. Also, what makes you think it's voltage drop and not too much current drawn from your power supply? \$\endgroup\$ Commented Feb 1, 2017 at 16:05
  • \$\begingroup\$ My power suplly says 11A from the 12V rail. It should work. It was working with 1 meter cable. The problem is that when I put a lot of cable lengh the voltage drops a lot when the motors turn on. \$\endgroup\$ Commented Feb 1, 2017 at 16:06
  • 1
    \$\begingroup\$ You say the cable is 0.5mm. Is that the cable diameter? Also, you say the 4 motors use around 3A, is that 3A each for a total of 12A, or 0.75A each for a total of 3A? Please answer both questions. The voltage drop in a cable can be calculated if the current and cable diameter and length are known. \$\endgroup\$
    – user57037
    Commented Feb 1, 2017 at 16:19

2 Answers 2


Get a power supply that has a remote sense feature — extra connections that allow you to run separate sensing wires to the point of load. Since these wires do not carry any significant current, they experience no voltage drop and provide accurate feedback to the regulator. When voltage drop occurs in the power wires, the regulator can sense it and provide extra voltage at the source to precisely compensate for it.

You can use a single supply if the motors are close to each other. If they are widely separated, you'll need a separate regulator for each one.

Edit: Obviously, there is a limit to how much drop can be compensated for; you also need to select wire that is appropriate for the current being carried.


Do not use PC power supply for single supply use, the power supply is designed with single output transformer for multiple outputs like +12, -12v, 5V, with the reference to 5V supply load, so using only 12V may not work as expected on full load condition. Also PC power supplies are not designed to take care of the initial surge current required by initial motor start conditions

Use a dedicated 12V power supply that can source 15A to cover the initial spike current when all motor is powered on. Also use a good cable


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