Recently I have asked a question, why my sensors do not work on external power supply (link). I have found out, that I was limiting the current too much with the resistors. I have tried using two sensors:

My logic is, if they are rated at that current, I should put a resistor in the Vin, to restrict the current to given value. But it turned out that I was wrong, because they started working only after I removed my resistors.

My questions is - should I put a resistor in there? If yes, then how do I know what resistance should I have, if the data sheet values are misleading?

1 Answer 1


You should have NO resistor.

The datasheet states the current values the device will pull from the supply. Supplies DO NOT PUSH CURRENT.

Remove all resistors.

As long as the voltage is correct and the supply can provide at least as much current as all devices combined want to use then it will work.

  • And I was wondering, why every electrical component had clearly specified the operating voltage, but the current was somewhere below in the details section. That would explain things. Thank you!
    – ojek
    Oct 21, 2017 at 22:26
  • 1
    99% of components and devices require a specific voltage to operate, and the current varies depending on what it is doing at the time. The main exception is LEDs which have to have a specific current instead of a specific voltage.
    – Majenko
    Oct 21, 2017 at 22:33

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