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I have an Arduino board which is controlling a servo. I think I read that I could only supply about 100 mA through the Arduino's 5v pin. Because of that the power supply I use is able to deliver about 2A I would like to split the power before the Arduino. How do I do that?

Do I have to take some safety for the Aduino in concern or could I just split the wire?

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  • Is your power supply 5V regulated?
    – jfpoilpret
    Nov 26 '14 at 19:44
  • It is a supply that is used to load a tablet, an AC/DC adapter. How do I know if it is regulated?
    – rablentain
    Nov 26 '14 at 20:00
  • I think 500mA would be a more accurate rating. That is the rating of the fuse on the board. I don't know where you got the 100mA from?
    – Gerben
    Nov 26 '14 at 20:36
  • Actually my question rather was: do your power supply output 5V or more than 5V? If it is 5V, it is likely to be regulated. A second question is where do you plug it to your Arduino (USB, power jack, Vin, 5V)?
    – jfpoilpret
    Nov 27 '14 at 6:21
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If you have a 7V to 12V - 2A regulated supply, you can directly power your board using the 2.1mm connector. Do not go above 12V or you may destroy the voltage regulator on the board.

If you have a 5V to 6V - 2A regulated supply, you can supply your servo with this supply and rely on USB to supply the rest of the board (make sure you have a common ground for both the USB and the regulated supply).

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  • "Do not go above 12V or you may destroy the voltage regulator on the board" I don't agree with this. First of all it depends on the board. Then, if we take the UNO as example, if you are you trying to get 800mA from the 5V rail nything above 7.5-8V will cause problems. If OTOH you are you trying to power only a 20mA LED even 20V is fine. Saying that the limit is 12V is correct in a limited amount of cases (max current ess than 200mA)
    – frarugi87
    Mar 21 '18 at 9:31
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There is a page with information about the current limits of Arduino pins. There's also a question on the Electrical Engineering SE site that addresses the current limits of the board overall.

From the accepted answer on that question:

The 5V output pin is good for ~400 mA on USB, ~900 mA when using an external power adapter

So that's more than the 100 mA you mentioned in your question. (But go read the whole answer; there's more good info there.)

The easiest way to split the power is to use a separate, regulated power supply.

Except for simple tests (e.g., a single small unloaded servo), I use the digital i/o pins only for very low current signals: buttons, status LEDs, sensors, serial communication, etc.

For example, to control an IR LED that can handle up to 50 mA, I'll supply power to the LED from the Arduino board's Vcc pin and control it with a transistor attached to a digital output pin. Drawing 50 mA from the board's supply is well under the limit, and the digital output pin draws practically nothing.

For more than one servo, I use a peripheral PWM controller that takes power separately. That peripheral is powered by a separate 5V 2A power adapter, which supplies the current to actually turn the motors. I send commands to the controller using I2C from the Arduino, which is running from its own power supply.

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  • Please note that "can source 200 mA (milliamps) from the Vcc pin" is NOT correct. That part comes from the datasheet of the microcontroller, and means that the maximum current that can flow inside the uC Vcc pin or outside the GND pin is 200mA. This means that the sum of all the currents sourced/sinked by the digital pins is 200mA (so 40mA for each pin, but max 200mA total). This is not for the Arduino +5V pin
    – frarugi87
    Mar 21 '18 at 10:23
  • @frarugi87: Ah, I misunderstood. Thanks for the clarification. I'll try to incorporate that correction into this answer. Mar 21 '18 at 15:47

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