# How does Arduino power a servo if the Arduino pin output is only 20 mA?

HI

I’m wondering how the Arduino can power 1 small 9g servo (the standard blue ones of multiple brands) direct from the pins when the DC Current per I/O Pin puts out a maximum of 20 mA? I believe my servo can spike to 600 mA.

I’m also wondering if it makes a difference to power the Arduino with anything more than 5V because doesn’t the voltage get regulated to 5V anyway? A recent project I have been working on seems to work only at battery voltages higher than 9V when I power through the V-In pin. I thought this might be because more current gets supplied but then I found out that lowering the voltage increases current. Not sure why that is true also because V=IR and looking at that formula it tells me that when you increase either V or I, you should increase the other right?

Confused as fog

Thanks

You don’t power a servo from an I/o pin, you simply control it.

bodkin77: I'm also wondering if it makes a difference to power the Arduino with anything more than 5V because doesn't the voltage get regulated to 5V anyway?

It just allows you to use a wider range of supply voltages, depending on what's convenient.

A recent project I have been working on seems to work only at battery voltages higher than 9V when I power through the V-In pin.

You need about 7V minimum when you power via the DC power jack, to allow for the series diode and the dropout voltage of the regulator. Powering by the Vin pin, you can get away with slightly less, because you bypass the diode. That diode provides reverse-polarity protection. If you use the DC jack, accidentally connecting with reverse polarity will do no harm.

I thought this might be because more current gets supplied but then I found out that lowering the voltage increases current.

I don't know where you heard that lowering the input voltage increases the current, but it's not true. As you point out, I = V/R. In the case of an Arduino DC jack, because the voltage applied to the load is a constant 5V, increasing the voltage won't increase the current, only power dissipation in the regulator. As long as it's above about 7V, the lower the input voltage the better, due to the above-mentioned power dissipation. P = VI. Assuming a current of 200mA, due to the Arduino's current consumption added to that of other connected devices:- If you supply 12V to Vin, the dissipation in the regulator P = (12V-5V)*200mA = 1.4W. If you supply 7V to Vin, the dissipation in the regulator P = (7V-5V)*200mA = 400mW.