Power supply probelms

Hello, i recently purchased an arduino UNOto power 2 servos, how ever, there seem to be a problem with the power supply, the project can only work if i plug both the USB and 9V to the UNO. if i plug only one, the UNO wont work. is it the UNO or could there be some other reasons? Thanks!

Servos often need more current than the USB can supply. You should power them separately.

That is because your two servos require more current then your wimpy 9 volt battery can supply. Even using USB power is not proper for powering servos, you really need to provide an independent voltage source to power servos on arduino projects.

Lefty

hi, thanks for the reply, i am actually using a Ac-Dc 9 v 1A power supply, but even that is not enough, however when i plug BOTH the USB and 9V, it works. i have even tried 12 V but it will not work till i plug the USB inside.

desmondttm123:
hi, thanks for the reply, i am actually using a Ac-Dc 9 v 1A power supply, but even that is not enough, however when i plug BOTH the USB and 9V, it works. i have even tried 12 V but it will not work till i plug the USB inside.

Again it's not the voltage it's the current demand that is giving you the problems you are seeing. Servos require voltage of 4.8 to 6.0 vdc and I budget 1 amp of current capacity per servo.

Lefty

Ic, so if i want to only use 1 power supply, what would you recommend me to use? would a 2A be sufficient?