power requirement for 2 hobby servo and ethernet shield

Hello, I'm working on a project with an ethernet shield (Wiznet 5100), and two hobby servos (TowerPro SG90). I'm concerned about current consumption and want to ask before connecting things. I don't have a good sense for these things.

Can an an Arduino power both servos and the ethernet shield? For the servos, only one of them will be running at a time. But I read that servos consume current even if not moving.

I tried looking this up myself, but couldn't find current for the ethernet shield (only the datasheet 5100 chip). For the servo, one of them is moving freely and the other has a 10 gram weight that it's moving around. I couldn't find a source to estimate this current consumption, but maybe if someone has a good feel for this, and can give me a guess?

Thanks!

NEVER power a servo from the Arduino: control it yes (the yellow or orange wire), but power it no.

Pic below shows how to hook them up; main thing is to have a common ground so the signal has a reference 0V to measure from.

servo power.png

JimboZA:
Pic below shows how to hook them up; main thing is to have a common ground so the signal has a reference 0V to measure from.

Thank you for the wiring diagram!

If I use two different USB chargers (one charger to power the Arduino, the other to power the servo), I’m not sure if I can assume that their commons are at the same level. Can I tap off the Servo’s USB charger’s DC common and tie it directly to the GND pin on the Arduino? Would the two USB chargers “fight” each other if only their commons are tied? Also, I’m powering the Arduino from the USB cable, not the barrel connector. Not sure if that makes a difference.

I “drew” the circuit I was thinking of below:

Yeah that pic looks right. When you join the -ves together you are making sure they're at the same level, no assumptions necessary.

You might not get enough current for the servos though: they can draw up to an amp depending on the load, so you may find it worthwhile to measure that current and check / spec the supply accordingly.