Powering Two 7.4V Servos on UNO

Hi,

I am trying to power two servos on the UNO board. I am fairly new to electronics and wanted to seek help before I do anything to fry my board.

This is the servo I am using:

I am wanting to use 7.4V to achieve the 180 rpms. The Arduino obviously can not handle two servos at over 14V and 360mA of current. I've researched countless articles and seen multiple solutions (who knows if they are correct) but before I made any decisions I decided to ask someone with knowledge of the Arduino.

I understand I'll probably need a external power source such as batteries or regulated power supply. Any help would be greatly appreciated. If any other details are needed please let me know and I will respond quickly.

Thank you!

In examples a 5V servo motor is sometimes powered by an Arduino 5V pin. But the 5V pin of the Arduino is often not strong enough to power a single servo motor.

Rule of thumb: Always use an external power supply for a servo motor.

Your servo motor accepts normal 5V signal for the white control wire.

This is what you could do:
Connect Arduino GND to servo motors GND (black wire). Let's call that: the common GND.
Get an external power supply, either 7.2V battery or regulated power supply of 7.2V (6V to 8V). Connect the GND of the power supply to the common GND, and connect the 7.2V to both servo motors red wire.
Connect two Arduino outputs to the white wires of the servo motors.
Use the Servo library : Servo - Arduino Reference

Peter_n:
In examples a 5V servo motor is sometimes powered by an Arduino 5V pin. But the 5V pin of the Arduino is often not strong enough to power a single servo motor.

Rule of thumb: Always use an external power supply for a servo motor.

Your servo motor accepts normal 5V signal for the white control wire.

This is what you could do:
Connect Arduino GND to servo motors GND (black wire). Let's call that: the common GND.
Get an external power supply, either 7.2V battery or regulated power supply of 7.2V (6V to 8V). Connect the GND of the power supply to the common GND, and connect the 7.2V to both servo motors red wire.
Connect two Arduino outputs to the white wires of the servo motors.
Use the Servo library : Servo - Arduino Reference

I could not have asked for a better reply. Very simple and helpful. Many thanks!

Quick questions though, if I have two servos at 7.2V each would I need a 14.4 battery or regulated power supply? Also, would current play any part in selecting my alternate power source?

Don't try 14.4V, it will damage the servo motors, and perhaps the Arduino as well.

Suppose you have 100 servo motors. They all should be connected with the black wires to the common GND. They all should have the red wire to the 7.2V power supply. The GND and 7.2V will be like a power rail that powers all the servo motors. That way every servo motors gets 7.2V.

A servo motor can often require 0.5A or 1A. These seems to be very low current with only 130mA (+/- 50mA).
Since you want 180 rpm, you could use a switching power supply of 7.5V 1A. That can be a wall wart with a few selectable voltages.
Please don't buy the cheapest power supply from Ebay, buy a certified power supply.

P.S.: You don't have to Quote my post (what I have written is already there :wink: ). You could use the Reply button or the Quick Reply text field.

From the Parallax documentation for that particular servo:

Servo current draw can spike while under peak load; stall current can approach 1 ampere

So you need a 6-8 volt regulated power supply capable of supplying 2 amperes, for two servos.

Incidentally, the servo documentation clearly shows the recommended wiring as requiring TWO power supplies, one for the microcontroller and one for the servo(s). The data sheet is your best guide to proper use.

Thanks jremington. I didn't read the datasheet very well :-[ Indeed it says: "stall current can approach 1 A".
jamyers1, jremington is right. you need a power supply of 2A.