How can I power 8 servos simultaneous using a battery?

Hello,

I been working on a small project at home. I have a mobile robot with 2 servos operating the wheels and 6 others operating an arm, making it a total of 8 servos. I'm currently using Arduino Mega and an external power supply, a modified ATX power supply (5V 30A). I have a battery from a previous R/C car project, 7.2V 4500mAh. I would like to use this battery to power the robot. I've tried connecting it directly but the servos do not switch on. I get a big voltage drop and current drop, as many of you figured out already. I thought if I made a simple voltage follower it would work, but didn't. How else can I power these servos without buying a Servo Controller. I would like to make a circuit with parts that can easily be found locally. Any help that can be offered, would be great.

Those servos do not need to be fed power from the arduino. I'd connect them directly to the battery. If using an arduino with a built in voltage regulator all you'd need to do is connect it to the battery.

Most hobby servos will happily run on 7.2V. You only need to connect the grounds together between the arduino and all the servos, connect all the power wires to the battery and the signal wires would be connected to the controller as you currently have them.

There's a guy over here:

witha very similar problem to yours.

:0

Most hobby servos will happily run on 7.2V. You only need to connect the grounds together between the arduino and all the servos, connect all the power wires to the battery and the signal wires would be connected to the controller as you currently have them.

That's strange. My experiance with R/C servos is that voltage must be between 4.8 to 6.0vdc. I'm sure 7.2vdc directly fed to a servo's power wire could damage 'most' servos. Perhaps you can show us where 'most' servos have specified voltage requirements that would include 7.2vdc?

Bottom line, always refer to the manufactures datasheet for requirements for your specific servo model before excepting on blind faith things you read on the web.

Lefty

Thank you for the information everyone and Lefty I agree with you. I will be using a voltage regulator to operate all my servos.

The RC types that use a lot of servos, use UBECs like below, which are very efficient.

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6233