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Topic: Power source making a difference? (Read 641 times) previous topic - next topic


I have an Arduino Duemilanove, and my program is 100% working and running great when being powered through USB, however, when I switch over to a 9V 100MA power adapter nothing seems to run.

I have two servos, an LED, and a WII nunchuck connected to the Arduino... Can anyone think of something that I can do to correct this?

Thank you.


The first thing to do is rule out the 9V adapter as the cause.  Try running it off of a pack of 4 or 6 AA batteries and see if you still have the same problems.  If you do, then it's a problem in the wiring or programming.  If not, then the 9V adapter is the cause and should be replaced with something better.  Don't use a 9V battery as a test replacement power source.  You need a battery pack that can deliver enough current.  The USB ports on a computer are rated for up to 500 mA. So you may just be pulling too much current from the 9V, 100mA adapter.


Actually, I believe that is exactly the case... This page: http://www.arduino.cc/playground/Learning/WhatAdapter says 250 MA or more...

Thanks for your help.

Ran Talbott

That adapter is hopelessly inadequate to the job:  even micro-sized servos are likely to overload it.

It's always a good idea to power motors from a separate supply:  they generate a lot of electrical noise that can cause reliability problems,  and big ones are likely to overtax the Arduino's onboard voltage regulator.

These days,  you can get a 5V regulated power supply that's good for a couple of Amps for $10 or less.  I recommend doing that,  and wiring up the servos with their own supply.  Especially if they're going to be doing any heavy lifting or spinning.

Be sure it's a regulated supply:  the really cheap ones will put out a voltage much higher than the nominal one if they're not fully-loaded,  and might damage the servo electronics.


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