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Topic: Power source making a difference? (Read 596 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.
What about elevensies? Luncheon? Afternoon tea? Dinner? Supper?


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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