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Topic: Ethernet shield.. power supply and overheating (Read 1 time) previous topic - next topic


Hi all,

I have read in several threads that using external power with the Ethernet shield normally can produce overheating problems... and I need to tackle that :)

I have tried a 9V/444mA AC/DC transformer, using Vin and Gnd pins for connections,  and I get the shield to work, but the Duemilenova power regulator gets really hot.

Even so, I am not sure if this is within the operational range of the devices involved here... My piece of hardware project is quite critical and I need the set to work 24/7. I am not sure if in the long range I can damage the boards or if it will stop working properly.. after all, many electronic devices get like that

In case you guys think that I should change the AC/DC transformers, should I decrese the voltage or the current? Will I be safe with a 7.5V input?

Thanks a lot guys!


Mar 16, 2010, 04:53 pm Last Edit: Mar 16, 2010, 04:53 pm by Grumpy_Mike Reason: 1
should I decrese the voltage or the current?

I think that question shows exactly what stage you knowledge about electricity is.

You should decrease the voltage to 7.5V to reduce the power dissipation of the internal regulator. Alternatively use an external regulator.


Thanks grumpy_mike, exactly I donĀ“k know much about electricity..

thanks for your help.


Have you considered powering it with 5V?  That way you could bypass the voltage regulator and get power in through the USB port or directly to the VCC pin.  I've used USB power adapters with no problem.

Do you know how much current your project draws?
My Arduino blog: http://jmsarduino.blogspot.com
Comprehensive (?) Arduino-compatible board list: http://tinyurl.com/allarduinos


Does your Ethernet Shield start with an external power supply? Mine does not and i always have to push the reset button to have Ethernet Shield going to work.


Hi DRose,

there is a known HW bug with the ethernet shield.. apparently you can fix it by using capacitors in the reset pin. Check this thread:


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