Ethernet Shield + External Power Supply = Lots of heat!

Using Arduino Networking, Protocols, and Devices
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Just as a header, I wasn't sure which forum this was quite appropriate to post to (Networking or Power) since it crosses the line between two categories, so please let me know if I should move this. Also, while I have some electronics experience, I am a total newbie at understanding the subtleties of how the Arduino deals with power.

Hardware I am working with:
Arduino Duemilanove (both the 2009 and 2009 rev b model): http://arduino.cc/en/Main/ArduinoBoardDuemilanove
The most recent Arduiono Ethernet Shield: http://arduino.cc/en/Main/ArduinoEthernetShield
A standard 12v 600ma wall wart: Wall Adapter Power Supply - 12VDC, 600mA (Barrel Jack) - TOL-15313 - SparkFun Electronics

All the hardware works great! My eventual goal is to host a small website off of the arduino. So far I have a simple example running using the following library:
http://www.webweavertech.com/ovidiu/weblog/archives/000484.html

So far the software and hardware are running great while powering it over the USB cable. I would like to have this thing run on its own eventually, and this is where I am running into issues.

When running the Arduino with the Ethernet controller using the 12v power supply, the power regulator next to the power plug on the Arduino gets ULTRA hot. Too hot to touch! The regulator on the Ethernet shield gets hot too. Everything still works fine, but it's all very hot. Just to reiterate, the Arduino and shield do not get this hot when powered by USB. They get warm, but nothing to concerning. I'm a bit worried that the heat might eventually damage the hardware if I run it with the external power supply for a long time, or possibly affect the stability or performance of the code running on it.

Additionally, when powering the Arduino with the external supply, with the Ethernet shield REMOVED, it does not get hot. Warm (as to be expected), but not hot.

I have a couple questions about this.

  1. Anybody know whats going on here?
  2. Is there any discussion or documentation about this kind of issue regarding external power + Ethernet shield = lots of heat?

My initial idea is to just use a standard USB charger (like the iphone or digital camera chargers you get) to power this thing without so much heat. I have seen some people say that this method generally works to power Arduinos. It would be nice however, to know that I could always use a standard power supply so if anyone know how I could do that without so much heat generated I would love to hear.

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It apparently has a linear voltage regulator. And it was apparently designed to handle the Arduino and just a little more.

The higher the input voltage, the hotter it will get. Try a 9v wall wart instead. It will get really warm, but not like HOT.

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  1. Anybody know whats going on here?

Current. The USB cable limits the amount of current a device can pull, so the voltage regulators don't get hot.

A wall-wart does not limit the current (beyond what it can supply). If the wall-wart can supply 2 amps, it will. This is, of course, significantly above the 500mA that USB supplies.

The USB also supplies that voltage at a regulated 5V, so the voltage regulators don't have to waste the extra as heat.

A 9V supply (NOT a battery) would be a better choice.

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SurferTim:
It apparently has a linear voltage regulator. And it was apparently designed to handle the Arduino and just a little more.

The higher the input voltage, the hotter it will get. Try a 9v wall wart instead. It will get really warm, but not like HOT.

What do you think about powering it with a USB power adapter? I'm not making any ADC measurements that need accuracy.

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That is how I power my remote units. They are connected to a router that has a USB connector. The router's power supply is a switching type designed to support high power wifi radios. Plenty of power, and not much heat there! :slight_smile:

Add: I can also log in to that router with a special user name, and connect to the serial I/O of the Arduino by SSH.

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SurferTim:
That is how I power my remote units. They are connected to a router that has a USB connector. The router's power supply is a switching type designed to support high power wifi radios. Plenty of power, and not much heat there! :slight_smile:

Add: I can also log in to that router with a special user name, and connect to the serial I/O of the Arduino by SSH.

I didn't even think of that. Very slick! I'll give it a shot.

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Ckeck the +5v pin to see what the voltage actually is when supplying from external 12v. When I powered my arduino/ethernet shield from a 12v supply via the external power connector, the measured voltage at the +5v pin jumped to 8-9v! The arduino seems to have a tutti-frutti power supply swapping setup that might be the issue. The ethernet shield uses a lot of power and the w5100 chip temp runs ~20 deg F above ambient temp.

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I'll do the same check later this evening, although I bet it will do something similar. These devices get cooking when in this configuration!

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Open Sesame