In mm what is the power socket size?

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

Two simple questions from a beginner here.

  1. What size in mm is the power socket on a Duemillenove? (I assume 2.5mm, centre positive, but need confirmation. Sometimes things go pop unexpectedly)

2.If I load a sketch onto my arduino, then test it whilst supplied from the PC/USB power, When I then connect to a wall wart/other source, will the sketch automatically just run, or do I have to push the onboard microswitch? (If I don't push it to run, then what's the switch for?)

Simple questions, but everyone starts at the beginning.....
Thanks in advance. McP

2

From:
http://arduino.cc/en/Main/ArduinoBoardDuemilanove

External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector.

You should automagically get a power-on-reset.

3

If I don't push it to run, then what's the switch for?

The switch resets the Arduino, assuming it's plugged in to a power source and already running.

4

Thanks for the info, 2.1mm is an odd size, not rteally noticed that size in my travels
McP

5

2.1mm center positive has been pretty common in my experience - when I got my first Arduino, I just happened to have two or three compatible wall warts just sitting around.

FWIW, This plug size is occasionally listed as "5.5/2.1" since the OD is 5.5mm and the ID is 2.1mm.

Here is a vendor that has several compatible power supplies:

http://www.mpja.com/products.asp?dept=37&main=1

I'm using this one on a project right now:

http://www.mpja.com/prodinfo.asp?number=17836+PS

6

In practice most 2.5 mm power connectors work with the arduino as well as the official 2.1. 0.4 mm isn't much for the spring 'blades' in the plug to take up. You can't use a 2.1 plug in a 2.5 socket because the hole in the plug isn't big enough for the pin.

7

Thx for the clarification Pluggy, i'd seen both 2.1 and 2.5mm listed and hadn't considered that both might be correct.

8

That is something I questioned before. I knew it took a 2.1mm but in the "PLAYGROUND" under "Connecting and powering the Arduino" it states:
The short answer is: 9 to 12V DC, 250mA or more, 2.5mm plug, centre pin positive.

Which is wong and should be changed by the "GODS"
There is also another reference to it for making the 9v clip.

9

The 2.1 mm is the correct version, I merely stated that 2.5 mm connectors will often work. In some cases where there isn't enough spring in the connector in the plug, a 2.5mm won't work.

10

The short answer is: 9 to 12V DC, 250mA or more, 2.5mm plug, centre pin positive.

For what it's worth (< $0.02), I have always used 2.5mm power plugs because that's what it said, and when I compared 2.5mm with 2.1mm I found that 2.5mm had a pleasantly tight mechanical fit, whereas the 2.1mm seemed a bit sloppy.

GB

PS - SINE