Putting a coin cell on the bottom of a sheild?

Forum 2005-2010 (read only) Hardware Development
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I'm working on a design shield and have a "tricky" dimensional question. I don't have a Duemilanove in front of me to test, though that's the platform I'm ultimately designing for.

Here's the problem: I need a coin cell on the shield, but I want to put it on the "bottom" (the side that faces the Arduino) to preserve space on the "top" for other components.

It looks like clips for 12mm cells are available that are 2.34mm tall. Is there enough room? It looks like there would be enough room up by the digital headers, but since I can't actually measure, I'm not 100% sure. The holder is 13.2mm in diameter.

Short of me ordering a Duemilanove and waiting a week or two, can someone let me know if this would fit? Anyone done this before?

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I cant answer your question, as I am a bare bones user, but if plan A does not work out, may I offer a plan B

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on the diecimila you could easily fit something that size beside the headers down by the usb connector. that said, i'd want to mock it up with the real board and cell before i committed anything.

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You could also potentially use longer legged headers to raise the shield up higher from the Arduino. Another possibility is to buy a Seeeduino, which uses all SMT components (it would give you more room).

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well buying a Seeeduino doesn't work for everyone that would potentially buy this shield in the future

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Well the shields PCB doesn't have to be the same size as the arduino. So you can always have it a little wider or longer to fit a vertically mounted battery.

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The headers on the Arduino Duemilanove are 8mm high, and the circle in the picture below is 13mm in diameter. The circle could fit anywhere in that upper part of the board between the right edge and the USB connector, or in the area near the voltage regulator, though you probably want to avoid any heat over there. There is not enough height above the ATmega328 itself to fit anything. Still, you should have no problem finding a place for your coin cell on the bottom of your PCB.

If you want to scale your own drawing, you can use the picture at http://arduino.cc/en/Main/ArduinoBoardDuemilanove. According to the bottom of that page, the PCB for the Duemilanove is 2.1 inches (53.3mm) from the top edge to the bottom edge, and 2.7 inches (68.6mm) from left to right. My cheapo ruler confirms that closely enough.

Don't forget to consider that your shield may not be stackable with other shields unless it is the bottom of the stack.

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