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I'm building an open-source bio-research hardware (ask me how you can help!) and I've got this guy here:

enter image description here

My big questions are:

  • Can I get away with all the ground being common? (I've got a 12v and 5v needing to be grounded)

  • Do I need two sets of capacitors? There are 2 wired up to the 12v regulator and 2 wired to the 5v regulator. (These are shown in blue)

I've generally denoted connections which go UNDER the shield as orange, and those above as green.

If anyone happens to see something which might backfire, feel free to point it out. As this is also my first time making anything quite like this!

  • I've verified the regulator positions and they are correct.
  • This is a proto-shield for an Arduino R3 Uno.

A larger version of the image can be seen here: http://i.imgur.com/BPXjn.jpg

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    $\begingroup$ You might want to post a schematic and/or a bigger version of this image. It isn't that easy to figure out what is going on at first. $\endgroup$ Dec 3 '12 at 23:58
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    $\begingroup$ Just replacing this image with a block diagram should clear it up a great deal. $\endgroup$
    – Ian
    Dec 4 '12 at 12:39
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Can I get away with all the ground being common?

That's exactly what should be done.

Do I need two sets of capacitors?

Yes, you usually want to keep all capacitors as they are even if you are cascading voltage regulators. They help keep the regulator stable and avoid sharp voltage variations.

Be aware that either regulator might limit the amount of current that can be supplied to your system (if you have things hooked up in the 12V regulator besides the 5V regulator, for instance).

I find it odd that you need a 12V regulator though... Where is the input voltage coming from?

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  • $\begingroup$ Im pulling the 12v off of the Vin pin from the arduino ... I was advised to have a 12v regulator to ensure that I dont get spikes from the wall plug $\endgroup$
    – carl crott
    Dec 3 '12 at 23:59
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    $\begingroup$ OK, so you have 12V adaptor for the wall plug. Using a 12V regulator is a good idea, but you might be able to get away with simply using a capacitor to filter spikes if you don't actually use the 12V anywhere. Another option in that case is using a voltage regulator to an intermediate voltage (i.e. 8-9V) so that heat dissipation is more evenly distributed among regulators). $\endgroup$ Dec 4 '12 at 0:02
  • $\begingroup$ Oh I am feeding the 12v directly into the stepper driver pololu.com/catalog/product/1182 .. but it IS listed as having overcurrent protection ... so maybe I dont need it? $\endgroup$
    – carl crott
    Dec 4 '12 at 0:04
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    $\begingroup$ @georgebrindeiro - Since people edit their question, it's best to include the text of the question you are answering, rather than referring them to first/second question. Also, it's best to ask follow-up questions as comments on the question rather than putting them in answers. You can always edit your answer with new information in light of changes to the question. $\endgroup$
    – Mark Booth
    Dec 4 '12 at 13:48
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    $\begingroup$ @delinquentme, it all comes to what wall adapter are you using. If it is regulated i.e. open circuit voltage 12V ... you already have a 12V regulator, and adding a second one can only hurt. If it is unregulated i.e. open circuit voltage > 12V (maybe 14-15-16-17), then look at the datasheet of the motor driver under "Absolute maimum ratings" and check if it can handle this voltage. $\endgroup$
    – Vorac
    Dec 8 '12 at 9:30

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