I am looking for a 3.3 V power source in the Printrboard Rev. D pins.

I think there should be one somewhere... I do not know how to read the schematics that well.

Also, I am going to connect an HC-06, which draws 45 mA or less during operation. So, I need to know if it safe to get the power from the 3.3 V rail (if I find it).

So, the questions are:

  • Which one is the 3.3 V pin?
  • And how much current can I draw from it?

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  • $\begingroup$ To whoever comes after me: I do not think the 3.3 V rail is accessible in this board. You could tap from the 5 V rail, but in my case I do not think it makes sense. The LM2841 is what is used to convert from 12 V to 5 V, and that seems to be able to handle a max of 300 mA. I have no clue about how much is being used at this point... so I think I'll tap directly from the 12 V power supply. $\endgroup$ – rufo Feb 23 '19 at 12:12

On the schematic, the 3.3v is marked as "U7" and pointed out here:

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The 3.3v is marked as pin #2. You can find the three pints from U7 here on the board (blue circle):

enter image description here

I'm not exactly sure if the pins are accessed from the other side of the board, or even if they are marked at all on there. You can always check them with a multimeter to see what their output is. More than likely the bottom single pin is the ground and the top two are one or the other (5v & 3.3v).

As far as amperage draw, I'm thinking 45mA is not a lot of draw, but I'm not an expert. I'd think it should be able to handle it, but again, I really don't know.

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